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|Title: ||Foraging on variable resources: the behaviour and decision making of rufous hummingbirds|
|Authors: ||Bacon, Ida Elizabeth|
|Supervisor(s): ||Healy, Sue|
|Issue Date: ||2010|
|Publisher: ||The University of Edinburgh|
|Abstract: ||Supplementary food is less variable than natural food. While feeding from constant
food sources tends to be preferred by animals they must sometimes forage from more
variable resources. However, the ways in which animals deal with the temporal and
spatial variability of more natural food is not entirely understood.
I investigated the decisions free-living rufous hummingbirds made when
foraging from variable resources, where variability was encountered over time or
within a bout via four field experiments. In addition, I investigated their use of wild
flowers and differences in the use of supplementary food by these birds in different
regions using surveys and by manipulating the distribution of feeders at feeding sites.
I investigated the possibility of a genetic explanation for any differences in feeder
use between regions using analysis of microsatellite DNA and banding data.
Hummingbirds seemed to prefer to make foraging decisions based on past
behaviour or post-ingestive feedback rather than on sensory information such as
taste, which may be harder to assess accurately. Birds choosing between constant and
variable rewards with equal means preferred the constant rewards when variability
was high but tended to prefer the variable reward when variability was low. This
seems to be a result of hidden time and other costs associated with foraging on
highly variable resource but not on less variable ones, combined with potential
benefits of information seeking from less variable resources. In addition, these
preferences between constant and variable resources were affected by preceding
The number of birds using feeders was affected by population density and air
temperature. Microsatellite data showed the rufous hummingbird population to have
a fairly panmictic population structure.
Investigating influences on foraging decisions at a large scale (population
density) and small scale (resource variability) has provided a much wider
understanding of their foraging behaviour than either could alone.|
|Appears in Collections:||Biological Sciences thesis and dissertation collection|
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