Reproductive Ecology of the Island Scrub-Jay

Caldwell, Luke; Bakker, Victoria J.; Sillett, T. Scott; Desrosiers, Michelle A.; Morrison, Scott; Angeloni, Lisa M.

doi:10.1525/cond.2013.120028

Cited by 20 publications

(27 citation statements)

References 38 publications

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“…Birds were captured and fitted with a unique combination of four coloured leg bands and a unique USGS numbered leg band (see Caldwell et al . and Langin et al . for details), following protocols approved by the National Zoological Park's Institutional Animal Care and Use Committee, the U.S. Geological Survey Bird Banding Lab, and the California Department of Fish and Game.…”

Section: Methodsmentioning

confidence: 89%

Context‐dependent seed dispersal by a scatter‐hoarding corvid

Pesendorfer

Sillett

Morrison

et al. 2016

Journal of Animal Ecology

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Summary1. Corvids (crows, jays, magpies and nutcrackers) are important dispersers of large-seeded plants. Studies on captive or supplemented birds suggest that they flexibly adjust their scatterhoarding behaviour to the context of social dynamics and relative seed availability. Because many corvid-dispersed trees show high annual variation in seed production, context-dependent foraging can have strong effects on natural corvid scatter-hoarding behaviour. 2. We investigated how seed availability and social dynamics affected scatter-hoarding in the island scrub jays (Aphelocoma insularis). We quantified rates of scatter-hoarding behaviour and territorial defence of 26 colour-marked birds over a three-year period with variable acorn crops. 3. We tested whether caching parameters were correlated with variation in annual seed production of oaks as predicted by the predator dispersal hypothesis, which states that caching rates and distances should vary with seed abundance in ways that benefit tree fitness. We also tested whether antagonistic interactions with conspecifics would affect scatter-hoarding adversely, as found in experimental studies. 4. Caching behaviour varied with acorn availability. Caching distances correlated positively with annual acorn crop size, increasing by as much as 40% between years. Caching rates declined over time in years with small acorn crops, but increased when crops were large. Acorn foraging and caching rates were also negatively correlated with rates of territorial aggression. Overall foraging rates, however, were not associated with aggression, suggesting that reduced dispersal rates were not simply due to time constraints. 5. Our field results support laboratory findings that caching rates and distances by scatterhoarding corvids are context-dependent. Furthermore, our results are consistent with predictions of the predator dispersal hypothesis and suggest that large seed crops and social interactions among scatter-hoarders affect dispersal benefits for oaks and other masting tree species.

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Section: Methodsmentioning

confidence: 89%

Context‐dependent seed dispersal by a scatter‐hoarding corvid

Pesendorfer

Sillett

Morrison

et al. 2016

Journal of Animal Ecology

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“…Further natural history details are given in Curry and Delaney (), Caldwell et al. (), and Langin et al. ().…”

Section: Methodsmentioning

confidence: 99%

“…The Island Scrub-Jay is restricted to oak, chaparral, and pine habitats on Santa Cruz Island, California, part of Channel Islands National Park. Further natural history details are given in Curry and Delaney (2002), Caldwell et al (2013), and Langin et al (2015). The species' global population size was estimated in fall 2008 to be <3000 individuals based on single-visit, distance sampling surveys conducted at 307 points across the 250-km 2 island (Sillett et al 2012).…”

Section: Case Studymentioning

confidence: 99%

An integrated model decomposing the components of detection probability and abundance in unmarked populations

et al. 2019

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Accurate estimates of population abundance are essential to both theoretical and applied ecology. Rarely are all individuals detected during a survey and abundance models often incorporate some form of imperfect detection. Detection probability, however, consists of three components: probability of presence during a survey, probability of availability given presence, and probability of detection given availability and presence. We develop an integrated model to separate these three detection components and provide abundance estimates for the available, present, and superpopulation of individuals. Our framework integrates several common survey methods for unmarked populations: spatially and temporally replicated counts, distance sampling data, and time‐of‐detection data. Simulations indicated relatively unbiased estimates for detection and availability probabilities. Negative bias in estimated superpopulation abundance was present with three temporally replicated surveys, but greatly reduced with six surveys. In a case study of Island Scrub‐Jays (Aphelocoma insularis), posterior modes for presence, availability, and detection probabilities were 0.78, 0.96, and 0.26, respectively, from 10‐min point counts repeated at 97 sites on three occasions, with noticeable differences among available, present, and superpopulation abundance estimates. This generalizable framework integrates common sampling protocols and provides joint inferences on the components of detection probability, spatial and non‐spatial temporary emigration, and abundance in unmarked populations.

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“…1). On Santa Cruz Island, we selected 2 stands (one north facing, one south facing) on each of 3 study plots used for a long-term avian study (Caldwell et al 2013; Fig. 1).…”

Section: Island Comparisonmentioning

confidence: 99%

“…We augmented the island-wide survey in 2009 with additional surveys in 3 study plots (Coches Prietos Canyon, Portezuela, and the area around the University of California Santa Barbara Field Station in the central valley of the island; Fig. 1C) used since 2008 to monitor Island Scrub-Jays (see Caldwell et al 2013). We selected 150 trees throughout the total area of the Island Scrub-Jay research plots (~300 ha) by generating random GPS points a minimum distance of 20 m apart using Hawth's tools for ArcGIS 9.2 (Beyer 2004, ESRI 2009).…”

Section: Acorn Crop Surveys On Santa Cruz Islandmentioning

confidence: 99%