It is cold out — about -10 °C as the sun gets up on Thursday.
Now, that is the temperature of the air, and probably 0f the snow, but it is not the temperature of the lake. The liquid water has a temperature of about 0 or 1 °C, so it is much the warmer of the other two regions due to convection from below.
It is not surprising then, that mallards spend their time in the warmer shallows of the lake. Or is it? After all, humans (and deer) would not think about lounging in the water at these temperatures.
What is going on? Ducks prefer the lake, but mammals avoid it.
The first thing to realize is that both waterfowl and mammals have an internal heat supply. The question is, how are we each affected by conduction with the surrounding medium, whether air or water? This then is a question about thermal conductivity or how the body transfers its heat to the surroundings. What then differs in the thermal conductivity between waterfowl and (most) mammals?
Thermal conductivity is a question about the time it takes to adapt. A high conductivity means that adaptation to external temperature happens quickly; low conductivity means that adaption happens slowly. In particular, water has about 30 times the thermal conductivity of air.
Let us treat the ducks first, because they are slightly easier. Although cold, the water is a good deal warmer than the land. In addition, the ducks are very well insulated by thick fat layers and puffy feathers. This is enough to keep them adequately warm as they lose only a little of their heat to the water.
But without clothes, humans are rather poorly insulated and even the thermal conductivity of the air (although lower than that of water) causes them to lose heat quickly and get cold. A wrapping of clothes and mittens can balance this. But, wander into the water where regular clothes can make little progress against the much higher thermal conductivity found there.
The ducks are in the water, because it is much warmer there than out, but humans are out of the water because their clothes only just balance even the lower thermal conductivity found there.
In cold weather, ducks stay in the water.
Ducks in water
It is cold out — about -10 °C as the sun gets up on Thursday.
Now, that is the temperature of the air, and probably 0f the snow, but it is not the temperature of the lake. The liquid water has a temperature of about 0 or 1 °C, so it is much the warmer of the other two regions due to convection from below.
It is not surprising then, that mallards spend their time in the warmer shallows of the lake. Or is it? After all, humans (and deer) would not think about lounging in the water at these temperatures.
What is going on? Ducks prefer the lake, but mammals avoid it.
The first thing to realize is that both waterfowl and mammals have an internal heat supply. The question is, how are we each affected by conduction with the surrounding medium, whether air or water? This then is a question about thermal conductivity or how the body transfers its heat to the surroundings. What then differs in the thermal conductivity between waterfowl and (most) mammals?
Thermal conductivity is a question about the time it takes to adapt. A high conductivity means that adaptation to external temperature happens quickly; low conductivity means that adaption happens slowly. In particular, water has about 30 times the thermal conductivity of air.
Let us treat the ducks first, because they are slightly easier. Although cold, the water is a good deal warmer than the land. In addition, the ducks are very well insulated by thick fat layers and puffy feathers. This is enough to keep them adequately warm as they lose only a little of their heat to the water.
But without clothes, humans are rather poorly insulated and even the thermal conductivity of the air (although lower than that of water) causes them to lose heat quickly and get cold. A wrapping of clothes and mittens can balance this. But, wander into the water where regular clothes can make little progress against the much higher thermal conductivity found there.
The ducks are in the water, because it is much warmer there than out, but humans are out of the water because their clothes only just balance even the lower thermal conductivity found there.
In cold weather, ducks stay in the water.
