WHITKTHROAT 489 



on the scarped faces of cliffs, as did swallows in caverns ; and there 

 are places where both species still follow the ancient fashion. At 

 the present da}', however, martins $^encralh' construct their nurseries 

 under the overhanging eaves of houses, stables, or other buildings ; 

 but it is noteworthy that for many years past they have completely 

 deserted numerous buildings where their nests were once common, this 

 being doubtless due to the great slaughter of these birds which now 

 takes place on the Continent. The well-known semi-globular nest 

 is constructed of small pellets of mud collected by the parent birds 

 on the margins of rivers, ponds, or wayside pools, and cleverly pressed 

 together. Entrance and egress are effected through a round hole in 

 the upper edge ; and inside the globe of mud is lined with grass and 

 a few feathers, upon which is deposited the clutch of from four to 

 six white eggs, easily distinguishable from those of the sand-martin 

 by the glossiness of their shells. Such an excellent domicile as a 

 martin's nest affords an irresistible attraction to the aggressive 

 sparrow, who frequently expels the rightful owner and takes up his 

 own quarters in the mud dwelling-place. It is said, indeed, that the 

 surest way to secure the presence of martins about a house is to kill 

 off the sparrows. 



ixri.-.. ..u .. With the whitethroat (Sylvia sylvia of some natural- 

 Whitethroat . ^ , . , ^ , r , , 



._ , . . V ists), which forms the type of the group commonly 



(Sylvia einerea). ^' ., ."^ . ,, 



known among ornithologists as warblers, we revert 



to birds with ten primary quill-feathers to the wing. Although the 

 warblers, constituting the family Sylviidai, differ from the members of 

 the thrush-type, in that the first plumage of the young is like that of the 

 adult female, only brighter, in place of being spotted, there can be little 

 doubt that thrushes and warblers are related groups. Indeed, it has 

 been proposed to include both in the family Turdidai. This is, how- 

 ever, perhaps going rather too far, although it must be confessed that, 

 apart from the difference in the plumage of the young, it is not easy 

 to define the distinctive characteristics of the two groups. Warblers 

 are, however, smaller birds than thrushes, and in the British representa- 

 tives of the group, at all events, the front surface of the shank of the 

 leg shows more or less clear indications of being divided into large 

 transverse scales, in place of being wholly smooth. As a rule, the beak 

 is weak and slender, with a small notch near the tip of the upper half, 

 and there are frequently bristles at the gape ; these bristles may, 

 however, be wanting, while the beak may be broad and flat and devoid 

 of a notch. A distinctive feature of the group is to be found in the 



