SIDE LIGHTS ON BIRDS 



that are normally green or blue, is denoted by the 

 term er3rthrism. In some species the red eggs 

 are so nrmierous that they constitute a type : in 

 others they exist but are of extremely rare occur- 

 ence. 



In the tree-pipit and red-backed-shrike the 

 tendency to lay " red eggs" is marked: in the 

 sedge-warbler, common tern, guillemot and lapwing 

 it occurs less frequently, and instances are recorded 

 in the case of the raven, hooded crow, rook and 

 magpie. The Rev. F. C. R. Jourdain has stated 

 that in the Cape rook, the red type is foimd to the 

 exclusion of the blue usually associated with the 

 race. 



Among the many departures from type that are 

 recorded are the eggs of house-martins, hedge 

 sparrows, and starlings, freckled more or less thickly 

 with red spots. 



42 



