70 BllITISH BIRDS. [vol. xv. 



Sheld-Duck Nesting in Nottinghamshire.— Lt.-Col. 

 W. Coape Gates records {Field, July 2nd, 1921, p. 33) that a 

 pair of Sheld-Ducks {Tadorna tadorna) this spring frequented 

 his meadows adjoining a large sheet of water called Besthorpe 

 Fleet. They eventually nested in a large rabbit warren, 

 and on June 12th the 'duck was observed conducting ten 

 young ones towards the water. Col. Gates states that the 

 place is thirty-seven miles from the sea and that the birds 

 were wary and undoubtedly wild ones. 



Nesting Status of the Black-headed Gull in 

 Yorkshire.— Mr. H. B. Booth gives details {Nat., 1921, 

 pp. 159-166) of the Yorkshire nesting colonies of Lay us 

 ridibundus. 



I.ETTEHS. 



PARASITISM OF GULLS ON DUCKS. 



To the Editors of British Birds. 



Sirs, — In Vol. XIV., p. 260, instances were given of parasitism of 

 Black-headed Gulls on Tufted Ducks. I have seen similar cases with 

 the Cxlaucous-winged Gull {L. glaxtcescens) and the American Golden- 

 eye [B. clangula americana) on the river here (Courtenav, Vancouver 

 Island, B.C.). 



There is a big run of salmon up this river in the autumn which, 

 dying after spawning, sink or are washed up on the banks and provide 

 food for hundreds of Gulls (chiefly Glaucous-winged), Goldeneye, 

 Mergansers and other duck. The Goldeneye feed on the dead fish 

 lying on the bottom of the river, diving down, tearing a piece of the 

 rotten flesh off and coming up to the surface to eat it. I have on 

 several occasions seen a Glaucous-winged Gull swimming by a feeding 

 Goldeneye, watching its every move and as it returned to the surface 

 make a dart at the duck, and so causing it to drop the piece of fish, 

 which was at once picked up by the Gull. 



There is just a question in my mind whether this was really a case 

 of parasitism ; the Gulls I saw doing this were invariably either 

 birds of the year or a year old, and particularly in the birds of the year 

 there was a suggestion that they looked on the Goldeneye in loco 

 parentis to provide food. The time when my attention was particu- 

 larly drawn to the habit was in the late winter of 1919-20, when the 

 only fish left were those at the bottom of the river and when food was 

 getting scarce 



Here one might almost call the Bonaparte's Gull (L. phU adelphia) 

 (the counterpart of L. ridibundus) parasitic on the dog salmon, as 

 they hover over the spawning fish, watching for eggs to escape as 

 deposited, to get which they plunge right under the surface of the water. 

 There were hundreds (even thousands) of these Gulls picking up the 

 stray salmon eggs on this river last autumn when the run of the dog 

 salmon was exceptionally heavy. Theed Pearse. 



COURTENAY, B.C. 



