Uria Aalge Research Articles

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.

Predator–prey interactions influenced by a dynamic river plume

Marine predator–prey interactions are often influenced by oceanographic processes that aggregate prey. We examined density distributions of seabirds and prey fish associated with the Columbia River plume to determine whether variation in plume size (i.e., volume or surface area) or location influences predator–prey interactions. Common murre (Uria aalge), sooty shearwater (Ardenna grisea), and forage fish, including northern anchovy (Engraulis mordax) and juvenile salmon (Oncorhynchus spp.), occurred disproportionately in plume waters relative to adjacent marine waters. Water clarity, an indicator of plume-influenced waters, was a significant predictor of seabird and prey densities throughout the survey area. Murres occurred within 20 km of the plume center of gravity, whereas shearwaters occurred ∼100 km north of the plume center of gravity, concurrent with the highest densities of prey fish. Global indices of collocation were relatively low between murres and prey compared with the high values between shearwaters and prey. Seabird densities were negatively correlated with plume size, suggesting that seabirds concentrate in the plume to maximize foraging effort. We conclude that variation in Columbia River plume size and location influences predator distributions, which increases predation pressure on prey, including threatened salmonid species.

Breeding density, fine-scale tracking, and large-scale modeling reveal the regional distribution of four seabird species.

Population-level estimates of species' distributions can reveal fundamental ecological processes and facilitate conservation. However, these may be difficult to obtain for mobile species, especially colonial central-place foragers (CCPFs; e.g., bats, corvids, social insects), because it is often impractical to determine the provenance of individuals observed beyond breeding sites. Moreover, some CCPFs, especially in the marine realm (e.g., pinnipeds, turtles, and seabirds) are difficult to observe because they range tens to ten thousands of kilometers from their colonies. It is hypothesized that the distribution of CCPFs depends largely on habitat availability and intraspecific competition. Modeling these effects may therefore allow distributions to be estimated from samples of individual spatial usage. Such data can be obtained for an increasing number of species using tracking technology. However, techniques for estimating population-level distributions using the telemetry data are poorly developed. This is of concern because many marine CCPFs, such as seabirds, are threatened by anthropogenic activities. Here, we aim to estimate the distribution at sea of four seabird species, foraging from approximately 5,500 breeding sites in Britain and Ireland. To do so, we GPS-tracked a sample of 230 European Shags Phalacrocorax aristotelis, 464 Black-legged Kittiwakes Rissa tridactyla, 178 Common Murres Uria aalge, and 281 Razorbills Alca torda from 13, 20, 12, and 14 colonies, respectively. Using Poisson point process habitat use models, we show that distribution at sea is dependent on (1) density-dependent competition among sympatric conspecifics (all species) and parapatric conspecifics (Kittiwakes and Murres); (2) habitat accessibility and coastal geometry, such that birds travel further from colonies with limited access to the sea; and (3) regional habitat availability. Using these models, we predict space use by birds from unobserved colonies and thereby map the distribution at sea of each species at both the colony and regional level. Space use by all four species' British breeding populations is concentrated in the coastal waters of Scotland, highlighting the need for robust conservation measures in this area. The techniques we present are applicable to any CCPF.

Turn-taking ceremonies in a colonial seabird: Does behavioral variation signal individual condition?

ABSTRACT In species with biparental care, pairs share a cooperative interest in offspring survival but may be in conflict over their relative investments, as reported in recent turn-taking studies of chick-provisioning birds. Turn-taking in Common Murres (Uria aalge) involves the foraging bird returning to the colony to provision the chick and the brooding parent departing. We examined whether Common Murres in poor condition had slower or more irregular turn-taking behavior, as has been documented in Common Murres equipped with geologgers. Irregularities include the brooding bird not trading parental roles with its returning mate or a bird returning to the colony without a fish. Irregular turn-taking sequences generally took longer than normal turn-taking sequences and differed in the rate and synchrony of allopreening, the main interactive behavior between mates. There was a delayed onset of allopreening when nest reliefs were protracted, whereas returners that did not bring a fish started allopreening s...

