I’ll follow up from Chris and similar to Chris’s answer to the first question,
to my knowledge pretty much all birds use countercurrent heat exchange in their
legs so that could be a yes. Eric Atkinson on this list has worked on
wintering northern shrikes so he might be able to give some good tidbits! I
would doubt shrikes use torpor but I don’t know. In most regions they are one
of the earliest to nest (and build very cozy thick nests that probably provide
insulation to the eggs, so that might be something to add—although unlike
great-horned owls that are nesting now in most places, shrikes don’t usually
start until March in most places.
=c
Carola A. Haas (she/her)
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Dept of Fish & Wildlife Conservation
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On Feb 3, 2022, at 10:39 AM, Christopher Hill ("Chill")
<dmarc-noreply@xxxxxxxxxxxxx> wrote:
Joe (et al),
I’ll take a stab at a few just from general ornithological knowledge. I’m
not sure how much Northern-Shrike-Specific information there is on these
questions. Do you have access to the Birds of the World account on Northern
Shrikes? That’s an excellent compendium of what’s known. If you don’t have
access, email me off the list and I’ll try to help with that. OK, to the
specifics:
Does
the Northern Shirkes use piloerection to increase the insulation value of
their feather?
All birds do, so yes, Northern Shrikes certainly do use piloerection when
it’s cold.
Do
shrikes enter nightly torpor to conserve energy?
I don’t know about torpor. I have not heard of shrikes using true torpor.
Almost all birds of that size do have some degree of nighttime controlled
hypothermia - they let their internal temperature drop a few degrees. But
true torpor where the bird becomes inert and unresponsive seems unlikely.
Can’t say for sure.
Do
shrikes increase their body fat before the onset of cold weather?
Again from analogy with other birds, almost no birds do this. They lay on fat
to fuel migration, but they insulate with feathers, not with a layer of fat.
Most birds in winter, even in cold climates, are no fatter than they are at
other seasons. Small birds may lay on fat *daily* to get through the long
cold night, especially really small birds like Chickadees. I suspect
Northern Shrikes wake up lighter than when they go to sleep but how much fat
they burn overnight I wouldn’t want to guess.
DoPass.
shrikes use countercurrent heat exchange to avoid losing heat to their
unfeathered feet?
Hope that little bit helps.
Chris Hill
Conway, SC
The
blog is already being used in a few classrooms. You can see it at
https://wildlifeinwinter.com/ ;
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Thanks
for any help you can provide.
Joe
Riederer
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