Carry-over effects of breeding on molt timing and migration starting location in Adélie penguins

Abstract

**Abstract:** Adélie penguins (Pygoscelis adeliae) undergo complete molt shortly after the breeding season. Unlike most penguins, Adélies typically molt on the sea ice rather than on land, with molt lasting up to 3 weeks. Limited mobility and increased metabolic rate during this period create an energetic bottleneck and may be a critical period in the species annual cycle. The timing of molt may also play an important role in determining the start and route of the winter migration. We analyzed data from 120 recovered geolocating dive recorders that were deployed at two colonies on Ross Island, Antarctica. Devices were deployed over 3 winters (2017-2019) on individuals of known-age and breeding history at Cape Crozier (~300,000 breeding pairs) and Cape Royds (~2500 breeding pairs). Adélie penguins do not enter the water during molt so the timing and duration of molt was estimated from the recovered dive logs. We modeled molt timing in relation to several variables including colony, age, sex, breeding status, and breeding outcome. Results indicate molt timing did not differ between colonies but did vary significantly between years, with older individuals and successful breeders molting later. Finally, we examined the relationships between molt timing and the starting location of the winter migration. **Authors:** Annie Schmidt¹, Amelie Lescroel¹, Dennis Jongsomjit¹, Megan Elrod¹, Katie Dugger², Virginia Morandini³, Jean Pennycook⁴, David Ainley⁴, Grant Ballard¹ ¹Point Blue Conservation Science, ²U.S. Geological Survey, Oregon Cooperative Fish and Wildlife Research Unit, Department of Fisheries, ³Oregon Cooperative Fish and Wildlife Research Unit, Department of Fisheries and Wildlife, Oregon St, ⁴H.T. Harvey and Associates