2015 - When looking for a mate.

A chirp is a signal in which the frequency increases or decreases with time. Scientists hypothesise that bird songs have evolved through sexual selection, and experiments suggest that the quality of a bird song may be a good indicator of fitness. Bird vocalisation includes both bird calls and bird signals. Communication through bird calls can be between individuals of the same species or even across species. The alarm calls of most species, on the other hand, are characteristically high-pitched, making the caller difficult to locate. In a linear chirp, the instantaneous frequency f(t) varies linearly with time:

f(t) = fo + k t

In an exponential chirp, the frequency of the signal varies exponentially as a function of time:

f(t) = fo k^t

When looking for a mate, the male red-capped manakin snaps his wings and dances on a branch to catch a female's eye. A bird nerd rarely gets the girl. Just ask an avian Casanova — the manakin. There are over 50 species of this showy little bird, and they all go full out to court the ladies. At breeding time, the brightly coloured males stake out a staging area called a lek-the bird equivalent of a singles bar. A branch serves as the dance floor. The act isn't all snazzy steps. Sound is just as important. 

The buzzes, whirrs and snaps may catch a lady's eye, but the noise also warns other males — back off, she's mine. And if all else fails, show some leg. The competition is so fierce that only alpha males will mate. Now that makes zero-one dating look much more easy.

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