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SHOREBIRD HABITAT NESTING PREFERENCES IN ARCTIC NATIONAL

WILDLIFE REFUGE:

UNDERSTANDING NEST SUCCESS BASED ON ECOSYSTEM FACTORS

Alec Blair

TC660H

Plan II Honors Program

The University of Texas at Austin

April 29, 2020

J. Hayley Gillespie

Jackson School of Geosciences

Supervising Professor

Ashley Matheny

Jackson School of Geosciences

Second Reader

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ABSTRACT

Author: Alec Blair

Title: Shorebird Habitat Nesting Preferences in Arctic National Wildlife Refuge: Understanding

Nest Success Based on Ecosystem

Supervising Professor: Hayley Gillespie

On the Canning River Delta in the Northeast corner of the 1002 Region of the Arctic

National Wildlife Refuge (ANWR), shorebird biologists conduct surveys to map and study

nesting locations of Semipalmated sandpipers (Calidris pusilla), Pectoral sandpipers (Calidris

melanotos), Red-necked phalaropes (Phalaropus lobatus), and Red phalaropes (Phalaropus

fulicarius). These migratory birds find their way to ANWR during the end of May and

throughout June to begin mating and the strategic process of choosing nest location. U.S. Fish &

Wildlife Service botanists have divided ANWR into eight different habitat types based on

present vegetation and precipitation levels. This information can be useful to determine

environmental preferences that the shorebirds (surveyed in the summer of 2019) may have, and

the level of nest success under those local conditions. My objective was to determine priority

habitat areas to best preserve shorebird species that nest within the 1002 shore area by overlaying

2019 nesting locations with respect to multi-spectral data such as water proximity, avian predator

proximity, and habitat type. I want to understand if there are any significant differences in the

habitat preferences among the four species and what other environmental factors may impact

those differences in selection and in success. Results show that each individual species has

specific preferences relating to each environmental factor: both phalarope species heavily prefer

more saturated terrestrial habitat types with close proximity to a water source where they can

forage. Both sandpipers prefer drier habitat types with neutral distance to water sources (as they

are willing to travel further from their nest to forage). This information can inform the necessity

to preserve near shoreline freshwater sources of varying sizes and calls for further research into

how shoreline erosion, unpredictable future precipitation events, and oil and gas development

can implicate the coastal plain and shorebird nesting habitats. Results indicate that all four

species have heavy preference for one of three habitat classes that are marked by semi-moist

graminoid grasses, with some variation in preference for plant species to nest within. Both nest

initiation and nest termination dates have important roles in the nesting outcomes for all species,

but more so in the phalarope species. Vegetation coverage over nests was significant for

phalaropes but not sandpipers, indicating a need for more research into the changing nesting

phenology of phalaropes, especially in P. fulicarius which is more restricted in its breeding

habitat selection.

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Table of Contents

Introduction…………………………………………………………………………………...…...5

Focus Species…………………………………………………………………………….12

Methods…………………………………………………………………………………….….....22

Statistical Analysis……………………………………………………………………….28

Results…………………………………………………..…………………………………..……29

Discussion……………………………………………………………………………………..…42

Appendix…………………………………………………………………………………49

Reference List……………………………………………………………………………………58

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Acknowledgements

This paper would not have been possible without the help of my two advisors, Hayley

Gillespie and Ashley Matheny: their patience and grace during a chaotic time in the world was

helpful beyond the scope of this paper. Thanks to Christopher Latty and Tamara Zeller of

USFWS Alaska Region for providing the opportunity to work in Arctic National Wildlife Refuge

in the summer of 2019: it was an experience I will never forget. Finally, thanks to my friends,

family, coworkers, and anyone else who had to listen to me talk about birds over the last year.

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Introduction:

Hypotheses

The primary questions that this research seeks to answer are: what significant differences

in habitat nesting preferences exist between each of the two sandpiper species (C. melanotos and

C. pusilla) and the two phalarope species? Within each species, are there significant differences

in the nesting success based on the habitat type that is nested within? How does the initiation

date of the nest impact the likelihood of success? Does temperature at initiation or at termination

have any correlation with nest success? Does concealment have any correlation to nest success?

Background on Arctic National Wildlife Refuge

Roughly the size of South Carolina, Arctic National Wildlife Refuge (ANWR) is the

single largest remaining undeveloped tract of land in the United States. Located on the north

slope of Alaska, approximately 60 miles east of Prudhoe Bay, the refuge includes the lowlands

below the Brooks Mountain Range and extends all the way to the Beaufort Sea of the Arctic

Ocean. On the western border of the refuge lies the Staines River, part of the greater Canning

River Delta. On the eastern border, one refuge ends and another begins: ANWR adjoins its

Canadian equivalent called Ivvavik National Park. The Arctic coastal climate in the Canning

River area consists of low summer temperatures that averaged at 29.85˚F in May, 38.98˚F in

June, 51.35˚F in July, and 42.87˚F in August of 2019 (Figure 1). A general warming trend is

evident between 1999 and 2011 based on weather data taken from NOAA Kaktovik, AK weather

station (Figure 2). Northeasterly winds from the Beaufort Sea can be strong and dense fog can be

common in the summer months. Precipitation is low, with averages less than two inches per

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month during the summer months between 1999 and 2011 (Figure 3). Ice and snow cover can

persist into June, well into the breeding and nesting period of the shorebirds. Continuous

permafrost exists under the coastal plain extending from the coastline of the Arctic to the

foothills of the Brooks mountain range, however the permafrost has become a major climate

change research focus as its melting may have significant implications. During the summer

months (May to August) annual permafrost thaw creates thaw lakes through thermokarst: the

differential thawing of permafrost creating topographic incongruities on the land surface (Shaftel

2018). Thaw lakes also contribute to the landscape features, drained thaw lake basin (DTLB),

which are classified by low elevation tundra polygon depressions that formerly existed as thaw

lakes (Frohn 2009). These differential polygons create the foundation for the local topographic

changes that classify different local habitat conditions along the coastal plain, and their habitats

continue to shift as permafrost melting increases each year. Permafrost thawing poses an

immediate atmospheric threat with its increase in global methane circulating (Whiteman 2013).

Locally, the permafrost melt has been seen to have significant impact on snowmelt and icing

events annually, which directly impacts herbivorous populations. Further, thaw-induced collapse

of structures used by wildlife for reproduction can have significant impacts on annual

fluctuations in populations of arctic dwelling mammals (specifically shrews and lemmings).