Bayesian joint models with INLA exploring marine mobile predator-prey and competitor species habitat overlap.

Understanding spatial physical habitat selection driven by competition and/or predator–prey interactions of mobile marine species is a fundamental goal of spatial ecology. However, spatial counts or density data for highly mobile animals often (1) include excess zeros, (2) have spatial correlation, and (3) have highly nonlinear relationships with physical habitat variables, which results in the need for complex joint spatial models. In this paper, we test the use of Bayesian hierarchical hurdle and zero‐inflated joint models with integrated nested Laplace approximation (INLA), to fit complex joint models to spatial patterns of eight mobile marine species (grey seal, harbor seal, harbor porpoise, common guillemot, black‐legged kittiwake, northern gannet, herring, and sandeels). For each joint model, we specified nonlinear smoothed effect of physical habitat covariates and selected either competing species or predator–prey interactions. Out of a range of six ecologically important physical and biologic variables that are predicted to change with climate change and large‐scale energy extraction, we identified the most important habitat variables for each species and present the relationships between these bio/physical variables and species distributions. In particular, we found that net primary production played a significant role in determining habitat preferences of all the selected mobile marine species. We have shown that the INLA method is well‐suited for modeling spatially correlated data with excessive zeros and is an efficient approach to fit complex joint spatial models with nonlinear effects of covariates. Our approach has demonstrated its ability to define joint habitat selection for both competing and prey–predator species that can be relevant to numerous issues in the management and conservation of mobile marine species.

Effects of Added Lipids on Digestibility and Nitrogen Balance in Oiled Common Murres ( Uria aalge ) and Western Grebes ( Aechmophorus occidentalis ) Fed Four Formulations of a Critical Care Diet.

Nutritional support is a primary therapy administered to oiled animals during responses to oil spills, but data informing nutritional decision-making during events are limited. In this study, 44 common murres ( Uria aalge ) and 6 Western grebes ( Aechmophorus occidentalis ), naturally oiled by oceanic seeps off the coast of Ventura and Santa Barbara Counties, CA, USA, were assigned to 1 of 4 groups fed diets with varying levels (6.8% [no added oil], 11%, and 20%) and types (salmon, corn) of oil added to a partially purified basal diet. Birds used in the study ranged from extremely emaciated to thin body condition (62%-80% wild bird mean body mass). Acid-insoluble ash was used as an indigestible dietary marker to quantify nitrogen retention, apparent nitrogen digestibility, nitrogen-corrected apparent metabolizable energy, energy digestibility, fat retention, fat digestibility, and estimated fat excretion. Fat excretion is important in these species because once birds have been cleaned they are at risk of plumage recontamination from excreted fat during care. Lower fat diets resulted in lower fat excretion but higher nitrogen retention, higher apparent nitrogen digestibility, and higher apparent metabolizable energy. Decreases in nitrogen retention were significantly related to increases in fat excretion. Regardless of diet, energy digestibility significantly declined with declines in body mass, suggesting severity of emaciation reduced a birds' ability to extract energy from food. Energy digestibility was highest in the 11% (low) salmon oil diet; hence, this diet had the highest effective energy content despite a lower gross kcal/kg diet. Diets fed during oil spills historically have had high fat concentrations to provide maximum caloric support. Results of this study suggest that lower fat diets may be more efficacious for nutritionally depleted seabirds. This study provides valuable data to guide clinical decision making regarding nutritional support during oil spills and other mass stranding events.

