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. 



