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The Great Black-backed Gull Larus marinus is a generalist species that inhabits temperate and arctic coasts of the north Atlantic Ocean. In recent years, there has been growing concern about population declines at local and regional scales; however, there has been no attempt to robustly assess Great Black-backed Gull population trends across its global range. We obtained the most recent population counts across the species’ range and analysed population trends at a global, continental, and national scale over the most recent three-generation period (1985–2021) following IUCN Red List criteria. We found that, globally, the species has declined by 43%–48% over this period (1.2–1.3% per annum, respectively), from an estimated 291,000 breeding pairs to 152,000–165,000 breeding pairs under two different scenarios. North American populations declined more steeply than European ones (68% and 28%, respectively). We recommend that Great Black-backed Gull should be uplisted from ‘Least Concern’ to ‘Vulnerable’ on the IUCN Red List of Threatened Species under criterion A2 (an estimated reduction in population size >30% over three generations).

1. Timing of breeding, an important driver of fitness in many populations, is widely studied in the context of global change, yet despite considerable efforts to identify environmental drivers of seabird nesting phenology, for most populations we lack evidence of strong drivers. Here we adopt an alternative approach, examining the degree to which different populations positively covary in their annual phenology to infer whether phenological responses to environmental drivers are likely to be (i) shared across species at a range of spatial scales, (ii) shared across populations of a species, or (iii) idiosyncratic to populations. 2. We combined 51 long-term datasets on breeding phenology spanning 50 years from nine seabird species across 29 North Atlantic sites and examined the extent to which different populations share early versus late breeding seasons depending on a hierarchy of spatial scales comprising breeding site, small-scale region, large-scale region and the whole North Atlantic. 3. In about a third of cases we found laying dates of populations of different species sharing the same breeding site or small-scale breeding region were positively correlated, which is consistent with the hypothesis that they share phenological responses to the same environmental conditions. In comparison we found no evidence for positive phenological covariation among populations across species aggregated at larger spatial scales. 4. In general we found little evidence for positive phenological covariation between populations of a single species, and in many instances the inter-year variation specific to a population was substantial, consistent with each population responding idiosyncratically to local environmental conditions. Black-legged kittiwake (Rissa tridactyla) was the exception, with populations exhibiting positive covariation in laying dates that decayed with the distance between breeding sites, suggesting that populations may be responding to a similar driver. 5. Our

The Great Black-backed Gull Larus marinus is a generalist species that inhabits temperate and arctic coasts of the north Atlantic Ocean. In recent years, there has been growing concern about population declines at local and regional scales; however, there has been no attempt to robustly assess Great Black-backed Gull population trends across its global range. We obtained the most recent population counts across the species’ range and analysed population trends at a global, continental, and national scale over the most recent three-generation period (1985–2021) following IUCN Red List criteria. We found that, globally, the species has declined by 43%–48% over this period (1.2–1.3% per annum, respectively), from an estimated 291,000 breeding pairs to 152,000–165,000 breeding pairs under two different scenarios. North American populations declined more steeply than European ones (68% and 28%, respectively). We recommend that Great Black-backed Gull should be uplisted from ‘Least Concern’ to ‘Vulnerable’ on the IUCN Red List of Threatened Species under criterion A2 (an estimated reduction in population size >30% over three generations).

The endangered population of roseate terns (Sterna dougallii) in the Northwestern Atlantic Ocean consistsof a network of large and small breeding colonies on islands. This type of fragmented population poses anexceptional opportunity to investigate dispersal, a mechanism that is fundamental in population dynam-ics and is crucial to understand the spatio-temporal and genetic structure of animal populations. Dispersalis difficult to study because it requires concurrent data compilation at multiple sites. Models of popula-tion dynamics in birds that focus on dispersal and include a large number of breeding sites are rare inliterature. In this work, we propose a stochastic simulation model that captures the dispersal dynamics ofthis population of roseate terns. The colonization and decolonization (abandonment) of breeding coloniesare modeled as discrete events that follow different dynamics than dispersal. We show that our modelreproduces the properties of this population that have been observed in field data. We also analyzed thesensitivity of our model to alterations in different variables, and study the impact of these alterations inthe model dynamics. Our results suggest that large colony population size exhibits a threshold sensitivityto adult survival, and that regional persistence is maintained by the larger populations.

