Breeding biology and behaviour of the common murre (Uria aalge aalge (Pont.)) on Gull Island, Newfoundland

Abstract

The breeding biology and behavior of the Common Murre (Uria aalge aalge (Pont.)) was studied on Gull Island, Newfoundland during May through July in 1977 and 1978. -- The origin of the Gull Island population was discussed as were the ledge population changes recorded over the breeding season. Reasons for the different patterns of attendance were suggested. -- Breeding phenology was studied in detail. Eggs were weighed and measured and a number of the attributes (shape, volume etc.) were determined. Eggs of known age were collected, their embryos removed and their developmental patterns determined. Numbers of eggs laid and the chronologies of laying for both seasons were compared. Weights of eggs from replacement clutches and the time required to replace a clutch were defined. -- Chicks were measured to calculate growth curves for weight and a number of other body parameters. Numbers of chicks were compared for both seasons as were the growth curves of chicks from both years. Fledging of chicks was recorded and observations were made on adult and chick behavior at fledging. Different fledging schedules for both years were noted and possible reasons for the differences were suggested. -- Breeding success, expressed as the numbers of pairs successfully fledging a chick, was recorded. Causes of egg and chick loss were recorded and the influence of predation was discussed in detail. -- Observations were made on behavior with particular attention being paid to those displays which involved characters of aggression. These displays were noted and their postures illustrated. The effects of high density nesting on the evolution of behaviour was discussed. -- Results indicated that murres on Gull Island attained breeding success rates comparable with other areas but lower than most. Birds breeding at higher densities and on longer-established of “safe” ledges were most successful. Murres in this colony demonstrate a wide range of conflict behaviours with numerous appeasement displays functioning to maintain low levels of high intensity aggression.