Animals in south Florida don’t have to worry much about winter cold – and indeed many migrants from areas farther north find suitable living conditions here. But, a trip to the beach or on a rare blustery day sometimes makes one wonder. How do ducks, herons, egrets, and other birds tolerate wading or swimming in cold weather? Aquatic birds, for example, have bare skinny legs with leg muscles placed among insulating feathers. Blood vessels going to and from the very few muscles in the legs and feet lie right next to one another, and cold blood going back into the body is warmed by warmer blood coming from the body – and is nearly the same temperature as the blood circulating in the well-insulated body.
How do birds stay warm on a cold night or while resting? There are many ways. Choice of a resting place is important. Sharing a protected place with others also helps. Birds have a high rate of metabolism and, as a result, generate a normal body temperature much higher than ours. Perching with others on a limb or utility line can aid all in keeping warm. There are limits to these benefits of closeness, however. Being too close can facilitate movement of parasites among birds and can also delay escape from a potential predator. Take a look at a congregation of blackbirds on a utility line – they often seem to be evenly spaced. The distance between them tends to be about a wing length – thus allowing individuals to more easily flee from danger. But you might also notice that on colder days that distance is minimized to share warmth.
On a cold night resting birds generally tuck the bill into feathers of the back – which are directly over the heart. Their breath and body heat warm the air under the feathers, helping the bird to maintain its high body temperature.