Driving through Missouri farmland this afternoon, I saw two great blue herons fly across the highway, seemingly out of place in the snow-covered landscape. Yet, a minority of these large waders, which breed throughout most of the U.S. and southern Canada, are regular winter residents across central latitudes of North America. Despite their tropical appearance, many great blues manage to survive our Midwestern winter, gathering along the larger rivers and streams, where open water is found.
During the warmer months, great blue herons feed primarily on fish, amphibians, snakes, lizards and large insects, which they stab or grasp with their long, pointed bills. Those that remain through the winter are forced to broaden that menu, often consuming field mice, shrews, crayfish, invertebrates and small birds. Why some great blues stay for the colder months rather than migrate to southern climes (like most herons and egrets), is just another mystery of our natural world; some black-crowned nights herons also adhere to this pattern, foregoing a trip to the Gulf Coast in favor of a winter in the north.
While we are unable to explain such "choices," we should not attribute this behavior to any purposeful decision making. Survival instincts and genetics are at play here, nothing more. No doubt, many great blue herons succumb to severe cold, ice storms or heavy snow each year. That is nature's way.
