Temporal changes in the southern Maine black-capped chickadee (Poecile atricapillus) population do not correlate with changes in nearby resident and migrant songbird populations

Jessica Kane* and Noah Perlut, Ph.D.Department of Environmental Studies, University of New England, 11 Hills Beach Rd, Biddeford, ME 04005; *jkane3@une.edu

R² = 0.2474

R² = 0.1646

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RESULTS

Figure 1.

The number of each species caught (banding) or observed (eBird) from 2011-2014 and 2016 plotted against the number of BCCH. Banding data (blue diamonds) follows the left and bottom axes; eBird data (red squares) follows the right and top axes. Each point represents a given study year, not in chronological order. Resident birds (A, B) are compared to short-distance (C,D) and long-distance (E,F) migrants. r-values presented to show the correlation between populations. Species illustrations were gathered from audubon.org.

Correlations to Black-capped Chickadee Population

• ETTI strongest positive but nonsignificant correlation to BCCH population (r= 0.84, p= 0.07 Fig 1A).

• GCKI, HETH and RCKI showed positive but nonsignificant correlation with BCCH (r= 0.39, p= 0.87; r= 0.50, p= 0.39; and r= 0.50, p= 0.28, respectively, Fig 1 B,C,D).

• REVI and BLPW were not correlated with BCCH (r= 0.005, p= 1.0; and r= 0.02, p= 0.97, respectively, Fig 1 E, F).

Effect of Migratory Status on Correlations

• Migratory status did not explain the strength of correlation to the BCCH population (Fig 2).

RESULTS CONT.

Comparison of UNE and eBird Data

• No significant difference between correlations calculated with banding (x̄= 0.38, SE= 0.54) or eBird (x̄= 0.42, SE= o.70) data (t2= -0.20, p= 0.42, Fig 2).

Correlation to

BCCH

Species

codeCommon name

Migratory

statusBanding eBird

ETTI Tufted titmouse Resident r= 0.84 r= 0.92

GCKI

Golden-crowned

kinglet Resident r= 0.39 r= 0.73

HETH Hermit thrush SDM r= 0.50 r= -0.40

RCKI

Ruby-crowned

kinglet SDM r= 0.50 r= 0.41

REVI Red-eyed vireo LDM r= 0.004 r= 0.89

BLPW Blackpoll warbler LDM r= 0.02 r= -0.004

Figure 2 (right).The difference in average correlation to BCCH between residents, short-distance migrants (SDM), and long-distance migrants (LDM) in both datasets. Error bars represent + 1 SE from the mean.

INTRODUCTION

METHODS

Data Collection

• Banding data was collected from Sept-Oct 2011-2014, 2016 in a 363-acre forest on the University of New England’s campus in York County, ME.

• Three arrays of 12-meter long mist nets (5 nets per array) were used to catch and band birds to assess population trends. Nets were opened twice weekly between 0630-0920 and checked for birds every 15 minutes. Birds were identified, aged, sexed and banded according to Pyle (Pyle, 1997).

eBird Data

• Total number of individuals of each songbird species of interest (see Table 1) observed throughout York County, ME during the study period accessed from eBird.

Statistical Analysis

• Pearson’s r correlation coefficient compared the population trend of the black-capped chickadee to six songbird species in three different migratory classes (see Table 1).

• ANOVA tested the influence of migratory status (resident, short-distance migrant (SDM) and long-distance migrant (LDM)) on population correlation with black-capped chickadee.

• Paired t-test compared the mean correlations using banding data and eBird data to determine if these data sets differed significantly.

The Black-capped Chickadee as a Nucleus Species

• Nucleus species lead the movements and foraging rates of heterospecifics within a mixed-species group (Morse, 1970).

• The black-capped chickadee (BCCH; Poecile atricapillus) is a nucleus species (Loery et al., 1997) and its behavior may improve the survival of other nearby songbirds through processes such as food caching (Vander Wall and Jenkins, 2002) and alarm calling (Templeton et al., 2005).

• If these services do improve the survival of other species, then fluctuations in the chickadee population should affect changes in those populations as well.

Hypotheses

• Changes in the southern Maine BCCH population will be positively correlated with changes in the populations of other songbird species whose annual distribution overlaps with BCCH and not correlated with long-distance migratory species whose winter distribution does not overlap with BCCH.

• Population data collected at a banding station is representative of county-level citizen science data on eBird.org.

DISCUSSION

Migratory status did not influence correlation with population status

• Migratory bird populations are influenced by a myriad of factors at their breeding grounds, stopover sites, and wintering grounds (see Newton, 2004 for a review). The species used in the current study may face more influential pressures at their wintering grounds than in southern Maine breeding grounds.

• Future studies should collect data throughout the avian life cycle to confirm if this trend is consistent in breeding and non-breeding periods.

Banding and eBird data did not differ

• Data collected on avian populations on UNE’s campus can be generalized to at least the county scale.

Conclusion

• Overall, understanding which songbirds are and are not correlated with the black-capped chickadee does not appear to be useful in monitoring long-term changes in avian populations.

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REFERENCES

Loery G, Nichols JD, Hines JE. 1997. Capture-recapture analysis of a wintering black-capped chickadee population in Connecticut, 1958-1993. The Auk, 114: 431-442.

Morse DH. 1970. Ecological aspects of some mixed-species foraging flocks of birds. Ecol Monograph, 40: 119-168.

Newton I. 2004. Population limitation in migrants. Ibis, 146: 197-226.Pyle P. 1997. Identification Guide to North American Birds, Part I: Columbidae to Ploceidae. Slate

Creek Press.Templeton CN, Greene E, Davis L. 2005. Allometry of alarm calls: Black-capped chickadees encode

information about predator size. Science, 308: 1934-1937.Van der Wall SB and Jenkins SH. 2003. Reciprocal pilferage and the evolution of food-hoarding

behavior. Behav Ecol, 14: 656-667.

Table 1 (below).Displays the r-values for the correlations of each of the study species to the black-capped chickadee population in York County, ME. Correlations using both banding and eBird data are presented although they are not different (see above).

ACKNOWLEDGMENTS

The authors thank the University of New England for their support of this project and all of the students enrolled in ENV 318 for their contributions to data collection.