Four sympatrically nesting auks show clear resource segregation in their foraging environment

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 572:243-254 (2017) - DOI: https://doi.org/10.3354/meps12144 Four sympatrically nesting auks show clear resource segregation in their foraging environment Isabeau Pratte1,*, Gregory J. Robertson2, Mark L. Mallory1 1Department of Biology, Acadia University, Wolfville, Nova Scotia B4P 2R6, Canada 2Wildlife Research Division, Environment and Climate Change Canada, Mount Pearl, Newfoundland A1N 4T3, Canada *Corresponding author: pratteisabeau@gmail.com ABSTRACT: Auks share ecological similarities and are often found in sympatrically nesting assemblages at suitable nesting sites. It is expected that co-existing species would have evolved strategies to reduce niche overlap in response to resource competition. The presence of Atlantic puffins Fratercula arctica, razorbills Alca torda, thick-billed murres Uria lomvia and common murres U. aalge at the Gannet Islands, Labrador, is an opportunity to study interspecific interactions in a major seabird community. We compared the foraging movements of adult breeding birds and the diet of the birds inferred through (1) stable isotopes in the blood of adults, and (2) prey delivered to the chicks, as dimensions in the foraging niche among these 4 auks. Our results revealed that puffins and thick-billed murres headed offshore to forage, while razorbills and common murres were more coastal, heading towards mainland Labrador. The patterns of spatial segregation found among coastal and pelagic birds were mirrored by their stable isotope ratios, with one group of species foraging at a higher trophic level of an inshore food web and the other foraging on a lower trophic level of an offshore, pelagic food web. The ‘pelagic’ species segregated by prey choice for their chicks while differential alternate prey selection was the source of segregation between the ‘coastal’ species. Our research highlights the importance of segregation patterns in both spatial and diet dimensions of the foraging niche among the 4 auks—a potential mechanism for reducing interspecific competition among ecologically similar seabirds and explaining the persistence of such seabird assemblages through time. KEY WORDS: Seabird · Foraging distribution · Niche overlap · Diet · Isotopic niche Full text in pdf format Supplementary material PreviousNextCite this article as: Pratte I, Robertson GJ, Mallory ML (2017) Four sympatrically nesting auks show clear resource segregation in their foraging environment. Mar Ecol Prog Ser 572:243-254. https://doi.org/10.3354/meps12144 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 572. Online publication date: May 31, 2017 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2017 Inter-Research.

Environmental conditions and prey-switching by a seabird predator impact juvenile salmon survival

Abstract Due to spatio-temporal variability of lower trophic-level productivity along the California Current Ecosystem (CCE), predators must be capable of switching prey or foraging areas in response to changes in environmental conditions and available forage. The Gulf of the Farallones in central California represents a biodiversity hotspot and contains the largest common murre ( Uria aalge ) colonies along the CCE. During spring, one of the West Coast's most important Chinook salmon ( Oncorhynchus tshawytscha ) populations out-migrates into the Gulf of the Farallones. We quantify the effect of predation on juvenile Chinook salmon associated with ecosystem-level variability by integrating long-term time series of environmental conditions (upwelling, river discharge), forage species abundance within central CCE, and population size, at-sea distribution, and diet of the common murre. Our results demonstrate common murres typically forage in the vicinity of their offshore breeding sites, but in years in which their primary prey, pelagic young-of-year rockfish ( Sebastes spp.), are less available they forage for adult northern anchovies ( Engraulis mordax ) nearshore. Incidentally, while foraging inshore, common murre consumption of out-migrating juvenile Chinook salmon, which are collocated with northern anchovy, increases and population survival of the salmon is significantly reduced. Results support earlier findings that show timing and strength of upwelling, and the resultant forage fish assemblage, is related to Chinook salmon recruitment variability in the CCE, but we extend those results by demonstrating the significance of top-down impacts associated with these bottom-up dynamics. Our results demonstrate the complexity of ecosystem interactions and impacts between higher trophic-level predators and their prey, complexities necessary to quantify in order to parameterize ecosystem models and evaluate likely outcomes of ecosystem management options.

