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I examined the hypothesis that low-ranking White-throated Sparrows
(Zonotrichia albicollis) during winter are more likely than
high-ranking birds to find novel sources of food near a known feeding
site. If so, high- and low-ranking birds might use different tactics
while foraging, each with compensating advantages and disadvantages
(Rohwer and Ewald 1981). I presented small, partially hidden
concentrations of seed at random locations within 2 m of regularly
supplied feeding sites, which were used by individually marked birds with
known dominance relationships.
Individuals that found the novel sources of food included approximately
equal numbers of birds in all four quartiles of the distribution of
dominance proportions. Once the novel food
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was found, disproportionate numbers of high-ranking birds tended to feed
there. They gained access to the food in most cases by supplanting
subordinates, whereas the low-ranking birds waited until they could
approach the food without interactions. In addition, high-ranking birds
usually left the food of their own accord, whereas low-ranking birds were
usually supplanted by dominants.
These results suggest that high-ranking birds found new sources of food
as often as low-ranking birds and also appropriated sources of food once
found by others. I found no evidence that advantages in finding food
compensated birds with low rank for disadvantages in competing for food
once found.
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