Biology Reference
In-Depth Information
Fig. 4.22 Visual mimicry of host young by Australian bronze-cuckoo ( Chalcites ) chicks. From left to right :
A. Little bronze-cuckoo chick (above) and D. the host's chick (below), the large-billed gerygone. B. Shining
bronze-cuckoo (above) and E. the host's chick (below), the yellow-rumped thornbill. C. Horsfield's bronze-
cuckoo (above) and F. the host's chick (below), the superb fairy-wren. From Langmore et al . (2011).
to reject a cuckoo (Langmore et al ., 2009). Therefore, these hosts are likely to avoid
misimprinting by means of an innate template to guide selective learning, akin to that
involved in selective learning of own-species songs in songbirds.
Summary
Antagonistic interactions between predators and prey lead to the evolution of
adaptations and counter-adaptations. The result may be 'Red Queen' coevolution,
where tactics change over time but the relative success of each party remains the
same. Experiments involving birds searching for cryptic prey show that background
matching does indeed reduce predation, and that it can be enhanced by disruptive
colouration and counter-shading. Predation may also promote the evolution of
polymorphism in prey, which reduces the efficiency of search image formation by the
predator. Even slight crypsis, sufficient to impose a few seconds extra discrimination
time, can bring an advantage to prey and so serve as the starting point for an
evolutionary arms race.
Some prey are brightly coloured. Bright colours and eyespots may startle predators.
Bright colours are also effective warning signals for noxious prey (aposematism). The
evolution of aposematism involves a trade-off between increased conspicuousness to
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