Regionalizing indicators for marine ecosystems: Bering Sea–Aleutian Island seabirds, climate, and competitors

Seabirds are thought to be reliable, real-time indicators of forage fish availability and the climatic and biotic factors affecting pelagic food webs in marine ecosystems. In this study, we tested the hypothesis that temporal trends and interannual variability in seabird indicators reflect simultaneously occurring bottom-up (climatic) and competitor (pink salmon) forcing of food webs. To test this hypothesis, we derived multivariate seabird indicators for the Bering Sea–Aleutian Island (BSAI) ecosystem and related them to physical and biological conditions known to affect pelagic food webs in the ecosystem. We examined covariance in the breeding biology of congeneric pelagic gulls (kittiwakes Rissa tridactyla and R. brevirostris) and auks (murres Uria aalge and U. lomvia), all of which are abundant and well-studied in the BSAI. At the large ecosystem scale, kittiwake and murre breeding success and phenology (hatch dates) covaried among congeners, so data could be combined using multivariate techniques, but patterns of response differed substantially between the genera. While data from all sites (n=5) in the ecosystem could be combined, the south eastern Bering Sea shelf colonies (St. George, St. Paul, and Cape Peirce) provided the strongest loadings on indicators, and hence had the strongest influence on modes of variability. The kittiwake breeding success mode of variability, dominated by biennial variation, was significantly related to both climatic factors and potential competitor interactions. The murre indicator mode was interannual and only weakly related to the climatic factors measured. The kittiwake phenology indicator mode of variability showed multi-year periods (“stanzas”) of late or early breeding, while the murre phenology indicator showed a trend towards earlier timing. Ocean climate relationships with the kittiwake breeding success indicator suggest that early-season (winter–spring) environmental conditions and the abundance of pink salmon affect the pelagic food webs that support these seabirds in the BSAI ecosystem.

Density dependence and changes in the carrying capacity of Alaskan seabird populations

Evidence for regulation of animal populations by negative density dependence is ubiquitous across the animal realm, and yet the dynamics of carrying capacity (K) are often overlooked. K acts as a threshold below which population size tends to increase and above which it tends to decrease. Documenting changes in this threshold is particularly important to population viability analysis (PVA). We reconstructed the population sizes of five long-lived seabird species in Alaska, USA, and analyzed their population dynamics from the past four decades: Black-legged (Rissa tridactyla) and Red-legged Kittiwakes (R. brevirostris), Common (Uria aalge) and Thick-billed Murres (U. lomvia) and Tufted Puffins (Fratercula cirrhata). We evaluated a set of models that allowed for either density independence or density dependence, with or without a time trend in K. The best approximating models indicated that these seabird populations behaved in a negative density-dependent fashion. K increased significantly for murres, and remained relatively stable for Red-legged Kittiwakes. It decreased significantly (>40%) for Black-legged Kittiwakes and Tufted Puffins, particularly in the Gulf of Alaska, following the 1989 Exxon Valdez oil spill. Although we have less confidence in the puffin data, our PVA suggests that, in the next 100years, Tufted Puffins may become extirpated from the few colonies that are monitored in the Gulf of Alaska. Negative density dependence can help to prevent population crashes, but time lags and serial correlation in rates of change could suppress the recovery of contracted populations. Therefore, estimating the magnitude of population fluctuations around a changing carrying capacity is essential to managing and conserving declining populations.

The point of a Guillemot's egg

The adaptive significance of avian egg shape in birds is poorly understood. The pyriform (pear‐like) shape of the Common Guillemot's Uria aalge egg has long been considered to be an adaptation to prevent eggs rolling off the bare cliff ledges on which this species breeds. Rolling was thought to be prevented either by the egg spinning like a top, which is not the case, or by rolling in an arc, which it does but with little influence on whether the egg will fall from a ledge. We therefore sought alternative explanations for the pyriform shape of the Common Guillemot's egg. This species breeds in extremely dense colonies, which makes their eggs vulnerable to mechanical damage from conspecifics, and to contamination by debris such as faeces and soil. We present evidence consistent with both these possible explanations. First, the pyriform shape of Common Guillemot eggs means that a higher proportion of the eggshell lies in contact with the substrate and this may minimize the effect of impacts. Resistance to impacts may be further enhanced because their eggshells are especially thick where they are in contact with the substrate. Secondly, Common Guillemot eggs are often heavily contaminated with faecal material and other debris during incubation. Most contamination is on the pointed end of the egg where it is in contact with the substrate; the pyriform shape thus keeps the blunt end of the egg, which has the highest porosity, relatively free of contamination, which in turn may facilitate both gas exchange during incubation and the hatching process, because the chick emerges from the blunt end of the egg.

