Island Scrub-Jay Breeding Ecology Update

Posted by Scott Sillett on September 23, 2010

The breeding ecology of the island scrub-jay (Aphelocoma insularis), North America's only island-endemic bird, is the focus of an ongoing research and monitoring effort by personnel from the Smithsonian Institution, Colorado State University, the U. C. Davis Wildlife Health Center, and The Nature Conservancy.

big blue bird

Island Scrub-Jay by Colin Woolley

Our study began in February 2008 as part of a broader research program to understand the factors that limit and regulate the abundance of the island scrub-jay. This work is motivated by risks to the jay's viability posed by its limited range and small population size, and by emerging threats from climate change and disease. The 2010 field season lasted from February to June.

We monitored 52 territories and documented 141 nest attempts in 2010. Estimated daily survival probability of nests that reached the egg stage was 0.946 ± 0.006 (mean ± 1 SE; n = 95). Given our data and the jay's 43-day nesting period, we expect that, island-wide, less than 10% of nests with eggs survived to fledging in 2010. Reproductive success of the island scrub-jay appears to be most strongly limited by nest predation, rather than by food or weather.

We will continue and extend our research on the jay's behavior and demography in the coming year. In fall 2010, two Ph.D. students, Kathryn Langin and Mario Pesendorfer, will conduct the second year of study of the jay's population structure, foraging behavior, and acorn caching in the non-breeding season.

We plan to collect a fourth season of reproductive data in spring 2011, and will begin to quantify survival of juveniles during the post-fledging period. The overarching goal of our work will be to support proactive management efforts for the island scrub-jay that reduce the likelihood of future population problems.

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