Finally, thermal erosion of ice wedges has a very significant impact on avian species specifically,

as ice wedging can result in the drainage of wetland areas that birds, notably waterfowl species,

rely on (Berteaux 2017). The thaw will also increase soil carbon sinks by directly increasing

microbial respiration and vegetation productivity. This results in an increase of shrub plant

species, which may have significant ecohydrological impact on radiation by reducing surface

reflectance and increasing evapotranspiration (Loranty 2012). Notable shifts in vegetation have

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already been observed along the North shore of Alaska that are leading researchers to question

how plant productivity shifts may propagate upstream into the food web, through variation in

foraging, hunting and nesting locations that are available to wildlife (Tape 2006). The threat of

ice-wedge melting has the potential to dramatically change the topography of the landscape that

avian species rely on for both foraging and nesting by changing the local water balance in

lowland tundra habitats through increased surface runoff and decreased subsurface inundation to

contribute to renewing winter permafrost boundaries (Liljedahl 2016). Other recent studies

further question the threat that hydrological change may have on local environments in the

tundra. Since 2011, significant reductions in plant productivity have been observed and

correlated to increases in both temperature and precipitation--warning for an even greater

reduction of the tundra’s ability to serve as a carbon sink (Lara 2018). There is also a local threat

to existing biota because of other hydrological changes to the landscape: studies have found that

shifts in climatic conditions will make the Arctic tundra a sink for heavy metals including

cadmium, zinc and lead because of the impending and current increase in local precipitation

(McDonald 2005). All of these disruptions to the local hydrological, vegetative, and topographic

conditions of the Arctic coastal plain raise an alarm to how they may impact wildlife.

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Figure 1: Average temperature (F) in each of the summer months taken from the NOAA

Kaktovik, AK weather station between 1999 and 2011. General warming trends shown for both

June and July months.

Figure 2: Average daily temperatures (F) including minimum and maximum temperatures in

Prudhoe Bay, Alaska, the nearest weather station (Barter Island LRRS Airport Weather Station)

to the Canning River Delta field site (approximately 60 miles away).

R² = 0.0002

R² = 0.1911

R² = 0.1381

35

37

39

41

43

45

47

49

51

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Te

mp

era

ture

(F

)

Year

Kaktovik, AK Average Monthly Temperature 1999-2011

June

July

August

Linear (June)

Linear (July)

Linear (August)

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Figure 3: Average precipitation during the summer months taken from NOAA weather station in

Kaktovik, AK between 1999 and 2011. Low negative trend for August precipitation with no

trend for June or July.

Policy Background

Originally designated as a wildlife range by President Eisenhower in 1960, Arctic

National Wildlife Refuge earned its “refuge” status when congress passed The Alaskan National

Interest Lands Conservation Act (ANILCA) in 1980 (United States 1980). The act protected the

area oil and gas development, with the exception of a portion of the refuge called the “1002,”

located on the northern portion of the refuge in the Arctic coastal plain. Action to open the 1002

to drilling has been on and off over the last three decades, until in 2017 when the President

Trump signed P.L. 115-97 within H.R. 1 and H.R. 1370 which called for the begin of an oil and

gas program on the coastal plain (Comay et al. 2018). In 2019, the House responded by passing

The Arctic Cultural and Coastal Plain Protection Act (H.R. 1146) which restored protections of

the coastal plain that were removed by the 2017 law. The bill currently sits in the Senate

committee on Energy and Natural Resources for further review before a senate vote is held

(United States 2019).

R² = 0.0025

R² = 5E-05

R² = 0.0685

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

Av

erag

e P

reci

pit

atio

n

Year

Kaktovik, AK Average Summer Precipitation 1999-2011

June

July

August

Linear (June)

Linear (July)

Linear (August)

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Wildlife on the Arctic Coast

While the climatic conditions above the Arctic Circle are harsh, the area serves as an

essential habitat for many animals: from caribou to Arctic foxes. Some of these species include

migratory birds that use the Arctic as their breeding and nesting location for the summer until

they move as far as Antarctica (Arctic tern) for the winter. Migratory birds have been well

studied to understand the advantages of mobility to promote larger breeding ranges to improve

species fitness (Newton 2003). The adaptation of migration has become an area of concern under

the greater study of climate change, specifically as polar regions rapidly experience the impacts

of global temperature increase. The threat of habitat reduction to migratory species has been

found to be especially significant for coastal birds as their ranges are particularly restricted

(Henningsson 2008). Fourteen of the bird species that use ANWR for nesting are shorebirds of

the Scolopacidae family. The primary local nesting ground of these birds along the Arctic coastal

plain includes the “1002” region of the northwestern portion of ANWR that extends north of the

Sadlerochit Mountains, part of the Brooks Range, to the Beaufort Sea shoreline. This is the only

part of ANWR that was not designated as protected wilderness in The Alaskan National Interest

Lands Conservation Act (ANILCA) of 1980. Currently, annual research is being conducted on

ANWR in the 1002 region to better understand the wildlife that resides there currently and the

potential impacts of development may have on it. One such form of research is conducted by the

“Bird Camp” on the shoulder of the Staines River in the Canning River Delta in the northwest

corner of the 1002, just two miles south of the Beaufort Sea. Multiple projects take place in this

location relating to arctic dwelling species, ranging from Arctic fox den studies to loon surveys.

Over the course of June and July each year, ANWR becomes the home of researchers for a

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shorebird nesting project to collect data on the habits of the shorebird species that use the area to

forage, nest, and brood before flying south for the winter.

Previous Research

This study will work to expand on the ANWR shorebird abundance and distribution

study done by Brown et al. 2006. Drawing from the same habitat categorization that Brown et al.

applied to their own study (from Jorgensen et al. 2018b), this study will begin by comparing the

abundance and distribution results from Brown’s 2002 and 2004 shorebird surveys to the data

collected in the Summer 2019 field season to confirm the habitat preferences of the four

shorebirds, and then extend the research to include the nesting success of the birds based on the

habitat types in which they nested. The 2019 field season data will be analyzed for the success

rate of each of the bird species based on habitat type and will attempt to block for the presence of

avian predators (Arctic and Red foxes, Parasitic and Pomarine jaegers, and Glaucous gulls).

Brown et al. classified habitat types into five categories as opposed to Jorgenson’s 17, the

simplification of these habitat types is useful on the entire scale of the refuge which includes

upland drier habitat types, but because this study focuses on the coastal plain, it is necessary to

further differentiate the habitats by maintaining Jorgenson’s 17 classes. The initial assessment of

the Arctic coastal plain that now defines the oil and gas interest and the potential to redefine the

conservation status of ANWR is held within the Coastal Plain Resource Assessment (Clough

1987). The second chapter of the assessment discusses wildlife that live on the refuge and the

extent that it would be impacted based on FWS research conducted in the 70’s and 80’s. These

findings will be compared to a modern understanding of the local environment in the Discussion

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section, to give a better understanding of how both changes in climate and in human

development of the Arctic coastal plain may impact the studied shorebird species.

Focus Species

Four shorebird species are the focus of this study: two phalaropes from the genus

Phalaropus, the Red-necked phalarope (Phalaropus lobatus) and the Red phalarope (Phalaropus

fulicarius) as well as two birds from the Arctic shorebird family Calidris: Semipalmated

sandpiper (Calidris pusilla) and Pectoral sandpiper (Calidris melanotos). All of these migratory

birds find their way to ANWR during the end of May and throughout June. Having established

their local territories in ANWR, the birds begin the process of mating and the strategic process of

deciding nest location.

