Breeding together: modelling synchrony in productivity in a seabird community

With environmental conditions changing rapidly, there is a need to move

beyond single-species models and consider how communities respond to environmental

drivers. We present a modeling approach that allows estimation of multispecies synchrony in

productivity, or its components, and the contribution of environmental covariates as

synchronizing and desynchronizing agents.

We apply the model to long-term breeding success data for five seabird species at a North

Atlantic colony. Our Bayesian analysis reveals varying degrees of synchrony in overall

productivity, with a common signal indicating a significant decline in productivity between

1986 and 2009. Productivity in seabirds reflects conditions in the marine ecosystem so the

estimated synchronous component is a useful indicator of local marine environment health.

For the two species for which we have most data, the environmental contribution to overall

productivity synchrony is driven principally by effects operating at the chick stage rather than

during incubation. Our results emphasize the importance of studying together species that

coexist in a community. The framework, which accommodates interspecific clutch-size

variation, is readily applicable to any species assemblage in any ecosystem where long-term

productivity data are available.