Laura McFarlane Tranquilla

Individual Winter Movement Strategies in Two Species of Murre (Uria spp.) in the Northwest Atlantic

Individual wintering strategies and patterns of winter site fidelity in successive years are highly variable among seabird species. Yet, an understanding of consistency in timing of movements and the degree of site fidelity is essential for assessing how seabird populations might be influenced by, and respond to, changing conditions on wintering grounds. To explore annual variation in migratory movements and wintering areas, we applied bird-borne geolocators on Thick-billed Murres (Uria lomvia, nu200a=u200a19) and Common Murres (U. aalge, nu200a=u200a20) from 5 colonies in the Northwest Atlantic for 2–4 consecutive years. Thick-billed Murres ranged widely and among-individual wintering strategies were highly variable, whereas most Common Murres wintered relatively near their colonies, with among-individual variation represented more by the relative use of inshore vs. offshore habitat. Within individuals, some aspects of the wintering strategy were more repeatable than others: colony arrival and departure dates were more consistent by individual Common than Thick-billed Murres, while the sizes of home ranges (95% utilization distributions) and distances travelled to wintering area were more repeatable for both species. In consecutive years, individual home ranges overlapped from 0–64% (Thick-billed Murres) and 0–95% (Common Murres); and the winter centroids were just 239 km and 169 km apart (respectively). Over the 3–4 year timescale of our study, individuals employed either fixed or flexible wintering strategies; although most birds showed high winter site fidelity, some shifted core ranges after 2 or 3 years. The capacity among seabird species for a combination of fidelity and flexibility, in which individuals may choose from a range of alternative strategies, deserves further, longer term attention.

SEX DIFFERENCES IN NEST VISITATION BY CHICK-REARING MARBLED MURRELETS

Abstract We report a significant male bias in dawn and dusk nest visitations of breeding, radio-marked Marbled Murrelets (Brachyramphus marmoratus) during the chick rearing period in Desolation Sound, British Columbia, Canada, from 1998–2000. Overall visitation rates of males during chick rearing were 1.3 times greater than those of females. Dusk visitation rates by males with active nests were 1.8 times greater than those of females. Male visitation rates were similar between early and late chick rearing, both within and among individuals. However, female visitation rates during late chick rearing were significantly lower than female rates early in rearing, both within and between individuals. In addition, between-sex comparisons of nest visitation during early and late chick rearing showed significant reductions in female effort relative to males, only during late chick rearing. These results suggest that male birds may provision chicks more often than females, especially during the last half of chick rearing. These findings offer a behavioral explanation for the annual male bias of birds flying inland during the chick rearing period at Theodosia Inlet in Desolation Sound from 1994–1999. Although female-biased provisioning has been documented in several species, male-biased provisioning has not been widely reported in other alcids. Diferencias de Sexo en la las Visitas al Nido en Brachyramphus marmoratus durante la Crianza de Pichones Resumen.u2003Presentamos evidencia sobre un sesgo hacia los machos en las visitas a nidos efectuadas al amanecer y el crepúsculo durante la crianza de pichones, en individuos marcados con radios en Desolation Sound, Columbia Británica, Canadá, entre 1998–2000. La tasa de visitas de los machos fue 1.3 veces mayor que la de las hembras. La tasa de visitas de los machos al crepúsculo con nidos activos fue 1.8 veces mayor que las hembras. La tasa de visitas de los machos fue constante a través del período de crianza, tanto para un mismo individuo como entre individuos. Sin embargo, la tasa de visitas de las hembras fue significativamente menor al final que al inicio de la crianza, tanto para un mismo individuo como entre individuos. Además, la tasa de visitas de las hembras fue menor que la de los machos al final de la crianza. Estos resultados sugieren que los machos abastecen a los pichones en mayor medida que las hembras, especialmente en la última parte de la crianza. Asimismo, los resultados ofrecen una explicación conductual para la dominancia anual de machos volando tierra adentro durante la crianza en Theodosia Inlet, Desolation Sound, entre 1994–1999. En pocas ocasiones se ha descripto abastecimiento paternal en los álcidos, donde principalmente las hembras se encargan del abastecimiento.

