VARIATION IN LAYING SYNCHRONY IN A SMALL HERRING GULL COLONY

I measured the laying span and laying synchrony in a small Herring Gull (Larus argentatus) colony over a 12-year period. Herring Gulls in the study colony adjust their onset of breeding in relation to prevailing ice-conditions, likely to escape predation, so that late springs lead to late breeding. Measured with the standard deviation of laying (Gochfeld 1980) synchrony varied in accordance with timing of laying, so that late initiation of nesting produced a higher degree of synchrony. Synchrony did not correlate with the number of pairs in the colony, and variation in synchrony is thus mostly a product of variation in environmental conditions. The level of synchrony did not affect production of young in the colony. The studied group of pairs was very synchronous compared with other studied Herring Gull groups, possibly because of the pronounced seasonality of the breeding environment they experience.