Think about it: Birds only months out of the nest face the stark reality of winter survival. They must increase food intake to stay warm but have fewer daylight hours to forage.
It's not the cold that kills. Birds survive cold if they find enough high-fat foods to stay warm. Black-oil sunflower seeds and chips as well as peanuts and thistle seed all boast about 70 percent fat content, but corn and millet have only about 10 percent. Native berries like spicebush and dogwood have high levels of fats, while invasive and non-native berries contain little.
To oversimplify, food-for-cold also helps explain why the beautiful tropical birds leave us each fall, migrating to Central or South America. Our cold, snowy weather doesn't chase tanagers, grosbeaks, flycatchers, and warblers south, but wintertime absence of their dietary mainstay--nutritious juicy bugs--does. These tropical bug eaters, in general, shun seeds. Thus, they don't "get it" that fat-rich seeds would protect them from the cold.
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So this last week, when I watched a two-cup pile of shelled peanuts disappear over the course of a single day--even without the help of ever-voracious squirrels or marauding raccoons--I understood. Birds were after cold-fending high-fat foods. The trouble was, they weren't eating all those kernels.
First, tufted titmice found the morsels. Foolishly, I thought they were merely following their usual grab-and-run habit of eating, snatching a prized seed, zipping off a short distance to hammer it apart between their toes, and devouring it piece by piece in their preferred relative privacy. As I watched, however, I saw my error. They flew out of sight, way too far for even the most private of snacks. And back they came with uncommon speed--and frequency.
That's when I figured it out. They were caching the seeds, tucking them into tree bark, crevices, knotholes, even into window grooves designed to hold the screens in place. Little thieves? Not really. They were saving against the proverbial rainy day--or in this case, snowy, icy, bitter cold, hungry day. They have no way of knowing whether I'll measure out another two cups of peanuts tomorrow or the next day--or ever.
While titmice visited the peanut pile most frequently, Carolina chickadees and white-breasted nuthatches were right behind. They, too cache stores of seed.
Ditto blue jays. I watched one crafty jay snag a peanut, fly a short distance, drop the kernel at his feet, and using his beak, dig a hole, drop in the nut, and bill-rake dirt back in place. Then, using his feet, he patted the soil in place. I was about to whisper my congratulations on the jay's job well done when the bird did something that caught me totally by surprise. He picked up a nearby autumn leaf, dropped it over his treasure, surveyed the area, checked that no other jay was watching, and flew, knowing his cache was safe. He didn't catch me watching, but I'll not share his secret. He'll need the cache to keep warm--and alive.