neotropical flyways project...(bayly et al. 2014): a. capurganá, darién (fig. 2). surveys were...

SELVA: Investigación para la Conservación en el Neotropico

w w w . s e l v a . o r g . c o

NEOTROPICAL FLYWAYS PROJECT

2016 - Fall migration in northwest Colombia

Background

� Over one billion migratory landbirds migrate between the Neotropics and North

America.

� Many of these long-distance migrants are experiencing persistent long-term population

declines.

� Despite this massive movement of birds, the routes and strategies that migratory landbirds

adopt in the Neotropics are almost completely unknown.

� The Caribbean Sea represents a significant ecological barrier in the migration of many

species and the stopover sites they use to prepare for and recover from over-sea crossings

likely influence the success of migration.

� Only by identifying the stopover sites and habitats where birds lay down the energy

reserves to fuel long-distance flights, can we identify the needs of migratory birds at all

stages of their life cycle.

� To initiate the task of filling these knowledge gaps, intensive observations were carried

out in northern Colombia, along the length of the Caribbean coast, in order to identify

previously unknown fall migration routes and stopover sites.

� Support and funding was provided by Environment Canada & Cornell Lab of

Ornithology.

� Here we report on observational surveys from three sites in NW Colombia during fall

2016, detailing high concentrations of landbirds in seasonal tropical forests and

exceptional counts of diurnally migrating raptors, totaling more than 1 million birds.

� The results will contribute to a Conservation Business Plan for stopover sites along the

western Caribbean Flyway.

Yuly Caicedo


Methods

As part of surveys carried out along the length of the Caribbean coast

northwest Colombia where preliminary studies have found high concentrations of migratory landbirds

(Bayly et al. 2014): A. Capurganá, Darién

(Fig. 2). Surveys were carried out between the 12 September and 15 November 2016 by three observers

and were staggered between the three sites in order to ensure approximately equal coverage of each.

Figure 1. Location of study sites in northern Colombia as part of the wider survey effor

Flyways Project in Colombia during 2016. A

precipitation.

Passive transects – Eight (Marimonda) or sixteen (Darién & S. de Abibe) transects were

site, each 100 m in length. Transects were separated by a minimum of 150 m and placement was subjective,

in order to cover a representative sample of the habitats present at each site. Transects were surveyed on

at least three occasions every seven/nine

that, on average, each transect was surveyed during

repetitions. Surveys involved recording a

observers walked slowly up and down the length of the transect. Each individual

a distance band, >25 m or >25 m, or defined as overflying.



Where & When

As part of surveys carried out along the length of the Caribbean coast (Fig. 1), three sites were surveyed in


Darién; B. Ciénaga de Marimonda, Necoclí; C. La Bonga, Serranía de Abibe

between the 12 September and 15 November 2016 by three observers


in northern Colombia as part of the wider survey effor

Flyways Project in Colombia during 2016. A. Sites in relation to elevation; B. Sites in relation to

Survey techniques

Eight (Marimonda) or sixteen (Darién & S. de Abibe) transects were

100 m in length. Transects were separated by a minimum of 150 m and placement was subjective,


seven/nine days between the 12 September and the 2 November

each transect was surveyed during six separate periods, giving rise to 18

involved recording all migratory species seen in 10 minutes, during which time

up and down the length of the transect. Each individual detected

a distance band, >25 m or >25 m, or defined as overflying.

, three sites were surveyed in


La Bonga, Serranía de Abibe

between the 12 September and 15 November 2016 by three observers


in northern Colombia as part of the wider survey effort of the Neotropical

Sites in relation to elevation; B. Sites in relation to May

Eight (Marimonda) or sixteen (Darién & S. de Abibe) transects were established at each

100 m in length. Transects were separated by a minimum of 150 m and placement was subjective,


2 November 2016, such

arate periods, giving rise to 18 passive

es, during which time

detected was assigned to


Figure 2. Study sites in NW Colombia

Playback – In the same set of transects established in each site, a playback protocol was

least one occasion per transect during

of owl calls and migrant alarm calls, followed by one minute of silence. All migrants seen or heard during

the full six minute period were recorded but without

Visible migration counts – At each site a point

counts were carried out during a minimum of 20 minutes, typically on one occasion during each visit to a

site. In the case of the Darién, counts were carried out on a near daily basis, typically lasting

from the 15th October through 15th November, in order to record the passage of raptors through this site.