Red-necked phalarope

Both of the phalarope species are polyandrous: the male is responsible for incubating and

brooding the eggs and caring for chicks while the female lays eggs and moves on, potentially to

find another mate and lay more eggs. Breeding females are distinguished from males by their

brighter plumage and larger body size. Phalaropes determine nesting in a biparental manner,

where both the male and female participate in determining nesting location. The Red-necked

phalarope (Phalaropus lobatus) is one of the world’s smallest seabirds and is the smallest of the

phalarope species (Rubega 2020). The majority of the year (around nine months), the P. lobatus

spends its time on the ocean feeding on planktonic invertebrates, while the other three months

serve as the species’ breeding period where it nests inland in Alaska, northern Canada, northern

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Scandinavia and northern Russia. On its migration route it stops in the open ocean, or if

migrating inland, on large saline lakes to forage. Very little is known of the species while it is

overwintering, making its nesting period its most accessible for research. Nest site selection

begins with the female 5-7 days before selection and the male joins 1-2 days prior to selection.

Typical vegetation types chosen by P. lobatus include those where sedge is the primary plant,

also significantly moss hummocks with grass, sedge, forbs and low amounts of shrubs (Murphy

1981). Scrape formation occurs between two and five days before eggs are laid by the female

and young leave the nest within 24 hours of the first egg hatching (Rubega 2020). During its

nesting period, P. lobatus is known to forage on small aquatic invertebrates and flying aquatic

insects (most prominently Diptera and Coleoptera orders) in small pools and ponds near nest

locations (Baker 1977). Both phalarope species conduct foraging in a unique way by spinning in

circles in the small water sources that they forage in, using their beak to stir up subsurface

sediment layers that lift their prey to the surface so that they can pick them with their bill

(Rubega 1993). The clutch size of P. lobatus is typically four eggs. To avoid giving nest location

to predators when incubating, the male will walk between 10 and 50 cm from the nest before

taking off to fly to forage. In the presence of a predator the average flushing distance was found

to be five meters, although with some notable variability (between 1 and 30 meters; Sandercock

1997). Eggs begin starring (where small star-shaped perforations become noticeable on the egg

shell from the chick getting closer to its hatch) between two and four days prior to hatch and

pipping begins one to two days before hatch. Larger egg fragments are flown away from the nest

while some minute fragments are left behind.

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Red phalarope

Red phalaropes (P. fulicarius) spend up to eleven months of each year in their marine

environment and their migratory route is completely marine (unlike P. lobatus that migrates

continentally). The wintering and migratory diet of P. fulicarius consists typically of the

crustaceans that surround whales, while its breeding diet is mostly small invertebrates and

aquatic insects. P. fulicarius are sexually dimorphic, like P. lobatus, having larger females with

brighter plumage than males (Schamel and Tracy 1977). P. fulicarius breeding range is more

restricted to coastal Arctic than that of P. lobatus--closely nesting along the coastline of North

America and Russia. Overwintering takes place in the Pacific along the coastline of southern

North America and South America, in the Atlantic close to the coast of southern USA and the

Caribbean, and in the Atlantic along western Africa (Tracy 2020). Breeding takes place on moist

tundra near small pools (within at least 200 meters) with preference to vegetation that is poorly

drained and level with higher amounts of sedges and hummocks (Kischinski 1975). Notably, P.

fulicarius has less preference for saline pools for foraging than P. lobatus in northern Alaska

(Troy Ecological Associates 1994). Previous research has also identified a notable difference in

preference for moist vs dry habitat (with P. fulicarius showing preference for moist). This causes

even greater restriction for P. fulicarius, combining its preference for moist tundra with near

coastal areas. Foraging behavior differs from P. lobatus, where P. fulicarius edge feeds as

opposed to surfacing feeding and swimming (Elander and Blomqvist 1986). Scrape formation

begins two to four days before egg laying and is typically done in pairs (another notable

difference from P. lobatus --breeding strategy is much more mutualistic for P. fulicarius as both

sexes participate in nest site selection). Much like P. lobatus, it is unknown whether the male or

female ultimately chooses the nesting location. Vegetative preferences for nesting sites include

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most typically sedge and close to shallow water sources for foraging. Clutch size is typically four

eggs, and the female does not revisit the nest after the final egg is laid. Incubating males will

flush when predator is nearby from between 30 and 50 meters, but may also exhibit distraction

displays like a false broken wing or a “rodent run” where they do not fly away but only run on

the ground away from the nest (Mayfield 1979). Pipping and starring of eggs is on the same

timeline as P. lobatus, as is the disposal of egg shells.

Pectoral Sandpiper

The Pectoral sandpiper (C. melanotos) belongs to the Calidris sandpiper family, it is

larger than the Semipalmated sandpiper (C. pusilla) also in this study. C. melanotos breeds along

the north slope of North America and northern Russia and migrates to its wintering grounds in

southern South America and southern Australia and New Zealand. In its breeding range, C.

melanotos has preference for wet and well vegetated habitats where it prefers raised hummocks

with sedges and grasses—and does not nest in dry tundra areas (Troy Ecological Associates

1994). In the early summer, C. melanotos forages in tundra meadows and edges of polygons, but

midsummer it shifts to wetter areas surrounding ponds and lakes (MacLean 1969). C. melanotos

forages by probing and jabbing into substrate at water edges into substrate and pecking at both

larval and adult arthropods in northern Alaska (Holmes 1968). Males and females both arrive at

the breeding location in late May where males will immediately begin to establish territories to

defend against other males before females arrive. Females will spend several days to determine

appropriate mate and site location and begin egg laying in mid-June (Pitelka 1959). Females

select nesting sites without male participation, choosing drained areas within wet sedge tundra.

Nesting behavior has been previously examined for the relevance of the nesting construction,

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where it was found that nest scrapes are designed to reduce heat loss for clutches (Reid 2002). C.

melanotos constructs its nest with a nest scrape depression depth that is as small as possible to

ensure minimal heat loss through wind convection. Insulation material selected by sandpipers

maintain beneficial insulated properties when damp which is essential given the environmental

conditions that they nest in. Previous research relating to C. melanotos has found intense sexual

selection exists within males in the species because of their polygynous behavior calling them to

nomadically move through breeding range searching for females to mate with (Kempenaers

2017). This behavior can be significant for its inhibition of allopatric speciation, ensuring

unrestricted interbreeding within geographically different areas within the entire population’s

range. In the situation of the C. melanotos and C. pusilla, nest location is decided by the female,

as the species are polygynous. These habits can inform the nesting preferences of each species,

which are decided in a uniparental manner in the sandpipers, where males create nesting scrapes

in specific locations, but females ultimately determine which male to mate with and which nest

scrape to lay eggs in. Clutch size is typically four eggs, and the interval between laying each egg

is more than 24 hours (Parmelee et al. 1968). Only females incubate eggs and spend a large

portion of their incubation period on the nest. Females will attempt to hide nest location from

predators by leaving on the ground, but will flush if close (observationally from about 10-20

meters) and rodent-run to distract (the practice of scrambling on the ground to imitate a rodent to

attract the attention of the predator). Pipping and starring follows similar timeline as both

phalarope species.