The Reliability of Brood Patches in Assessing Reproductive Status in the Marbled Murrelet: Words of Caution

Abstract The assumption that brood patches identify incubating birds is a pervasive one in avian literature, and as a result, brood patches are often used to infer breeding status. Although the developmental stages of the brood patch with specific reproductive stages in passerines have been described, this information for seabirds is not often reported. Thus, for birds whose breeding activities are not easily observed, it is difficult to confirm (1) that it is valid to assume that a bird which has some stage of brood patch is a nester or putative nester, and (2) whether specific stages of brood patch development reflect specific stages of the breeding cycle. We tested the utility of brood patch scores to infer breeding status in a non-colonial seabird, the Marbled Murrelet (Brachyramphus marmoratus), a species always captured away from the nest site. We confirmed the breeding status of murrelets with brood patches, and assessed the specific stages of brood patch development to the timing of egg-production (using a physiological analysis) and the onset of incubation (using radio telemetry). Murrelets with brood patches were not always nesters or putative nesters (58% of birds with brood patches were producing eggs, and 56% of radio-tagged birds with brood patches began incubation), and brood patch score did not predict which birds were more likely to become egg-producers or incubators. Specific brood patch stages did not always correlate with specific breeding stages (e.g., the brood patch of egg-producers ranged from absent to fully-developed). Birds with fully developed brood patches took from 3-30 days to start incubation. Brood patch development accurately depicted the average population incubation time, but we caution against using brood patches to predict the timing of an individual breeding attempt, and suggest that when possible, researchers should try to confirm breeding activities using other methods.

USING VITELLOGENIN TO IDENTIFY INTERANNUAL VARIATION IN BREEDING CHRONOLOGY OF MARBLED MURRELETS (BRACHYRAMPHUS MARMORATUS)

Abstract Vitellogenin is a lipophosphoprotein found in plasma of egg-producing birds prior to laying that may be used to identify fecund females whose reproductive status is otherwise unknown. We captured Marbled Murrelets (Brachyramphus marmoratus) at sea in Desolation Sound, British Columbia, and used vitellogenin to (1) identify variation in egg production between 1999 and 2000, (2) predict timing of subsequent breeding stages on the basis of egg production, and (3) describe proportion of captured females producing eggs. We also used vitellogenin to investigate a capture bias previously detected in mist-netted birds in the study area and found a corresponding bias in number of egg producers caught. Dates that egg producers were present (27 April to 6 July 1999, 20 April to 6 July 2000) indicate that breeding is highly asynchronous in that species but was similar in both years. Predicted chick-fledging based on vitellogenin analyses was within one day of first sightings of fledglings at sea in both years, confirming that the vitellogenin technique provides accurate information on breeding chronology. Percentage of egg producers (54% in 1999, 56% in 2000) were similar in both years. Vitellogenin analyses provided a chronology very similar to that previously estimated using multiple techniques in the same study area (1996–1998), confirming that vitellogenin analyses alone may be used to describe chronology when sampling encompasses the entire laying period. We recommend that technique for use in other studies of secretive species where egg production cannot normally be monitored by direct observation.

Variation in Marine Distributions of Cassin's auklets (Ptychoramphus aleuticus) Breeding at Triangle Island, British Columbia

Abstract Approximately 55% of the worlds population of Cassins Auklets (Ptychoramphus aleuticus) nests at Triangle Island, British Columbia. To improve our understanding of the biology of these birds during the breeding season, we tracked 112 radiomarked individuals over three years, 1999–2001. We flew high-altitude surveys to describe the at-sea distributions of the marked birds during the chick-rearing period. Using radiotelemetry point locations, we determined that the location of marine use areas, distance from colony, and water depth varied significantly across years. In 1999 and 2000, radiomarked birds were, on average, ∼50 km southwest of Triangle Island in waters approximately 1400–1800 m deep. However, in 2001, radiomarked birds were, on average, ∼80 km northwest of Triangle Island in waters ∼725 m deep. Intra-annually (i.e., between surveys spanning days or weeks), there were no such large-scale directional shifts in marine use area. The size of marine use areas (quantified using kernel home range [KHR] analyses) varied across the three years, from approximately 650 to 1,400 km2 (50% KHR) and from approximately 3,200 to 8,200 km2 (95% KHR). Variation des distributions en mer de Ptychoramphus aleuticus se reproduisant sur lîle Triangle, en Colombie-Britannique

