Adult Murres Research Articles

Influence of sea ice concentration, sex and chick age on foraging flexibility and success in an Arctic seabird.

Declining sea ice and increased variability in sea ice dynamics are altering Arctic marine food webs. Changes in sea ice dynamics and prey availability are likely to impact pagophilic (ice-dependent and ice-associated) species, such as thick-billed murres (Uria lomvia), through changes in foraging behaviour and foraging success. At the same time, extrinsic factors, such as chick demand, and intrinsic factors, such as sex, are also likely to influence foraging behaviour and foraging success of adult murres. Here, we use 3 years of data (2017-2019) to examine the impacts of environmental conditions (sea ice concentration and sea surface temperature), sex and chick age (as a proxy for chick demand) on foraging and diving behaviour (measured via biologgers), energy expenditure (estimated from activity budgets) and foraging success (measured via nutritional biomarkers) of thick-billed murres during the incubation and chick-rearing stages at Coats Island, Nunavut. Murres only exhibited foraging flexibility to environmental conditions during incubation, which is also the only stage when ice was present. When more ice was present, foraging effort increased, murres foraged farther and made deeper dives, where murres making deeper dives had higher foraging success (greater relative change in mass). During incubation, murre behaviour was also influenced by sex of the individual, where males made more and shorter trips and more dives. During chick-rearing, murre behaviour was influenced primarily by the sex of the individual and chick age. Males made shallower dives and fewer dive bouts per day, and more dives. Birds made longer, deeper dives as chicks aged, likely representing increased intra-specific competition for prey throughout the season. Our results suggest variation in sea ice concentration does impact foraging success of murres; however, sex-specific foraging strategies may help buffer colony breeding success from variability in sea ice concentration.

Foraging ecology during nesting influences body size in a pursuit-diving seabird

ABSTRACT: Causes and consequences of differences in seabird foraging strategies between breeding colonies are not well understood. We tested whether body size of a pursuit-diving seabird, the thick-billed murre Uria lomvia, differs between breeding colonies and, if so, how size differences can be understood in the context of differences in foraging behavior, habitat use, and breeding performance. We measured adult murres over 3 seasons (2008 to 2010) at 2 of the Pribilof Islands, St. Paul and St. George, located on the continental shelf of the Bering Sea at different distances from the shelf break. Body mass and size were positively associated with deep diving and negatively associated with long flights, suggesting morphology influences foraging and commuting efficiency. Murres from St. Paul (farther from the shelf break) were larger than those from St. George (nearer the shelf break), foraged exclusively in the middle shelf domain, made deep dives during daylight, and fed on larger benthic prey. In contrast, smaller murres from St. George commuted greater distances to beyond the shelf break, made shallow dives at night, and fed on smaller, high-energy, schooling, vertical-migrating prey. Both foraging strategies resulted in similar chick-feeding rates and fledging success. The largest and the smallest murres experienced less stress during breeding compared to intermediate-sized murres, suggesting divergent selection for body size between islands. Nesting murres, as central-place foragers, may experience strong selection pressure on body size and other adaptive traits that reflect differences between breeding colonies in foraging ecology and the acquisition of resources for reproduction.

Multiple-colony winter habitat use by murres Uria spp. in the Northwest Atlantic Ocean: implications for marine risk assessment

Limited knowledge of year-round seabird distributions hinders efforts to assess consequences of anthropogenic threats and climate-induced changes in the marine environment. In particular, there is urgent need to understand how populations from different breeding colonies share and partition ocean habitat. Using geolocators, we identified winter habitat use patterns of 115 adult murres Uria spp. from 7 colonies, spanning the eastern Canadian coast from the high Arctic to Newfoundland, during 2007 to 2010. Thick-billed murres U. lomvia dispersed throughout the region (Davis Strait, Labrador Sea, Orphan Basin, Grand Bank) with 0 to 45% overlap of core wintering areas (50% kernel home range) among breeding populations. Common murres U. aalge concentrated on the Grand Bank and Orphan Basin, with 50 to 67% overlap among breeding populations. For both species, most individuals (up to 70%) wintered offshore, in shelf (≤500 m deep) and oceanic zones (>500 m); fewer than one-third (30%) of individuals used nearshore zones (≤50 km to shore). Tracked common murres representing >80% of the eastern Canadian breeding population converged in winter in areas of high risk from hydrocarbon exploration and extraction activity. In contrast, tracked thick-billed murres, representing ~34% of the eastern Canadian population, dispersed over a larger area and displayed more variable wintering strategies. Thus population vulnerability to spatially constrained risks may be greater for common than thick-billed murres. Populations from several colonies of both species converged on the Grand Bank and Orphan Basin, with the implications for each breeding population depending on its particular dispersal pattern. We demonstrate the utility of tracking data for highlighting areas of risk, and improving the targeting of broad-scale marine conservation efforts.

Peregrine Falcons Enable Two Species of Colonial Seabirds to Breed Successfully by Excluding Other Aerial Predators

Abstract. The breeding success of Common Murres (Uria aalge) and Pelagic Cormorants (Phalocrocorax pelagicus) at Triangle Island, off British Columbia, Canada, was high from 2003 to 2006; four years in which a pair of Peregrine Falcons (Falco peregrinus) nested in the vicinity. However, in three years when the falcon eyrie was inactive (2007 to 2009), adult murres were depredated on the colony by Bald Eagles (Haliaeetus leucocephalus) and murre eggs were taken by Glaucous-winged Gulls (Larus glaucescens) after eagles flushed incubating murres. Consequently, breeding success in both species was low in 2007, then in 2008 and 2009 no murres bred successfully and no cormorants built nests. That a single pair of falcons protected thousands of seabirds is noteworthy for its local conservation implications. Bottom-up control of seabird breeding success has been well documented, but there appears need for a better understanding of the role of top-down mechanisms as a result of both the direct (consumptive) and in...

