Distribution and Abundance of the Kittlitz\u27s Murrelet \u3ci\u3eBrachyramphus brevirostris\u3c/i\u3e in Selected Areas of Southeastern Alaska

We conducted boat-based surveys for the Kittlitz’s Murrelet Brachyramphus brevirostris during the breeding season in southeastern Alaska from 2002 to 2009. We completed a single survey in seven areas and multiple annual surveys in three areas. Although surveys spanned a broad geographic area, from LeConte Bay in the south to the Lost Coast in the north (~655 km linear distance), roughly 79% of the regional population of Kittlitz’s Murrelet was found in and between Icy and Yakutat bays (~95 km linear distance). The congeneric Marbled Murrelet B. marmoratus outnumbered the Kittlitz’s Murrelet in all areas surveyed except Icy Bay; in fact, Kittlitz’s Murrelet abundance constituted a relatively small proportion (7%) of the total Brachyramphus murrelet abundance in our survey areas. In areas for which there are multiple years of survey data, Kittlitz’s Murrelet abundance varied considerably, whereas Marbled Murrelet abundance was comparatively stable during the same time period. Since the southern distribution of this species has likely narrowed over the last 50 years, and the distribution of the Kittlitz’s Murrelet appears to be restricted to glacially influenced marine waters in southeastern Alaska, we expect that any future changes in glacial extent will likely affect this species and its long-term persistence in the region

Joint spatiotemporal models to predict seabird densities at sea

Introduction: Seabirds are abundant, conspicuous members of marine ecosystems worldwide. Synthesis of distribution data compiled over time is required to address regional management issues and understand ecosystem change. Major challenges when estimating seabird densities at sea arise from variability in dispersion of the birds, sampling effort over time and space, and differences in bird detection rates associated with survey vessel type. Methods: Using a novel approach for modeling seabirds at sea, we applied joint dynamic species distribution models (JDSDM) with a vector-autoregressive spatiotemporal framework to survey data collected over nearly five decades and archived in the North Pacific Pelagic Seabird Database. We produced monthly gridded density predictions and abundance estimates for 8 species groups (77% of all birds observed) within Cook Inlet, Alaska. JDSDMs included habitat covariates to inform density predictions in unsampled areas and accounted for changes in observed densities due to differing survey methods and decadal-scale variation in ocean conditions. Results: The best fit model provided a high level of explanatory power (86% of deviance explained). Abundance estimates were reasonably precise, and consistent with limited historical studies. Modeled densities identified seasonal variability in abundance with peak numbers of all species groups in July or August. Seabirds were largely absent from the study region in either fall (e.g., murrelets) or spring (e.g., puffins) months, or both periods (shearwaters). Discussion: Our results indicated that pelagic shearwaters (Ardenna spp.) and tufted puffin (Fratercula cirrhata) have declined over the past four decades and these taxa warrant further investigation into underlying mechanisms explaining these trends. JDSDMs provide a useful tool to estimate seabird distribution and seasonal trends that will facilitate risk assessments and planning in areas affected by human activities such as oil and gas development, shipping, and offshore wind and renewable energy

Temporal shifts in seabird populations and spatial coherence with prey in the southeastern Bering Sea

The Bering Sea is a highly productive ecosystem with abundant prey populations in the summer that support some of the largest seabird colonies in the Northern Hemisphere. In the fall, the Bering Sea is used by large numbers of migrants and post-breeding seabirds. We used over 22000 km of vessel-based surveys carried out during summer (June to July) and fall (late August to October) from 2008 to 2010 over the southeast Bering Sea to examine annual and seasonal changes in seabird communities and spatial relationships with concurrently sampled prey. Deep-diving murres Uria spp., shallow-diving shearwaters Ardenna spp., and surface-foraging northern fulmars Fulmarus glacialis and kittiwakes Rissa spp. dominated summer and fall seabird communities. Seabird densities in summer were generally less than half of fall densities and species richness was lower in summer than in fall. Summer seabird densities had high interannual variation (highest in 2009), whereas fall densities varied little among years. Seabirds were more spatially clustered around breeding colonies and the outer continental shelf in the summer and then dispersed throughout the middle and inner shelf in fall. In summer, the abundance of age-1 walleye pollock Gadus chalcogrammus along with spatial (latitude and longitude) and temporal (year) variables best explained broad-scale seabird distribution. In contrast, seabirds in fall had weaker associations with spatial and temporal variables and stronger associations with different prey species or groups. Our results demonstrate seasonal shifts in the distribution and foraging patterns of seabirds in the southeastern Bering Sea with a greater dependence on prey occurring over the middle and inner shelf in fall.Keywords: Spatial models, Seabird, Seasonal patterns, Krill, Forage fis

