Local population collapse of Ross's and lesser snow geese driven by failing recruitment and diminished philopatry

Dynamics of free-ranging animal populations can result from complex interplays survival, recruitment and movement. Yet incomplete understanding demography impedes conservation strategies intended to modify population dynamics focal species. We estimated survival per capita production young, as well emigration immigration, 1997 2017 in Ross's goose Anser rossii lesser snow caerulescens caerulescens, which are sympatric species migratory birds that nest the central Canadian Arctic at one largest breeding colonies North America. formed age-structured integrated models (IPMs) for each jointly analyzed live dead encounter data adult size fecundity understand drivers dynamics. compared between because both increased during 1990s early 2000s yet thereafter geese declined, while continued increase, then stabilized similarly declined. Declines were caused by reduced juvenile emigration. Stronger declines explain their earlier decline geese. Despite divergence trends geese, we found strong synchrony demographic rates suggested substantial this colony similar responses environmental conditions. Direct estimation patterns IPM framework permitted hypothesis testing inference about role even though immigrant sources unsampled. provide a novel m-array implementation specific multi-state Burnham model greatly improved computational efficiency convergence posterior estimates. Our findings an important reminder permanent movements play metapopulation structure.