Alison Davies's picture

How does a cuckoo know it's a cuckoo?

Observed: 4th April 2011 By: Alison Davies
Description:

The Cuckoo – a puzzle that surfaces in my brain every year or so – How does a cuckoo get to meet another cuckoo, to mate and continue the species?
It is laid as a single egg in a host's nest. Its real mother clears off before it is hatched, and takes no interest at all. It has a sensitive spot on its back which triggers it to shove the other “rightful” fledglings out of the nest. (Presumably the single-egg-laying thing has been worked out as inadvisable by evolution – if two cuckoo eggs were laid in a nest I guess the two little parasites could shove each other out of the nest, i.e. at the same time, then there would be none. But that doesn't matter, there is one egg laid.)
Anyway, how does the cuckoo, when it leaves the nest, find another cuckoo? How does it know it's a cuckoo and that it must mate with another cuckoo? It can't be visual, some sort of imprinting, because it has never seen another cuckoo, only seen the host parents. Plus there isn't a great population of cuckoos to bump into and recognise somehow innately, if visual plays any major part.
(Doubt it could be smell – they are pretty widely spaced out I would have thought.)
I had wondered if it was sound…and that could be it. I see on one website that the little cuckoo imitates the sounds of either the host parent or the host temporary fledglings, to attract the giving of food by the host parents. OK, it imitates the sounds of the host family, but the same website says that the eventual call that emerges is that of a cuckoo, so the true call is innately determined.
Could it therefore recognise the similar sound of another cuckoo, once it has started making its own call, i.e. something like its own voice? Possible, BUT – male and female cuckoos make different calls. The well-known cuckoo call is from the male, the female apparently makes a sort of bubbling call. So whichever sex of cuckoo is calling out would only recognise the sound of a same-sex cuckoo, IF it is recognising a similar call to home in on.
This leads me to think that even the recognition of the call of an opposite-sex cuckoo is also innate.
Other thing – the chances must be quite high of them mating with one of their brothers or sisters, given that the egg-laying female must operate in a particular area, visiting host nests. Wouldn't this likelihood tend to diminish the viability of the species, in a gene-pool way?
DOES ANYONE KNOW OF ANY SOURCE OF INFORMATION THAT GIVES AN ANSWER TO THIS PUZZLE?

Identifications

No identification made yet.

Species interactions

No interactions present.

Comments

Carstairs's picture

forum

I think this is posted in the wrong place. This is for identification of sightings. Your question should be placed in the forum. Some interesting points I'm sure would be discussed in the forum.

Jonathan's picture

You will find the bird forums

You will find the bird forums here:

http://www.ispot.org.uk/node/2/og/forum/117

Jonathan
University of Edinburgh and Biodiversity Observatory (OU)