Archive for January 16th, 2010

The Friday Ark

Three's Company: Moey, Capone and Tonka

For an assortment of posts about dogs and cats and other animals, drop by the Friday Ark! This week, Willow House Chronicles is represented by Muskratville.

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Blue Jays (Cyanocitta cristata)

While birds have feathers to keep them warm, their stick-like bare legs and feet are exposed to the cold. Why don’t they freeze? Well, they do get pretty cold. While birds maintain a body temperature around 104°F, their feet don’t require as much warmth and may be only slightly above freezing. A bird’s legs and feet are made up of tough tendons and don’t have a lot of fleshy muscle. They are protected by scales that may be less prone to frostbite than skin.

Several behavioural adaptations help to warm feet. A bird may tuck one foot up into its feathers to warm it while it stands on the other foot. Birds may also sit with their feathers fluffed out over their feet to warm them.

To help prevent heat loss from the body through a bird’s feet and legs, the blood vessels to the feet may be constricted to reduce blood flow. In some bird species, the arteries and veins in the legs come in contact with each other. The heat in the blood flowing out from the body is conducted into the cool blood returning to the body in the veins. Thus, arterial blood reaching the feet is already cooled, while venous blood returning to the body is already warmed, reducing the loss of valuable heat from the body.

Some birds have a harder time dealing with cold weather. Mourning Doves (Zenaida macroura) in particular are more sensitive to the cold and sometimes lose a toe to frostbite.

Downy Woodpecker (Picoides pubescens)

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