Blending census and paleolimnological data allows for tracking the establishment and growth of a major gannet colony over several centuries.

Seabird colonies with long-term monitoring records, i.e., > 50 years, are rare. The population data for northern gannets (Morus bassanus) in Cape St. Mary's (CSM) Ecological Reserve (Newfoundland and Labrador, Canada) is robust, extending back to 1883 when the colony was presumed established. We inferred the colony's historical population shifts by measuring ornithogenic proxies in a dated sediment record collected from a nearby pond. Our record extended to the early eighteenth century, but the proxy data only began to show significant signs of seabird presence between ca. 1832 and 1910, aligning with the period gannets were first observed at CSM. Through the twentieth century, we observed significant increases in δ15N, P, Zn, Cd, and chlorophyll a, coeval with a shift in the dominant diatom species, indicating rapid colony growth. The proxies were overall highest in ca. 2005, corresponding to the reported historical maximum of the gannet colony in 2009. Our results validate that paleo-reconstructions using ornithogenic proxies can accurately reflect population trends and provide a stronger understanding of the colony's establishment and growth. This study highlights the value of applying paleolimnological methods in seabird population studies to frame the history of a colony's dynamics and inform conservation efforts.

Reduction of coastal lighting decreases seabird strandings.

Artificial light at night (ALAN) is negatively impacting numerous species of nocturnally active birds. Nocturnal positive phototaxis, the movement towards ALAN, is exhibited by many marine birds and can result in stranding on land. Seabird species facing major population declines may be most at risk. Leach's Storm-Petrels (Hydrobates leucorhous) are small, threatened seabirds with an extensive breeding range in the North Atlantic and North Pacific Oceans. The Atlantic population, which represents approximately 40-48% of the global population, is declining sharply. Nocturnal positive phototaxis is considered to be a key contributing factor. The Leach's Storm-Petrel is the seabird species most often found stranded around ALAN in the North Atlantic, though there is little experimental evidence that reduction of ALAN decreases the occurrence of stranded storm-petrels. During a two-year study at a large, brightly illuminated seafood processing plant adjacent to the Leach's Storm-Petrel's largest colony, we compared the number of birds that stranded when the lights at the plant were on versus significantly reduced. We recorded survival, counted carcasses of adults and juveniles, and released any rescued individuals. Daily morning surveys revealed that reducing ALAN decreased strandings by 57.11% (95% CI: 39.29% - 83.01%) per night and night surveys revealed that reducing ALAN decreased stranding of adult birds by 11.94% (95% CI: 3.47% - 41.13%) per night. The peak stranding period occurred from 25 September to 28 October, and 94.9% of the birds found during this period were fledglings. These results provide evidence to support the implementation of widespread reduction and modification of coastal artificial light as a conservation strategy, especially during avian fledging and migration periods.

Factors influencing mercury levels in Leach's storm-petrels at northwest Atlantic colonies.

Mercury (Hg) is a globally distributed heavy metal, with negative effects on wildlife. Its most toxic form, methylmercury (MeHg), predominates in aquatic systems. Levels of MeHg in marine predators can vary widely among individuals and populations. Leach's storm-petrels (Hydrobates leucorhous) have elevated levels of Hg but the role of Hg in storm-petrel population declines is unknown. In this study, we used egg and blood samples to study variation in Hg exposure among several northwest Atlantic colonies during breeding seasons, thereby evaluating relative toxicity risk within and among colonies. Total mercury (THg) concentrations were higher with increasing colony latitude, and were more pronounced in blood than in eggs. THg concentrations in blood were mostly associated with low toxicity risk in birds from the southern colonies and moderate risks in birds from the northern colonies; however, those values did not affect hatching or fledging success. THg concentrations in both eggs and blood were positively correlated with δ34S, emphasizing the role of sulfate-reducing bacteria in methylation of THg acquired through marine food webs, which is consistent with enriched δ34S profiles. By associating tracking data from foraging trips with THg from blood, we determined that blood THg levels were higher when storm-petrel's intensive search locations were over deeper waters. We conclude that spatial variation in THg concentrations in Leach's storm-petrels is attributable to differences in ocean depth at foraging locations, both at individual and colony levels. Differences in diet among colonies observed previously are the most likely cause for observed blood THg differences. As one of the few pelagic seabird species breeding in Atlantic Canada, with limited overlap in core foraging areas among colonies, Leach's storm-petrels can be used as biomonitors for less sampled offshore pelagic regions. The global trend in Hg emissions combined with legacy levels warrant continued monitoring for toxicity effects in seabirds.

