( 246 ) 

 ERYTHRISM IN THE EGGS OF BRITISH BIRDS. 



BY 



The rev. F. C. R. JOURDAIN and CLIFFORD BORRER. 



Although many scattered notes on this subject may be 

 found in the various ornithological journals, very little has 

 hitherto been done to collect these separate records ; and 

 beyond a short note by Adolf Kricheldorff in the Zeitschrift 

 fur Oologie, XIII., Jahrg., p. 10 (1903), " Ueber vote Varia- 

 tionen der Vogeleier," and a paper by F. C. R. Jourdain 

 " On Colour Variation in the Eggs of Palsearctic Birds," 

 which appeared in the Proceedings of the 4ih International 

 Ornithological Congress, 1905, pp. 580-93, there is practically 

 no literature on the subject. 



In the present paper we have treated in detail those 

 cases where either a definite type, or, at any rate, a variety 

 of the egg, has been recorded in which the colouring 

 matter consists of oorhodein alone, i.e. the markings are 

 of shades of red or reddish-brown only, but the range of 

 colour -variation in the species includes eggs which are also 

 coloured with biliverdin (bile pigment), either alone or 

 with other colouring matter, to form the various shades 

 of blue and green. 



For this reason it has not been thought necessary to 

 notice such eggs as those of the Accipitres, which are 

 normally marked with red, and only rarely show traces 

 of any other colouring matter, though in the literal sense 

 they are, of course, erythristic. In Section II. we have 

 briefly dealt with those species which normally lay white 

 or blue eggs, but occasionally produce specimens more or 

 less distinctly marked with red or red-brown. 



Section I. 



Raven {Corvus c. corax). — One set of erythristic eggs 

 was taken in 1854 in Unst, Shetland, and is now in the 

 Cambridge University Museum {Ootheca Wolleyana, Vol. I., 

 p. 524, §2796).* 



Hooded Crow (C. c. comix). — ^A clutch of five erythristic 

 eggs, obtained about 1887 near Gothenburg, Sweden, by 

 J. Ramberg, is now in the Gothenburg Museum. A set 

 of three dull brick -red eggs was taken at Dunessan, Mull, 

 about May 1st, 1877 (R. H. Mitford, Zoologist, 1882, p. 69). 



* The red variety is also said to have occurred in the Canarian 

 Raven (C corax canariensis). 