Common Murre Egg Recovery

Abstract Common Murre (Uria aalge) breeding success has been monitored in 1996-2004 at Devil’s Slide Rock, California as part of a restoration project related to the Apex Houston oil spill. During the 2001 breeding season, two separate cases of egg recovery by parent murres were observed. During the first event an egg was secured and incubated 60 cm from the original nesting site, while in the second case an egg was retrieved after rolling 85 cm. The first egg was lost within 24 hours, and the second disappeared within a day of its expected hatching date. We describe the circumstances surrounding these events, including the behavior of the parent murres during the egg recovery attempts, the subsequent fate of the recovered eggs, the microhabitat features associated with egg loss and other factors affecting the egg recovery ability of adult murres.

DIRECT AND INDIRECT EFFECTS: INTERACTIONS BETWEEN BALD EAGLES AND COMMON MURRES

We have studied the changing demography of a colonial seabird, the Common Murre, Uria aalge, at a single site on the Washington coast. Whereas informal estimates suggest a steep population increase at Tatoosh Island from ∼1975 to 1990, more rigorous censuses from 1991–1999 indicate that the population has subsequently declined at a rate of ∼3% per year. The primary factor causing this decline appears to be increasing numbers of Bald Eagles, Haliaeetus leucocephalus, visiting the site, where eagles inflict both direct mortality due to eagle predation on adult murres and indirect mortality due to eagle facilitation of gull and crow predation on murre eggs. To explore the contribution of eagles to the observed population decline, we used age-specific vital rates drawn from the literature to develop a wide range of plausible models of murre demography. We found that the match between the projected and observed murre numbers is generally much improved by the inclusion of eagle effects. Our study highlights thr...

Population Characteristics of Common Murres and Rhinoceros Auklets Entangled in Gillnets in Puget Sound, Washington, from 1993 to 1994

Common murres, Uria aalge, and rhinoceros auklets, Cerorhinca monocerata, were the 2 species entangled most frequently in sockeye and chum salmon gillnets in northern and central Puget Sound, Washington, in 1993 and 1994; they comprised more than 90% of all entangled seabirds. The ratio of entangled murres to auklets decreased about 5-fold from approximately 10:1 in 1993 to 2:1 in 1994. Most murres (63%) entangled were adults, whereas most auklets (63%) entangled were hatch-year birds. No significant differences in sex ratio could be detected among age classes of these species within or between fisheries (sockeye versus chum) or years, nor did observed sex ratios deviate significantly from an expected 1:1 sex ratio. During the sockeye fishery (early July through early September), 52% of subadult and adult murres were in breeding plumage, whereas 46% had begun molting flight feathers; by the chum fishery (late September through late November), only 18% were still molting flight feathers, whereas 77% had completed molting their flight feathers. All auklets were in breeding plumage having not yet begun flight-feather molt. No adult murres had visible incubation patches during the sockeye fishery. Because murres fledge from Oregon colonies at least a month earlier than they do from Washington colonies, adult murres from Oregon grow their incubation patches back at least a month earlier as well; this suggests that at least some entangled adult murres came from Oregon. Similarly, some hatch-year murres were entangled in Puget Sound before murre chicks fledged from Washington (or more northerly) colonies, again indicating that at least some hatchyear murres fledged from Oregon colonies.

Factors Affecting the Success of Colony Departure by Thick-Billed Murre Chicks

Young Thick-billed Murres leave their natal colony while still incapable of flight, jumping directly to the sea. The brief period of transition from cliff ledge to open ocean results in significant mortality. At Coats Island, Northwest Territories, Canada, we investigated the effects of predation by gulls, murre nest site characteristics, and adult murre aggression on the likelihood that chicks departed to sea. Approximately 20% of chicks that jumped from the cliff failed to depart successfully to sea. Live chicks were rarely taken by predators. Most mortality was caused by drowning, as a result of aggression by adult murres. However, chicks accompanied by defending parents usually were unaffected by aggression from other adult murres. As a result, the most important cause of chick mortality at colony departure was the separation of chick and parent before reaching the sea. Chicks landed alone because either they or their parent were knocked from the nest ledge during fights with neighbors as they moved to the jump site, or because chicks struck cliff ledges during the descent to the water. Apparently, the nearer the nest site was to the edge of the ledge, and the fewer obstructions below the jump site, the greater the departure success of chicks. Site characteristics that determine success during departure may differ from those associated with success in incubation and chick-rearing. Hence the effect of breeding site on reproduction may be incorrectly assessed if departure success is not taken into account.

The Autumn Migration of Thick-billed Murres near Southern Baffin Island and Northern Labrador

Aerial surveys were used to assess the timing and route of the swimming migration of Thick-billed Murres (Uria lomvia) near southern Baffin Island and northern Labrador in the autumn of 1977, 1978 and 1979. Several hundred thousand adults and chicks from six southern Baffin area colonies departed east through Hudson Strait, in the direction of surface currents, in the latter half of August. Most murres from three eastern Hudson Strait colonies were in offshore waters in early September, arrived in the northern Labrador Sea within a few days, and were followed later in September by murres from three western Hudson Strait colonies. From the Labrador Sea, murres go to marine wintering sites around Newfoundland. Murres from a large colony on southeast Baffin Island apparently did not migrate to the Labrador Sea through western Davis Strait; instead, they either migrated through central Davis Strait en route to Newfoundland, or east to west Greenland, which was also the probable destination of many adult murres which flew by a drillship in southwest Davis Strait.Key words: Thick-billed Murre (Uria lomvia), migration, Baffin Island, Davis Strait, Labrador Sea, eastern Canada, colonial seabird