68 Proceedinr/s of the Royal Physical Society. 



YIII. Variation in the Phtmage of the Common Rook 

 (Corvus frugilegus, Linn). By Professor Duns, D.D., 

 r.R.S.E. 



(Read 20th March 1889.) 



I had occasion recently to inquire into the seasonal 

 changes of colour in the varying hare {Lepus variablis), and 

 to review the data which some think warrant the inference 

 of identity with the Irish hare (X. Hihernicus) , but which 

 others hold to point to relationship with the common 

 species (X. timidus) — a form subject to occasional white 

 variation. More weight is given in the latter case to the 

 colour element than to features which are both persistent 

 and better marked. I refer to this with the view of 

 indicating that such variations are of no value in deter?- 

 mining family relationship. They have no meaning beyond 

 the individual instance. The only question of interest 

 raised by them relates to the cause of departure from the 

 normal colour — a departure which is more frequent among 

 birds than mammals. But my present object is not the 

 explanation of the variation — it is only the statement of 

 it as a fact common to the Corvidce, and, chiefly, to one of 

 the best known of the family — the Eook. 



The bird now on the table belongs to Mr J. D. F. 

 Gilchrist, M.A., one of my students. It was shot in 1888 

 about two miles north of Anstruiher, Fife ; probably a bird 

 from the Kookery at Kilrenny. The colour is a bright 

 dark brown, with here and there, as on the wing coverts, 

 slight, almost doubtful, shades of black. The bill, legs, and 

 claws are of the same hue. This as a variation colour is 

 not, so far as I remember, common. I have a record of it 

 in the Eaven (C. corax), and a fine instance in a Skylark, in 

 my possession. 



For about six weeks in the beginning of this winter an 

 interesting variety of rook was frequently seen in the 

 gardens of Greenhill Place. It may be best described by 

 saying that its colours were similar to those of the Grey 

 Crow {C. comix), only the head and body were black and 



