Why do birds flock in winter?

If you live in a temperate climate and pay attention to your local birds, you have probably noticed that their preferences for companionship change with the seasons. In spring, pairs stick close by each other and three’s a crowd—any third-wheel interloper is likely to be chased off in a flurry of angry wingbeats. But in fall and winter, the birds suddenly become community minded, travelling around in flocks of dozens of their fellows. In Chicago in the winter you can find trees liberally decorated with the round orange forms of fluffed-up American Robins, bearing more than a passing resemblance to Christmas tree ornaments. Even in the Bay Area, not generally known for its seasonal variation, huge flocks of quietly chirruping Dark-eyed Juncos make it clear that (mild, occasionally rainy) winter has arrived.

robin

Not pictured: about fifteen of this robin’s winter friends.

Why flock in winter? Or, why flock only in winter?

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What do birds do when it rains?

I’ve been meaning to write about this topic for a while—now xkcd has beaten me to it:

Oh, well. Since the comic doesn’t actually answer the question, I’m hoping you’re all still interested! (Also, at the end there will be a bonus discussion of ant rain. Yes, ant rain. You won’t find that on xkcd!)

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The sky is falling: birds and hail

The season of the summer disaster movie is upon us: Godzilla is stomping San Francisco, and I’m sure we’re all eagerly anticipating the premiere of Sharknado 2. To liven up the cinemas a bit, as a relief from the overabundance of sequels (I mean really, Sharknado 2!), I would like to propose a new genre mash-up: the animated talking birds disaster movie. It would be like those dancing penguin movies, or the solemn-looking owl movie (I have seen none of these…), plus disasters. The first one could be called Hailstorm!

It would not be a children’s movie. It would be terrifying.

It hailed on us a few days ago for about half an hour. The hail was mostly small, not larger than 1 cm in diameter, and the only animal reaction I saw was a decidedly alarmed chickaree—although to be fair, chickarees almost always look alarmed. I saw no evidence of damage afterwards; all of the junco nests we were monitoring weathered the storm just fine.

We hid in our tents.

You know the hail isn’t too bad when you can safely hide from it in a tent.

But sometimes hail is a sharper-fanged beast.

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I might have started the field season a little too early

Last year, I started the field season as soon as the university spring semester ended, because my field assistants were undergraduates and needed to take their finals before heading off into the mountains. That turned out to be too late, as we found that some of the juncos had started breeding without us. So this year I found some awesome non-undergraduate volunteers and went out earlier.

But I might have started a little too early.

My tent, our first morning in the field.

My tent, our first morning in the field.

We’d known it was going to rain, and I thought it had – a particularly light-sounding rain pattering on my tent throughout the night. When I woke up I thought my tent had been covered in seeds washed loose by the rain. Then I stuck my head outside.

In fact it was better than rain: drier, and still permitting us to boil water for breakfast.

Our stoves boiling water for breakfast.

Our stoves boiling water for breakfast.

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Could ducks in the water melt ice?

Female Wood Duck in Chicago in the winter.

Female Wood Duck in Chicago in the winter.

A reader question today! Dolores asks: Would the body heat of a modest mixed gathering of water birds (gulls, ducks etc) melt ice at the edges of a pond?

The answer to this depends on context. We can start by establishing some extreme end-points: one duck at the edge of a huge lake in way-below-freezing weather would not be able to melt any ice.

Female Common Goldeneye in Lake Michigan: it's a good thing the lake is already melted, 'cos you're not going to melt anything.

Female Common Goldeneye in Lake Michigan: it’s a good thing the lake is already melted, ‘cos you’re not going to melt anything.

Twenty ducks splashing around spiritedly in a kiddie pool with the barest skin of ice in weather just at the freezing point would probably, if you waited long enough, cause the ice to melt.

Between our two endpoints are more “normal” circumstances: a group of waterbirds hanging out at a pond. Could they melt any ice?

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What happens to the animals when there is a fire?

Rim Fire. Photo by Steve Ryan

Rim Fire.
Photo by Steve Ryan

You have (I hope!) seen news lately about the Rim Fire, which has been burning in Stanislaus National Forest next to Yosemite National Park. It began near the “Rim of the World” scenic viewpoint off Highway 120, and has been making Yosemite visitors and residents of Groveland quite nervous. It has burned over 200,000 acres and is reportedly 32% contained. A collection of pretty incredible photos of the fire is here.

First: no, this year’s juncos are not currently on fire. My field sites this year are in Stanislaus National Forest, but considerably further north. We have, however, seen smoke and had bits of white ash falling around us.

But of course, even if my juncos aren’t in the fire, other juncos are. And Chipping Sparrows, and American Robins, and mice, and gopher snakes… So what does wildlife do when the world starts burning around it? Are all the animals in that 200,000+ acres doomed?

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KKRA, thunderbird

Two weeks ago, it rained on us for a solid 22 hours. (Which, I discovered, is exactly the time it takes for puddles to start forming inside my tent.) So when it got grey and thundery at the beginning of last week, I jumped: “We’ve got to process this junco quickly! Take down the nets! We have to get back to camp to cover the firewood!”

Of course, it didn’t rain. The next time it got grey and thundery, I jumped less: “Let’s take down one net and keep this one. Tell me if you see lightning.” It didn’t rain.

The third time it got grey and thundery, I didn’t jump at all. Then it actually started raining—but I really wanted another junco. So we caught a male in (very light) rain and banded him under a tree, naming him KKRA, which sounds a bit like the thunder that was rolling in the distance.

KKRA

KKRA, who has one white feather on his cheek

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