Egg shape in the Common Guillemot Uria aalge and Brunnich\u2019s Guillemot U. lomvia: not a rolling matter?

The adaptive significance of avian egg shape is poorly understood, and has been studied only in those species producing pyriform (pear-shaped, or pointed) eggs: waders and guillemots (murres) Uria spp., albeit to a limited extent. In the latter, it is widely believed that the pyriform shape has evolved to minimise their likelihood of rolling off a cliff ledge: the idea being that the more pointed the egg, the narrower the arc in which it rolls, and the less likely it is it will fall from a cliff ledge. Previous research also claimed that the rolling trajectory—the diameter of the arc they describe—of Common Guillemot U. aalge eggs is influenced not only by its shape but also by its mass, with heavier (i.e. larger) eggs describing a wider arc than lighter eggs. The finding that both shape and mass determined the rolling trajectory of Common Guillemot eggs (the shape–mass hypothesis) was used to explain the apparent anomaly that Brünnich’s Guillemot U. lomvia produce eggs that are less pointed, yet breed on narrower ledges than Common Guillemots. They are able to do this, it was suggested, because Brünnich’s Guillemot eggs are smaller and lighter in mass than those of Common Guillemots. However, since some populations of Brünnich’s Guillemots produce eggs that are as large or larger than those of some Common Guillemot populations, the shape–mass hypothesis predicts that that (1) larger (i.e. heavier) eggs of both guillemot species will be more pyriform (pointed) in shape, and (2) that eggs of the two species of same mass should be similarly pointed. We tested these predictions and found: (1) only a weak, positive association between egg volume and pointedness in both guillemot species (<3% of the variation in egg shape explained by egg volume), and (2) no evidence that eggs of the two species of similar mass were more similar in shape: regardless of their mass, Brunnich’s Guillemot eggs were less pointed than Common Guillemot eggs. Overall, our results call into question the long-held belief that protection from rolling is the main selective factor driving guillemot egg shape.

Nocturnal colony attendance by Common Guillemots Uria aalge at colony in Shetland during the pre-breeding season

Time-lapse photography was used to describe daily and seasonal trends in attendance by Common Guillemot Uria aalge at a colony in Shetland prior to the breeding season, including detection of nocturnal presence. A camera took a photo every 30 minutes from 30 January until 21 April 2015. A total of 3,435 photos were analysed, of which 3,232 photos allowed birds to either be accurately counted (2,552) or estimated (680) within a representative plot. High quality moonlit shots showed that large numbers of Common Guillemots were present ashore at Sumburgh throughout the night, while manipulated non-moonlight night photos revealed attendance at the colony, even when counting was not possible. Clear cycles of attendance at the colony were apparent with day-time peaks of 90–120 birds occurring on average every 7 days over the study period. Pre-breeding attendance is described, as is the nocturnal presence of Common Guillemots in the three months prior to breeding.

Monitoring the breeding success of Common Guillemots Uria aalge: the value of multiple plots

Results from seabird monitoring programmes are increasingly being used to assess the state of the marine environment, but data are time consuming to collect. We used monitoring data from a colony of Common Guillemots Uria aalge in the North Sea to determine whether temporal changes in breeding success over a 34- year period were reflected in six consistently monitored plots and if individual plots showed significant differences in breeding success. Annual mean breeding success showed a four-fold difference over the study period varying from 0.261 to 0.848 young fledging per pair laying. Although the annual pattern of change was broadly reflected in all six monitoring plots there were significant differences in annual breeding success and changes in breeding success over time among the plots. Monitoring any single plot thus gave an approximate indication of the overall patterns of change over time, including periods when breeding success was reduced. However, significant among plot differences indicated that at least at this colony, robustness of colony level estimates of breeding success and changes over time were improved by monitoring multiple plots.