Author Posting. © The Author(s), 2016. This is the author's version of the work. It is posted here by permission of American Chemical Society for personal use, not for redistribution. The definitive version was published in Environmental Science & Technology 50 (2016): 10226–10235, doi:10.1021/acs.est.6b02108., Common and roseate terns are migratory piscivorous seabirds with major breeding colonies within feeding range of the PCB-contaminated New Bedford Harbor (NBH, MA, USA) Superfund site. Our longitudinal study shows that before PCB discharges into NBH ceased (late 1970s), tern eggs had very high but variable PCB concentrations. But egg concentrations of PCBs as well as DDE, the degradation product of the ubiquitous global contaminant DDT, have since declined. Rate constants for temporal decline of PCB congeners in tern eggs varied inversely with log10KOW (n-octanol-water partition coefficient), shifting egg congener patterns away from those characterizing NBH sediment. To estimate the toxic effects on tern eggs of PCB dioxin-like congener (DLC) exposures, we extrapolated published laboratory data on common terns to roseate terns by characterizing genetic and functional similarities in species aryl-hydrocarbon receptors (AHRs), which mediate DLC sensitivity. Our assessment of contaminant risks suggests that terns breeding near NBH were exposed historically to toxic levels of PCBs and DDE; however, acute effects on tern egg development have become less likely since the 1970s. Our approach demonstrates how comparative genetics at target loci can effectively increase the range of inference for chemical risk assessments from tested to untested and untestable species., This work was supported in part by NOAA grant number NA14OAR4170074 (Woods Hole Sea Grant Project R/P-80) and by National Institute of Environmental Health Sciences (NIEHS) grant P42ES007381 (Superfund Basic Research Program at Boston University)., 2017-08-26

Little is known of the endangered and declining western North Atlantic population of the Roseate Tern Sterna dougallii outside the breeding season, when most mortality probably occurs. We used geolocators to track Roseate Terns in 2007 and 2009 and retrieved six units with useful data. In the post-breeding period in July-August, all six birds staged around Cape Cod, close to the breeding site. They started southward migration from 28 August to 14 September and flew directly across the western North Atlantic Ocean to staging areas around Puerto Rico and the Dominican Republic. We identified five major areas and four minor areas in the West Indies and along the north and east coasts of South America where birds stopped over for 2-24 d during southward and northward migrations. Birds arrived at (Northern Hemisphere) wintering areas from Guyana/Suriname on the north coast of South America to eastern Brazil between 3 October and 2 November. They left wintering areas from 7-23 April and arrived back at the breeding area from 5-30 May. Although this study is based on data for only six birds, it identifies several stopover and wintering areas that should receive priority for future studies and potential conservation measures. Geolocators did not impair Roseate Terns' ability to raise young in the year the devices were attached, but lower than expected rates of return suggest that the geolocators reduced survival, and most of the birds that returned had lost body-mass and did not breed in the year of return.

Ten geolocators (light-level data loggers) were attached to Common Terns (Sterna hirundo) at a breeding site in the northeastern USA in 2007 and 2008; six were retrieved (five with useful data) in 2008 and 2009. The birds wintered in four discrete areas on the north and east coasts of South America, from Guyana (6–7°N) to northeastern Argentina (36–42°S); three remained within restricted areas for most or all of the winter, whereas two ranged more widely. They left the breeding area at various dates between 1 August and 14 September; three migrated directly from the breeding area while two first moved southwest to stage near Cape Hatteras. All five birds flew directly to the vicinity of Puerto Rico, then moved along the north and east coasts of South America, staging at scattered locations for periods of 3–11 d, before reaching their winter quarters at various dates from 6 September to 26 October. Two birds left their winter quarters on 2 March and 4 April, staged in northern Brazil for 47 and 6 d, then traveled via the Bahamas to reach the breeding site on 1 May. During breeding and post-breeding periods, the birds spent a mean of 7 min each day and virtually no time at night resting on the water, but during the rest of the year they often rested on the water for up to 6 h by day and up to 11 h at night. Leg-mounted geolocators caused several adverse effects but did not reduce survival.