This series of photos, from WTOP in Washington D.C., will of course make you go “awww” as you see the lengths an eagle will go to to keep his/her eggs warm (I don’t know the sex of this one). But of course it’s instinct, just like our own protective instincts towards our kids, for the eagles who didn’t sit on eggs when snow was falling didn’t leave as many descendants.
Still, it’s an amazing series of photos. Here’s one of ten, and the others show what happens when the other eagle comes in to change places.
Remember that the eagle is covered with nice warm feathers, and the snow acts as an insulator from the wind, so she may actually be warmer than if she wasn’t covered with snow.
Now that’s the textbook example of “cold comfort”!
b&
Snow is 32F (0C). Right now, it is 16F (-9C) in Hanover, PA. So the snow is warmer than the air. And it is good at insulating the air the eagles have warmed with their bodies.
The eagles are no longer covered with snow – but they have made no attempt to clear snow from the nest. You can see live video here:
http://www.portal.state.pa.us/portal/server.pt?open=514&objID=1592549&mode=2
Er…32°F / 0°C is the maximum temperature for snow. It can get much, much, much colder than that. The limit is probably only a degree or two above absolute zero, in the range of -450°F / -270°F.
Snow that’s exactly 32°F / 0°C will certainly have initially formed at colder temperatures, meaning that it’s warming…which, in turn, means that some of it is already melting. And wet snow is not at all going to be a good insulator.
b&
Well, if we’re talking specifically about snow, i.e. hexagonal crystals of ice Ih, the lower limit is more like -200°C, at which point it gives way to orthorhombic ice XI.
(phase diagram)
Thanks for that! Not only did I not know that there was another phase of ice that formed at standard atmospheric pressure, I didn’t even realize we were up to seventeen different phases!
Also of note is that there’s another standard pressure phase between XI and Ih (Ih is normal ice): Ic.
What I didn’t find in the Wikipedia article or a quick bit of searching…is any description of the properties of these different forms of ice. What do they look like, what sort of hardness / flexibility / etc., they have, that sort of thing. Anybody got any pointers?
b&
Just so long as none of them are Ice-IX 😉
In fact you can find ice IX in the phase diagram around -200°C and several kilobars of pressure. But obviously that’s not the ice-nine Vonnegut wrote about.
The closest thing to ice-nine in the real world is prion diseases such as Creutzfeldt-Jakob and mad cow disease, where malformed proteins infect normal protein molecules with their malformedness.
Digging in to make a snow cave is a good part of anyone’s mountain survival toolkit. It takes a surprising (to the person who has never done it before) amount of effort to achieve. It’s not a task you leave until you’re crawling on hands and knees through exhaustion.
Downthread, someone points out that the snow may be melting. Fine – that does reduce it’s insulating effect. However it just makes it better at keeping the wind off. Wind chill is often the real killer in exposure cases – there’s nothing uncommon about people dying of hypothermia on the Scottish hills at temperatures above freezing because of wind chill.
Digging a snow cave can be a life-saver. Digging a snow cave at the right time is even more useful. And if you don’t have enough snow for a cave, that’s why you’ve got a bivouac bag or a rucksac large enough to function as such.
Or…you could always avoid those parts of the world where it gets that cold. At least, avoid them during the cold season….
So long as you’ve got shade and water and are smart enough to limit your exertion suitably, there’s generally no existential danger in the heat here in the Sonoran Desert, even when the highs are over 120°F / 50°C. People get into trouble mostly when they don’t drink enough water, especially when they compound it by not seeking shade and rest at the first signs of head exhaustion. But, if, say, you’re carrying a few liters of water and you’re dressed in long-sleeved long-legged loose-fitting clothing and you maintain a relaxed pace, you can keep going all afternoon.
Of course, if you’re lost in the middle of nowhere, your first priority is shade until dusk, and then your first priority is water, after which you can worry about finding your way home. Plan on finding shade again by midmorning and sleep through the afternoon.
b&
I take it the humidity is very low, so as long as you drink enough water you get evaporative cooling and can keep going.
Here in Auckland a couple of nights ago it was 80 degrees at 10pm and the humidity was through the roof – made doing anything uncomfortably sweaty.
Not sure whether Chicago would want to swap with us…
Somehow I’m incapable of going “awww” when it comes to eagles. They always look so angry, as if their happiest thoughts are about new techniques to dissect prey. I apologize for my bigotry towards eagles.
http://media.tumblr.com/58ac90e799f97eb62975165d42468f00/tumblr_inline_mkljfyv25C1qz4rgp.jpg
APOLOGY NOT ACCEPTED
To make it even worse for the eagle community, I laughed at that picture. :’)
I’m glad humans don’t have to go through this kind of ordeal for their offspring. We children would never hear the end of it. Forget the “I used to walk to school 4 miles up to my knees in snow” bit. This would put all those “woe-as-me” stories to shame.
Humans are such romantics. Even knowing that it is merely instinct it engenders admiration and other warm feelings. Even brings a lump to the throat, and perhaps a tear to the eye. But then, that too is largely due to instinct. I am very pleased that it is so.
Eagles’s head feathers turn to white at sexual maturity. Coincidence?
“Let’s build the nest here, he says. There’s a nice view of the lake, he says. Plenty of fresh clean air in this open area, he says…I’m going to pull his eyeballs out of their sockets”.
Sub
years ago snowshoeing along a favourite forest trail, on the St Laurent north shore, on a perfect cloudless morning after two feet of new snow I just about had a heart attack when the snow a few yards ahead exploded as a grouse took off with a loud clattering of wings. Apparently they will allow the new snow to cover them as an insulator. Typically when the snow ends the sky clears, often quite quickly, and the temps fall rapidly so the grouse ensure at least one warm night by just letting the snow cover them. This particular morning IIRC the temp had dropped fom about +20F during the storm to -20F in a very few hours.