Q: I saw a story recently about an eagle carrying off someone's pet dog. Does this mean my little dog is in danger when she's out in the backyard?
A: These kinds of stories swirl around the internet from time to time, and they seem plausible on the face of it, because bald eagles are such large birds. But I'm going to go out on a limb here and state that there's almost no chance an eagle will snatch your dog.
Bald eagles typically carry off their prey — most often, a fish — to consume while perched in a tree, and that prey needs to be fairly small. The reason? Under all those feathers, bald eagles (in Minnesota) weigh between 8 and 13 pounds. Gail Buhl, who manages education programs at the Raptor Center, says eagles generally can carry about a quarter of their weight, some 2 to 3 pounds. An eagle might catch something larger than this but wouldn't be able to carry it very far. (She notes that eagles have been known to catch fish too large to carry, then must swim to shore with their prey. Yes, eagles are known to swim.)
Since few dogs weigh less than 3 pounds, they're pretty safe from eagles. Even more compelling, dogs are not usually part of the "search image" for bald eagles, which instead keep an eye out for fish, waterfowl and carrion.
Roadside ramblers
Q: Whenever I'm driving in the country I see flocks of small birds on the ground along the road. What are they doing there?
A: The roadside birds you're seeing in the winter are likely to be goldfinches, tree sparrows, horned larks or snow buntings. They're all seed eaters, and, lacking teeth, they need some way to grind up their food. This happens in the gizzard, and the gizzard needs to be stocked with small stones to do the grinding. So the roadside flocks of birds that swirl up every time a car passes are swallowing small stones and grit to help digest their food.
Winter butterballs
Q: Why do birds look fatter in winter than they do in the summer? I'd have thought it would be the other way around, with more food available in warm seasons.
A: That's an excellent observation and for an answer you need look no further than your closet, provided that you have a down-filled coat. Feathers are the best insulation on Earth, and birds fluff out their feathers to trap air between them and the skin. The trapped air gets warmed by body heat and keeps the bird warm. Bird body temperature, on average, is about 105 degrees F., and the more they fluff out their feathers, the more air is trapped, providing greater warmth and a plumper profile.