Foraging behavior – During afternoons or between transects, focal individuals of the commonest species at

each site were selected for foraging observations. Recording no more than two sequences for each

individual, we recorded the number of attacks (movements of the bill towards a potential prey item) made

against each of three food sources –

duration of foraging sequences, habitat, date and time

species, ground, air, etc.

Habitat variables – For each transect the following information was recorded: coordinates; habita

distance to water; elevation; canopy height (4 points); canopy cover (4 points); % natural vegetation (4

points); number of trees >15 m in height in 10 m radius (4 points); % ground cover (4 points); density of

understory (4 points).



. Study sites in NW Colombia covered during the fall migration of 2016.

In the same set of transects established in each site, a playback protocol was

transect during each periodic visit. This involved reproducing a 5 minute


the full six minute period were recorded but without assigning them to distance bands.

site a point/s for undertaking migration counts was established and


In the case of the Darién, counts were carried out on a near daily basis, typically lasting

November, in order to record the passage of raptors through this site.

During afternoons or between transects, focal individuals of the commonest species at

raging observations. Recording no more than two sequences for each


– insects, fruits and flowers. In addition to attacks, we recorded the

duration of foraging sequences, habitat, date and time, and where possible the foraging substrate, e.g. tree

For each transect the following information was recorded: coordinates; habita



In the same set of transects established in each site, a playback protocol was employed on at

. This involved reproducing a 5 minute sequence


distance bands.

for undertaking migration counts was established and


In the case of the Darién, counts were carried out on a near daily basis, typically lasting two hours,

November, in order to record the passage of raptors through this site.

During afternoons or between transects, focal individuals of the commonest species at

raging observations. Recording no more than two sequences for each


acks, we recorded the

and where possible the foraging substrate, e.g. tree

For each transect the following information was recorded: coordinates; habitat type;





Carlos Bran and Martha Rubio survey a transect in the Serranía del Abibe during a practice run.

Results

Survey effort

Number of sites: 3

Elevations covered: 1 – 850 m

Number of individual transects: 32

Number of repetitions passive transects: 802

Number of repetitions playbacks: 195

Minutes of migration observations: 100.6 hours

Number of foraging sequences and total duration: 171 sequences totaling 4938 seconds

Species diversity and composition

We recorded 62 species of Nearctic-Neotropical migratory birds, 54 classed as landbirds and 8 as

waterbirds. A total of 6,367 individuals were recorded during transects when excluding overflying diurnal

migrants and 1,724,323 individuals during migration counts. The most commonly recorded species on

transects were, in descending order (Fig. 3; Table 1): Red-eyed Vireo, Yellow Warbler, Prothonotary

Warbler, Dickcissel, Swainson’s Thrush, Bay-breasted Warbler and Tennessee Warbler, each of which was

conservatively estimated to occur at densities of >100 individuals/km2. During diurnal counts three

raptors - Turkey Vulture, Broad-winged Hawk and Swainson’s Hawk - were extremely abundant, followed

by three species of swallows whose combined total exceeded 100,000 individuals (Table 2).

Photo -Carlos Bran



While most species that winter in South America were recorded during surveys, there were notable

absences or low abundances that are believed to be associated with alternative routes either to the east

over the Caribbean or to the west over the Pacific. These species include Connecticut Warbler, Blackpoll

Warbler, Yellow and Black-billed Cuckoo, Bobolink and Black Swift.

Figure 3. Raw count data for the 20 commonest species in northwest Colombia during fall migration as

determined through transect counts.

