Demographic consequences of early development and extreme climate events for alcids on Triangle Island, British Columbia

In long-lived species like seabirds, population growth rate is most sensitive to changes in adult survival, although juvenile survival and recruitment can also be important. The reproductive success of seabirds often varies greatly depending on climate-driven food availability, but less is known about juvenile and adult survival of seabirds. Females of the small-bodied, zooplanktivorous Cassin’s Auklet (Ptychoramphus aleuticus) had high mortality in extreme climate years. In contrast, adult survival of two larger-bodied, more piscivorous species, Rhinoceros Auklet (Cerorhinca monocerata) and Tufted Puffin (Fratercula cirrhata) showed no adult survival response. Furthermore, we demonstrate that even in two of the most successful years on record for Tufted Puffin reproduction, the juvenile survival of each cohort can differ greatly. Early development, reflected in fledging wing length and mass, impacted juvenile survival and the age at which individuals returned to their natal colony.