Geolocator tagging links distributions in the non-breeding season to population genetic structure in a sentinel North Pacific seabird

Abstract

We tested the hypothesis that segregation in wintering areas is associated with population differentiation in a sentinel North Pacific seabird, the rhinoceros auklet (Cerorhinca monocerata). We collected tissue samples for genetic analyses on five breeding colonies in the western Pacific Ocean (Japan) and on 13 colonies in the eastern Pacific Ocean (California to Alaska), and deployed light-level geolocator tags on 12 eastern Pacific colonies to delineate wintering areas. Geolocator tags were deployed previously on one colony in Japan. There was strong genetic differentiation between populations in the eastern vs. western Pacific Ocean, likely due to two factors. First, glaciation over the North Pacific in the late Pleistocene might have forced a southward range shift that historically isolated the eastern and western populations. And second, deep-ocean habitat along the northern continental shelf appears to act as a barrier to movement; abundant on both sides of the North Pacific, the rhinoceros auklet is virtually absent as a breeder in the Aleutian Islands and Bering Sea, and no tagged birds crossed the North Pacific in the non-breeding season. While genetic differentiation was strongest between the eastern vs. western Pacific, there was also extensive differentiation within both regional groups. In pairwise comparisons among the eastern Pacific colonies, the standardized measure of genetic differentiation (FꞌST) was negatively correlated with the extent of spatial overlap in wintering areas. That result supports the hypothesis that segregation in the non-breeding season is linked to genetic structure. Philopatry and a neritic foraging habit probably also contribute to the structuring. Widely distributed, vulnerable to anthropogenic stressors, and exhibiting extensive genetic structure, the rhinoceros auklet is fully indicative of the scope of the conservation challenges posed by seabirds.

Interannual measures of nutritional stress during a marine heatwave (the Blob) differ between two North Pacific seabird species

“…In contrast, fCort levels in female rhinoceros auklets were largely unchanged from mid-winter 2013, when the Blob was forming offshore but had not yet overlapped their migratory range, to 2014–2016, when the Blob had entirely overlapped their range and after the Blob’s decline in 2017 ( Hipfner et al , 2020b ; Kintisch, 2015 ; Fig. 1B ).…”

“…One of the most conspicuous effects of the Blob was a reduction in phytoplankton abundance ( Kintisch, 2015 ; Lotze et al , 2019 ; Suryan et al , 2021 ) and a decrease in cold-water copepods with a northward shift of warm-water copepods within the migratory range of both auk species ( Hipfner et al , 2020b ; Jones et al , 2018 ; Studholme et al , 2019 ). For Cassin’s auklets, which rely heavily on specific cold-water copepod species (e.g.…”

“…Although seabirds may experience the effects of marine heatwaves year-round, fCort and feather isotope measurements in this study provide insights into pre-breeding conditions of surviving individuals as feathers are grown during the migratory period in February and March, just prior to spring breeding (April in Cassin’s auklets and May in rhinoceros auklets). Variation in fCort can therefore reflect the pre-breeding, oceanic conditions experienced when individuals ranged throughout the Northeast Pacific from California to Alaska ( Hipfner et al , 2020b ; Studholme et al , 2019 ).…”

Temporal and spatial segregations between phenotypes of the Diablotin Black-capped PetrelPterodroma hasitataduring the breeding and non-breeding periods

“…The spatial segregation we observed in marine distributions of Black-capped Petrel phenotypes may also contribute to non-breeding isolation. Although our limited dataset prevents us from inferring whether individuals in our study were from sympatric or distinct breeding areas, segregation in marine distributions is common within species with allopatric breeding (Rayner et al 2011, Priddel et al 2014, Clay et al 2016, Hipfner et al 2020) and between species breeding in sympatry (Friesen 2007a, McFarlane et al 2015, Jones et al 2020). Furthermore, differences in morphometrics between dark and light forms (Howell and Patteson 2008, this study) suggest that niche partitioning may also be occurring (Ryan et al 2014, Rayner et al 2016, Miller et al 2018).…”

Perfluoroalkyl Substances in Seabird Eggs from Canada’s Pacific Coast: Temporal Trends (1973–2019) and Interspecific Patterns

“…56 Auklets from our monitoring colonies appear to be feeding on an exclusive diet of fish (e.g., sandlance) and/or higher trophic level zooplankton. 57,62 The latitudinal gradient in δ 15 petrel eggs suggests a diverse diet of crustaceans/euphausiids, 68 myctophid fish, 65 and other omega-3 rich prey, 69 and perhaps, much more spatial heterogeneity in baseline δ 15 N caused by denitrification and advection of eastern Tropical Pacific water masses. 70,71 Values for δ 15 N across species were nonlinearly correlated with lnΣ 17 PFASs (t 158 = −5.08; p < 0.001), long-chain ΣPFASs (t 158 = −5.14; p < 0.001), Σ 4 PFSAs (t 156 = −2.88; p < 0.01), Σ 13 PFCAs (t 157 = −5.73; p < 0.001), and PFOS (t 156 = −3.06; p < 0.01), but not short-chain ΣPFASs (t 101 = −0.51; p = 0.61).…”