| Summary: | Foraging theory provides a framework for understanding why animals make
certain foraging decisions yet provides few insights into how these decisions are made.
Psychological studies provide understanding of cognitive mechanisms but without the
needed ecological context. This thesis continues the study of spatial association memory
in rufous hummingbirds (Selasphorus rufus) in an attempt to understand its possible
utility in the wild.
In laboratory settings, rufous hummingbirds make associations between two
spatially separate objects (a cue and a reward/response site) using spatial association
memory. In Chapter Two, I investigated the ability of rufous hummingbirds to switch
from using spatial memory to spatial association memory when visible cues remained
reliable indicators of food location, even when the food location was changed repeatedly.
Regardless of how often birds obtained food from the same location, they quickly used
spatial association memory to relocate the reward when it was moved. Birds initially
used spatial memory to locate the reward but once this failed they used the available light
cue to learn the spatial association. Once birds were using spatial association memory,
the spatial memory of the rewarding location was not reinforced in memory as they relied
only on the association to locate the reward.
In Chapter Three, I found evidence that the components of spatial association
memory (the cue and the reward/response site) can be utilized separately from the
association itself. Once birds learned a spatial association, a spatial memory of the
currently and previously rewarding location remained in the absence of the light cue and
this spatial memory was strengthened when birds fed repeatedly from the same location. This supports Brown (1992) who suggested that hummingbirds make spatial associations
according to Gestalt theory, in which both the association and its parts are presumed to be
perceived and remembered. I uncovered this information through analysis of intertrial
activity, previously presumed to be independent of within trial behavior. Spatial
association memory is more complex and flexible than expected and has characteristics to
be useful in the wild, possibly to adjust quickly to profitability changes in flowers and
patches.
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