Bay-breasted Warbler – a common species in the northwest of Colombia

Variation between sites

0

200

400

600

800

1000

1200

1400



Despite the relative geographic proximity of the three study sites, there were marked differences in species

composition and abundance between them (Table 1). These are likely explained in part by proximity to the

Caribbean Sea and the narrow corridor of land that connects Colombia to Central America, as well as

marked differences in precipitation giving rise to different vegetation types (Fig. 1). The greatest species

diversity and abundance was recorded in the Darién, with notable densities of Catharus thrushes, Yellow

Warbler, Tennessee Warbler and declining species such as Bay-breasted Warbler and Prothonotary

Warbler. Despite being separated from the Darién site by little more than 50 km of open water, densities of

Catharus thrushes, in particular, were lower in Marimonda, while species that prefer more open and dryer

habitats, such as Yellow Warbler and Dickcissel, were more abundant.

The site with the lowest species richness and abundance was the Serranía de Abibe. Relative to the spring,

migrant densities were lower in the fall and this may be related to the high levels of precipitation

experienced at this site, especially between September and November. Nonetheless, it is noteworthy that

this was the only site where Cerulean Warbler was recorded and there were also reasonable numbers of

Olive-sided Flycatcher, another declining migrant. Further, roosting Mississippi Kites and Swainson’s

Hawks were recorded in the forests of the Serranía, potentially indicating an important role for the forests

that still cover much of this mountain range.

Diurnal migration counts

As previous studies have shown, the Darién concentrates large numbers of diurnal migratory birds along

its Caribbean slope (Bayly et al. 2014) but nonetheless the counts realized in fall 2016 were exceptional

(Table 2). For the first time, counts of migrating raptors in the Darién exceeded one million birds, such that

the Darién now joins an illustrious list of just four sites with a passage >1 million individuals. Turkey

Vultures made up the vast bulk of the passage as elsewhere in the Americas, e.g. Veracruz, Mexico and

Ancon Hill, Panama, but the season total of over 200,000 Broad-winged Hawks was also notable. We

hypothesize that the high counts in 2016 were associated with the formation of La Niña, which increases

rainfall in this region and may also reverse typical wind patterns, both factors that may favor migration

along the Caribbean slope versus the Pacific slope of the Darién.

The intense passage of diurnal migrants through the region was not restricted to raptors and excellent

numbers of declining aerial insectivores, such as Barn and Bank Swallow, and Common Nighthawk were

also recorded. Due to the need to carry out the transects during the first hours of daylight, counts in the

Darién of these species were lower than in previous years (see Bayly et al. 2014). Nonetheless, the

confirmation of large numbers of Nighthawks and Dickcissels over Marimonda was an important addition

to our knowledge of the breadth of the migration front that passes through the region.



Table 1. Migratory landbirds recorded on transects during fall migration at three sites in NW Colombia. Raw totals and a density estimate

without correction for detectability are presented, the latter conservatively assumes that all birds within 50 m of transects were detected.