ECOLOGICAL SITUATION ON THE TYULENIY ISLAND IN THE OKHOTSK SEA (2015): POPULATION INTERACTIONS BETWEEN PINNIPEDS, BIRDS, IXODIDAE TICKS AND VIRUSES

Objective. Analysis of environmental status Tyuleniy Island after a 25-year break in ecological and virological expeditions. Discussion. The paper presents the first results of the ecological and virological expedition to the Tyuleniy Island in August 2015 – the first after a 25 year break. Species of colonial seabirds and pinnipeds are described as well as their population interactions with each other and with Ixodidae ticks Ixodes uriae, which parasite in breeding colonies of birds and are hosts and vectors of several arboviruses that pose a potential risk to mammals. Two strains were isolated from common murre cloaca swabs using chicken embryo biological model. Complete genome sequencing permitted to identify these strains as NDV/Uria aalge/Russia/Tyuleniy Island/109/2015 (GenBank ID: KU601398) and APMV-4/Uria aalge/Russia/Tyuleniy Island/115/2015 (GenBank ID: KU601399). Strain of new virus (Bunyaviridae, Nairovirus) was isolated from homogenate of I. uriae on the model of intracerebrally inoculated newborn mice and was identified by sequencing of the fragment (240 nucleotides) of the N-gene. Conclusion. The Tyuleniy Island confirmed its importance as a reservoir of arboviruses. The ecological conditions of the Tyuleniy Island requires urgent action to clean up the island from the old buildings and giving it the status of the reserve.

Ophthalmic effects of petroleum dispersant exposure on common murres (Uria aalge): An experimental study

The safety of chemical dispersants used during oil spill responses is largely unknown in birds. We captured common murres in Monterey Bay, CA and exposed them to Corexit EC9500a, crude oil, or a combination in artificial seawater. We performed ophthalmic examinations and measured intraocular pressures and tear production before and after exposure. Loglinear analysis found that exposure to oil or dispersant was related to the development of conjunctivitis and corneal ulcers. Odds ratios for birds exposed to oil or dispersant were positive and significant for the development of conjunctivitis, while odds ratios for the development of corneal ulcers were positive and significant only for birds exposed to a high concentration of oil. Ocular exposure to dispersants and petroleum in seabirds may cause conjunctivitis and may play a role in the development of corneal ulcers. These results have implications for policymakers who develop protocols for the use of dispersants during marine oil spills.

Resource partitioning between sympatric seabird species increases during chick‐rearing

AbstractPartitioning of resources by competing species of seabirds may increase during periods of food shortages and elevated energy demands. Here, we examined whether food resource partitioning (differential use of foraging habitat or the consumption of different prey species) between common murres (COMU, Uria aalge) and thick‐billed murres (TBMU, U. lomvia) breeding on the same colony in the Bering Sea increases with a predictable increase in energy demands between the incubation and chick‐rearing stages of reproduction. We assessed the seasonal dynamics of food availability via corticosterone (CORT) levels and examined adult diet (via stable isotope analysis of nitrogen and carbon, SI) and chick diets (based on nest observations). We compared chick provisioning patterns and examined the characteristics of parental foraging habitat via deployment of bird‐borne temperature‐depth recorders. We found that CORT levels remained low and similar between the species and reproductive stages, reflecting relatively stable and favorable foraging conditions for both murre species during the study period. Comparisons of SI between murres and their potential prey indicated that diets were similar between the species during incubation and diverged during chick‐rearing. Chick‐rearing common and thick‐billed murres also used different foraging habitats, as reflected in travel distances to foraging areas and sea surface temperature distributions of their foraging dives. TBMUs performed shorter foraging trips, deeper dives and delivered squid to their chicks, while COMUs foraged farther from the colony, performed shallower dives, and delivered fish species to their chicks. These results suggest that food resource partitioning between murre species increased during chick‐rearing under favorable foraging conditions. Whether the dietary segregation reflected species‐specific differences in adults' foraging efficiency, differences in chicks' dietary requirements, or was a way of reducing competition remains unknown. Regardless of the causal mechanism(s), food resource partitioning might ameliorate interspecific competition between sympatrically breeding birds during periods of increased energy demands.

