Family BUBONIDAE. 



Syrnium aluco (L.) — Tawny Owl. 



(Plate 98, fig. a-c). 

 (Snouckaert: Avifauna Neerlandica, p. 62, No. 148). 



Colour of surface of shell: 



Average dimensions: 

 Average weight of shell : 

 Texture of shell: 

 Shape: 



Nest: 



Site of nest: 



Number of eggs: 

 Breeding season: 

 Duration of incubation: 



white. 



Thienemann 1 ), only, distinguishes - rightly, 

 I believe - two types in respect of tint: 

 1°. pure white, and 2°. dirty white (grey- 

 yellowish) eggs ; the shade, mentioned 

 under 2°. has in my opinion no connection 

 with any change which the eggshell under- 

 goes through incubation, but is proper to 

 it „ab utero". 



Brownish spots, which these eggs frequently 

 exhibit, arise from impregnation with humus 

 acids from the decayed parts of plants on 

 which the eggs lie. 



47 X 37.9 millimetres. 



2.8 grams. 



see the general review of the Family. 



the ends of the eggs are mostly both of the 

 same shape. 



the eggs lie on a layer consisting of a little 

 moss, a few stalks and feathers, or they 

 lie immediately on decayed wood. 



in hollow trees; also in deserted nests of 

 Crows and Birds of Prey, and in holes in 

 the ground, e.g. in rabbit burrows. 



3—5. 



March— beginning of May. 

 3 to 4 weeks. 



l ) Systematische DarstellungderFortpflanzungder VogelEuropa's (Leipzig, 1825). 