Raw transect Totals Density Estimate

Common Name Scientific Name Darién Marimonda S. de Abibe Darién/km2

Marimonda/km2

Abibe/km2

Yellow-billed Cuckoo Coccyzus americanus 1 3 - 0.5 3.2 -

Olive-sided Flycatcher Contopus cooperi 13 1 11 6.2 1.1 5.6

Eastern Wood-Pewee Contopus virens 140 40 60 66.8 43.2 30.5

Western Wood-Pewee Contopus sordidulus 4 1 3 1.9 1.1 1.5

E/W Wood-Pewee Contopus virens/sordidulus 5 5 3 2.4 5.4 1.5

Acadian Flycatcher Empidonax virescens 2 1 8 1.0 1.1 4.1

Alder Flycatcher Empidonax alnorum 8 2 - 3.8 2.2 -

Trails Flycatcher Empidonax traillii/alnorum 60 9 3 28.6 9.7 1.5

Great-crested Flycatcher Myiarchus crinitus 16 6 4 7.6 6.5 2.0

Sulphur-bellied Flycatcher Myiodynastes luteiventris 5 5 - 2.4 5.4 -

Gray Kingbird Tyrannus dominicensis 2 1 - 1.0 1.1 -

Veery Catharus fuscescens 153 1 - 73.0 1.1 -

Gray-cheeked Thrush Catharus minimus 196 6 2 93.6 6.5 1.0

Swainson's Thrush Catharus ustulatus 530 35 34 253.0 37.8 17.3

Gray Catbird Dumetella carolinensis 3 - - 1.4 - -

Yellow-throated Vireo Vireo flavifrons 5 - - 2.4 - -

Red-eyed Vireo Vireo olivaceus 1073 279 42 512.2 301.6 21.4

Yellow-green Vireo Vireo flavoviridis 69 10 - 32.9 10.8 -

Black-whiskered Vireo Vireo altiloquus 2 1 - 1.0 1.1 -

Baltimore Oriole Icterus galbula 53 15 - 25.3 16.2 -

Orchard Oriole Icterus spurius - 1 - - 1.1 -

Bobolink Dolichonyx oryzivorus 2 - - 1.0 - -

Black-and-white Warbler Mniotilta varia 21 2 1 10.0 2.2 0.5

Golden-winged Warbler Vermivora chrysoptera 1 - - 0.5 - -

Tennessee Warbler Oreothlypis peregrina 312 90 2 148.9 97.3 1.0

Yellow Warbler Setophaga petechia 311 355 3 148.4 383.8 1.5

Cerulean Warbler Setophaga cerulea - - 5 - - 2.5



Raw transect Totals Density Estimate

Common Name Scientific Name Darién Marimonda S. de Abibe Darién/km2

Marimonda/km2

Abibe/km2

Blackburnian Warbler Setophaga fusca 34 17 6 16.2 18.4 3.1

Blackpoll Warbler Setophaga striata 6 5 2.9 5.4 0.0

Bay-breasted Warbler Setophaga castanea 321 117 24 153.2 126.5 12.2

American Redstart Setophaga ruticilla 20 7 9 9.5 7.6 4.6

Ovenbird Seiurus aurocapilla 1 - - 0.5 - -

Northern Waterthrush Parkesia noveboracensis 87 41 2 41.5 44.3 1.0

Louisiana Waterthrush Parkesia motacilla 6 - - 2.9 - -

Prothonotary Warbler Protonotaria citrea 215 440 - 102.6 475.7 -

Mourning Warbler Geothlypis philadelphia 13 - - 6.2 - -

Canada Warbler Cardellina canadensis 30 - 8 14.3 - 4.1

Summer Tanager Piranga rubra 107 34 16 51.1 36.8 8.1

Scarlet Tanager Piranga olivacea 56 23 15 26.7 24.9 7.6

Dickcissel Spiza americana 126 510 - 60.1 551.4 -

Rose-breasted Grosbeak Pheucticus ludovicianus 22 12 - 10.5 13.0 -

The humid forests of the Serranía de Abibe



Table 2. Season totals for diurnal migrants recorded during migration counts at three sites in NW

Colombia during the fall migration of 2016.

Common Name Darién Marimonda Serranía de Abibe Total All Sites

Turkey Vulture 1,153,119 - - 1,153,119

Osprey 63 7 - 70

Mississippi Kite 4,493 - 1,865 6,358

Broad-winged Hawk 217,786 - 1,579 219,365

Swainson's Hawk 118,534 - 3,215 121,749

Hawk sp. 60,304 - 533 60,837

Merlin 12 6 2 20

Peregrine Falcon 82 9 3 94

Common Nighthawk 2,730 3,288 - 6,018

Chimney Swift 210 312 522

Eastern Kingbird 17,320 12,047 - 29,367

Bank Swallow 3,511 2 58 3,571

Barn Swallow 31,257 24 211 31,492

Cliff Swallow 11,428 4 440 11,872

Swallow sp. 58,750 9,250 4,340 72,340

Dickcissel 2,875 4,704 - 7,579

1,682,474 29,341 12,558 1,724,373

Phenology

Passage times varied markedly between species (Fig. 4) and were also somewhat different to the expected

pattern, primarily due to the presence of several tropical storms during key moments in the migration. So

while some of the early migrant species appeared to arrive earlier than normal, those that migrate around

mid-October appeared to be “blocked” by the passage of tropical storm Matthew through the Caribbean

before it stalled off the eastern US, occupying the main route used by trans-Caribbean migrants.



