But they have amazing memories when it comes to food sources and nesting habitat.
Consider blue jays. They stash acorns or other grains all fall to guard against leaner times. Over the course of winter, they excavate about 80 percent of what they've hidden, remembering precisely under which leaf or twig they've buried each morsel. Ditto for chickadees and titmice that cache sunflower seeds or other tidbits. Or white-breasted nuthatches that jam sunflower seeds into tree bark for later retrieval. They all remember where they've stashed the goods.
Chickadees can also erase memories, eliminating the clutter of remembering last year's cache sites to have room to remember this year's. Honest.
A Mt. Vernon resident had a single out-of-range yellow-headed blackbird feeding in her yard for two consecutive winters. The likelihood of that being two different birds is so remote that we have to assume the repeat visit was from the same bird. It remembered a reliable source of winter seed--all the way from its breeding ground up north, perhaps as far north as central Canada.
Southern migrants remember, too. Last spring a rural West Side couple entertained a female hooded warbler, watching it gulp down meal worms upon its return from Central America. This spring, as a one-day wonder, a handsome male returned to the same bush on the same date. Apparently, then, last year's female-lookalike was really a first-year male, now returning in breeding plumage. Again, the coincidence seems too great for it not to be the same bird, given the rarity of the bird and the exact date and location of return. Surely it remembered those fat meal worms.
Ospreys migrate to the heart of South America but return to ancestral breeding sites, reusing a nest or building another nearby. While eagles also repeatedly reuse nests, the difference between them and ospreys is the thousands of miles ospreys fly to and from their winter home. They remember the nest spot and how to find it.
Because of banding studies, perhaps hummingbirds provide the best clues about avian memory. The little gems return to their ancestral homes to nest, so they remember not only the spot but the route there. They also remember migratory stopovers abundant with food to fuel their way. They remember where your feeders hung last year, where nectar plants grew. And every fall, they visit the spots where jewleweed blooms, a native plant thousands of hummers rely on during fall migration. How do we know? The same birds have been captured in the same place on the same day for as many as seven consecutive years.
Hummers also know from which flowers they've already nectared so they don't waste energy repeatedly visiting the same flower.
Apparently avian memories focus on food sources and nest sites--in short, on survival.