Changes in ecological conditions can induce changes in behavior and demography of wild organisms, which in turn may influence population dynamics. Black brant (Branta bernicla nigricans) nesting in colonies on the Yukon–Kuskokwim Delta (YKD) in western Alaska have declined substantially (~50%) since the turn of the century. Black brant are herbivores that rely heavily on Carex subspathacea (Hoppner's sedge) during growth and development. The availability of C. subspathacea affects gosling growth rates, which subsequently affect pre‐ and postfledging survival, as well as size and breeding probability as an adult. We predicted that long‐term declines in C. subspathacea have affected gosling growth rates, despite the potential of behavior to buffer changes in food availability during brood rearing. We used Bayesian hierarchical mixed‐effects models to examine long‐term (1987–2015) shifts in brant behavior during brood rearing, forage availability, and gosling growth rates at the Tutakoke River colony. We showed that locomotion behaviors have increased (β = 0.05, 95% CRI: 0.032–0.068) while resting behaviors have decreased (β = −0.024, 95% CRI: −0.041 to −0.007), potentially in response to long‐term shifts in forage availability and brood density. Concurrently, gosling growth rates have decreased substantially (β = −0.100, 95% CRI: −0.191 to −0.016) despite shifts in behavior, mirroring long‐term declines in the abundance of C. subspathacea (β = −0.191, 95% CRI: −0.355 to −0.032). These results have important implications for individual fitness and population viability, where shifts in gosling behavior putatively fail to mitigate long‐term declines in forage availability.
Black brant Behavioral Data
Data was collected on the Yukon Kuskokwim Delta, Alaska, USA from 1987-2015. Observers stayed in towers with observation blinds and opportunistically selected broods to record behaviors for every minute in an hour. Some observations were shorter or longer than 60 minutes. Data was produced using program R from data collected in the field to calculate the proportion of time an individual spent on a behavior in an observation bout. Column Headers: YEAR is the year data was collected; DATE is the Julian date of the observation in the year data was collected; BAND is the leg band ID of the individual being observed; MBAND is the leg band ID of the brood's observed male; FBAND is the leg band ID of the brood's observed female; NUMGOS is the number of goslings observed; ZERO is the proportion of foraging behavior observed; ONE is the proportion of preening behavior observed; TWO is the proportion of alert while standing behavior observed; FOUR is the proportion of bathing behavior observed; FIVE is the proportion of alert while sitting behavior observed; SEVEN is the proportion of running behavior observed; P is the proportion of walking behavior observed; L is the proportion of aggressive behavior observed; O is the proportion of swimming behavior observed; I is the proportion of resting behavior observed; U is the proportion of unknown behavior observed, often when one member of the brood was out of view; SEX is the sex of the observed individual
behaviordata.csv
Black brant Growth Data
Data was collected on the Yukon Kuskokwim Delta, Alaska, USA from 1987-2014. Goslings were web-tagged at hatch, so age in days was able to be calculated at recapture. Goslings were recaptured and weighed at approximately 30 after hatching. Column Headers: MASS is individual gosling's mass in grams at capture at approximately 30 days; AGE is individual gosling's age at recapture; YEAR is the year an individual gosling's mass was recorded; TAGDAY is the Julien date of an individual gosling's web-tagging.
growthdata.csv
Carex subspathacea Lawn Data
Data was collected on the Yukon Kuskokwim Delta, Alaska, USA from 1991-2016. Data was collected with aerial photography and videography along transects. Photos captured approximately 69m squared of ground space and were spaced at least 200m from one another. 10x10 (1991-1999) or 12x15 (1993-2016) overlaid photographs and the number of points on the grid primarily occupied by various habitat types was recorded. In program R, data was cleaned to identify the number of points per grid occupied by Carex subspathacea grazing lawns. Column Headers: SIZE is the number of points overlaid as a grid on a photo; SUB is the number of points in a grid occupied primarily by Carex subspathacea; YEAR is the year the sample was taken.
lawndata.csv
