Sex-specific foraging behaviour by a low-arctic, diving seabird over the annual cycle

This thesis examines the seasonal foraging ecology of the Common Murre (Uria aalge), a circumpolar seabird with physiological adaptations for efficient pursuit-diving and a specialized reproductive strategy (male-biased parental care). The primary research objectives are to assess the behavioural strategies drawn upon by adult murres to survive a seasonally dynamic, Arctic-influenced marine environment, and to investigate how seasonal differences in parental care roles influence sex-specific foraging and survival strategies. To engage this question, I use bird-borne data loggers that collect behavioural observations relating to the distribution, diving and daily activity patterns of individual murres over eight months (July - February) in their annual cycle. Behavioural metrics are integrated with analyses of stable isotope ratios from a variety of tissues that provide corresponding information on seasonal trophic position and dietary niche breadth. Murres exhibited flexibility in their foraging behaviour over the annual cycle. This was evident in a switch from increased foraging effort with a specialized, high trophic level diet during periods of peak energy demand (summer chick-rearing and late winter) to significantly reduced foraging effort and a generalized, low trophic level diet during the less demanding post-breeding period. Energy savings during moult-induced flightlessness and a flexible moult schedule facilitated by a resident, over-wintering strategy resulted in low energy demands during the post-breeding wing moult. I hypothesise that the post-breeding period represents a buffer event in the annual cycle of adult murres, and may be a key component of survival for a seabird with an otherwise costly pace of life. Single-parenting males spent twice as much time foraging (self and offspring provisioning) relative to independent females (self provisioning only) and occupied relatively poor quality habitat over the estimated 63 days of paternal care at sea. Despite this, there was no evidence of an energy constraint as single-parenting males consumed the same low trophic-level diet as independent females and allocated equivalent time to self-feeding. Nonetheless, adult males could face time constraints to rear their offspring to independence and complete post-breeding wing moult before the onset of winter if energy limitations during poor-food years are resolved by the extension of either (or both) fitness-related activities. During late winter, murres experienced a significant increase in estimated daily energy expenditures (DEE), driven in part by high thermoregulatory costs during prolonged exposure to cold water. Murres were able to overcome this energetic challenge by pushing the limits of their diving capabilities but regardless, late winter appears to be an extremely challenging time in their annual cycle. Overall, this thesis demonstrates remarkable behavioural plasticity by murres over their annual cycle, characterized by highly plastic foraging tactics, dietary strategies and flexibility in the scheduling of wing moult, which may allow them to mediate some of the environmental disruptions predicted to occur with climate change. Yet, persistent declines in the biomass and condition of capelin Mallotus villosus, the keystone forage species in the NW Atlantic food web and the primary prey of breeding murres (and their offspring) could challenge this resiliency

Miniaturized data loggers and computer programming improve seabird risk and damage assessments for marine oil spills in Atlantic Canada

Obtaining useful information on marine birds that can aid in oil spill (and other hydrocarbon release) risk and damage assessments in offshore environments is challenging. Technological innovations in miniaturization have allowed archival data loggers to be deployed successfully on marine birds vulnerable to hydrocarbons on water. A number of species, including murres (both Common, Uria aalge, and Thick-billed, U. lomvia) have been tracked using geolocation devices in eastern Canada, increasing our knowledge of the seasonality and colony-specific nature of their susceptibility to oil on water in offshore hydrocarbon production areas and major shipping lanes. Archival data tags are starting to resolve questions around behaviour of vulnerable seabirds at small spatial scales relevant to oil spill impact modelling, specifically to determine the duration and frequency at which birds fly at sea. Advances in data capture methods using voice activated software have eased the burden on seabird observers who are collecting increasingly more detailed information on seabirds during ship-board and aerial transects. Computer programs that integrate seabird density and bird behaviour have been constructed, all with a goal of creating more credible seabird oil spill risk and damage assessments. In this paper, we discuss how each of these technological and computing innovations can help define critical inputs into seabird risk and damage assessments, and when combined, can provide a more realistic understanding of the impacts to seabirds from any hydrocarbon release