Cold Case: The Death of Common Guillemots in the Barents Sea

Abstract When guillemot populations collapsed in the Barents Sea in the winter of 1986–7, a lack of food was blamed. But did climate play a role in this collapse? Michel d. S. Mesquita and Kjell Einar Erikstad went looking for an answer

Age-related effects on breeding phenology and success of Common Guillemots Uria aalge at a North Sea colony

ABSTRACTCapsule: Common Guillemots Uria aalge show delayed breeding and marked age-related changes in reproductive success consistent with improved performance with experience.Aims: To determine age of first breeding and age-related effects on breeding phenology and success of Common Guillemots.Methods: Resighting data from a long-term colour-ringing study of Common Guillemot chicks were combined with observations of breeding phenology and success to follow the recruitment process, breeding phenology and success of 62 birds at a major North Sea colony over a 30-year period.Results: The median age of first breeding of Common Guillemots was 6.6 years. There were no detectable costs of first breeding on return rates or the likelihood of breeding the next season but first time breeders bred later and less successfully. Age of first breeding and lifetime breeding success both varied among individuals but there was no clear optimal age of first breeding and early first breeding was not associated with higher lifetime breeding success.Conclusions: Common Guillemots in the Isle of May population delayed breeding for 3–4 years beyond physiological maturity. The marked increase in breeding success with age was consistent with improved performance with experience rather than selection for higher quality individuals. Findings from this study will inform population models by providing improved estimates of age of first breeding and age-related changes in reproductive performance.

MORTALITY DURING TREATMENT: FACTORS AFFECTING THE SURVIVAL OF OILED, REHABILITATED COMMON MURRES (URIA AALGE).

After major oil spills, hundreds to thousands of live stranded birds enter rehabilitative care. To target aspects of rehabilitative efforts for improvement and to evaluate which initial physical examination and biomedical parameters most effectively predict survival to release, medical records were examined from 913 Common Murres ( Uria aalge ; COMUs) oiled during the November 2001-January 2003 oil spill associated with the sunken S.S. Jacob Luckenbach off San Francisco, California, US. Results showed that 52% of all deaths occurred during the first 2 days of treatment. Birds stranding closest to the wreck had greater amounts of oil on their bodies than birds stranding farther away. More heavily oiled birds were in better clinical condition than birds with lesser amounts of oil, as shown by higher body mass (BM), packed cell volumes (PCV), total plasma protein (TP), and higher survival proportions. Additionally, BM, PCV, TP, and body temperature were positively correlated. For comparison, medical records from all nonoiled COMUs admitted for rehabilitation at the same facility during 2007-09 (n=468) were examined, and these variables were also found to be positively correlated. Oiled birds with BM under 750 g had approximately 5% lower PCV than BM-matched nonoiled COMUs. More heavily oiled COMUs may be in better condition than less oiled birds because heavily oiled birds must beach themselves immediately to avoid drowning and hypothermia, whereas lightly oiled birds may postpone beaching until exhausted due to extreme body catabolism. The strong relationship of PCV to BM regardless of oiling provides evidence that anemia commonly encountered in oiled seabirds may be a sequela to overall loss of body condition rather than solely due to toxic effects of oiling. Clinical information garnered in this study provides guidance for triage decisions during oil spills.