Seabirds such as the black-legged kittiwake breed in colonies distributed around the coast, that are connected through the movement of individuals—particularly young birds seeking breeding locations. In such metapopulation networks, colony prospects depend on both local growth and exchanges with other colonies. Despite this, most population viability analyses (PVAs) for seabirds have treated colonies as isolated units, assuming that their growth is unaffected by how crowded or sparse they are. These simplifications may lead to inaccurate assessments of viability, risk, and recovery potential.

This matters for the kittiwake, a red-listed UK species in long-term decline. Conservation efforts have typically focused on colonies within Special Protection Areas (SPAs), yet many important colonies fall outside the SPA network. Little is known about how colonies are linked, whether non-SPA colonies support protected ones, or how the entire system responds when colonies experience disturbance.

To address these shortcomings, we developed the first seabird metapopulation model to integrate three crucial features:

• Connectivity, or the exchange of individuals between colonies;
• Multiple forms of density dependence, including limits imposed by nest-site availability, competition for food at sea, and Allee effects—processes that hinder the growth of very small colonies; and
• Floaters, non-breeding, surplus adults that could help stabilise colony numbers after high mortality events.

We assembled nearly four decades of data (1985–2023) from colonies across the UK and Ireland, including information on population size, breeding success, survival rates, and bird movements derived from ringing projects. We then evaluated three versions of our modelling framework, each differing in how demographic rates were grouped across regions. All versions produced a consistent conclusion: the kittiwake metapopulation has been in long-term decline, with only limited persistence observed in central and eastern Britain.

Using the most parsimonious version of the model, we projected the next 50 years under conditions without major environmental change. These forecasts suggest continued declines across all colonies, with connectivity offering little relief because the entire metapopulation functions as a set of sink colonies—sites that would require external donations to persist.  

We then examined what demographic improvements would be required to reverse these trends. Adjustments to breeding success, adult survival, juvenile survival, and floater survival were tested in various combinations. Adult survival emerged as the most influential driver of long-term recovery. We also evaluated potential management interventions, including artificial nesting structures, and provided a framework for assessing where such measures may offer the greatest benefit.

In summary, our findings indicate that reversing widespread decline will require substantial and coordinated improvements across the metapopulation. Nonetheless, a thorough understanding of connectivity and density dependence—particularly the challenges faced by small colonies—is essential for developing effective conservation strategies. While our modelling framework represents a significant advance, further refinement is needed, especially through the incorporation of environmental drivers such as climate and ocean change, and by linking specific conservation actions to measurable demographic benefits.