Sketches of Spanish Bird-Life 401 



quoted was at first at fault. For the great spotted cuckoo differs 

 ill one essential point from that " wandering voice " with which we 

 are familiar at home. The latter deposits a single egg in casual 

 nest of titlark, hedge-sparrow, wagtail — in short, of any small Ijird, 

 regardless of the fact that its own egg may differ conspicuously 

 from those of its selected foster-parent. The spotted cuckoo is 

 more circumspect. Everywhere it restricts the delegated duty to 

 some member of the Corvidae,^ and in Spain exclusively to the 

 magpies. Moreover, whether by accident or evolution, the cuckoo 

 has so admirably adapted the coloration of its own egg to resemble 

 that of its victim, as to deceive even so cute a bird as the mao-pie. 

 Earlier ornithologists (as above suggested) failed for a moment to 

 distinguish the difference — it was, in fact, the zygodactylic foot 

 of an unhatched embryo that first betrayed the secret (Tristram, 

 Ihis, 1859). On close examination the cuckoo's eggs difter in their 

 more elliptic form and granular surface ; but, unless previously fore- 

 warned and specially alert, no one would suspect that these were 

 not magpies' eggs, any more than does the magpie itself. 



The spotted cuckoo deposits two, three, and even four eggs in 

 the same magpie's nest, sometimes leaving the lawful owner's eggs 

 undisturbed, in other cases removing all or part of them — we have 

 noticed spilt yoke at the entrance. It would appear difficult, in 

 these domed nests, for the young cuckoos to eject their pseudo- 

 brothers and sisters ; but this detail of their life-history remains, 

 as yet, unsolved. 



Crossbills. — Nature delights in presenting phenomena which 

 no tangible cause appears to warrant. Such were the thrice- 

 repeated invasions of Europe by " Tartar hordes " — they were 

 only sand-grouse — that occurred during the past century (in 

 1863, 1872, and 1888) ; and in 1909 an analogous problem, 

 though on minor scale, was offered by crossbills. From north 

 to extreme south of our Continent these small forest-dwellers 

 precipitated themselves bodily westwards. This was in July. 

 All the west - European countries, from Norway to Spain, 

 recorded an unwonted irruption. In Andalucia (at Jerez) 

 crossbills were first noticed about mid-July, and their appearance 

 so impressed country-folk little accustomed to discriminate small 

 birds, as to suggest to them the idea that the strangers must 



^ In Egypt the hooded crow {Corvus comix) is invariably the cuckoo's diijie ; in Algeria, 

 Pica mauretanica. 



'2 1) 



