Family CORVIDAE. 



Corvus frugilegus L. — Rook. 



(Plate 1, fig. a-d). 

 (Snouckacrt: Avifauna Neerlandica, p. 8, No. 4). 



Colour of surface of shell 



Colour of spots: 



Average dimensions: 

 Average weight of shell : 



Texture of shell: 



Shape : 



Nest: 



Site of nest: 



Number of eggs: 

 Breeding season: 

 Duration of incubation: 



green, in various variegations; blue (= cy- 

 anic) or bluish white (= leucitic objects); 

 mostly of a lighter shade than those of 

 corone. 



olive in various green and brown shades; 

 sometimes a few pitch-black spots on the 

 outermost (glutinous) layer; when lying 

 deeper they are of a grey appearance. 



40.25 X 27 millimetres; as a rule, therefore, 

 smaller than those of corone. 



1.08 grams; this smaller weight is one of 

 the most decisive criteria for determinat- 

 ion against corone. 



has no special characteristic. 



oblong oval, or more shortened. 



consists of dry twigs, sticks and lumps of 

 earth ; lined with dry grass, roots, and 

 straw, sometimes wool. 



by preference in very tall trees, in colonies, 

 which are sometimes joined by jackdaws. 



4—5, sometimes 6. 



about the middle of April— May. 



about 21 days. 



