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 use of gape-area to help assess how much food to bring means that the quantity automatically increases as the chicks grow, without them having to cheep more in order to get extra food.

ECONOMIST: Bird-brained | The

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