Kittlitz’s Murrelet Seasonal Distribution and Post-breeding Migration from the Gulf of Alaska to the Arctic Ocean

Kittlitz’s Murrelets (Brachyramphus brevirostris) nest during summer in glaciated or recently deglaciated (post-Wisconsin) landscapes. They forage in adjacent marine waters, especially those influenced by glacial meltwater. Little is known of their movements and distribution outside the breeding season. To identify post-breeding migrations of murrelets, we attached satellite transmitters to birds (n = 47) captured at sea in the Gulf of Alaska and Aleutian Islands during May – July 2009 – 15 and tracked 27 birds that migrated from capture areas. Post-breeding murrelets migrated toward the Bering Sea, with short periods of movement (median 2 d) separated by short stopovers (median 1 d). Travel speeds averaged 79.4 km d-1 (83.5 SD, 449.1 maximum). Five Kittlitz’s Murrelets tagged in Prince William Sound in May migrated to the Bering Sea by August and four continued north to the Arctic Ocean, logging 2500 – 4000 km of travel. Many birds spent 2‒3 weeks with little movement along coasts of the Alaska Peninsula or eastern Bering Sea during late August through September, also the pre-basic molt period. Ship-based surveys, many of which were conducted concurrently with our telemetry studies, confirmed that substantial numbers of Kittlitz’s Murrelets migrate into the Arctic Ocean during autumn. They also revealed that some birds spend winter and spring in the Bering Sea in association with ice-edge, polynya, or marginal ice zone habitats before returning to summer breeding grounds. We conclude that this species is best characterized as a sub-Arctic and Arctic species, which has implications for future risk assessments and threat mitigation.Les guillemots de Kittlitz (Brachyramphus brevirostris) nichent pendant l’été dans des lieux englacés ou récemment déglacés (post-Wisconsinien). Ils se nourrissent dans les eaux de mer adjacentes, surtout celles influencées par l’eau de fonte glaciaire. On en sait peu sur leurs mouvements et leur répartition en dehors de la saison de reproduction. Afin de déterminer les migrations des guillemots après la reproduction, nous avons fixé des émetteurs satellitaires à des oiseaux(n = 47) capturés en mer dans le golfe d’Alaska et sur les îles Aléoutiennes, de mai à juillet 2009 à 2015, ce qui nous a permis de suivre 27 oiseaux qui ont migré depuis l’endroit où ils ont été capturés. Après la reproduction, les guillemots ont migré vers la mer de Béring, avec de courtes périodes de mouvement (médiane de 2 d) parsemées de brèves escales (médiane de 1 d). Leurs vitesses de déplacement ont atteint 79,4 km d-1 en moyenne (écart type de 83,5 et maximum de 449,1). Cinq guillemots de Kittlitz étiquetés au golfe du Prince William en mai ont migré vers la mer de Béring avant le mois d’août, et quatre ont poursuivi leur route vers le nord, jusqu’à l’océan Arctique, ce qui s’est traduit par des déplacements de 2 500 à 4 000 km. De nombreux oiseaux ont passé de deux à trois semaines à se déplacer très peu sur les côtes de la péninsule d’Alaska ou de l’est de la mer de Béring de la fin d’août jusqu’en septembre, ce qui correspond également à la période de mue de prébase. Des dénombrements effectués par bateau, dont grand nombre ont été réalisés en même temps que nos études télémétriques, ont permis de confirmer qu’un nombre important de guillemots de Kittlitz migrent dans l’océan Arctique à l’automne. Ils ont également permis de révéler que les oiseaux passent l’hiver et le printemps dans la mer de Béring, plus précisément dans les habitats de lisières de glace, de polynie ou de zones de marge glaciaire avant de regagner leurs lieux de reproduction d’été. Nous concluons que cette espèce est mieux caractérisée comme espèce subarctique ou espèce arctique, ce qui a des incidences sur l’atténuation des menaces et sur les évaluations des risques futures