Double Brooding in Cassin's Auklets
A common strategy for maximizing reproductive output in birds is to produce two broods in a single season, a behavior known as double brooding. Cassin’s auklets (Ptychoramphus aleuticus) are the only seabird in the northern hemisphere to regularly use this strategy; however, the proportion of breeding pairs that attempt double brooding is highly variable among years. Point Blue Conservation Science has carried out a continuous monitoring effort of Cassin’s auklets on Southeast Farallon Island (SEFI) since 1972. Information on reproductive timing, parental age, sex, nesting attempts and successes has been collected from over 900 known-age birds that have breed in artificial nest boxes since research first began on the Farallones. I am currently using these data to determine the environmental and demographic drivers of double brooding, and test whether the added effort of double brooding multiple times over a lifetime effects survival and longevity of this species.
Johns ME, Warzybok P, Bradley RW, Jahncke J, Lindberg M, Breed G. In Prep. Double brooding associated with greater survival and higher fitness in Cassin's Auklets.
Johns ME, Warzybok P, Bradley RW, Jahncke J, Lindberg M, Breed G. 2017. Age, timing, and a variable environment affect double brooding in a long-lived seabird. Marine Ecology Progress Series. 564: 187-197. https://doi.org/10.3354/meps11988 : Full Text
Winter Movements of Cassin's Auklets
Understanding the distribution and habitat needs of seabirds is essential for effective long-term management. Until recently, studies of long-term movements have been restricted to species with sufficient mass to carry GPS or similar satellite tags. Miniature archival global light sensing tags, or “geolocators”, are an alternative to heavier restrictive devices that have been widely used in tracking studies on small bird species. Unlike global positioning systems, geolocators record the timing and duration of ambient light levels, which are later used to estimate daily latitude and longitude positions over long temporal periods. Cassin’s auklets are an ideal candidate for the application of geolocators. Much is known about the conditions they experience during the summer season, where they breed on offshore islands and isolated headlands from Baja California, Mexico, to the western Aleutian Islands of Alaska. Little is known, however, about the lives of these birds once they depart their respective breeding colonies.