How western scrub-jays (Aphelocoma californica) select a nut: effects of the number of options, variation in nut size, and social competition among foragers |
| |
Authors: | Tom A Langen |
| |
Institution: | (1) Department of Organismic Biology, Ecology and Evolution, University of California, Los Angeles, CA 90095-1606, USA, US |
| |
Abstract: | Western scrub-jays (Aphelocoma californica) often visually assess and handle several whole (unshelled) peanuts before selecting one to transport and cache; this behavior
is a search for a preferred heavy nut. I repeatedly video-taped individually identifiable jays as they landed on a feeding
platform and chose from presentations of peanuts that varied in the number of items or in the distribution of sizes. I examined
how differences among these presentations and a bird’s social status affected the amount of assessment and the economic consequences
of choice. I also examined the specific patterns of handling peanuts, called sampling, to quantify the degree to which sampling
sequences were typified by repeated comparisons among sampled peanuts (retrospective sampling), or sequential assessment and
rejection of peanuts (prospective sampling). Peanut assessment was more extensive and prospective when there were many options
from which to choose than when there were few. Peanut assessment was more extensive and retrospective when options were similar
in size than when they varied. Scrub-jays were more likely to make repeated comparisons immediately before selecting a peanut
than elsewhere in a sampling sequence. Subordinate scrub-jays, who were at the greatest risk of pre-emption by competitors,
assessed peanuts less extensively and were more prospective in their sampling than dominants. Unless peanuts were very similar
in size, jays were more accurate at selecting a high-quality peanut and achieved a higher rate of food storage than if they
had not assessed. These results show that scrub-jays can adaptively modify how they search to improve their rate of food storage,
and also suggest some of the specific search tactics used by jays when assessing peanuts.
Received: 26 April 1999 / Accepted after revision: 10 October 1999 |
| |
Keywords: | Assessment Dominance Foraging Optimal choice behavior Aphelocoma californica |
本文献已被 SpringerLink 等数据库收录! |
|