South polar skuas from a single breeding population overwinter in different oceans though show similar migration patterns

Abstract

Seabirds in seasonal environments are often long-distance migrants and, for many species and populations, their ranges throughout the non-breeding period are unknown. As conditions during the non-breeding season often affect subsequent performance, the choice of migration strategy can have major implications for timing of breeding and success and, ultimately, population dynamics. We tracked south polar skuas Catharacta maccormicki from a single breeding population at King George Island in the South Shetland Islands (Antarctica). Overall, 27 birds (69%) migrated to the northern Atlantic (3 regions), 10 birds (26%) to the northern Pacific Ocean (2 regions), and 2 birds wintered in the southern hemisphere. Individuals tracked in consecutive non-breeding seasons chose the same ocean for wintering. Despite migrating to different oceans, birds showed a similar figure-ofeight flight pattern and equivalent residency periods in the main wintering areas. In addition, 87% of the migrants used terminal stop-over sites off South America shortly before returning to the breeding site. High diversity of migration patterns may buffer south polar skuas from climate change and other anthropogenic threats.KEY WORDS: Migratory connectivity · Annual cycle · Seabird · Antarctic · Pacific · Trans-equatorial · Geolocator Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 435: [263][264][265][266][267] 2011 & Larsson 1997). However, in the absence of tracking data, there were no studies of the routes or wintering destinations used by specific breeding populations. The purpose of this study was to determine intrapopulation variability in migration patterns of south polar skuas breeding on King George Island, which might theoretically overwinter in either the Pacific or Atlantic oceans. MATERIALS AND METHODSWe equipped 58 adult south polar skuas (27 females, 29 males, 2 unknown sex) with light recording geolocators (British Antarctic Survey, Cambridge) during 3 breeding seasons (2006)(2007)(2008) at King George Island in the Maritime Antarctic (62°12' S, 58°58' W). The geo locators (MK5 and MK9) weighed 9.4 and 8.2 g including the steel ring, respectively, which corresponded to ca. 0.8% of the mean adult body mass. Thirty-nine individuals (18 females, 20 males, 1 unknown sex; all birds were later genetically sexed, Fridolfs son & Ellegren 1999) were recaptured at the same breeding site during consecutive seasons until 2010, resulting in 52 annual tracks. Re-sighting rate did not differ between equipped birds (83%) and breeding birds without a device (78%, logistic regression, Wald = 7.28, p = 0.393). Two positions per day were calculated from light measurements using TransEdit and BirdTracker software (British Antarctic Survey, Cambridge), based on a standard approach (Phillips et al. 2006). Positions that were derived from interrupted light curves around dawn or dusk, that were close to equinoxes, or were obviously erroneous, were excluded, resulting in an average of 331 ± 25 valid...

Consistent variation in individual migration strategies of brown skuas

“…2 & 3). Individual consistency in migration strategies was also recorded for 17 south polar skuas Catharacta maccormicki and 3 great skuas C. skua tracked in 2 and 3 consecutive nonbreeding seasons (Kopp et al 2011, Magnúsdóttir et al 2012, Weimerskirch et. al.…”

Year-round distribution and habitat preferences of the Bugio petrel

“…Four main stopover areas were identified for Bugio petrels, located around the Cape Verde archipelago, the northeast coast of Brazil, northwest of the Azores and off the north coast of Brazil. Specific stopover sites, where birds are assumed to recover lost body condition, have been identified for most long -distance migratory seabirds in the Atlantic (Guilford et al 2009, Kopp et al 2011, Stenhouse et al 2012. Immersion data for some of these species, including Cory's shearwater and Manx shearwater Puffinus puffinus, indicate that like Bugio petrels, birds in stopover areas reduce flight speed and increase the proportion of time on the water (Guilford et al 2009.…”

“…The at-sea area used by Bugio petrels during this stage seems to overlap with the distribution of Zino's petrels Pterodroma madeira from Madeira (Zino et al 2011), Cory's shearwater Calonectris diometea from Desertas (Paiva et al 2010a) and Selvagens (Paiva et al 2010c), and Cape Verde shearwater Calonectris edwardsii from Cape Verde (Roscales et al 2011). The African shelf area along the coast of Mauritania appears to be very important for populations of these 4 seabird species for part or all of the year and also for migrant seabirds from elsewhere, including Sabine's gull Larus sabini (Kopp et al 2011), northern gannet Morus bassanus (Stenhouse et al 2012), great skua Stercorarius skua (Magnusdottir et al 2012) and south polar skua S. maccormicki (Fort et al 2012). In fact, this area is within one of the most important large marine ecosystems in the world -the Canary Current -with strong and nutrient-rich upwelling, which naturally elevates primary productivity and progressively increases the abundance of plankton and small planktivorous pelagic fish, cephalopods and crustaceans, which ultimately attracts seabirds to the area (Mann & Lazier 2006, Sherman & Hempel 2009).…”

Individual variability in the migratory path and stopovers of a long-distance pelagic migrant

“…Several studies have revealed the exceptional migratory performances of many seabirds Phillips et al 2005;Egevang et al 2010;Kopp et al 2011), in particular of shearwater species (e.g. Shaffer et al 2006;González-Solís et al 2007;Guilford et al 2009;Dias et al 2012a).…”