POPULATION DYNAMICS OF DUCKS AND GEESE 95 



work on 'island' colonies has yielded data from which the rate of loss after 

 hatching and before fledging can be assessed. 



A. Watson: Do the figures take into account total loss of broods 

 through the death of females? 



H. Boyd: Yes. 



J. G. Skellam: Are the estimates of the numbers reaching maturity, 

 based on the progeny of a hundred breeding females, and the other estimates 

 of adult survival rate independent ? Do they agree, when taken together, and 

 show a steady state for the population? 



H. Boyd: Yes. 



J. C. Coulson: You have made a distinction between clutch sizes in 

 ducks and geese. Is this hard and fast separation really vahd? Surely sea- 

 ducks, like eider and scoters, are intermediate? The eider clutch size averages 

 about five in my experience — which is near to the goose range. 



H. Boyd: The clutch size in eider is very variable. But I think they 

 accord fairly well with my figure on the whole and normally fall within 

 the duck range. 



