While most Iowans will spend the holidays celebrating with family and friends, a few will be devoting the next three weeks to binoculars and a notebook. The annual Christmas Bird Count started Sunday at thousands of sites in North and South America. If the weather allows, Kelly McKay — a wildlife biologist in the Quad Cities (Hampton, Illinois), will spend 23 days in a row in “field counts” across eastern Iowa and northwestern Illinois.

He says the main variable each year is the weather. For example, harsh weather means fewer members of the “semi-hardy” species will be counted. “Things like robins, waxwings, and yellow-bellied sapsuckers…these are all semi-hardy birds. And when you get really harsh weather, it tends to push them out or they don’t survive it,” McKay says.

Ice on rivers and lakes also means fewer eagles and ducks and other waterfowl. Up to 50,000 people participate in the Christmas Bird Count each year. Results are tabulated by the National Audubon Society. This year, there are about 40 count locations in Iowa with counts running between December 15th and January 5th.