194 THE ZOOLOGIST. 



ON THE INTERBREEDING OF THE SONG-THRUSH 

 AND BLACKBIRD IN MIDDLESEX. 



By Gilbeet E. Adamson. 

 (See. Middlesex Zoological Society ; Soc. d'Orn. Eur.). 



In March, 1910, I found a nest of the Song-Thrush {Turdus 

 musicus) in a lane leading from Edgware to Elstree, about three- 

 quarters of a mile south of Edgwarebury. It contained three 

 eggs, which bore a very strong resemblance to those of the Red- 

 wing {T. iliacus). As the winter had not been particularly 

 severe, I conjectured that a straggling pair might possibly have 

 remained in England to breed. Richard Jeffries has recorded 

 this from Surrey ('Wild Life in a Southern County,' chap. xvi.). 

 I, accordingly, awaited the return of the parent birds. In a few 

 minutes the mother bird returned, and I was rather surprised to 

 find that she was not a Redwing, but a mature and healthy Song- 

 Thrush. Shortly afterwards she was joined by her mate, a male 

 Blackbird {T. merida). Upon my approaching the nest the two 

 birds flew to an adjacent hedge. The nest was a typical nest of 

 the Song-Thrush, lined with the usual layer of mud. I took one 

 of the three eggs, and noted the following points of difference : — 



Normal T. musicus. Normal T. merula. Hybrid. 



Ground colour : — Light greenish blue . . Light greenish Whitish green 



Markings: — Deep brown ; not clus- Deep brown; clus- Light brown ; clus- 



tered tered tered 



Size :— 28 x 20 mm 28 x 22 mm 29 x 21 mm. 



Shape : — Polycinic* Polycinic Chenistic* 



This occurred on Marish 30th. On the following Tuesday 

 another egg resembling the former three in size and appearance 

 was laid, after which the nest was abandoned. I am inclined 

 to think that the egg last laid was never incubated, but the first 

 three undoubtedly were. In all these cases of interbreeding I 



* Polycinic: The usual " egg-shape " {TurdidcB,&c.). Aethistic : Shape 

 of the eggs of the Gull tribe. Eotund: Round (Strigidce). Isoplatic: Of 

 equal width {Alcedinidcs). Chenistic : Shape of eggs of the Goose tribe 

 (Anseridce). Pyriform: Pear-shaped (C/iaracZrufZ^, &c.). 



