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Effect of Temperature on Birds Although temperature is related to photoperiod, temperature as a single factor does affect bird behavior. A freeze kills much of the vegetation and the insects that many northern birds need. The loss of reliable food source without a change in the photoperiod could cause some birds to migrate. Maintenance of a constant high body temperature becomes increasingly difficult in cold environments, especially for smaller birds. Thus, many of the small northern birds that overwinter in cold environments must take advantage of tree cavities or other shelter, or they must roost in groups to minimize heat loss. For example, 20 or more Brown Creepers might roost in a tight mass beneath a piece of loose tree bark. On a cold Tennessee night, several bluebirds might crowd into the same birdhouse or roosting box for warmth. Left: The Brown Creeper has the distinctive habit of spiraling up a tree trunk, then dropping to the base of another tree to repeat the performance.
Some Roosting House Plans
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