Re: How does a cuckoo know which bird species' egg her egg imitates?

In the essay on brood parasitism in The Birder's Handbook (also available
on-line at http://www.stanford.edu/group/stanfordbirds/text/essays/Brood_Parasitism.html)
the authors state that some cuckoos specialize in parasitizing specific
host species and that this specificity may differ for females within the
same brood. The ability of females to mimic their host's eggs appears to
reside genetically in the females, as females parasitizing a specific
species will mate with random males. Recent research (Aviles, et al. 2006)
indicates that females to some degree choose eggs which will more closely
match their own. This matching seems to incorporate both cues we humans can
see as well as elements visible in the ultraviolet end of the spectrum.
These findings argue that there is some cognizance on the part of the
female European cuckoo for visual elements of the hosts eggs which lead to
her laying in that specific nest. For a good overview of cuckoo nest
parasitism see Brooker and Brooker (1990) which is also available on-line.
In this article the authors raise the question of whether the females
imprint on their hosts and possibly the other eggs in the nest to guide
them when it comes time to dump their own broods. 


Aviles JM, BG Stokke, A Moksnes, E Roskaft, M Asmul, AP Moller. Rapid
increase in cuckoo egg matching in a recently parasitized reed warbler
population. 2006. Journal of Evolutionary Biology 19:1901-1910(10)

Brooker, LC and MG Brooker. 1990. Why are cuckoos host specific? Oikos
57:301-309.

Ehrlich P, DS Dobkin and D Wheye. 1988. The Birder's Handbook�. Fireside.