Figure 4. Phenology of fall migration during 2016 in selected species through three study sites in

northwest Colombia.

Swainson’s Thrush

0

10

20

30

40

50

60

70

12 Sep 19 Sep 26 Sep 03 Oct 10 Oct 17 Oct 24 Oct 31 Oct

Bay-breasted Warbler

Darien

Marimonda

Abibe

0

5

10

15

20

25

30

35

40

45

50

12 Sep 19 Sep 26 Sep 03 Oct 10 Oct 17 Oct 24 Oct 31 Oct

Swainson's Thrush

Darien

Marimonda

Abibe



Foraging data

171 foraging sequences were obtained from 24 species, for which there were more than 5 sequences in 13

species. Food or prey items differed between species, with some species like Swainson’s and Gray-cheeked

Thrushes largely consuming fruit, while others mostly attacked insects, e.g. Eastern Wood-Pewee and

several warbler species (Table 3). In contrast to data collected during spring migration at the same study

sites, less species were observed consuming fruit: for example both Bay-breasted and Tennessee Warblers

regularly consumed fruit during spring migration.

Table 3. Species for which more than five foraging sequences were recorded during fall migration. The

total number of attacks recorded on three different food sources is given, where attacks on flowers are

assumed to be associated with nectar drinking.

Common Name

No Sequences &

Duration (s)

Insects

Flowers

Fruit

Eastern Wood-Pewee 10 (801) 26

Alder Flycatcher 7 (181) 7

Eastern Kingbird 5 (107) 6

Gray-cheeked Thrush 5 (115) 5

Swainson's Thrush 8 (363) 34

Red-eyed Vireo 21 (541) 58 13

Yellow-green Vireo 6 (161) 12 3

Baltimore Oriole 6 (159) 17

Yellow Warbler 29 (610) 161 2

Blackburnian Warbler 7 (200) 35

Bay-breasted Warbler 11 (277) 12 2

Northern Waterthrush 7 (136) 17

Prothonotary Warbler 18 (426) 121

Evidence for stopovers

Several species were extremely abundant in NW Colombia during the fall migration of 2016. These

included several species that do not or winter only very rarely at the study sites, such as the three species

of Catharus thrushes, Red-eyed Vireo, Eastern Wood-Pewee and Dickcissel. All six of these species showed

prolonged periods of presence at the study sites, suggesting that at least some individuals were likely

undertaking multi-day stopovers, as has been shown previously for Catharus thrushes in the Darién

(Gómez et al. 2014). Other highly abundant species, such as Bay-breasted Warbler, Summer Tanager and

Prothonotary Warbler, all winter in the region and it is difficult to separate wintering populations from

those on stopover. Nonetheless, the exceptional abundance of Prothonotary Warblers in Marimonda

suggests that wintering populations are likely boosted by birds on stopover.



Among the species of conservation concern, the presence of both Olive-sided Flycatcher and Cerulean

Warbler is noteworthy but it is unclear how these species are using this region during fall. Above all, this

region appears to act as a bottleneck, concentrating large numbers of individuals from a diverse array of

species into a relatively limited area of land. This effect is exemplified by a remarkable fallout experienced

on the 13th October, in which from a stationary point in a river valley approximately 3 km inland, over 1000

landbird migrants were recorded moving rapidly upriver and inland during 2.5 hours, under near constant

drizzle (Table 4).

Table 4. Species and totals recorded from a stationary point over the course of 2.5 hours during a fallout in

Capurganá, Darién on the 13th October 2016.

