Double Brooding in Cassin's Auklets


Cassin’s auklets are the only member of the Alcids (puffins, murres, auklets) known to regularly double brood, where a second late-season clutch is produced after the successful fledging of chicks from the first. Point Blue Conservation Science has carried out a continuous monitoring effort of Cassin’s auklets on the Farallones 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. These data were used to identify 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. 

Winter Movements of Alcids


Understanding the distribution and habitat needs of seabirds is essential for effective 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. Much is known about the conditions experienced by breeding alcids, such as Cassin's auklets, rhinoceros auklets, and pigeon guillemots, on the Farallon Islands during the summer season. Little is known, however, about the lives of these birds once they depart the breeding colony. Geolocators can shed some light on the non-breeding winter distributions of these species, and can help characterize key habitat as well as potential environmental and anthropogenic stressors. 


Johns ME, Warzybok P, Bradley RW, Jahncke J, Breed G. 201X. Winter dispersal and habitat preference of Cassin's auklets in the California Current System. In Prep. Target: Marine Ecology Progress Series.

Johns ME, Warzybok P, Bradley RW, Jahncke J, Lindberg M, Breed G. 2018. Increased reproductive investment associated with greater survival and longevity in Cassin's auklets. In Revision: Proceedings of the Royal Society B

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. : pdf

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