84 BRITISH BIKDS. [vol.xv. 



to " Black-eyed Susan." The difference, rendered semi- 

 diagrammatically, is as represented in the two sketches. 

 Fig. I shows the darkly-pigmented iris, and Fig. 2 the 

 hyahne, practically unpigmented iris of the normal bird. 

 In both the shaded outer ring represents the ring of bright 

 blue naked skin which surrounds the eye, and which is quite 

 normal in the dark-eyed bird. 



What the physiological significance of the deep-brown 

 pigmentation may be I am unable to say. Possibly it may 

 indicate a persistence of the iris-pigmentation of the newly- 

 hatched nesthng, which is described by E. T. Booth {Rough 

 Noies, III., " Gannet," p. 10) as dark hazel. At later stages 

 the iris of immature birds is described (Gurney, p. 491) as 

 ranging from pale grey at twelve weeks old, to purplish- 

 grey at seven months, so that, if it is a case of persistence 

 of an early condition, it must be from a very early, almost 

 embryonic, stage. 



The clever drawing of a Gannet 's head by Mrs. Hugh 

 Blackburn (Birds Draivn from Nature, 1862) suggests a dark- 

 eyed bird similar to the one I am referring to. But this is 

 evidently accidental, as the drawing was made from a 

 specimen picked up dead, and the appearance of the eye 

 seems to have been guessed at by the artist when filling in 

 the details. 



A point of considerable interest in regard to the dark-eyed 

 Gannet is the fact that " she " has returned to nest on the 

 identical spot in the gannetry which " she " occupied in 1914. 

 Mr. White, it is true, says that the bird was not occupying 

 this particular nesting-site from 1915 to 1919, so that there 

 appears to have been a break in the sequence ; but both in 

 1920 and 192 1 " she " nested within a foot or two of the 

 1914 site, and was again photographed there with "her" 

 young. This seems to suggest very strongly that individual 

 Gannets select, if possible, the old spots on the ledges, when 

 they renew nidification, and that there is a more or less 

 permanent- claim upon a given " pitch." The evidence of a 

 readily distinguishable bird is of importance in this connection. 



I am much indebted to Mr. White for having caught the 

 bird for me for close examination. After " her " detention 

 in the cause of science, against which " she " protested 

 vigorously and aggressively, " Susan " was carefully placed 

 upon the wall of the lighthouse terrace and, with a parting 

 arrah, sailed away in the direction of " her " nest. Very 

 shortly afterwards she was seen by my son on the nest, 

 apparently none the worse for "her" adventure. 