Common Name Scientific Name Number

Chimney Swift Chaetura pelagica 161

Olive-sided Flycatcher Contopus cooperi 1

Eastern/Western Wood-Pewee Contopus virens/sordidolus 9

Trails Flycatcher Empidonax traillii/alnorum 8

Great-crested Flycatcher Myiarchus crinitus 2

Sulphur-bellied Flycatcher Myiodynastes luteiventris 3

Red-eyed Vireo Vireo olivaceus 606

Yellow-green Vireo Vireo flavoviridis 208

Veery Catharus fuscescens 2

Gray-checked Thrush Catharus minimus 6

Swainson’s Thrush Catharus ustulatus 11

Northern Waterthrush Parkesia noveboracensis 3

Black-and-white Warbler Mniotilta varia 5

Prothonotary Warbler Protonotaria citrea 8

Tennessee Warbler Oreothlypis peregrina 15

Blackburnian Warbler Setophaga fusca 1

Yellow Warbler Setophaga petechia 5

Warbler sp. Parulidae sp. 16

Summer Tanager Piranga rubra 28

Scarlet Tanager Piranga olivacea 80

Rose-breasted Grosbeak Pheucticus ludovicianus 19

Baltimore Oriole Icterus galbula 4

Conclusions

Northwest Colombia supports both a high species richness and abundance of landbird migrants during fall

migration. Exactly how each species uses the region is unclear but given the abundance and duration of

passage in certain species, e.g. the Catharus thrushes, the evidence would appear to suggest that some

species are making multi-day stopovers there. The region is also a major flyway for diurnal migrants and

with each year of monitoring in the Darién, the magnitude of this passage becomes ever clearer (Bayly et al.

2014). For the first time in six years of monitoring raptors from Capurganá and Sapzurro, over one million

raptors were recorded, confirming the critical importance of the Caribbean slope of the Darién as a globally



important flyway for migratory raptors. Above all, the narrow corridor formed by the Darién is clearly a

major bottleneck for a wide variety of migratory species and the remaining natural habitats in the region

support extremely high densities of migrants during fall migration.

Next steps

The provisional analyses outlined above are the first step in determining how and when NW Colombia is

used by migratory birds and for being able to compare this region to others in Colombia and throughout

Central America. Initial analyses of data collected in spring throughout northern Colombia highlight the

power of these data to determine patterns of use at both the geographical and habitat scale using

occupancy models, and identify likely but previously undescribed stopover regions (see Box 1). In the

coming year, occupancy models will be applied to both the fall and spring data to determine how patterns

vary between seasons and identify priority areas for more in depth studies of stopover behavior. The

inclusion of sites in Central America, particularly Panama for 2017, is another critical step for the

Neotropical Flyways project and the main focus of current fundraising activities.

Box 1. Hotspots for Yellow-billed Cuckoo during spring migration in northern Colombia.

Hotspots were determined by combining weekly estimates of occupancy rates across northern Colombia

and selecting pixels with an average occupancy >0.5 for the main passage period. Hotspots overlap entirely

with the previous extent of tropical dry forest in the Caribbean lowlands of Colombia. Of all the ecosystems

in Colombia, dry forest has lost a greater area than any other, with just 8% of the original forest cover

remaining. The fact that Yellow-billed Cuckoo appear to rely on this habitat prior to crossing the Caribbean,

suggests that loss of dry forest may be one of the factors contributing to the 54% population decline

observed in this species.



Research Team

Project Director – Nicholas Bayly (SELVA)

Technical support – Ken Rosenberg (Cornell)

Field Researchers – Marta Rubio, Carlos Bran, Nicholas Bayly

Guides – Wilberto Peñalosa, William Licona, Alex Monslave, William Ramon.

Project Administration – Maria Isabel Moreno, Yuly Arcos, Nicholas Bayly.

References

Bayly, N.J., Cárdenas-Ortiz, L., Rubio, M. & Gómez, C. (2014) Migration of raptors, swallows and other

diurnal migratory birds through the Darién of Colombia. Ornitología Neotropical 25: 63-71.

Gómez, C., Bayly, N.J. & Rosenberg, K.V. (2014) Fall stopover strategies of Catharus thrushes in northern

South America. Auk 131(4): 702-717.

Contact

For more information on this project please contact:

Nicholas Bayly [email protected] or (+57) 312 3283647 / (+57) 17027623.

Webpage: www.neotropicalflyways.com

Recommended Citation

Bayly N.J. (2016) Neotropical Flyways Project: Fall migration in NW Colombia 2016. Technical

Report NFP02. SELVA: Investigación para la Conservación en el Neotropico, Bogotá D.C. 14 pp.

neotropical flyways project...(bayly et al. 2014): a. capurganá, darién (fig. 2). surveys were...

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