Marine pollution in fledged Leach's storm-petrels (Hydrobates leucorhous) from Baccalieu Island, Newfoundland and Labrador, Canada.

The Leach's storm-petrel (Hydrobates leucorhous) is one of the most abundant and widely distributed marine birds in the North Atlantic but is under global population decline, possibly linked to marine pollution. We determined levels of ingested plastic and hepatic total mercury (THg) in recently fledged juveniles that stranded in Newfoundland and Labrador, Canada, and assessed the relationship to body condition, size and diet. Plastic prevalence was high (87.5%) but hepatic THg was relatively low (mean 486.7 ng/g dry weight) compared to other studies. Levels of neither pollutant were significantly related to body metrics of health. Our data confirm that plastic and mercury are pervasive in the western North Atlantic Ocean, prominent even in young birds.

Linking 19th century European settlement to the disruption of a seabird's natural population dynamics.

Recent estimates indicate that ∼70% of the world's seabird populations have declined since the 1950s due to human activities. However, for almost all bird populations, there is insufficient long-term monitoring to understand baseline (i.e., preindustrial) conditions, which are required to distinguish natural versus anthropogenically driven changes. Here, we address this lack of long-term monitoring data with multiproxy paleolimnological approaches to examine the long-term population dynamics of a major colony of Leach's Storm-petrel (Hydrobates leucorhous) on Grand Colombier Island in the St. Pierre and Miquelon archipelago-an overseas French territory in the northwest Atlantic Ocean. By reconstructing the last ∼5,800 y of storm-petrel dynamics, we demonstrate that this colony underwent substantial natural fluctuations until the start of the 19th century, when population cycles were disrupted, coinciding with the establishment and expansion of a European settlement. Our paleoenvironmental data, coupled with on-the-ground population surveys, indicate that the current colony is only ∼16% of the potential carrying capacity, reinforcing concerning trends of globally declining seabird populations. As seabirds are sentinel species of marine ecosystem health, such declines provide a call to action for global conservation. In response, we emphasize the need for enlarged protected areas and the rehabilitation of disturbed islands to protect ecologically critical seabird populations. Furthermore, long-term data, such as those provided by paleoecological approaches, are required to better understand shifting baselines in conservation to truly recognize current rates of ecological loss.

Foraging areas, offshore habitat use, and colony overlap by incubating Leach's storm-petrels Oceanodroma leucorhoa in the Northwest Atlantic.

Despite their importance in marine food webs, much has yet to be learned about the spatial ecology of small seabirds. This includes the Leach's storm-petrel Oceanodroma leucorhoa, a species that is declining throughout its Northwest Atlantic breeding range. In 2013 and 2014, we used global location sensors to track foraging movements of incubating storm-petrels from 7 eastern Canadian breeding colonies. We determined and compared the foraging trip and at-sea habitat characteristics, analysed spatial overlap among colonies, and determined whether colony foraging ranges intersected with offshore oil and gas operations. Individuals tracked during the incubation period made 4.0 ± 1.4 day foraging trips, travelling to highly pelagic waters over and beyond continental slopes which ranged, on average, 400 to 830 km from colonies. Cumulative travel distances ranged from ~900 to 2,100 km among colonies. While colony size did not influence foraging trip characteristics or the size of areas used at sea, foraging distances tended to be shorter for individuals breeding at the southern end of the range. Core areas did not overlap considerably among colonies, and individuals from all sites except Kent Island in the Bay of Fundy foraged over waters with median depths > 1,950 m and average chlorophyll a concentrations ≤ 0.6 mg/m3. Sea surface temperatures within colony core areas varied considerably (11-23°C), coincident with the birds' use of cold waters of the Labrador Current or warmer waters of the Gulf Stream Current. Offshore oil and gas operations intersected with the foraging ranges of 5 of 7 colonies. Three of these, including Baccalieu Island, Newfoundland, which supports the species' largest population, have experienced substantial declines in the last few decades. Future work should prioritize modelling efforts to incorporate information on relative predation risk at colonies, spatially explicit risks at-sea on the breeding and wintering grounds, effects of climate and marine ecosystem change, as well as lethal and sub-lethal effects of environmental contaminants, to better understand drivers of Leach's storm-petrel populations trends in Atlantic Canada.