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Semipalmated sandpiper

Roughly half the size of C. melanotos, the Semipalmated sandpiper (C. pusilla) breeds in

the Arctic and overwinters along the coastline of northern and central South America. It is

seasonally monogamous and territorial--it has proven to be nonsocial in its breeding choices,

behaving in a non-conspecific manner (Hicklin 2010). In very rare circumstances, the C. pusilla

has been found nesting in a colonial manner, making the phenomena something worth

investigating in this study (Jehl 2006). There have been numerous studies on C. pusilla that have

found significant population decline (more notable than any of the other three species included in

this study) at its migration staging areas (Morrison et al. 2001). C. pusilla most commonly breeds

in low, sub-Arctic tundra near river deltas. It forages on benthic invertebrates by pecking and

probing, but has been noticed to also suck biofilm from water surfaces (Ginn 2009). Diet

preferences in Alaska are most commonly Diptera order insect larvae (Holmes and Pitelka 1968).

Arrival to breeding grounds begins in late May and early June, with males arriving prior to

establishing territories. Males are known to establish the same territory that they used in the

previous year (Gratto et al. 1985). Pairing occurs quickly and both male and female C. pusilla

participate in nest-scraping. Males select nest sites that are near water sources and on small

hummocks or in a clump of sedges and do reuse previous sites. Egg laying begins roughly one

week after pair formation (Ashkenazie and Safriel 1979). Average clutch size is four eggs with

the interval of egg laying being as long as 30 hours between each egg, giving a total laying time

of over four days (Gratto-Trevor 1991). Both sexes participate in incubation and in relatively

equal intervals, with males during the day and females at night (Jehl 2007). Pipping and starring

signs are similar to other species, and parents dispose of shells in similar manners to other

shorebird species (Hicklin and Gratto-Trevor 2020).

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Nest Site Determination

There are many factors that shorebirds consider when determining the location of their

nesting site: food availability, timing of snowmelt and vegetation greening, predator abundance,

and alternative prey abundance. Species may exhibit conservative or opportunistic settlement

strategies in their site determination (Saalfeld 2015). Conservative species, which exhibit high

site fidelity, are more impacted by previous year conditions than current local conditions. Those

who exhibit natal philopatry will nest in the same area that they were born and can be defined as

highly conservative. P. lobatus and C. pusilla have been observed to follow this trend.

The timing of arrival and departure are also essential considerations for nesting success in

shorebirds. Higher latitudes like the Arctic have reduced (compressed) breeding schedules,

making a small window for nesting to brood success for all shorebird species that summer in the

area. Different species react differently to the temporal stress: P. fulicarius have reduced their

incubation periods, while C. pusilla have higher risk of paternal abandonment in the late summer

(Sandercock 1998). The potential for phenological mismatch, especially in regards to trophic

availability, is becoming a research topic of significant value for migratory birds.

Incubation Periods and Initiation Dates

Clutch initiation dates (CIDs) are an essential part of the reproductive biology of avian

species. Understanding the variability within individual species’ phenology to being nesting is an

important assessment of climate change adaptability. Previous research has found that all four

shorebird species have advanced CIDs that range from 0.40 to 0.80 days (within the nine year

study; Liebezeit 2014). Research found that snowmelt was an especially important

environmental factor in determining the nest initiation (which further alludes to the significance

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that changing climatic conditions will have on the species). Advancement of CIDs has been

shown to help the shorebird species avoid mismatch on a trophic level: allowing them to access

the invertebrates that they forage on during their nesting period. Also significant to the

reproductive biology of the shorebirds is their incubation period. Table 1 represents the

respective incubation periods of each species in the study averaging to a 20.75 day incubation

period among the four (between laying of eggs and hatching of eggs). This does not include the

vulnerable time after egg laying where hatchling brooding takes place (typically less than a 24

hour period) and the scrape formation that occurs prior to the egg laying (typically between four

and seven days for all study species). In this study, incubation period does not begin until the

final egg is laid (which serves to offer even more vulnerable time that the adult is on ground at

the nest site). The data in Table 1 is based off of previous research on the species in the local

range, but still closely match those used in other studies (discrepancies like these are addressed

in Sandercock 1998).

Table 1: Average incubation period of the four focus species based on data provided by the

Canning River Delta “Bird Camp” Research Group (Freeman 2017)

Species Incubation

Period in days

PESA 22

REPH 20

RNPH 21

SESA 20

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Nest Success

Data collected from Canning River Delta between 2010 and 2016 recorded only two

instances of weather induced nest failure (out of the 1,860 nests recorded) according to the

Canning River Delta “Bird Camp” USFWS site (Freeman 2017). Another important factor for

shorebird nest success is the presence of avian predators that feed on shorebirds and their eggs.

The most common avian predators are the Pomarine jaeger (Stercorarius pomarinus), the

Parasitic jaeger (S. parasiticus), and Glaucous gull (Larus hyperboreus). Each of these predators

overlap in their nesting time and location with the shorebirds and can impact sample data

accuracy when they predate in specific areas decreasing the nesting success of the shorebirds.

Another direct predator of the shorebirds and their eggs are the Arctic fox (Vulpes lagopus) and

Red fox (V. vulpes) which both den and raise their young in the same areas as shorebird nests

and can contribute to significant decline in local annual shorebird abundance when nearby. A

notable contributor to the likeliness of predation is the activity of the parent nesting. Martin

(2000) found that parental activity increases during the nesting stage (as opposed to the

incubation stage pre-birth) when caloric intake of the parent is at its highest to supplement the

diet of the chicks. This at-risk period can contribute to greater depredation and is the source of

convergence between parental activity and nesting sites and should be considered in the

assessment of nesting success. It is important to acknowledge that while not being directly

assessed in this study, parental behavior to avoid depredation is a significant variable in nesting

success (Smith 2007). Local stress conditions created by the presence of avian and mammalian

predators can significantly change the survey results on an annual basis. Simultaneous fox

research was being conducted at the camp to understand the presence of predator species and

their proximity to the survey site.

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The nesting behavior of shorebirds can differ significantly between species. In the

situation of both sandpiper species, research found that enhanced tundra microrelief increased

nesting site selection (Cunningham 2016). Further, the research found that these two species also

had statistically significant preference for non-conspecific nesting locations: these species

avoided nesting closely to those of their same species. This affirms the conclusion of the

Cunningham study that shorebirds make preference first to habitat type and then to proximity to

other species. The study also found preferences in P. fulicarius for moist environments; a habitat

distinction relating to the wetland habitat type to be used in this study. While this study will not

cover sex ratio, it is beneficial to note that sex-ratio distribution within populations can have a

significant impact on the overall fitness of the population. A study conducted with P. lobatus

determined that their polyandrous behavior still result in greatest fitness within a 1:1 female to

male sex-ratio (English 2014). An aggregation of biotic and abiotic factors directly implicate the

success of shorebird nesting, and while it is difficult to determine the actual cause of nesting

success and failure, it is beneficial to understand the correlations present between the rate of

success and failure of the different species and the environmental conditions that were present

within one summer.

