On the Fly – Early Birds

Bay Area children learn to expect a gap between what they hear about nature and what they see. Just what is a white Christmas? Where are all those cardinals you see on the greeting cards? And what’s all this about showers in April? Still, I’ve always believed that robins were a sign of spring. And that large flock of red-breasted birds I saw across the street in December, well…were they really robins?

Yes, they probably were. And they’ve probably been somewhere nearby all year. It seems this idea that spring arrives with the robins was imported from Europe, and it’s about a completely different bird than the one we have here. The European robin (Erithacus rubecula) is a member of the Old World flycatcher family, and our own American robin (Turdus migratorius) is a thrush. And robins who summer in cold northern places do migrate, but throughout the US many are happy to stay in the same latitudes year-round, enjoying the berries that abound in our landscaping and the earthworms that wriggle beneath our suburban lawns. If the robins seem to disappear in the winter, it’s probably because they found a good source of food a few blocks or miles away.

But in one sense American robins are harbingers of spring: they’re among the first to pair off and build nests, so we hear the males’ territorial songs around the time things start to really green up and the narcissus and daffodils are showing signs of blooming. They’re often the first birds to sing in the morning and the last at night, seeming to greet the sun and send it off, the last rays of the sun warming their billowing chests and making them that much redder.

In the words of William Leon Dawson (Birds of California, 1923), the robin’s song is “too well known to most of us to require particular description, and too truly music to lend itself well to syllabic imitation. There is something homey and substantial about it which makes us give thanks for common things, and accept without analysis—as we do salt and sunshine and breath of orange blossoms.” But if you would like to hear samples of the robin’s songs and calls, I recommend the Cornell Lab of Ornithology’s “All About Birds” website.

While they may be as common as salt and sunshine, robins really are spectacular in size, coloring, and marking—almost exotic-looking. Males and females look similar except that the females’ heads are paler.

Incidentally, the real early birds here are the Anna’s hummingbirds, which begin nesting as early as December. Red-tailed hawks and golden eagles also begin to build nests in mid-December, and some have eggs by early March. Black phoebes, dark-eyed juncos, bushtits, red-winged blackbirds, and western bluebirds, as well as the robins, all pair off around February and are building nests by March. And of course the mallards are at it as soon as possible.

The other day someone spotted eighty-nine robins at Contra Loma Regional Park in Antioch, and you have to wonder if a flock that big isn’t migrating. Some robins fly thousands of miles, from Canada to Central America, for instance, and then arrive back in the north just in time for earthworms to emerge. In fact, in colder climates it’s earthworms that should be considered the harbingers of spring. They migrate vertically, heading down below the frostline in the fall and tunneling back up to the surface when ground temperatures reach about 36°F. Migrating robins synchronize their flights with rainy weather, when migrating earthworms must come out of their tunnels or drown.

There’s been a great deal of science directed at the question of how robins spot worms—whether by sight, sound, or smell. Recently researchers ruled out sight and smell and, after distorting the sound underground to see if this affected their subjects’ catch, concluded that they hunt by sound. This concurs with common folk wisdom, i.e., what most of us believed in the first place. When the birds run along, stop, and cock their heads, it’s because they’re listening.

Robins’ other favorite food, especially in fall and winter, is berries. A very stretchy esophagus allows them to eat huge quantities, enough to tide them over till morning on a cold winter night. If you see a robin (or other bird) flying into a window it might be drunk on fermented berries, but more likely it’s a territorial male attacking his reflection. Or he just might not know there’s anything there: birds usually can’t see glass. Plate glass windows and windows at 90° angles to each other on the corner of a building are particularly problematic, as are lights on high-rise buildings at night. For a very thorough explanation with information on how best to mark your windows for the birds' sake, visit this page on the Cornell Lab of Ornithology website.

☼

The 16th annual San Francisco Bay Flyway Festival will be held at Mare Island on February 10–12. The web page is still set for the 2011 festival, but it will give you an idea of the wealth of activities that will be available. And if you're interested in the Great Backyard Bird Count, you might want to mark your calendar now—it's February 17–20 this year.