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Data from: An urban bird population exhibits more fear in the non-breeding season

Zhou, Xiaodong1; Karthikeyan, Prasheetha1; Di Liberto, Joseph1; Yeh, Pamela1

Published Apr 30, 2026 on Dryad. https://doi.org/10.5061/dryad.905qftv10

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Abstract

Fear response in birds is affected by environmental factors, many of which are related to seasonality, such as temperature or resource availability. The evolutionarily novel conditions of the urban environment may alter avian seasonal behaviours. We ask whether fear response behaviour in urban birds is associated with the differing constraints of the breeding and non-breeding seasons. To examine this, we measured the escape behaviour of an urban, resident population of Dark-eyed Juncos (Junco hyemalis). We quantified escape behaviour from 2023-2025 by measuring the flight initiation distance (FID) of individually color-banded juncos and compared junco FID throughout the year. We found that junco FID was significantly reduced during the breeding season. Other significant predictors of FID in our model were observer starting distance and group size. Our results suggest that while seasonality plays a major role in determining urban species’ behavioural responses, other factors make this relationship more complex. During the breeding season, the perceived threat of predation may be diminished for juncos focusing on parental care, resulting in lower fear responses. Meanwhile, differing social dynamics during the non-breeding season such as flocking behaviour may cause complex effects on urban juncos’ fear response. Our study provides evidence that urban wildlife exhibit a flexible fear response that is seasonally dependent and related to breeding behaviour. These results help us more accurately understand the priorities of animals in urban environments, as well as how they continue to persist under changing conditions.