Monday, April 6, 2009

Of spring, robins, and...other birds

The front page of the local section of the morning paper featured a lovely photograph of an American robin against a background of snow-covered crabapples, marred by the caption: "Being the first robin of spring was no picnic Sunday in David City. A weekend blizzard dropped 8 inches of snow in the region."

News flash, people: we have robins winterlong. Granted, you might have to go looking for them, since they're not hopping around in pairs on people's front lawns. (They form flocks and tend to winter in dense vegetation offering both food and shelter from the elements—I often encounter them in groves of red cedar while out hawking.) But Turdus migratorius is not completely migratory even at our latitude.

Common but erratic regular wintor visitor statewide....CBC data demonstrate the erratic winter occurrence of this species. In CBCs from 1983-84 through 1992-93, the total count of robins has varied from a high of 10,410 in 1987-88 to a low of 213 in 1986-87. The highest individual count total was 9500 at Calamus-Loup in 1987-88.

An amazing count was an estimated 20,000 flying over in Brown Co[unty] 11 Jan 1988; 4800 were estimated in 6 minutes, and the flight lasted for 30 minutes.

—Sharpe, Silcock & Jorgensen, Birds of Nebraska: Their Distribution and Temporal Occurrence (2001)

At least Nebraskans stand a fair chance of missing robins in a low winter like '86-'87. I used to hear this "first robin of spring" nonsense even when I lived in Georgia. Robin numbers in Georgia actually drop in the spring as northern migrants return to their breeding grounds, so maybe I'm a bit oversensitized on this score.

In my opinion, for an avian harbinger of spring in Nebraska, the place to look is up.

Spring arrivals appear in early and mid-Mar, but most arrive in very late Mar and early Apr, a little later in the west. Numbers observed rarely exceed a dozen, and thus no clear migratory peak can be established.

—Sharpe, Silcock & Jorgensen, Birds of Nebraska

What bird is this that brings the promise of warmer weather to the northern Great Plains? Cathartes aura, the turkey vulture. This unlovely (to most people) bird depends, of course, on carrion for its food. It locates carcasses through both visual and olfactory cues—it is one of a very few birds with a well-developed sense of smell—and since death is a constant presence in the natural world, it can count on a steady supply of food wherever sufficient "prey" exists. Assuming, that is, that said "prey" is accessible. The extended sub-freezing temperatures of a typical Nebraska winter create plenty of carrion but quickly render it inaccessible to the TVs by freezing it solid; a dead deersicle is more or less useless to a turkey vulture.

I coached three lacrosse games up in Omaha this past Saturday. When we started, the weather was fine, and I enjoyed watching a small kettle of TVs soaring over the Missouri River bluffs. (I pointed them out to some of the Lincoln midfielders, telling them that they'd better show some signs of life. We did get more hustle out of the kids this weekend, but I don't know if that was attributable to the vultures.) Later on, the weather turned cold and windy, and the second game of the day was interrupted by a storm that included heavy sleet. I shivered along with everyone else, but I knew for sure that spring was really here. We're not necessarily done with cold weather—in fact we cancelled this evening's practice due to temps in the low 30s and 20+ mph winds—but it will be short-lived. By their return, the vultures told me so.

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