Juvenile age classes contribute measurably to population growth and survival of long-lived species: Case study of chick mortality on albatross population stability

Adult mortality is considered a major threat to population survival for long-lived species with low annual fecundity and high adult survivorship.  However, for albatrosses, long-lived seabirds that raise at most one chick per year, mortality of juvenile age classes can measurably impact population growth and stability and therefore warrants the attention of conservation programs. Lead-based paint is a known cause of mortality for Laysan albatross (Phoebastria immutabilis) chicks on their primary breeding ground, Midway Atoll, part of the Hawaiian archipelago. We used population viability analysis (PVA) to explore the relationship between lead poisoning of albatross chicks and population growth. As many as 10,000 albatross chicks per year are lead poisoned, resulting in substantial reduction in Laysan albatross annual growth rate (lambda) using a demographic population-based model. The reproductive value of approximately five chicks is equal to one adult, demonstrating how juvenile mortalities, traditionally considered to have a negligible effect on population growth for long-lived species, may be important for long-lived species with low annual fecundity. Our results point to the benefits of reducing and/or eliminating logistically straightforward threats to juvenile age classes while efforts are underway to prevent adult mortalities through more complicated processes such as a reduction in international bycatch rates