State of wildfires 2023–24

Climate change is increasing the frequency and intensity of wildfires globally, with significant impacts on society and the environment. However, our understanding of the global distribution of extreme fires remains skewed, primarily influenced by media coverage and regional research concentration. This inaugural State of Wildfires report systematically analyses fire activity worldwide, identifying extreme events from the March 2023–February 2024 fire season. We assess the causes, predictability, and attribution of these events to climate change and land use, and forecast future risks under different climate scenarios. During the 2023–24 fire season, 3.9 million km2 burned globally, slightly below the average of previous seasons, but fire carbon (C) emissions were 16 % above average, totaling 2.4 Pg C. This was driven by record emissions in Canadian boreal forests (over 9 times the average) and dampened by reduced activity in African savannahs. Notable events included record-breaking wildfire extent and emissions in Canada, the largest recorded wildfire in the European Union (Greece), drought-driven fires in western Amazonia and northern parts of South America, and deadly fires in Hawai’i (100 deaths) and Chile (131 deaths). Over 232,000 people were evacuated in Canada alone, highlighting the severity of human impact. Our analyses revealed that multiple drivers were needed to cause areas of extreme fire activity. In Canada and Greece a combination of high fire weather and an abundance of dry fuels increased the probability of fires by 4.5-fold and 1.9–4.1-fold, respectively, whereas fuel load and direct human suppression often modulated areas with anomalous burned area. The fire season in Canada was predictable three months in advance based on the fire weather index, whereas events in Greece and Amazonia had shorter predictability horizons. Formal attribution analyses indicated that the probability of extreme events has increased significantly due to anthropogenic climate change, with a 2.9–3.6-fold increase in likelihood of high fire weather in Canada and a 20.0–28.5-fold increase in Amazonia. By the end of the century, events of similar magnitude are projected to occur 2.22–9.58 times more frequently in Canada under high emission scenarios. Without mitigation, regions like Western Amazonia could see up to a 2.9-fold increase in extreme fire events. For the 2024–25 fire season, seasonal forecasts highlight moderate positive anomalies in fire weather for parts of western Canada and South America, but no clear signal for extreme anomalies is present in the forecast. This report represents our first annual effort to catalogue extreme wildfire events, explain their occurrence, and predict future risks. By consolidating state-of-the-art wildfire science and delivering key insights relevant to policymakers, disaster management services, firefighting agencies, and land managers, we aim to enhance society’s resilience to wildfires and promote advances in preparedness, mitigation, and adaptation

Scenario set-up and forcing data for impact model evaluation and impact attribution within the third round of the Inter-Sectoral Model Intercomparison Project (ISIMIP3a)

This paper describes the rationale and the protocol of the first component of the third simulation round of the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP3a, www.isimip.org) and the associated set of climate-related and direct human forcing data (CRF and DHF, respectively). The observation-based climate-related forcings for the first time include high-resolution observational climate forcings derived by orographic downscaling, monthly to hourly coastal water levels, and wind fields associated with historical tropical cyclones. The DHFs include land use patterns, population densities, information about water and agricultural management, and fishing intensities. The ISIMIP3a impact model simulations driven by these observation-based climate-related and direct human forcings are designed to test to what degree the impact models can explain observed changes in natural and human systems. In a second set of ISIMIP3a experiments the participating impact models are forced by the same DHFs but a counterfactual set of atmospheric forcings and coastal water levels where observed trends have been removed. These experiments are designed to allow for the attribution of observed changes in natural, human and managed systems to climate change, rising CH4 and CO2 concentrations, and sea level rise according to the definition of the Working Group II contribution to the IPCC AR6

Effects of an Arctic Fox Visit to a Low Arctic Seabird Colony

A visit by an arctic fox (Alopex lagopus) to Funk Island, Newfoundland, during 2009 had a negative impact on the breeding performance of five of the nine breeding seabird species. Species that nest in burrows (Atlantic puffin Fratercula arctica) or on the ground (northern fulmar Fulmarus glacialis, great black-backed Larus marinus and herring gulls Larus argentatus) did not fledge any offspring in 2009, and common murres (Uria aalge) at this colony, the largest for this species in North America, experienced an estimated 4.9% (~19 712.4 breeding pairs) reduction in the number of nesting birds. Later-than-normal persistence of Arctic sea ice on the Newfoundland-Labrador Shelf in 2009 likely provided the fox access to the colony up until late April, which coincided with the seabirds’ return. The persistent predation threat near the onset of breeding likely resulted in large-scale abandonment of breeding attempts by vulnerable seabirds

