Figure 1
From: Syntax errors do not disrupt acoustic communication in the common cuckoo
Examples of male (and female) common cuckoo calls. (a) The natural forms of 2-note (“cu-coo”) and 3-note (“cu-cu-coo”) calls of males, together with a female-specific bubbling call also indicated on the sonogram. (b) A “cu-coo” call and the first two calls in a series of “cu-coo” calls with a syntactic error, where the second note is repeated (the “coo” element, i.e. ”cu-coo-coo”). (c) A normal “cu-coo” call and calls from a series of “cu-cu-coo” syntax errors. A proportion of (b,c) were uttered by the same individual cuckoo. Note that the natural 3-note call in (a) is normal (natural), but the 3-note call in (c) differs from it in several respect (see more details in the text): it specifically suffers from a syntactic error, where the first note of the normal “cu-coo” call (“cu”) is repeated. In (c) the decreasing frequencies of the first two “cu” elements are a unique case, showing that cuckoos are capable of frequency modulation (typically, the second note is about as high as that of first element).