Balancing personal maintenance with parental investment in a chick-rearing seabird: physiological indicators change with foraging conditions.

Seabird parents use a conservative breeding strategy that favours long-term survival over intensive parental investment, particularly under harsh conditions. Here, we examine whether variation in several physiological indicators reflects the balance between parental investment and survival in common murres (Uria aalge) under a wide range of foraging conditions. Blood samples were taken from adults during mid-chick rearing from 2007 to 2014 and analysed for corticosterone (CORT, stress hormone), beta-hydroxybutyrate (BUTY, lipid metabolism reflecting ongoing mass loss), and haematocrit (reflecting blood oxygen capacity). These measures, plus body mass, were related to three levels of food availability (good, intermediate, and poor years) for capelin, the main forage fish for murres in this colony. Adult body mass and chick-feeding rates were higher in good years than in poor years and heavier murres were more likely to fledge a chick than lighter birds. Contrary to prediction, BUTY levels were higher in good years than in intermediate and poor years. Murres lose body mass just after their chicks hatch and these results for BUTY suggest that mass loss may be delayed in good years. CORT levels were higher in intermediate years than in good or poor years. Higher CORT levels in intermediate years may reflect the necessity of increasing foraging effort, whereas extra effort is not needed in good years and it is unlikely to increase foraging success in poor years. Haematocrit levels were higher in poor years than in good years, a difference that may reflect either their poorer condition or increased diving requirements when food is less available. Our long-term data set provided insight into how decisions about resource allocation under different foraging conditions are relating to physiological indicators, a relationship that is relevant to understanding how seabirds may respond to changes in marine ecosystems as ocean temperatures continue to rise.

Circumpolar dynamics of a marine top-predator track ocean warming rates.

Global warming is a nonlinear process, and temperature may increase in a stepwise manner. Periods of abrupt warming can trigger persistent changes in the state of ecosystems, also called regime shifts. The responses of organisms to abrupt warming and associated regime shifts can be unlike responses to periods of slow or moderate change. Understanding of nonlinearity in the biological responses to climate warming is needed to assess the consequences of ongoing climate change. Here, we demonstrate that the population dynamics of a long-lived, wide-ranging marine predator are associated with changes in the rate of ocean warming. Data from 556 colonies of black-legged kittiwakes Rissa tridactyla distributed throughout its breeding range revealed that an abrupt warming of sea-surface temperature in the 1990s coincided with steep kittiwake population decline. Periods of moderate warming in sea temperatures did not seem to affect kittiwake dynamics. The rapid warming observed in the 1990s may have driven large-scale, circumpolar marine ecosystem shifts that strongly affected kittiwakes through bottom-up effects. Our study sheds light on the nonlinear response of a circumpolar seabird to large-scale changes in oceanographic conditions and indicates that marine top predators may be more sensitive to the rate of ocean warming rather than to warming itself.

A PELAGIC OUTBREAK OF AVIAN CHOLERA IN NORTH AMERICAN GULLS: SCAVENGING AS A PRIMARY MECHANISM FOR TRANSMISSION?

Avian cholera, caused by the bacterium Pasteurella multocida , is an endemic disease globally, often causing annual epizootics in North American wild bird populations with thousands of mortalities. From December 2006 to March 2007, an avian cholera outbreak caused mortality in marine birds off the coast of Atlantic Canada, largely centered 300-400 km off the coast of the island of Newfoundland. Scavenging gulls ( Larus spp.) were the primary species detected; however, mortality was also identified in Black-legged Kittiwakes ( Rissa tridactyla ) and one Common Raven ( Corvus corax ), a nonmarine species. The most common gross necropsy findings in the birds with confirmed avian cholera were acute fibrinous and necrotizing lesions affecting the spleen, air sacs, and pericardium, and nonspecific hepatomegaly and splenomegaly. The etiologic agent, P. multocida serotype 1, was recovered from 77 of 136 carcasses examined, and confirmed or probable avian cholera was diagnosed in 85 cases. Mortality observed in scavenging gull species was disproportionately high relative to their abundance, particularly when compared to nonscavenging species. The presence of feather shafts in the ventricular lumen of the majority of larid carcasses diagnosed with avian cholera suggests scavenging of birds that died from avian cholera as a major mode of transmission. This documentation of an outbreak of avian cholera in a North American pelagic environment affecting primarily scavenging gulls indicates that offshore marine environments may be a component of avian cholera dynamics.

