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Animals usually only hang around an area when food is available. When there is no food, animals tend to move on.

Birds are no different. American Robins eat bugs and worms. When the ground freezes in the fall, the robin's food source is no longer available. When the warm air returns toward spring and the ground thaws, that is when you start seeing robins.

I have a tree that is especially for robins. The berries ripen during the winter. When the robins return early before the ground thaws, the berries provide the robins with a food source. However, robins prefer worms and bugs. The berries typically are all eaten by the time the ground thaws and the worms and bugs are available.

Birds sense the days getting longer and the south winds that start blowing toward spring carry the birds north. Just as birds sense the days getting shorter and the north winds blow in the fall to carry the birds south.

People in Pennsylvania believe a groundhog on Groundhog's Day can predict when spring will arrive.

I tend to look for solid evidence like the Dark-eye Junco (who prefer cold weather) leaving the area and then more warm weather birds like Barn Swallows arriving to area too for indications that spring is right around the corner.

Have fantastic day!
Steem on,
Mike