Thursday, April 26, 2012

Bird that calls the rain has a wide repertory of calls

The arrival of the rainy season brings a phenomenon intimately familiar in Costa Rican folklore, as the national bird “calls the rain.” The clay-colored thrush responds to the change of seasons by starting its breeding cycle with frantic bouts of singing while the matter of establishing a territory and finding a mate is settled.

The yigüirro was named the national bird in a vote of schoolchildren in the 1960s. It sometimes fails to time the first burst of singing with the rains, though this year was more accurate than the Instituto Meteorológical Nacional, which said there wouldn’t be storms until May.

The clay-colored thrush has profited greatly from habitat changes caused by humans and is now abundant in non-forested areas of low- to middle-elevations. Its association with inhabited areas makes it one of the country’s most familiar birds. It will come to feeders with bananas for a closer view. Despite the species’ omnipresence in the Central Valley, few people are much aware of its habits, which include one of the largest vocal repertories of any Costa Rican bird. 

The most important is the territorial song, an extended caroling that makes birds that actually were everywhere but inconspicuous suddenly obvious as the males sing from telephone wires, high in trees, and rooftops. Unlike many resident birds which can keep a territory year-round, the thrush wanders widely in search of food in the non-breeding season, and individuals are even faithful to different areas during their winter, as documented by banding studies in Costa Rica’s Caribbean lowlands. So it is imperative to get nesting underway and profit from the burst of insects associated with the arrival of the rain. Singing often starts well before dawn and lasts all day, until a few weeks into the season when they relax a bit.

The song so beloved by the Ticos can be heard here at the Xeno-canto Web site.

Any of the tracks labeled song from Costa Rica or Panamá are good examples, while those from further north are a different subspecies with a somewhat different territorial song.
popular bird
Photo by Steve Heinl
Clay-colored thrush is a master musician.

Occasionally a bird sings a quiet version of the song, almost whispered. This is mostly heard just before the season starts, perhaps to tune up for the coming bout of action.

Heard year-round is a call “tock-tock-tock” with a varying number of notes. Sometimes this is sped up and prolonged when the effect is rather different. The third xeno-canto track, from Oaxaca, is a good example. Click HERE!

Another common call heard mostly at dawn or when the thrush is concerned about a predator is a meowing churrrup. This can be heard at the end of a song recording from Santa Rosa National Park or also a track from Las Cumbres, Guatemala. Click HERE!

Less likely to be heard by anything but a predator is a squealing distress call when captured. It is, of course, normal for banders to have a bird in hand and it tends to presume the worst about its impending fate. Another track from Oaxaca gives this call. HERE!

Begging juvenals can be seen as the breeding season progresses, as they are still dependent on the parents for food even after they are full-size and have left the nest. The juvenile plumage is characterized by dark spots over the otherwise tan plumage of the adult. The begging call is the fifth track.

Nestling chatter is the first or last on the list, after all, “what came first, the yigüirro or the egg.” The blind and helpless nestlings put their orange mouth linings in the air to be fed when they feel an adult arrive at the nest.

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