Every-other-day clutch-initiation synchrony in ring-billed gulls (Larus delawarensis)

Fraser Darling suggested that reproductive synchrony enhances reproductive success of colonial seabirds as a result of predator satiation. However, the cost of yearly reproductive synchrony is high for colonial species for which intraspecific predation is the primary cause of egg and chick loss. A few studies indicate that egg-laying synchrony on a daily time scale within the annual breeding pulse may be an adaptive response to intraspecific predation. Here, we report everyother-day clutch-initiation synchrony in densely nesting cohorts of Ring-billed Gulls (Larus delawarensis). This is the second known case of clutch-initiation synchrony on a daily time scale in larids, the first being for Glaucous-winged Gulls (L. glaucescens). In both Ring-billed Gulls and Glaucous-winged Gulls, the degree of clutch-initiation synchrony is inversely related to nearest neighbor distance. Further studies are needed to test whether clutch-initiation synchrony in Ring-billed Gulls is adaptive in the presence of cannibalism, or if it is simply a neutral byproduct of colonial nesting. Received 10 July 2015. Accepted 7 January 2016. Key words: clutch initiation, egg laying, Fraser Darling effect, Larus delawarensis, Ring-billed Gull, synchrony.
Fraser Darling (1938) famously argued that if an individual synchronizes its reproductive efforts in time and space with others of the same species, its offspring will be more likely to [...]