Saturday, April 29, 2017

Why Don't Ducks' Feet Freeze? And Other Spring Thoughts

The bike trails are now pretty much snow and ice free.  There's sun.  No time to blog, time to be out.

Goose Lake still has ice.

This grebe is riding the waves at a windy Potter Marsh Friday afternoon.

A gull on the final approach to its nest.

Potter Marsh from the boardwalk.

Waiting for the new green to push up through to the sun.

This morning I had ride by Goose Lake again and there were two mallards sleeping on the ice.  If you're wondering, like I was, why their feet don't freeze, Ask a Naturalist explains why:

"It’s all about heat exchange, and the smaller the temperature difference between two objects, the more slowly heat will be exchanged. Ducks, as well as many other birds, have a counter-current heat exchange system between the arteries and veins in their legs. Warm arterial blood flowing to the feet passes close to cold venous blood returning from the feet. The arterial blood warms up the venous blood, dropping in temperature as it does so. This means that the blood that flows through the feet is relatively cool. This keeps the feet supplied with just enough blood to provide tissues with food and oxygen, and just warm enough to avoid frostbite. But by limiting the temperature difference between the feet and the ice, heat loss is greatly reduced. Scientists who measured it calculated that Mallards lost only about 5% of their body heat through their feet at 0o C (32o F)."

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