Plastic and metal ingestion in three species of coastal waterfowl wintering in Atlantic Canada.

Relatively little attention has been paid to the occurrence of anthropogenic debris found in coastal species, especially waterfowl. We examined the incidence of ingested plastic and metal in three waterfowl species wintering in Atlantic Canada: American black ducks (Anas rubripes) and mallards (A. platyrhynchos), two species that use marine and freshwater coastal habitats for foraging in the winter, and common eider (Somateria mollissima), a coastal marine species that feeds on intertidal and subtidal benthic organisms. Plastic was found in the stomachs of 46.1% (6/13) of mallards and 6.9% (6/87) of black ducks, the first report of ingested anthropogenic debris in these species, while 2.1% (1/48) of eider stomachs contained plastic. Metal was found in the stomachs of 30.8% (4/13) of mallards, 2.3% (2/87) of black ducks, and in 2.1% (1/48) of eiders. Our results indicate that species using coastal marine and freshwater environments are exposed to and ingest anthropogenic debris.

Evaluation of seabirds in Newfoundland and Labrador, Canada, as hosts of influenza A viruses.

Influenza A viruses infect a wide range of hosts, including many species of birds. Avian influenza A virus (AIV) infection appears to be most common in Anseriformes (ducks, geese, and swans) and some Charadriiformes (shorebirds and gulls), but many other birds also serve as hosts of AIV. Here, we evaluated the role of seabirds as hosts for AIV. We tested 3,160 swab samples from 13 seabird species between May 2008 and December 2011 in Newfoundland and Labrador, Canada. We also tested 156 serum samples for evidence of previous infection of AIV in Common Murres (Uria aalge) and Atlantic Puffins (Fratercula arctica). Avian influenza A virus was detected in breeding Common Murres and nonbreeding Thick-billed Murres (Uria lomvia), and Common Murres also had high antibody prevalence (44%). From these findings, combined with other studies showing AIV infection in murres, we conclude that murres are important for the ecology of AIV. For other species (Razorbill, Alca torda; Leach's Storm-Petrel, Oceanodroma leucorhoa; Black-legged Kittiwake, Rissa tridactyla; Atlantic Puffin) with good coverage (>100 samples) we did not detect AIV. However, serology indicates infection does occur in Atlantic Puffins, with 22% antibody prevalence found. The possibility of virus spread through dense breeding colonies and the long distance movements of these hosts make a more thorough evaluation of the role for seabirds as hosts of AIV important.

Ingestion of plastic marine debris by Common and Thick-billed Murres in the northwestern Atlantic from 1985 to 2012.

Plastic ingestion by seabirds is a growing conservation issue, but there are few time series of plastic ingestion with large sample sizes for which one can assess temporal trends. Common and Thick-billed Murres (Uria aalge and U. lomvia) are pursuit-diving auks that are legally harvested in Newfoundland and Labrador, Canada. Here, we combined previously unpublished data on plastic ingestion (from the 1980s to the 1990s) with contemporary samples (2011-2012) to evaluate changes in murres' plastic ingestion. Approximately 7% of murres had ingested plastic, with no significant change in the frequency of ingestion among species or periods. The number of pieces of plastic/bird, and mass of plastic/bird were highest in the 1980s, lowest in the late 1990s, and intermediate in contemporary samples. Studying plastic ingestion in harvested seabird populations links harvesters to conservation and health-related issues and is a useful source of large samples for diet and plastic ingestion studies.

Re-evaluating the use of beached bird oiling rates to assess long-term trends in chronic oil pollution.

