Oliver P. Love’s research while affiliated with University of Windsor and other places

Climate change is altering the marine environment at a global scale, and these changes could affect the distribution and migration patterns of marine species throughout their annual cycle. Arctic regions are already experiencing some of the most dramatic changes in marine climate, and there is a need for predictive models to understand how these changes could alter the spatio-temporal distributions of Arctic marine species. We used a species distribution model to predict potential future changes in the non-breeding distribution of thick-billed murres Uria lomvia from a colony in Hudson Bay, Canada, from 2021 to 2100 using 3 Coupled Model Intercomparison Project Phase 6 (CMIP6) climate scenarios: low (SSP1-2.6), intermediate (SSP2-4.5), and high (SSP5-8.5) emissions. Under the intermediate- and high-emissions scenarios, suitable habitat within Hudson Bay would become available year-round during the next century. This could lead to a portion of this migratory population becoming year-round residents within the next 80 yr. We predicted a significant northward shift in the winter range, such that little or no habitat would be available below 55°N by 2100. This shift would have significant implications for the murre harvest in Canada because the winter distribution would no longer include coastal Newfoundland where most harvesting occurs, particularly if murres from other colonies show a similar shift in distribution. Although there were projected changes in seasonal distributions under all 3 climate scenarios, dramatic re-distribution of non-breeding habitat could be avoided with policies that limit future emissions.

Central place foraging may lead to local prey depletion as foragers select nearby prey (“Storer-Ashmole’s halo”), causing individuals to forage progressively farther from the central place. We tested this idea by coupling GPS tracking (foraging behavior) and plasma metabolites (nutritional biomarkers) when studying thick-billed murres (Uria lomvia; N = 237), a colonial-nesting seabird where central place foraging constraints are expected to be particularly pronounced due to high transit costs. Foraging range decreased when birds were constrained to visit the central place several times per day (chick-rearing) compared to self-feeding (incubation), illustrating the constraint of central place foraging. Moreover, adult feeding frequency, as determined by plasma triglycerides, were higher during incubation, consistent with the longer fasts (incubation shifts) during that period. Transit time (foraging distance) increased with date during chick-rearing but not incubation, consistent with prey depletion due to central place foraging within the restricted chick-rearing foraging range. During late chick-rearing, when a diet switch to low-quality, smaller prey occurs, birds switched to foraging near the colony, consistent with the foraging range being overextended. Unlike other, smaller colonies where foraging success is higher due to a smaller halo, sexes had similar foraging behaviour in our study, except during early incubation when females foraged more (more flying, more swimming) as they overcame the cost of producing the egg. When we take our results with other lines of evidence (increased foraging distance with colony size, prey switching as birds “feed down the food chain”), we conclude that central place foraging seabirds may cause prey depletion at one of the world’s largest murre colonies.

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.

Birds maintain some of the highest body temperatures among endothermic animals. Often deemed a selective advantage for heat tolerance, high body temperatures also limits birds’ thermal safety margin before reaching lethal levels. Recent modelling suggests that sustained effort in Arctic birds might be restricted at mild air temperatures, which may require reductions in activity to avoid overheating, with expected negative impacts on reproductive performance. We measured within-individual changes in body temperature in calm birds and then in response to an experimental increase in activity in an outdoor captive population of Arctic, cold-specialised snow buntings (Plectrophenax nivalis), exposed to naturally varying air temperatures (− 15 to 36 °C). Calm buntings exhibited a modal body temperature range from 39.9 to 42.6 °C. However, we detected a significant increase in body temperature within minutes of shifting calm birds to active flight, with strong evidence for a positive effect of air temperature on body temperature (slope = 0.04 °C/ °C). Importantly, by an ambient temperature of 9 °C, flying buntings were already generating body temperatures ≥ 45 °C, approaching the upper thermal limits of organismal performance (45–47 °C). With known limited evaporative heat dissipation capacities in these birds, our results support the recent prediction that free-living buntings operating at maximal sustainable rates will increasingly need to rely on behavioural thermoregulatory strategies to regulate body temperature, to the detriment of nestling growth and survival.

