On the Origin of Raptor-Pattern and Hawk-Mimicry of Cuckoos

pattern of cuckoos, based on the behaviour of a captive Himalayan Cuckoo Cuculus saturatus, which suddenly spread its wings and tail in a threatening attitude to my finger, thus displaying the hawk-like pattern of underwing and tail. This was very similar in appearance to a photograph of Accipiter nisus in a treatening posture. In that note I mention that the hawk-pattern of birds of prey may have an intimidatory effect against the prey (even to human eyes), and here I want to extend this idea a little more. The hawk-pattern, the bold black barring on white, is more distinct on the under-than upper-surface of the wings and tail of the birds of prey, and this pattern is most strikingly exhibited at the moment when they swoop down upon the prey with fully spread wings and tail (as is often shown by excellent photographs). After they have caught the prey, their wings and tail are kept spread to help maintain balance over the struggling victim, and their underwing hawk-pattern should further intimidate the prey, and thus facilitate the kill. If this is so, the hawk-pattern should be found better developed, as the result of natural selection, in the species which pursue prey of their own size and are therefore more difficult to kill. We can say that this is generally the case in Falco, Accipiter, Spizaetus, and notably in the mighty Crowned Eagle Stephanoaetus coronatus or the Harpy Eagle Harpia harpyja; while the pattern is not so marked in many Buteo species or kites, etc. which chiefly prey on rodents or reptiles, nor in fish-eating sea-eagles (though the Osprey Pandion haliaetus is hawk-patterned) and carcass-eating vultures and condors, although there are exceptions to this rule (e. g. the Golden Eagle Aquila chrysaetos which is however considered to have evolved from smaller species (A. pomarina, etc.) that only prey on weakened animals). The above suggestion could be demonstrated if birds reacted to hawk-patterned models more than to non-or less markedly patterned ones. This I tried only tentatively with a tame jay and a few other cage birds, but with inconclusive results. However, such experiments