Comparative foraging ecology of parental common murres (Uria aalge) and Atlantic puffins (Fratercula arctica) in response to changes in forage fish availability

To ensure successful reproduction, seabirds must make continuous and adaptive foraging decisions in the face of uncertain prey conditions. I compared the foraging behavior (foraging ranges and diet choices) of parental common murres and Atlantic puffins at a high density, offshore colony (Funk Island) during 2 years of different forage fish availability. In a poor food year (2005), characterized by an order of magnitude decline in forage fish densities and smaller fish, murres and puffins increased the mean distance they traveled to forage by 36% and preferentially selected larger fish. These responses show flexible foraging behavior, but significantly lighter murre fledglings in 2005 (203.0 ± 4.6 g) relative to 2004 (215.0 ± 3.9 g) suggests that specialized feeding on unpredictable prey can have consequences for reproductive success. Puffins that are generalist foragers and have multiple prey load capacity were more resilient to declines in prey availability

Taking the Bite Out of Winter: Common Murres (Uria aalge) Push Their Dive Limits to Surmount Energy Constraints

Diving seabirds that overwinter at high latitudes experience persistent cold exposure, short days and associated declines in ocean productivity that can challenge their ability to balance daily energy budgets. We used dive-immersion geo-locators to test the hypothesis that pursuit-diving Common murres (Uria aalge) will respond to the challenges of winter in the North Atlantic through increased daily energy expenditures (DEE) that will be met by increased foraging effort and adjustments in dive tactics. Largely flightless in winter (<5% of daylight hours flying), murres spent most of their time on the water (>85% resting and swimming). Accordingly, when sea surface temperatures (SST) were consistently near freezing in late winter (1.9 ± 0.8°C), mean DEE (2463.2 ± 10.9 kJ day−1) exceeded the theoretical limit to sustainable energy expenditure in vertebrates (i.e., 7 X Basal Metabolic Rate or 2450 kJ day−1 for murres). Consistently deep (70% >50 m) and long dives in late winter, 38% of which exceeded their calculated aerobic dive limit indicate that targeted prey was distributed in deep (dark) waters. Consequently, foraging was largely diurnal; likely because capture efficiency of deep-water prey is poor under low light. Murres responded to these late winter time and energy constraints with a nearly two-fold increase in daily time spent diving (95.2 ± 5.6 and 178.3 ± 6.3 min day−1 during early and late winter, respectively), an increase in dive bout frequency and duration, and correspondingly less time resting between bouts. Uniquely adapted for deep-diving, pursuit-diving can push their dive limits to maximize daily energy intake when energy demands are high and prey are distributed in deep water. Our study highlights late winter as an extremely challenging phase in the annual cycle of North Atlantic murres and provides critical insights into the behavioral mechanisms underlying their winter survival

DataSheet2.pdf

<p>Diving seabirds that overwinter at high latitudes experience persistent cold exposure, short days and associated declines in ocean productivity that can challenge their ability to balance daily energy budgets. We used dive-immersion geo-locators to test the hypothesis that pursuit-diving Common murres (Uria aalge) will respond to the challenges of winter in the North Atlantic through increased daily energy expenditures (DEE) that will be met by increased foraging effort and adjustments in dive tactics. Largely flightless in winter (<5% of daylight hours flying), murres spent most of their time on the water (>85% resting and swimming). Accordingly, when sea surface temperatures (SST) were consistently near freezing in late winter (1.9 ± 0.8°C), mean DEE (2463.2 ± 10.9 kJ day⁻¹) exceeded the theoretical limit to sustainable energy expenditure in vertebrates (i.e., 7 X Basal Metabolic Rate or 2450 kJ day⁻¹ for murres). Consistently deep (70% >50 m) and long dives in late winter, 38% of which exceeded their calculated aerobic dive limit indicate that targeted prey was distributed in deep (dark) waters. Consequently, foraging was largely diurnal; likely because capture efficiency of deep-water prey is poor under low light. Murres responded to these late winter time and energy constraints with a nearly two-fold increase in daily time spent diving (95.2 ± 5.6 and 178.3 ± 6.3 min day⁻¹ during early and late winter, respectively), an increase in dive bout frequency and duration, and correspondingly less time resting between bouts. Uniquely adapted for deep-diving, pursuit-diving can push their dive limits to maximize daily energy intake when energy demands are high and prey are distributed in deep water. Our study highlights late winter as an extremely challenging phase in the annual cycle of North Atlantic murres and provides critical insights into the behavioral mechanisms underlying their winter survival.</p

