Social and Metabolic Costs of Flock-Switching Vary with Dominance Status in Dark-Eyed Juncos, Junco Hyemalis
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Authors
Striegle, Dennis A.
Issue Date
1992
Type
Thesis
Language
en_US
Keywords
Alternative Title
Abstract
Individual dominance status in flocks of wintering birds is reported to
influence an individual's access to limited food resources. The question of
why subordinate birds remain in a flock, despite lowered access to resources,
may be explained by significant costs of re-establishing relationships with
unfamiliar individuals. This study investigated possible costs experienced by
both dominant and subordinate individuals that leave flocks of familiar birds
and join unfamiliar groups. In 18 experimental flocks of juncos, a dominant
or subordinate member was assessed for changes in both dominance behavior
and metabolic rate as it was switched from its familiar flock to a
corresponding unfamiliar flock over a 2-day period. When switched to an
unfamiliar flock, dominant birds displayed a significant decrease in their
ability to displace other flock members, while subordinate birds showed no
change in ability to dominate. Through analysis of oxygen consumption,
changes in metabolic rate were ascertained for each subject. Dominant
individuals displayed a significant increase in metabolic rate after flock-switching,
while no significant change was seen for birds of subordinate rank.
Individuals of lowest dominance rank in flocks of juncos incur fewer social
barriers, when flock-switching, than do birds of highest rank. Because costs of
flock-switching for dominant birds are relatively high, and there are virtually
no gains for subordinate birds, continued association with familiar
individuals provides the greatest benefits for all flocked birds. In wild
populations, factors such as resource scarcity and wide dispersal of
conspecifics may have a significant impact on the benefits of aggregation.
Description
v, 28 p.
Citation
Publisher
Kalamazoo College
License
U.S. copyright laws protect this material. Commercial use or distribution of this material is not permitted without prior written permission of the copyright holder.