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Methods:

Habitat Differentiation

One of the most important distinctions of this study is the qualification of the different

habitat types that exist within the study area. The breakdown of habitat types will follow

previous analysis of similar environments in the same area (Brown 2006). The first and easiest

way to break down the habitat types found in the study area is to distinguish between land and

non-land. Non-land includes any water formation: ponds, lakes, and the Staines River that runs

through the study site. Land can be broken into four habitat types: wetland, riparian, moist and

upland. When viewing the Arctic tundra plain from above, it appears to be a mosaic of low and

high centered polygons of vegetation patterning the land alongside different sized water bodies.

The low centered polygons are typically classified as wetlands due to their moistness and are

most abundantly composed of sedges (Carex aquatilis and C. chordorrhiza, and Eriophorum

angustifolium). The moist habitat type is composed of flat centered polygons and are

characterized by improved drainage. Moist areas are most abundantly composed of mosses

(Tomenthypnum nitens and Hylocomium splendens), sedges (Eriophorum angustifolium and

Carex bigelowii), willows (Salix planifolia and Salix reticulata) and Dryas integrifolia. The

upland habitat type includes high centered polygons that are abundant with tussock sedge

(Eriophorum vaginatum) and shrubs (Betula nana and Salix planifolia). This is the least moist

habitat type in the survey. The final habitat type, riparian, includes gravel bars and floodplains

with riparian shrub vegetation (Salix lanata, S. alaxensis, and S. glauca). These habitat types are

distinguished partially by the species of vegetation that they include, but more so based on the

23

available Landsat data that Jorgenson et al. (2018b) used to determine the first baseline study of

vegetation present throughout ANWR.

Study Site

In order to collect data on the nesting location and success of the four bird species, a

sample area in ANWR was established in proximity to the Staines River that covers all of the

habitat types. The study area is the two kilometer radius surrounding Bird Camp itself: the

surrounding area is broken into 37 roughly evenly sized plots, each around 600 square meters

(excluding water formations). During the months of June and July of 2019, each plot was

surveyed by two to three of the crew members to identify any active shorebird nests as well as

any other bird nests that may be occupied on the plot. Shorebird nests were found when parental

behavior was exhibited that alluded to the presence of a nest through different means such as: a

parent flushing from a specific spot, staying unexpectedly close to a certain area, or using

distraction displays to confuse or divert the attention of the observer. When suspect behavior was

exhibited, the origin area of the behavior was closely examined to determine the exact location of

the nest. If the observer was unable to find the nest from the initial flush, they moved away from

the area (roughly 20-40 m away) until the parent returned to the location. In the first round of

surveys, each plot was searched in a group for a human time amount of twelve hours: two people

could search a single plot for six hours, or three people for four hours. All plots were searched a

second time for a total of four human hours (two people searching for two hours) to determine

the presence of any remaining nests on the plots. Nests located during surveys were GPS tagged

and randomly determined to be revisited or to remain undisturbed. They were marked by a line

of three popsicle sticks leading towards the nest from the North in a five meter spacing between

24

each popsicle stick, with the final stick being located within a meter of the nest bowl. Those that

were revisited were done so based on the results of an egg floating test which determined an

approximate incubatory period of the clutch so that revisit timing could be assigned to minimize

nest disturbance and potential nest failure. Egg floating has been proven in previous

experimentation to be an effective form of incubation date estimation (Mabee 2006). To conduct

the float test, each egg from the bowl was carefully removed and then placed into a small

container filled with warm water. The egg was pushed to the bottom of the container in the water

and then released: the height and angle at which the egg would float gives accurate information

as to the likely amount of time until the hatch of the egg. Cracked eggs were not floated, and

previous research has shown that floating uncracked eggs does not impact their hatch likelihood

(Sandercock 1998). Using the method in Mabee 2006, C. pusilla incubation age was estimated to

an accuracy between one and three days. This temporal information allowed for later visitation to

determine the health and eventual outcome of the eggs in the nest. Later visits with later signs of

hatch were not floated, but instead closely examined for signs of piping to determine an

oncoming hatch. Eventually, both nest re-visits and undisturbed nests were visited after the hatch

date of the nest had passed to assess and distinguish between a nest success and failure. Eggshell

evidence has become a common methodology to determine the fate of a nest (Mabee 2006).

Eggshell fragments between 1-5 mm proved to be prominent at successful nests (96% of the time

in the Mabee study) and eggshell tops and bottoms were only present at successful nests. Final

post-fates could result in one of three different outcomes: abandonment, depredation, or hatched.

Signs of abandonment came from revisitation to a nest with eggs feeling cold when examined.

Depredated eggs may have completely disappeared when not at a time expected to have hatched

during visitation, or the nest could have signs of predator activity (fox urine scent or shell

25

fragments found outside of the nest bowl). Hatched nests could be signified by the actual

presence of chicks during the late visitation or presence of eggshell top or bottom or other

appropriately sized fragments. These “post-fate” results were used to determine the relationship

between the success of nests of different species to the habitat type that they nested in as well as

the relationship between nest success and other environmental variables that may have

implicated the nest and the adult incubating it.

Use of Remote Sensing

The use of light detection and ranging (LiDAR) and normalized difference vegetation

index (NDVI) overlay imagery has historically been used in experimentation when dealing with

Arctic tundra polygonal terrain (Gangodagamage 2014). This study employed the work of

Jorgenson et al., specifically through their creation of the “Landcover and Vegetation Map,

Arctic National Wildlife Refuge” composed of data from Landsat Thematic Mapper, multiple

Digital Elevation Maps (DEMs), aerial photography, and ground surveys (Jorgenson 2018b). By

overlaying the feature classes of vegetation over the GPS location of nests, the specific habitat

type of each nest can be determined. Issues with the significance of the findings of habitat

preference arise based on the rapidly changing landscape of the Arctic coastal plain. Each year,

the hydrology that determines the vegetation classification system may differ, but the underlying

value of the classes is still significant to understanding the preferences of the different species.

The classification scheme used contained 17 different habitat types based on the features

examined.

26

Table 2: Vegetation classification system based on the classification system used in Jorgenson

2018b.

# Habitat Class Description of Class

1 Wet Graminoid

Tundra

Poorly drained tundra with sedges or grasses, with few shrubs

or mosses

2 Graminoid Tundra With 10-50% moist inclusions, often on low-centered polygons

or strangmoor

3 Sedge-Willow Tundra 10-50% moist inclusions, often on low-centered polygons or

strangmoor

4 Moist Sedge-Willow

Tundra

Moist tundra with sedges, mosses and willows

5 Moist Sedge-Dryas

Tundra

Moist tundra sedges, mosses, and Dryas. Sedge hummocks and

frost scars give hummocky appearance

6 Moist Sedge-Tussock

Tundra

Moist tundra dominated by cottongrass tussocks with

understory of dwarf shrubs and mosses

7 Moist Shrub-Tussock

Tundra/Water-track

Shrub Tundra

Tussock tundra dominated by erect willow and birch, or

shrubby drainage complexes in foothills

8 Moist Low Shrub

Tundra

Upland slopes with erect willow and birch

9 Moist Shrub Tundra Shrubby polygonized tundra with herbaceous types in polygon

troughs

10 Dryas-Graminoid

Alpine Tundra

Moist to dry alpine tundra with dwarf shrubs, graminoids,

forbs, lichens, and bare ground

11 Riparian Shrub Well-drained river terraces with low or tall willows

12 Dryas River Terrace Well-drained river terraces with Dryas mat, other dwarf

shrubs, forbs, and lichens

13 Partially vegetated 10-15% vegetated

14 Barren <10% vegetated

15 Ice Ice and snow

16 Water

17 Shadow

27

Table 2 includes all tundra ecosystem habitats that were surveyed, but this study only

encompasses the area immediately on the coastal plain, about two miles from the Arctic Ocean:

this means that fewer habitat classifications existed within the study than in Brown 2006. Only

six habitat types were found within the study area that included nests: 1, 2, 3, 5, 14, and 16.

