Environmental and demographic mechanisms underlying population dynamics provide relative stability in an island songbird
This study uses an integrated population model to examine the environmental and demographic drivers of Island Scrub Jay population dynamics from 2009 to 2019. Researchers found that precipitation, food availability, and density dependence influenced reproduction and survival, while breeder survival remained relatively stable. The findings highlight resilience to drought but also underscore potential risks associated with small island populations.
Subject Tags
- Biodiversity
Abstract
Understanding demographic and ecological mechanisms underlying population dynamics is a key goal in population ecology and can inform effective conservation and management. Species may be well adapted to persist under normal ranges of environmental conditions, but increasingly novel conditions due to climate change may strain their demographic buffering mechanisms. Small isolated populations on islands are expected to be especially vulnerable to declines caused by novel environmental conditions, but the ecological drivers of population dynamics on islands are often unknown. We used an integrated population model to (1) examine ecological drivers of population growth and (2) assess global population trends of the Island Scrub-Jay (Aphelocoma insularis) from 2009 to 2019. Our results suggest that population size increased slightly over this interval despite declines during severe drought. We also found evidence that density dependence, precipitation, and food availability affected fecundity and the survival of nonbreeding individuals. Breeder survival was relatively stable and had a weak effect on population growth as expected for long-lived species. Overall, our results provide an optimistic snapshot for this species by demonstrating resilience to contemporary drought but also emphasize the species' potential vulnerability due to its small population size.
Citation
Mouton, J. C., Pesendorfer, M., Hostetter, N. J., Morrison, S. A., & Sillett, T. S. (2026). Environmental and demographic mechanisms underlying population dynamics provide relative stability in an island songbird. Ecology, 107(5), e70409.
TNC Authors
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Scott A. Morrison
Director of Conservation Science & Programs
The Nature Conservancy
Email: smorrison@tnc.org