Cuckoo
(Cuculus canorus)
C. canorus is a familiar herald of
spring and a species that is thinly distributed over a wide breeding range throughout
most of Britain, Europe and the Palearctic. It is a fairly common but rapidly declining
summer visitor to Sussex, where the males commence singing soon after their
arrival; typically in early April. Recent satellite tracking technology has
shown that the males usually leave the UK to their wintering area south of the
Sahara only a few weeks after first arriving here in the spring.
C. canorus has a well-known
breeding strategy as a brood parasite, laying its eggs in the nests of other
birds; typically those of the Dunnock (Prunella
modularis), Meadow Pipit (Anthus
pratensis), Pied Wagtail (Motacilla
alba) and Reed Warbler (Acrocephalus
scirpaceus) in the UK. The
female, who will specialise in one particular host species, will only ever lay
one type of egg and will always target her egg-laying appropriately. The genes
for egg pattern and colour are thought to be carried on the female chromosome,
so they are passed down from mother to daughter regardless of who the female
mates with. This means that a Cuckoo targeting a Reed Warbler always produces
eggs with a Reed Warbler pattern and she knows which nests to target thanks to
the process of imprinting. As a young chick, she will have learned to recognise
the song and appearance of her foster mother; and as a returning adult she will
seek out the nests of females that match this mental image and lay her eggs
accordingly.
The
above images of a female were recently taken on North Uist in the Outer
Hebrides.
References:
Yates,
B. (2014). Common Cuckoo. The Birds of Sussex. Thetford: British Trust
for Ornithology (BTO) Books on behalf of the Sussex Ornithological Society, pp.
360-361.
Whitcomb,
P. (1996). Cuckoo. Birds of Sussex. Sussex Ornithological Society, pp.
358-359.