Among birds, several body composition traits typically decrease in size or mass during breeding likely as a result of competing demands during this critical life history stage. However, a recent outdoor captive study in an Arctic-breeding cold-specialist songbird (snow buntings – Plectrophenax nivalis) demonstrated that these birds maintain winter cold acclimatization during the spring and summer, despite facing summer temperatures much warmer than on their Arctic breeding grounds. This suggests that buntings may face a cumulative physiological cost during breeding: having to support a winter phenotype while also upregulating additional traits for reproduction. The current study aimed to test this hypothesis. Between 2016 and 2019, we examined how body composition and metabolic performance (thermogenic capacity and physiological maintenance costs) changed from pre-breeding to chick provisioning in free-living birds captured at the northern limit of their breeding range in the Canadian Arctic (Alert, NU, 82°). While body mass and fat reserves deceased significantly between pre-breeding and territory defense independent of thermal conditions, cold endurance and associated traits remained stable and elevated up to the nestling provisioning period, as long as ambient temperature remained below a threshold level of 0–2°C. These results indicate that snow buntings must maintain a high thermogenic capacity after arrival on the breeding grounds if temperatures remain below freezing, regardless of whether birds are actively breeding or not. In this context, our research suggests that these birds, and possibly other arctic breeding songbirds, may experience cumulative physiological costs during years with a late onset of spring, when breeding activities (i.e., egg production and incubation) begin while temperatures are still below 0–2°C.

Interspecific foraging associations (IFAs) are biological interactions where two or more species forage in association with each other. Climate‐induced reductions in Arctic sea ice have increased polar bear ( Ursus maritimus ) foraging in seabird colonies, which creates foraging opportunities for avian predators. We used drone video of bears foraging within a common eider ( Somateria mollissima ) colony on East Bay Island (Nunavut, Canada) in 2017 to investigate herring gull ( Larus argentatus ) foraging in association with bears. We recorded nest visitation by gulls following n = 193 eider flushing events from nests during incubation. The probability of gulls visiting eider nests increased with higher number of gulls present (β = 0.14 ± 0.03 [SE], p < .001) and for nests previously visited by a bear (β = 1.14 ± 0.49 [SE], p < .02). In our model examining the probability of gulls consuming eggs from nests, we failed to detect statistically significant effects for the number of gulls present (β = 0.09 ± 0.05 [SE], p < .07) or for nests previously visited by a bear (β = −0.92 ± 0.71 [SE], p < .19). Gulls preferred to visit nests behind bears (χ ² = 18, df = 1, p < .0001), indicating gulls are risk averse in the presence of polar bears. Our study provides novel insights on an Arctic IFA, and we present evidence that gulls capitalize on nests made available due to disturbance associated with foraging bears, as eiders disturbed off their nest allow gulls easier access to eggs. We suggest the IFA between gulls and polar bears is parasitic, as gulls are consuming terrestrial resources which would have eventually been consumed by bears. This finding has implications for estimating the energetic contribution of bird eggs to polar bear summer diets in that the total number of available clutches to consume may be reduced due to avian predators.

Several predator–prey systems are in flux as an indirect result of climate change. In the Arctic, earlier sea-ice loss is driving polar bears (Ursus maritimus) onto land when many colonial nesting seabirds are breeding. The result is a higher threat of nest predation for birds with potential limited ability to respond. We quantified heart rate change in a large common eider (Somateria mollissima) breeding colony in the Canadian Arctic to explore their adaptive capacity to keep pace with the increasing risk of egg predation by polar bears. Eiders displayed on average higher heart rates from baseline when polar bears were within their field of view. Moreover, eiders were insensitive to variation in the distance bears were to their nests, but exhibited mild bradycardia (lowered heart rate) the longer the eider was exposed to the bear given the hen's visibility. Results indicate that a limited ability to assess the risks posed by polar bears may result in long-term fitness consequences for eiders from the increasing frequency in interactions with this predator.

Birds maintain some of the highest body temperatures (Tb) among endothermic animals. Often deemed a selective advantage for heat tolerance, high Tb also limits the capacity to increase Tb before reaching lethal levels. Recent thermal modelling suggests that sustained effort in Arctic birds might be restricted at mild air temperatures (Ta) during energetically demanding life history stages, which may force reductions in activity to avoid overheating, with expected negative impacts on reproductive performance. Consequently, understanding how Arctic birds will cope with increasing Ta has become an urgent concern. We examined within-individual changes in Tb in response to an experimental increase in activity in outdoor captive Arctic cold-specialised snow buntings (Plectrophenax nivalis), exposed to naturally varying Ta from -15 to 36 °C. Calm buntings exhibited a modal Tb range from 39.9 %—42.6 °C. However, we detected a dramatic increase in Tb within minutes of shifting birds to active flight, with strong evidence for a positive effect of Ta on Tb (slope = 0.04 °C/°C). Importantly, by Ta of 9 °C, flying buntings were already generating Tb ≥ 45°C, approaching the upper thermal limits of organismal performance (i.e., Tb = 45—47 °C). Under scenarios of elevated Tb, buntings must increase rates of evaporative water loss and/or reduce activity to avoid overheating. With known limited evaporative heat dissipation capacities, we argue buntings operating at peak energy levels will increasingly rely on behavioral thermoregulatory strategies (i.e., reducing activity) to regulate Tb, at the potential detriment to nestling growth and survival.