DataSheet1.pdf

<p>Diving seabirds that overwinter at high latitudes experience persistent cold exposure, short days and associated declines in ocean productivity that can challenge their ability to balance daily energy budgets. We used dive-immersion geo-locators to test the hypothesis that pursuit-diving Common murres (Uria aalge) will respond to the challenges of winter in the North Atlantic through increased daily energy expenditures (DEE) that will be met by increased foraging effort and adjustments in dive tactics. Largely flightless in winter (<5% of daylight hours flying), murres spent most of their time on the water (>85% resting and swimming). Accordingly, when sea surface temperatures (SST) were consistently near freezing in late winter (1.9 ± 0.8°C), mean DEE (2463.2 ± 10.9 kJ day⁻¹) exceeded the theoretical limit to sustainable energy expenditure in vertebrates (i.e., 7 X Basal Metabolic Rate or 2450 kJ day⁻¹ for murres). Consistently deep (70% >50 m) and long dives in late winter, 38% of which exceeded their calculated aerobic dive limit indicate that targeted prey was distributed in deep (dark) waters. Consequently, foraging was largely diurnal; likely because capture efficiency of deep-water prey is poor under low light. Murres responded to these late winter time and energy constraints with a nearly two-fold increase in daily time spent diving (95.2 ± 5.6 and 178.3 ± 6.3 min day⁻¹ during early and late winter, respectively), an increase in dive bout frequency and duration, and correspondingly less time resting between bouts. Uniquely adapted for deep-diving, pursuit-diving can push their dive limits to maximize daily energy intake when energy demands are high and prey are distributed in deep water. Our study highlights late winter as an extremely challenging phase in the annual cycle of North Atlantic murres and provides critical insights into the behavioral mechanisms underlying their winter survival.</p

Seasonal Variation in Parental Care Drives Sex-Specific Foraging by a Monomorphic Seabird

<div><p>Evidence of sex-specific foraging in monomorphic seabirds is increasing though the underlying mechanisms remain poorly understood. We investigate differential parental care as a mechanism for sex-specific foraging in monomorphic Common Murres (<i>Uria aalge</i>), where the male parent alone provisions the chick after colony departure. Using a combination of geolocation-immersion loggers and stable isotopes, we assess two hypotheses: the reproductive role specialization hypothesis and the energetic constraint hypothesis. We compare the foraging behavior of females (n = 15) and males (n = 9) during bi-parental at the colony, post-fledging male-only parental care and winter when parental care is absent. As predicted by the reproductive role specialization hypothesis, we found evidence of sex-specific foraging during post-fledging only, the stage with the greatest divergence in parental care roles. Single-parenting males spent almost twice as much time diving per day and foraged at lower quality prey patches relative to independent females. This implies a potential energetic constraint for males during the estimated 62.8 ± 8.9 days of offspring dependence at sea. Contrary to the predictions of the energetic constraint hypothesis, we found no evidence of sex-specific foraging during biparental care, suggesting that male parents did not forage for their own benefit before colony departure in anticipation of post-fledging energy constraints. We hypothesize that unpredictable prey conditions at Newfoundland colonies in recent years may limit male parental ability to allocate additional time and energy to self-feeding during biparental care, without compromising chick survival. Our findings support differential parental care as a mechanism for sex-specific foraging in monomorphic murres, and highlight the need to consider ecological context in the interpretation of sex-specific foraging behavior.</p></div