What condition might cause many Cedar Waxwings to undertake a much shorter southward migration?

Answer

If a winter is mild and local fruit crops remain accessible

The extent of southward movement is highly variable; if local fruit crops remain accessible through the cold months due to mild weather, many waxwings might opt for a much shorter migration, perhaps only moving a few hundred miles.

What condition might cause many Cedar Waxwings to undertake a much shorter southward migration?
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