Data from: The influence of diet-mediated exposure of avian influenza on adult survival, recruitment and territory occupancy in peregrine falcons

Watts, Bryan 1 ; Hines, Chance 1 ; Clark, Kathleen E.2

Published Mar 04, 2026 on Dryad. https://doi.org/10.5061/dryad.t76hdr8f6

Data files

Mar 04, 2026 version files 85.44 KB

CCB_PEFA_occupancy.csv

48.18 KB
CCB_PEFA_survival.csv

19.51 KB
PEFA_Recruitment_for_Avian_Flu_12-3-25.xlsx

12.95 KB
README.md

4.80 KB

Abstract

We investigated the influence of waterbird exposure on breeding peregrine falcons within the mid-Atlantic region of North America by comparing inland and coastal subpopulations. We monitored individually marked adults (N = 205) and breeding territories (N = 79) to estimate spatial and temporal patterns of adult survival, recruitment age, and territory occupancy (2016-2025). Three tables are included addressing PEFA survival, site occupancy, and age at recruitment.

Dataset DOI: 10.5061/dryad.t76hdr8f6

Description of the data and file structure

We determined territory occupancy and the identification of breeding adults by regular monitoring (2016-2025). We monitored known territories 2-5 times from March through July to determine occupancy status. We considered territories that supported a pair of adults during the breeding season to be occupied. Broods produced throughout the study area have been double-banded with standard USGS bands and field-readable alpha-numeric bands since the 1980s. We used a combination of cameras affixed to nesting structures that record adult activity and single lens reflex cameras to take photographs of adults during nest visits to read band combinations. Breeding peregrines are suggested to have high (>95%) site fidelity. Of 205 adults followed in this study, 6 (2.9%) were documented to change territories during the study period. For this reason, we assume that adults that were replaced or disappeared from their breeding territory between years and were not detected elsewhere were lost from the population.

We evaluated birds that colonized territories following the loss of a breeding adult to assess patterns of recruitment. For birds that could be positively identified, we determined recruitment age. We considered birds entering their second calendar year to be one year old, birds entering their third calendar to be two years old and so forth. We also examined plumage for both identified and unidentified birds within breeding territory in order to examine patterns of juvenile recruitment. Although variable with latitude, juvenile peregrines progress through their juvenile to prebasic I molt during their second calendar year from late spring through fall such that juvenile-plumaged birds are readily identified during the breeding season. We recorded the age class (juvenile vs adult) of identified and unidentified birds.

Files and variables

CCB_PEFA_occupancy.csv

Description: occupancy of each nest within each site and the region and state that each lies

Fields:

· Year=Year

· Region=categorization of nest site into either “Outer Coast” or “Inland”

· Site.Code=Each nest was given a specific code following this structure

· Nest.Name= Each nest was given a specific name by the author the first year it was monitored and applied to each subsequent year

· Occ.Terr=was the nest/territory occupied within that given year

· State=which state did the nest lie in (VA/NJ)

· Occupied=1 is for an occupied nest, 0 is for an unoccupied nest

PEFA_Recruitment_for_Avian_Flu_12-3-25.xlsx

Description: What was the sex of each bird that was recruited into the population (recruitment=incorporated into the breeding population via holding a territory) and what age were they entered the breeding population. Second tab is the plumage of the bird at recruitment.

Fields, Sheet 1/Known-Age Recruitment:

· Gender=Male or Female

· Year=Year

· Age at Recruitment=1,2,3,4…. We recorded the age class (juvenile vs adult) of identified and unidentified birds. We considered birds entering their second calendar year to be one year old, birds entering their third calendar to be two years old and so forth.

Fields, Sheet 2/Plumage at Recruitment

· Adult, Juvenile (second calendar year)

Although variable with latitude, juvenile peregrines progress through their juvenile to prebasic I molt during their second calendar year from late spring through fall such that juvenile-plumaged birds are readily identified during the breeding season.

CCB_PEFA_survival.csv

Database of all individuals observed in study areas throughout study period

· indiv_id_fixed=ID or band combination of individual bird

· Region= categorization of nest site into either “Outer Coast” or “Inland”

· State=which state does the bird reside

· min_age=age at which bird was recruited

· Gender=sex of bird

· min_Year=first year that bird was recruited

· “year” columns/2016,2017…= was the individual present in the year column. 0=no, 1=yes, NA=haven’t yet entered population

· ch=capture history-all “year” columns concatonated

Code/software

Microsoft Suite. Any program that will open a spreadsheet, such as Excel is recommended.

Survival: We used the package ‘marked’ in Program R [59] to fit POPAN capture–recapture models. These models account for individuals entering the population throughout the study period and provide an estimate of population entry probability (pent) as well as apparent survival. Candidate models included combinations of additive and interactive effects of region (Inland/Coastal) and time (Year) on population entry probability (pent), while detection probability and superpopulation size were held constant. Model selection was based on Akaike’s Information Criterion (AIC). When more than one model was effectively equivalent (ΔAIC ≤ 2.00), and one model was a nested version of the other, we evaluated whether the additional predictor improved model fit and retained the simpler model when it did not. To test for regional differences in estimated survival and population entry probabilities, we conducted pairwise comparisons between inland and outer coast predictions derived from the POPAN survival models.

Recruitment: We provide descriptive statistics on known-age birds recruiting into the breeding population and compare age-at-recruitment for males and females using a two-tailed t-test. We compiled the frequency of juvenile-plumaged birds recruiting into the breeding population and investigated possible temporal patterns in frequency using a G-test with Yates correction.

Occupancy: We used the package ‘glmmTMB’ to construct mixed models with territory-level occupancy as a binomial response (occupied/unoccupied). Fixed predictors included year and region. Year was included as a categorical factor to allow non-linear and non-monotonic temporal patterns in occupancy. The model also included the interaction between year and region (inland vs. coastal) to test for differences in region-specific temporal dynamics, and we included territory location as a random intercept to account for repeated observations of the same territory over multiple years. We compared models using all combinations of additive and interactive effects of region and year, and selected the most parsimonious based on AIC, following the same procedure as we did for survival. To test for differences in predicted occupancy between regions while accounting for site-level random effects, we used a parametric bootstrap approach based on our top model. For each bootstrap iteration, we simulated a new response vector from the fitted model using the estimated fixed and random effects and refit the model to the simulated data. Using each refitted model, we generated predicted occupancy probabilities for all observed site × year combinations, including random site effects. We then averaged predicted probabilities across sites within each region and year and calculated the difference in mean occupancy between regions. This procedure was repeated across 10,000 bootstrap replicates, producing an empirical sampling distribution of the regional occupancy difference for each year.