Dane asked -

<description of birdless hoar frost areas trimmed>

>Question: Do birds tend to avoid foggy and/or hoar frost areas? I've not
>heard any discussion on this topic.

Hoar frost can form by sublimation under calm wind conditions but really
needs some air movement, albeit very little, to get a good buildup of
ice crystals going. Up here in Prince George in central B.C., the days I
hate the most are the sub-zero, foggy days 'cuz until the car engine is
well-heated there is no way that the defroster can keep the rime from
forming on the windshield when the car is in motion. This means frequent
stops to scrape, scrape, scrape.

As for birds avoiding hoar frost areas: I can see no reason that hoar
frost would not form on a bird's superstructure, likely not as easily as
on a car's windshield but the risk would still be there. Thus the bird
would have to stop frequently and preen the frost off, a costly energy
expense on an already cold and challenging day. Much better to find that
sunny spot and let the sun evaporate the frost away.

- Jack



Jack Bowling
Prince George, BC
CANADA
jcbowling at mindlink.bc.ca