The Cetti's warbler was saved from the blaze at Wigan Flashes on Tuesday.

BBC: Cetti's warbler

The first time you identify that palm warbler, it's kind of a rush.

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Nests thus attacked yielded, on average, but a single fledgling, whereas those with a cowbird egg in them yielded three warbler fledglings.

ECONOMIST: How cowbirds run protection rackets

Of course, it has only one beak (albeit a bigger one than that of a warbler chick), but it can cheep as much as it chooses.

ECONOMIST: Bird-brained | The

The cowbirds' dastardly tricks do not stop at this protection racket, either, for a fifth of those warbler nests that had never had cowbird eggs in them also got destroyed.

ECONOMIST: How cowbirds run protection rackets

Warbler chicks, however, seem not to subscribe to it.

ECONOMIST: Bird-brained | The

If a cowbird female fails to lay in a warbler nest in time for her egg to hatch with those of the host, she can reset the clock in her favour by killing the first clutch.

ECONOMIST: How cowbirds run protection rackets

The team found that it adjusted its cheeping-rate as it grew, so that the combined signals of cheep and gape, when plugged into the formula, exactly matched the value that would have come from four warbler nestlings.

ECONOMIST: Bird-brained | The

Paying protection money in the form of food for the cowbird nestling thus looks a good deal from the warbler's point of view, and explains why cowbirds do not need to disguise their eggs to look like those of prothonotaries.

ECONOMIST: How cowbirds run protection rackets

The Warbler was just getting started.

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