550 Mr. D. A. Bannerman on the [Ibis, 



Archipelago, The island Blackcap {Sijlvia atricapilla oh- 

 scurci) probably occasionally inteibreetls with the typical 

 European species, which passes regularly through the islands 

 on migration. If these visitors to the island sometimes 

 interbreed with the residents, and we can hardly believe 

 tlint they do not, then the purity of the island races is 

 not ke[)t vip and intermediate forms are found. As this is 

 probably the case with the Blackcaps, at any rate, it may 

 explain why some systematists prefer to unite the Canarian 

 Blackcaps with the typical race on the ground that com- 

 plete intergradation exists. 



The case of the Canarian Chiffchaffs (P. c. canariensis and 

 P. c. exsid) is rather different ; these two forms are so 

 distinct that the European Chiffchaffs (P. coUybita collybita), 

 which pass regularly through the Archipelago on migration, 

 do not appear ever to interbreed with them. 



In a group of islands such as the Canaries we must 

 remember that Altitude plays its part, if only a small part, 

 in its bearing on the bird-life. It was long ago noticed that 

 the Quails inhabiting the higher ground in the Canaries 

 were of a darker and richer coloration than those in the 

 lowlandsj and it has now been estaijlished that this highland 

 Quail is a distinct subspecies — resident in the Canaries and 

 in the highlands of Madeira — Coturnix coturnix confisa. 



In 'The Ibis/ 1914, pp. 240-243 and again in this 

 paper (Part I., pp. 107-109) I have drawn attention to the 

 cui'ions fact that Corn Buntings living in the high lands 

 of Gran Cauaria (above 1500 feet), known as Emheriza 

 caJandra ihatweri, are darker than the Corn Buntings which 

 I shot on the coast, as can be verified by examining the skins 

 I obtained, in the National Collection. 



If the island of Tcnerife, which rises above 12,000 feet, 

 had been clothed with tropical vegetation we should find the 

 Zones of Vegetation more pronounced than they are at 

 present, and this would undoubtedly have influenced the 

 bird population more than is now evident, witness the re- 

 markable avifauna to he found on the (Cameroon Mountain, 

 13,353 feet (cf. Ibis, 1915, pp. 473-526). 