Using ArcGIS Pro, the Jorgenson Map was overlaid on the GPS locations of each of the

individual species to determine what class they lay within. Some discrepancies were significant

enough to determine that the summer 2019 had been significantly altered compared to the

Jorgenson map fifteen years since its initial survey.

Other Environmental Factors

Further analysis included the parameters of the initiation date and its average, minimum,

and maximum air temperatures based on the nearby Kaktovik Weather Station, as well as for the

“last date alive” which was determined to either be the day of hatch or the day of failure or

depredation. Concealment percentage was also included in the study based on the percent of

grass and sedge coverage that was identified while looking down onto the nest from above.

Concealment percentage was identified by surveyors into 5s from 0% coverage to 100%

coverage. After all concealment percentages were gathered, they were then grouped into four

different categories 1-4 by average the total amount and evenly distributed to make four even

concealment categories.

28

Table 3: Using the “ntile” feature in R Studio, the concealment percentages were broken into

four groups to lessen the significance of observer bias as discrepancies in percentages may have

existed between the surveying biologists

Concealment Category Concealment Percentage

1 0-29

2 30-50

3 51-68

4 69-100

Statistical Analysis

Statistical testing compared categorical variables (vegetation, ultimate call, and

concealment) with each other by creating contingency tables between each of them. The Fisher’s

Exact Test was run on each of their contingency tables to determine any statistical significance.

Categorical variables were also compared against each of the quantitative variables (initiation

date, initiation date air temperature (average, minimum, maximum, variance), termination date,

and termination date air temperature (average, minimum, maximum, variance) to gain a better

understanding of how environmental conditions on the day of both initiation and termination

(through both success and failure) may implicate each species. Bar graphs were used to display

the visual results of nesting success based on the habitat. After habitat preference was modeled,

the ultimate call of each available nest (excluding N/A nests) was included to understand how

habitat type location may correlate to the success of that nest. The initial habitat assessment

conducted in Table 5 includes all individuals of the four species group, regardless of the fate of

their nest. This includes nests that were determined “N/A” and were not able to be declared to

have failed or succeeded.

29

Results:

A total of 245 nests of both shorebird and avian predators were observed during the

summer of 2019 making for a total of 237 shorebird nests. Table 4 shows that the most abundant

species was C. melanotos followed by C. pusilla. The least abundant species were the

phalaropes, with only 16 P. lobatus nests being identified in the study. Individuals that were

determined “N/A” were not able to be given a significant probability of having succeeded or

failed. These individuals were included in statistical testing that dealt with species preference but

not in any testing that dealt with nest success. After removing all N/A values, a total of 219 nests

were able to be included in the statistics testing related to nest success. Success rate of species

varied between 44 and 63% with C. pusilla and C. melanotos having similar success rates

around 44% and P. lobatus having the highest success rate at roughly 63% (notably because of

its low total abundance). This does not account for the potential double counting of an individual

that attempted to brood a second time after an initial failure. Figure 2 visualizes the findings of

success and failure within species.

30

Table 4: Species listed by abbreviation code with their respective nesting hatches and failures.

Nesting status was only determined for phalarope and sandpiper species. Total (H/H+F)

represents the total amount of individual nests in the study. % H represents the percentage of

individual nests that succeeded in hatching within a species.

Fail Hatch N/A Total

(H/H+F)

% H

L.

hyperboreus

N/A N/A 7 N/A N/A

S.

parasiticus

N/A N/A 1 N/A N/A

C. melanotos 62 49 4 111 44.14

P. fulicarius 10 17 1 27 62.96

P. lobatus 7 9 1 16 56.25

X. sabini N/A N/A 1 N/A N/A

C. pusilla 37 30 9 67 44.77

Habitat Preference Assessment

Results from the initial habitat assessment show that a significant amount of nests were

found to be water (classification 16) or barren (classification 14) when overlaid on the in

Jorgenson (2018b) map (Table 5). The initial discrepancy is an important note to confirm that

ice-wedge melting has been a significant source of wetland draining in the local habitat. Refined

results show the edited data that was included in the statistical testing (Table 6). Editing this data

was done by confirming nest location with available field data regarding nest location and

confirmed by assessing the location on Arc Pro. The primary sources of error came from the

wetland area in the northern corner of the field site (where nests were assigned values in water as

31

opposed to the feature class closest to water), and from the riparian zone surrounding the

Canning River (nest sites were reassigned to closest habitat class to their location). In total, 50

nests were relocated through this process. Tests were run to gain a better understanding of

potential preferences of shorebirds for habitat types with some level of confidence in

understanding that the classes that they were reassigned to were reasonable based on the gradient

of succession that the tundra habitat experiences. Barren land and open water in the remote

survey is almost always surrounded by habitat classification values 1 and 2: moist, poorly

drained graminoids in low-lying polygons. Figures 4 and 5 visually represent the habitat

preferences of the shorebird species after editing. There is a strong preference in sandpiper

species for habitat types 1 and 2 with occasional usage of habitat types 3 and 5. Phalaropes also

preferred use of habitat types 1 and 2, with no use of habitat 3 and occasional use of habitat 5. A

notable observation is that the sandpipers made use of habitat class 3: Moist sedge-willow

tundra. This could be useful in understanding a distinction is plant species utilization by

sandpipers as opposed to phalaropes.

32

Table 5: Habitat types against individual species, species families, and total individuals for

amount of nests within each.

Wet

graminoid

tundra

Graminoid

tundra

Sedge

willow

tundra

Moist sedge-

dryas tundra

Barren Water Total

C.

melanotos

29 43 8 22 5 8 115

C. pusilla 14 29 2 10 7 14 76

Sandpiper

total

43 72 10 32 12 22 191

P. lobatus 4 3 0 3 1 6 17

P.

fulicarius

8 10 0 1 1 8 28

Phalarope

total

12 13 0 4 2 14 45

Total 55 85 10 36 14 36 236

33

Table 6: Species habitat preference after adjustment based on observational data and closest

proximate habitat type as number of nests within each type.

Wet

graminoid

tundra

Graminoid

tundra

Sedge

willow

tundra

Moist sedge-

dryas tundra Total

C.

melanotos

33 52 8 22 115

C. pusilla 18 46 2 10 76

Sandpiper

total

51 98 10 32 191

P. lobatus 9 4 0 4 17

P. fulicarius 16 11 0 1 28

Phalarope

total

25 15 0 5 45

Total 76 113 10 37 236

34

Figure 4: Sandpiper nesting preference displaying C. melanotos vs C. pusilla nesting abundance

in each of the 4 used habitat types.