Breeding chronology of Marbled Murrelets varies between coastal and inshore sites in southern British Columbia

Abstract We used four methods to compare the breeding chronologies of Marbled Murrelet at two sites at similar latitudes in British Columbia: Desolation Sound on the mainland, inshore of the Strait of Georgia, and Clayoquot Sound on the west coast of Vancouver Island. At both sites, we estimated breeding chronologies from the timing of (1) nest initiation dates determined by radio-telemetry, (2) the chick feeding period determined from observations of fish-holding adults, (3) hatch dates determined from observations of juveniles on the water, and (4) brood patch scores determined from captured birds. At Desolation Sound, these methods each produced a similar distribution of nesting dates, but at Clayoquot Sound, the distribution of nesting dates of radio-tracked birds were substantially biased towards later nests. Despite these methodological difficulties, we found that Marbled Murrelets at Desolation Sound bred ca. 30 d later than at Clayoquot Sound. Regional differences in breeding chronology of this magnitude, if not properly calibrated, would bias estimates of peak inland activity, and should be considered in forestry operations, the interpretation of census data, and the design of monitoring programs.

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

Abstract 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; Leachs 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.

DO TWO MURRELETS MAKE A PAIR? BREEDING STATUS AND BEHAVIOR OF MARBLED MURRELET PAIRS CAPTURED AT SEA

Abstract Marbled Murrelets (Brachyramphus marmoratus) observed at sea usually are in pairs throughout the year. Although it has been assumed that these pairs are mates, this assumption has not been formally examined. Using data from three study sites during the breeding seasons of 1997–2001, we found that 92% of the birds that were paired at capture were of male-female pairs, and that paired females were more likely (73%) to be producing eggs than were single females (8%). Fourteen of fifteen pairs were tracked to a single nest location per pair. No pair members caught at sea were found breeding at separate nest sites. One pair was caught in two successive seasons, suggesting that at least some pairs are long lasting. Notably, pair members breeding together and radio tracked throughout the summer were detected without their breeding partners for 77% of the time. Thus, while pairs of Marbled Murrelets observed at sea most likely are members of a breeding pair, single murrelets observed at sea should not be assumed to be unpaired or nonbreeders.

Employing Predictive Spatial Models to Inform Conservation Planning for Seabirds in the Labrador Sea

Seabirds are vulnerable to incidental harm from human activities in the ocean, and knowledge of their seasonal distribution is required to assess risk and effectively inform marine conservation planning. Significant hydrocarbon discoveries and exploration licenses in the Labrador Sea underscore the need for quantitative information on seabird seasonal distribution and abundance, an area known to provide important habitat for seabirds year-round. We explore the utility of density surface modeling to improve seabird information available for regional conservation and management decision-making. We 1) develop seasonal density surface models for seabirds in the Labrador Sea using data from vessel-based surveys (2006–2014; 13,785 linear km of surveys), 2) present measures of uncertainty in model predictions, 3) discuss how density surface models can inform conservation and management decision making, and 4) explore challenges and potential pitfalls associated with using these complex modeling procedures. Models predicted large areas of high seabird density in fall over continental shelf waters (max. ~ 60 birds·km-2) driven largely by the southward migration of murres (Uria spp.) and dovekies (Alle alle) from Arctic breeding colonies. The continental shelf break was also highlighted as an important habitat feature, with predictions of high seabird densities particularly during summer (max. ~100 birds·km-2). Notable concentrations of seabirds overlapped with several significant hydrocarbon discoveries on the continental shelf and large areas in the vicinity of the southern shelf break, which are in the early stages of exploration. Some, but not all, areas of high seabird density were within current Ecologically and Biologically Significant Area (EBSA) boundaries. Building predictive spatial models required sophisticated analytical skills, and significant investments of time and computational power. Visualization of predictions and their uncertainty needed to be considered for appropriate interpretation by end users. Model uncertainty tended to be greater where survey effort was limited or where predictor covariates exceeded the range of those observed. Predictive spatial models proved useful in generating defensible estimates of seabird densities in many areas of interest to the oil and gas industry in the Labrador Sea, and will have continued use in marine risk assessments and spatial planning activities in the region and beyond.

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.