158 THE NESTS AND EGGS OF BRITISH BIRDS. 



Rivelin valley, in South Yorkshire, in a rotten stem of a 

 silver birch, the wood so brittle as to crumble away like 

 paper. The hole is at various heights from the ground, 

 sometimes but a few feet, at others as much as twenty 

 feet. The nest is a loosely-made structure, composed of 

 dry grass, dead leaves, and moss, lined either with fine 

 roots, horsehair, wool, or feathers sometimes with two or 

 more of these substances. The birds never make a hole 

 for themselves, neither do they alter a selected site in 

 any way. The bird is a close sitter, often allowing itself 

 to be taken from the eggs ; it is not at all demonstrative 

 at the nest. 



RANGE OF EGG COLOURATION AND MEASUREMENT : 

 The eggs of the Pied Flycatcher are from five to eight 

 or even nine in number. They are uniform pale blue 

 in colour. It is said that sometimes a few spots occur, 

 but I have never seen anything of the kind. Average 

 measurement, 7 inch in length, by '54 inch in breadth. 

 Incubation, performed by both sexes, lasts fourteen 

 days. 



DIAGNOSTIC CHARACTERS: It is impossible to dis- 

 tinguish eggs of the Pied Flycatcher from those of the 

 Redstart, so that they require the greatest care in their 

 identification. 