Figure 5: Phalarope nesting success displaying P. lobatus vs P. fulicarius nesting abundance in

each of the 6 used habitat types accounting for both hatches and failures.

35

Habitat Nesting Success

Habitat type did not significantly impact the nesting success of any of the bird species.

Running Fisher Exact Tests for the contingency tables for each species did not reveal any

statistical significance (Figures 6-8).

Figure 6: All species nesting success based on ultimate determination after tiny tag and

observational determination.

36

Figure 7: Both phalarope species habitat preference overlaid with the ultimate call to determine

how habitat may have impacted nest success—no significant relations were found.

Figure 8: Both sandpiper species habitat preference overlaid with the ultimate call to determine

how habitat may have impacted nest success--no significant relations were found.

37

Concealment Results

P. lobatus nests showed significance in the relationship between increased coverage and

increased nest success. Contingency tables were created for each of the species based on their

preference for concealing their nests to different degrees of coverage. The initial observations of

concealment were grouped into averaged categories 1-4, one being least covered and four being

most covered to understand if coverage actually played a role in nest survival. Fisher Exact Tests

were run for each of the tables (Figures 9-11).

Figure 9: Nest coverage percentage compared to the ultimate call of nesting success or failure

based on the unfiltered original findings for concealment.

38

Figure 10: Grouped coverage into four classes (1-4) compared to the nest success for the

sandpiper species. 1 represents least covered and 4 represents most covered. No significant

relations were found.

Figure 11: Grouped coverage into four classes (1-4) compared to nest success for the phalarope

species. 1 represents least covered and 4 represents most covered. Significant results for both

species determined that coverage had important correlation to nest success.

39

Initiation and Termination Date Results

The initiation average identified that warmer temperatures significantly impacted the

likelihood of nest initiation of both sandpiper species (Figure 12). C. melanotos was the only

species that was not averse to colder initiation dates. Notably, all C. melanotos nests were

initiated on days that had average temperatures below 45 degrees F. The termination date of each

nest was grouped with that day’s respective average, minimum, and maximum air temperature to

determine if temperature had any correlation to the success of the nest (Figures 14-17). Figure 17

is especially important in identifying that variance is less prevalent in the phalarope species than

in the sandpiper species.

Figure 12: Box plots for both sandpiper species vs. the average temperature on the day of nest

termination (through failure or success).

40

Figure 13: Box plots for both phalarope species vs. the average temperature on the day of nest

termination (through failure or success).

Figure 14: Box plot demonstrating the initiation date average temperature of each nest for all

four species.

Figure 15: Box plot demonstrating the initiation date maximum temperature of each nest for all

four species.

41

Figure 16: Box plot demonstrating the initiation date minimum temperature of each nest for all

four species.

Figure 17: Box plot demonstrating the initiation date variance temperature of each nest for all

four species.

42

Discussion:

Habitat Preference

The four species in this study provide a necessary range of shorebird species to gain a

better understanding of how the greater shorebird community will respond to changing

conditions in the Arctic tundra. More importantly, these birds serve to represent not only

shorebird species, but the entire ecosystem that exists in the Arctic tundra: insect species that

they forage on, and the predatory species that they provide resources to. C. pusilla is already

designated as near threatened (Hicklin and Gratto-Trevor 2020) and both phalarope species have

shown some population decline (Tracy et al. 2020). Disparities between the sandpiper and

phalarope species is a useful basis to understand local preference differences within Arctic

National Wildlife nesting shorebirds. While habitat preference did not reveal any immediate

significant habitat preferences on the classification system used from Jorgensen 2018, the

general importance of habitat classes 1, 2, 3, and 5 reveal necessary conservation preference

when determining essential habitat for shorebird species. Pairing this understanding with

takeaways from the mismatching that occurred in comparison of the nest locations and their

overlay with the map may raise the alarm on how changes to the local habitat composition of the

Arctic coastal plain may negatively impact all shorebird species. It is important to note that the

reassigning of nests operates under multiple assumptions that reduce their significance: the local

differences between habitat classifications 1, 2, 3, and 4 are based on very detailed plant genus

identifications which were remote sensed and compared over ten years ago. The most recent use

of the vegetation remote sensing (done in 2015-2017) showed changes in vegetation cover, most

notably in thermokarst-wetting and in river deposition in the tundra ecosystem (Jorgenson et al.

43

2018a). This counters the oversampling of water and barren land in the habitat assessment

findings and further demonstrates the variability of the local conditions of the coastal plain.

Further research needs to conduct habitat assessment of nest sites upon their identification to

avoid this issue. Previous research on P. lobatus preferences for specific habitat conditions has

confirmed aversion to shrub cover and mud (Walpole 2008). Jorgensen and other important

Arctic research has confirmed that increase in shrub cover has been significant over the past

twenty years and that ice-wedge melting has done significant wetland and open water drainage to

shift habitat conditions on the coastal plain, yet phalarope preference for graminoid nesting

locations in close proximity to open water sources has remained the same. Sandpiper species

showed greater habitat versatility in this study, but still proved to have a significant preference

for one of the three habitat classes that consisted of graminoid vegetation with semi-moistness

(Figure 8). No species were supported on barren rock near the river or on completely dry high

terrace polygons, which research has found may become increasingly dominant in the near future

(Jorgenson et al. 2018b). River deposition is increasing which could in turn increase the amount

of the barren land habitat class that surrounded the Canning River offshoot that ran through the

study area (Ladegaard-Pedersen 2017). These changing conditions emphasize a need for greater

habitat assessment at CRD to better understand both how birds are utilizing habitat, and how the

habitat itself is changing locally. P. fulicarius and their restricted habitat selection during

breeding is especially at risk in the coming years as the Arctic coastal plain will continue to shift

towards more dramatic cover changes that will redesign the entire landscape (Jorgenson et al.

2018b).

44

Air Temperature

Air temperature differences in initiation and in termination revealed the significance of

local weather conditions in the nesting success of the different shorebird species. The phenology

shifts of migratory birds have been well studied, specifically in leaving from wintering grounds

based on changing temperatures in those locations (Cotton 2003). Shifts in both arrival and

departure at the Canning River Delta have been identified by previous CRD research, and have

noted the significance of snow melt as a contributor to the advancement in arrival (Freeman

2017). The lack of temperature variance in the phalarope species initiation and termination may

allude to a cautious future where the Arctic tundra may experience even more fluctuation in

average daily temperatures as climate change advances. Previous studies have confirmed that

egg laying is non-random in relation to climate conditions, and opportunistic breeding is a

significant trait allowing for quicker initiation of nests (Duursma 2019). This may confirm the

need for greater monitoring effort towards phalarope species conservation as they may become

more reproductively stressed in the coming years.

Coverage

Coverage results confirmed that both phalarope species relied heavily on using vegetation

to cover their nests (CITE). This behavior requires a specific habitat types that meet both the

restrictions of their foraging preferences (close proximity to open water source), essential access

to graminoids and sedges, and reduction of shrub coverage or barren ground. While coverage

results were less significant for the shorebird family species, they still made significant use of

such features in their nest construction, implying that the condition is still essential for their

nesting (CITE).

