A Field Guide to the Sky Dance
A sign of spring for my family is a trip to the theater to watch what Aldo Leopold called the sky dance in his 1949 classic A Sand County Almanac. Our theater has no roof or seats. Its just a small field next to a shrubby wetland near our house with a show that something to behold. It’s the annual courtship flights of the American Woodcock and this year on a crisp, clear night with a moon rising above the Green Mountains it was an especially beautiful show.
The dancers in this annual show have a long bill with a flexible tip specialized for probing and capturing earthworms, a stout head with large eyes set far back for rearview vision without a mirror, and plumage with mottled, leaf-brown patterns that blend superbly with the forest floor.
The theaters they use are made of moist woodlands or thickets near fields or open areas. The audience is encouraged to arrive early and remain quiet while they let their eyes slowly adjust to the dimming light. The curtain usually opens with the male woodcock flying onto the stage at exactly 22 minutes after sunset when the lights are dimmed to precisely 0.05 foot-candles. With the crowd hushed, the dancers begin.
The males are loosely clustered about the stage. Each defends a small area on the ground were the peent, a short (~0.2 seconds) buzzy note is repeated over and over. If you are close enough you can also hear each peent preceded by a short (0.3 seconds) tuukoo, wukoo or ka-rurr sound. The two sounds often merge into one, tuukooeeent. He may also give tuukoo calls at widely separated intervals (0.2–30 seconds) initially after alighting on display area or when alert to strange sounds.
The sky dance begins when the peenting bouts end. There are five parts to the flight:
1. a silent, gradual ascent lasting about 2 seconds;
2. a continued gradual ascent with light wing twittering for about 12 seconds;
3. the wing twittering becomes melodious as he climbs steeper and then loops into spirals for about 15 seconds;
4. the apex of the flight lasts for about 12 seconds and may be 300 feet high, as the wing twittering becomes intermittent with rapid, short bursts, overlapping with loud, vocal chirping during the initial descent as he zig-zags, dives, and banks, then pitching down again precipitously;
5. a silent descent lasts up to 8 seconds as he brakes to the ground with soft but audible flapping wings and lands back on his stage to resume another bout of peenting.
The twittering sound is produced by air passing between three attenuated outer primary feathers on the wing. The outer primaries of a male American Woodcock are narrowed (called emarginated), which produces whistling twitters during the sky dance. The chirping calls made during the sky dance are a fast, repetitive series of 4–6, melodious notes – chirp-chirp-Chirpchirpchirp, repeated.
Sometimes they will give a rapid, harsh cackle, ca-ca-ca-ca-ca , as they fly low over another peenting male. Cackling is probably an aggressive challenge. Sometimes the peenting bird may chase the aggressor and cackle back. If two peenting males are too close to each other, they may give aggressive cackle calls on the ground too.
As many as 24 sky dances can be performed by an individual during an evening performance, but most average a half dozen per night. As twilight disappears from the western sky, the performers retire for the night and wait for the curtain to rise in the dim light of the morning for another bout of sky dancing.