380 BRITISH BIRDS. 



Genus HYPOLAIS. 



The Tree- Warblers were included by Linnaeus in his comprehensive 

 genus Motacilla. Bechstein afterwards placed them in the genus Sylvia, 

 which Scopoli had made for the Warblers. Various writers have at 

 different times separated the Warblers into different groups, amongst 

 whom was Brehm, who, in the ' Isis ' for 1828, p. 1283, founded the genus 

 Hypolais for the Icterine Warbler, which therefore becomes its type. 

 Brehm, following Linnaeus, misspelt this word "Hippolais," under a 

 mistaken idea of its derivation. 



The genus Hypolais contains a small group of birds chiefly remarkable 

 for laying eggs having a French-grey or salmon-coloured ground-colour. 

 They form the connecting-link between Phylloscopus and Acrocephalus, 

 having the nearly even tail of the former and the large bill of the latter. 

 From the large-billed subgeneric group of the former (Acanthopneustes}, 

 besides the difference in the coloration of the eggs already alluded to, 

 they can only be distinguished by the absence of the pale tips to the wing- 

 coverts which in Acanthopneustes form one, and often two pale bars across 

 the wings. There are four well-defined species belonging to this genus, 

 three of which do not exhibit any great variation of size, wing- formula, or 

 colour. The other species is perhaps more variable than any other member 

 of this large subfamily, and may be divided into six or more races, which 

 are tolerably distinct, although connected together by intermediate forms. 



The Tree-Warblers frequent wooded localities, bush-covered marshy 

 districts, gardens, and thickets. All the species of this genus possess con- 

 siderable powers of song. They build beautiful cup-shaped nests ; and their 

 eggs are from four to six in number. Their food is chiefly composed 

 of insects, which they search for amongst leaves and twigs and frequently 

 capture in the air. 



The basin of the Mediterranean appears to be the centre of distribution 

 of this genus one or two species extending their range more to the east, 

 one of them as far as Lake Baikal. One species only is a rare straggler to 

 the British Islands. 



