Mimicry of Cuckoos 265 



The likeness is truly remarkable — grey colour above — 

 rufous bands on breast — yellow eye — banded tail — and bars 

 on the latter. To complete the similitude the Cuckoo has 

 large overhanging feathers on the thigh, just as in a Spar- 

 row-hawk. Our common Cuckoo {Ciiculus caiioriis) also so 

 closely resembles the Sparrow-hawk in appearance and still 

 more in flight, that small birds mob both of them impar- 

 tially, and the appearance of a Hawk or a Cuckoo is the 

 signal for every Swallow and Martin in the neighbourhood 

 to join in the assault, unheeded in the case of the Cuckoo, 

 but sometimes resented, and with fatal effect to one of its 

 assailants, by the Sparrow-hawk. To an unpractised eye 

 it is difficult to distinguish the latter from a Cuckoo in full 

 flight, and the small birds seem to be unable to tell the one 

 from the other, unless it be that their instinct leads them to 

 regard both as their natural enemies, and to attack them 

 equally on that account. 



An e.xact copy of a large crested Hawk-eagle {Spisactus 

 ornatus) exists in some South American countries in a 

 Goshawk {Astur pectoralis), but whereas the latter is one of 

 the rarest of Accipitrine birds in collections, the Hawk- 

 Eagle is comparatively a common bird. Again, in the 

 Island of Celebes in the Moluccas, a Hone)--Kite {Pernis 

 celebensis), a comparativel)' harmless insect-eating species, 

 is an exact mimic of the Crested Hawk-Eagle of the 

 island {Spizai'tus lanceolatiis), and this not only in the adult 

 but also in the young stages of plumage. In Borneo, the 

 dark form of the Honey-Buzzard of the country {Pernis 

 ptilonorhynchns) is almost an exact copy of the Hawk- 

 Eagle {SpizactHs alboniger) which inhabits the same dis- 

 tricts. Thus one may ask whether, in these instances of 

 apparent " mimicry " between species inhabiting the same 

 tropical areas, it may not have been induced by a combina- 

 tion of circumstances in their surroundings, which may 

 have resulted in a similar change of plumage being adopted 