The oiling rate (oiled birds/total birds) has become the international standard to analyze beached bird survey data. However, this index may not reliably track long-term changes in marine oil pollution in regions where other activities that kill seabirds vulnerable to oil, such as hunting and gill-netting, are also changing. We compare the oiling rate from beached bird surveys conducted in southeastern Newfoundland between 1984 and 2006 to an alternative approach, namely trends derived from a model examining the linear density of oiled birds (birds/km). In winter, there was no change in the oiling rate since 1984, while in summer oiling rates significantly increased. In contrast, the number of oiled birds/km showed a significant decline in both winter and summer. The discrepancy in these trends was attributed to steep declines in the number of unoiled birds found in both seasons. In winter, the decline in unoiled birds/km was related to a reduction in the legal murre hunt and less onshore winds, while in summer a reduced cod fishery resulting in fewer murres drowning in nets and warming summers may have lead to the decline. The significant declines in oiled birds/km over the past three decades are hopefully an indication of less oil being present in the marine environment. Although oiled bird densities since 2000 have remained relatively low for the region (winter: 0.58 birds/km, summer: 0.27 birds/km), they still exceed densities reported elsewhere in the world.

The effects of variable foraging conditions on common murre (Uria aalge) corticosterone concentrations and parental provisioning.

This study investigated how total corticosterone concentrations, chick-feeding rates, and adult body mass changed with food availability from 1998 to 2000 in the same individually marked common murres (Uria aalge). Capelin, the main prey species, arrived inshore by the onset of murre chick hatching in 1998 and 1999 (prey match years); whereas in 2000, hatching began approximately 1 week before the capelin arrived inshore to spawn (prey mismatch year). Serum corticosterone concentrations were higher in the same individuals in the prey mismatch year than they were in either of the match years. Birds sampled before peak capelin spawning in the mismatch year had higher corticosterone levels than murres sampled after peak spawning. Murres with higher corticosterone levels had higher chick-feeding rates and less mass loss in the mismatch year (compared to the match year 1999) than birds with lower levels. Corticosterone levels did not differ between birds that had not foraged for at least 12 h (brooded chick overnight) and those that had, suggesting that short-term food deprivation did not affect corticosterone concentrations. Taken together, these findings suggest that the difference between years reflects a baseline shift in corticosterone levels, particularly in the high-quality birds that were able to increase both corticosterone concentrations and foraging effort.

Comparing an estimate of seabirds at risk to a mortality estimate from the November 2004 Terra Nova FPSO oil spill.

On 21 November 2004, about 1000 barrels of crude oil were accidentally released from the Terra Nova FPSO (floating production, storage and offloading) onto the Grand Banks, approximately 340 km east-southeast of St. John's, Newfoundland. We estimated the number of vulnerable seabirds (murres (Uria spp.) and dovekies (Alle alle)) at risk from this incident by multiplying observed densities of seabirds with the total area covered by the slick, estimated at 793 km(2). A mean density of 3.46 murres/km(2) and 1.07 dovekies/km(2) on the sea surface was recorded during vessel-based surveys on 28 and 29 November 2004, with a mean density of 6.90 murres/km(2) and 13.43 dovekies/km(2) combining those on the sea and in flight. We calculated a mean of 9858 murres and dovekies were at risk of being oiled, with estimates ranging from 3593 to 16,122 depending on what portion of birds in flight were assumed to be at risk. A mortality model based on spill volume was derived independently of the risk model, and estimated that 4688 (CI 95%: 1905-12,480) birds were killed during this incident. A low mortality estimate based strictly on spill volume would be expected for this incident, which occurred in an area of relatively high seabird densities. Given that the risk and mortality estimates are statistically indistinguishable, we estimate that on the order of 10,000 birds were killed by the Terra Nova spill.

Social and hormonal bases of individual differences in the parental behaviour of birds and mammals.

We present an overview of research on how social experiences and hormonal responses affect individual variation in parental care of birds and mammals. The parental roles of prolactin and glucorticoids (corticosterone or cortisol) have many similarities in birds and in mammals. Prolactin may be involved in the initiation of parental interactions, with prolactin variation possibly explaining individual differences in parental decision-making. Glucocorticoid levels increase when parents have to work harder, with some individuals showing greater hormonal and behavioural responses than others. Testosterone interferes with paternal behaviour in birds, but its role is more complex and species-specific in male mammals. We examine these differences in an adaptive framework, where retaining flexibility of response has allowed individuals to respond differentially to social opportunities and environmental change.