CHAEADEIITS. 



161 



Insular 

 forms. 



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



/•.ol (i i ci"ri nil - 



species are generally smaller than their continental allies ; for example, the Merulce 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 

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

 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 Fiji 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 PLOVER. 



Charadrius, subgen. JEgialophili minores, pedibus pallidis : pectoris lateribus pallidis vix. brunneo Diagnosis. 

 lavatis : nuchae collari 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, Traite d'Orn. p. 544 (1831). 

 Hiaticula marginata (Viei/I.), Gray, List Birds Brit. Mus. iii. p. 69 (1844). 

 Hiaticula leueopolia (Wayl), 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. 