45

Future Research

Overall, the study results provide a basic confirmation of the necessarily complex local

environment that makes up the Arctic coastal plain and how its continued changing will have

even more complicated effects on the species that depend on it. In a basic way, the study

confirmed that there have been dramatic changes to the local landscape that need to be measured

alongside the data that is collected about the birds themselves (Table 5-6). The easiest way to

tailor these changes to the study would be to conduct thorough assessments in nest areas using an

organized collection method across the entire research group collecting data. Soil moisture

would be an important collection note, taken at a specific distance in the radius surrounding the

chosen nest site: potentially at the three markers placed near each nest. This could useful to do

more intensive ecohydrological testing of the changes to the local water cycle, but also to better

classify the habitat type in the specific location in accordance with the Jorgenson classification

system. Even basic botanical observations through rapid ecology surveys of nest sites could be

useful to understand if there are even greater complexities to the choices of the birds in their

nesting locations. Closely monitoring the date of nest establishment and termination will

continue to serve as important markers of the phenological shifts that the species are

experiencing and may even shift the methodology in the coming years to understand if any shifts

in the nest selection process have taken place. At a minimum, data collection dates must advance

as all species continue to arrive earlier each year.

Other Variables

There are other important factors worth addressing outside of the study objectives. This

study does not assess the potential for multiple broodings within a season: the possibility that the

46

parent or parents of a depredated nest may breed a second time in an attempt to hatch. There are

studies that have identified the behavior in C. pusilla, alluding to the possibility that failed nests

could be of the same parents of later nests (Jehl 2007). While colonialism was not exhibited by

the species in this study during this survey year, it is still very possible that the C. pusilla could

participate in the practice--attention should still be given to the proximity of C. pusilla nests to

each other. Finally, little in this research covered the trophic research being done elsewhere to

understand how aquatic insects and other invertebrates that birds rely on in their foraging are

being impacted by the changing conditions. Future research should seek to understand how other

trophic levels are implicated by the changing environment.

Human Impact

Climate change has been referred to frequently in this paper, but with little mention of the

anthropogenic development through oil and gas that may occur in the local coastal tundra that

will exacerbate the effects discussed, and also bring about its own implications. The immediate

impact that climate change and continued human development on the Arctic coast will have on

shorebirds and their nesting locations in the future is being studied with focused energy on the

immediate impacts: discrete changes in conditions that will alter the availability of resources and

shift environmental factors that may detriment the shorebird species. However, there is also the

potential question of how birds themselves will be able to react and adapt to these conditions.

Spring migration phenology is one area of study that questions the ability of migratory birds to

be able to shift their seasonal timeline in movement. Plasticity of migratory behavior is found to

be strongest in social species that do not restrict to very specific habitat conditions, but exhibit

choice in stop over locations (Lameris 2017). Ongoing and further investigation into the

47

plasticity of each shorebird species will be essential for conservation measures to understand

locations that should be emphasized in their preservation, especially if they can be conducted in

non-restrictive locations like the Arctic coastline. Multiple studies have shown relative fitness

differences within species being exacerbated by the ability of an individual to migrate earlier

within a season (Rainio 2006). This is especially important to understand initiation date data on a

larger timeline within a local area.

This 1.5-million-acre coastal plain region has been a source of contention for oil and gas

development over the past four decades, with multiple USGS oil surveys conducted on it to

determine its underground oil content. Many factors contribute to the controversy surrounding

the impending oil and gas development, which has reemerged under the Trump administration as

recently as September 2019 where the 1002 was called to be completely opened to leasing by the

end of year (Eilperin 2017). The House responded quickly with legislation to ban all leasing on

the Pacific and Atlantic coast of the US, which passed but is unlikely to pass in the Senate

(Bennet 2019). Questions about the impact that oil and gas development on the refuge have

implications that extend far beyond their immediate impact on wildlife and transcend into the

human rights of the indigenous people that have occupied the Refuge’s land for thousands of

years--their understanding of the land supersedes any scientific research conducted and the basis

of their opposition to development is the most important argument against development

(Delcomyn 2004). The scope of this paper only considers the impacts on bird species, but it is

important to acknowledge the land of the indigenous Gwich’in Tribe that is being threatened as

an extension of the colonialist oppressive history that has exploited them and their land for

hundreds of years. Oil and gas has been researched for its impact on plant life and has been

found, in the same region of Alaska as the ANWR coastal plain, to have detrimental effects to

48

drier habitat classes, as well as to mosses and lichens (Walker 1978). While these are not the

immediate nesting locations found to be the essential nesting sites for the shorebirds in this

paper, they are still occupied by the sandpiper family birds in some cases, and can serve as

foraging grounds for both species. Drilling sites have been investigated for their use of gravel

and its impact on tundra vegetation and have been found to have persistent effects that last as

long as two decades (Jorgenson et al. 2010). Just the impact of oil site development--not even

drilling itself, could provide noticeable changes to the landscape that will reduce the already

restricted breeding grounds of shorebirds. The understanding of the impact that oil pools have on

aquatic insects also threatens the foraging of these birds to impact their nesting success as well.

Future research should consider the implications that development will have on the trophic

cascade from micro and macroinvertebrates to shorebird species to better understand what

management techniques should be implemented. In the coming years it will be essential to

continue to monitor how shorebird species react to changing conditions locally and globally, and

attempt to discern how specifically local conditions may be the source of declining populations.

Especially in the scenario of the P. fulicarius that is already being pushed to the limits of its

breeding habitat range, it will be important to get annual data on population levels, as its status as

early threatened may become heightened within this decade.

49

Appendix

Map 1: Habitats overlaid onto the study area polygon

50

Map 2: The entire field site with all nest species found on site

51

Map 3: All P. lobatus nest locations

52

Map 4: All P. fulicarius nests

53

Map 5: All C. melanotos nests

54

Map 6: All C. pusilla nests

55

Photo 1: Adult C. melanotos foraging on site at the Canning River Delta “Bird Camp”

Photo 2: Two adult C. pusilla foraging in the shallow part of a small thermokarst formed pond

on site

56

Photo 3: A female P. fulicarius brooding her recently hatched chicks (not visible) in a cluster of

sedges on site

Photo 4: A female P. lobatus foraging in a pond on site

57

Photo 5: View of field map with surveying lines for each of the 21 plots visited during the study

58

Literature Cited

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Alec Blair graduated from the Plan II Honors Program in the College of Liberal Arts and

the Environmental Science Program in the College of Natural Sciences from the University of

Texas at Austin in 2020. While at UT he was a part of Natural Sciences Council, Texas Blazers,

and the Plan II/KIPP KREWE. He worked as an intern at the Environmental Sciences Institute,

mentored in the Biodiversity FRI Lab, and was a server at the Red River Café. The summer

before his senior year he interned with the US Fish and Wildlife Service in Alaska where he

visited Arctic National Wildlife Refuge and fell in love with ornithology.