The Seasonality of Pennsylvania Birds
Below are excerpts from writings by Daniel Brauning of the Pennsylvania Game Commission. The complete series of articles are available on the Game Commission website under Bird Watching.
The change of seasons causes a dramatic fluctuation in bird populations. We generally understand that the movement of birds is a response to food availability, rather than directly to cold temperatures. Birds that feed on insects or fruit can make a living in Pennsylvania only during the warmer months, when abundant insect life abounds. Frozen water restricts access to abundant aquatic life for water birds. Such movement of birds also has an effect on the best times of the year for Pennsylvania birdwatching.
