CHAEADEIUS. 



161 



It IS described as an inland bird, but confined to the island of St. Helena. Island treograplu- 



n nil- • 1 11- n n cal clistribu - 



species are generally smaller than their continental allies ; tor example, the MerulcR of tion. 



Ceylon and the Fiji Islands are smaller than their very close allies in the Himalayas and 



China, and the Little Ringed and Kentish Plovers of Ceylon are both small races of 



Palsearctic species. The cause of all these variations of size is probably a climatic one, and insular 



has no relation to the insular or continental locality. Merula and Charadrius are both forms. 



arctic genera, and the smaller species are small not because they live on islands, but 



because they are somewhat out of their element in tropical climates. The mean 



temperature of Ceylon and the Piji Islands is 78°, at least 10° higher than that of the 



Himalayas or South China, The mean temperature of St. Helena is about 10° lower than 



that of West Africa, so that C. pecuarius, when it emigrated to St. Helena, found a more 



congenial climate, and did not decrease in size as the descendants of the birds which 



remained in the tropics were obliged to do. 



The much more rounded wings of the St.-Helena species may be accounted for by the 



comparatively equable climate of the island making it unnecessary for its bird population 



to wander far in search of food, or periodically to change their residence. 



CHARADRIUS MARGINATUS. 



WHITE-BREASTED PLOFEB. 



Chaeadrius, subgen. jEgialopMU minores, pedibus pallidis : pectoris lateribus pallidis vix brunueo Diagnosis, 

 lavatis : nuchse coUari albo obscurissimo. 



Tropical forms of this species are smaller and have much less white on the inner Variations. 

 secondaries, and may consequently be regarded as subspecifically distinct. 



Charadrius marginatus, Vieillot, N. Diet. d'Hist. Nat. xxvii. p. 138 (1818). 

 Charadrius leucopolius, Wagler, Syst. Av. p. 65 (1827). 

 Charadrius nivifrons, Cuvier,fide Lesson, Traited'Orn. p. 544 (1831). 

 Hiaticula marginata {Vieill.), Gray, List Birds Brit. Mus. iii. p. 69 (1844). 

 Hiaticula leucopolia {Wagl), Lichtenstein, Norn. Av. p. 94 (1854). 

 Leucopolius nivifrons [Less.), Bonap. Compt. Rend, xliii. p. 417 (1856). 

 iEgialitis marginatus {Vieill.), Hartlaub, Orn. Westafr. p. 216 (1857). 



Synonymy. 



