Warming in the land of the midnight sun: breeding birds may suffer greater heat stress at high- vs low-Arctic sites

Rising global temperatures are expected to increase reproductive costs for wildlife as greater thermoregulatory demands interfere with essential breeding activities such as parental care. However, predicting the temperature threshold where reproductive performance is negatively impacted remains a significant hurdle. Using a novel thermoregulatory polygon approach, we predicted the threshold temperature at which an Arctic songbird-the snow bunting (Plectrophenax nivalis)-would need to reduce activity and perform below the 4-times basal metabolic rate (BMR) required to sustain nestling provisioning to avoid overheating. We then compared this threshold to operative temperatures recorded at high (82°N) and low (64°N) Arctic sites to estimate how heat constraints translate into site-specific impacts on sustained activity level. We predict buntings would become behaviourally constrained at operative temperatures above 11.7°C, whereupon they must reduce provisioning rates to maintain thermal balance. Low Arctic sites had larger fluctuations in solar radiation, producing consistent daily periods when operative temperatures exceeded 11.7°C. However, high-latitude birds faced entire, consecutive days where parents would not be able to sustain required provisioning rates. These data indicate that Arctic warming is likely already disrupting the breeding performance of cold-specialist birds, but also suggests counterintuitive and severe negative impacts of warming at high-latitude breeding locations.

An anti-narcolepsy drug reveals behavioral and fitness costs of extreme activity cycles in arctic-breeding songbirds

ABSTRACT Sleep loss impairs cognitive function, immunological responses and general well-being in humans. However, sleep requirements in mammals and birds vary dramatically. In circumpolar regions with continuous summer light, daily sleep duration is reduced, particularly in breeding birds. The effect of an anti-narcolepsy drug (modafinil) to putatively extend wakefulness was examined in two species of closely related arctic-breeding passerine birds: Lapland longspurs (Calcarius lapponicus) and snow buntings (Plectrophenax nivalis). Free-living adult males were implanted during the nestling phase on day 4 (D4; 4 days post-hatching) with osmotic pumps containing either vehicle or modafinil to extend the active period for 72 h. Nestlings were weighed on D2 and D7 to measure growth rates. Additionally, focal observations were conducted on D6. Male longspurs receiving modafinil made fewer feeding visits and spent less time at the nest but tended to spend more time near the nest than controls. We observed no change in longspur nestling growth rates, but fledging occurred significantly later when males received modafinil, suggesting a fitness cost. In contrast, modafinil had no measurable impact on male or female snow bunting behavior, nestling growth rates or time to fledging. We suggest male longspurs compromise and maintain vigilance at their nests in lieu of sleeping because of the increased predation risk that is characteristic of their tundra nesting habitat. Snow buntings are cavity nesters, and their nests do not require the same vigilance, allowing males to presumably rest following provisioning. These life-history differences between species highlight the role of predation risk in mediating behavioral modifications to prolonged wakefulness in arctic-breeding songbirds.

Life in the extreme environment: Structure and species richness of bird assemblages on Yuzhny Island of Novaya Zemlya, Russia

Birds play a vital role in arctic environments, being multi-functional ecosystem engineers, but these animals are heavily impacted by recent climate warming. Bird assemblages on the Arctic Ocean archipelagoes are poorly known, because many such areas are hardly accessible to scientists. Novaya Zemlya, one of the most enigmatic places in the World, was a closed military area from the late 1940s. This gigantic mountainous archipelago can be considered a terra incognita by means of modern faunal, taxonomic, and ecological research. In the present study, we provide the first qualitative data on bird assemblages of the Yuzhny Island of Novaya Zemlya, estimate the diversity of bird species through a range of habitats, and underscore environmental factors determining the spatial distribution of avifauna in the arctic tundra biome. In terrestrial habitats, Tundra Bean Goose (Anser fabalis rossicus), Barnacle Goose (Branta leucopsis) and Snow Bunting (Plectrophenax nivalis) were the most abundant species. In freshwater and coastal marine habitats, both these Arctic-breeding goose taxa, and Black-legged Kittiwake (Rissa tridactyla), Common Eider (Somateria mollissima) and Thick-billed Murre (Uria lomvia) were the dominant species. The most species-rich bird assemblages (11-15 species) were associated with willow tundra, freshwater lakes, and coastal sea habitats, while only a few species were recorded in dry rocky habitats, open sea environments, and littoral areas of lakes and the sea. Mountain rocky heathlands covering most of the area of Yuzhny Island were scarcely populated by birds, with only a few species recorded frequently there, such as the Rough-legged Buzzard (Buteo lagopus) and Snow Bunting. Our findings highlight that the bird assemblages on Novaya Zemlya share low species richness and that these assemblages contain a large proportion of sea and shore bird species even in terrestrial habitats. Among the terrestrial birds, only four cold-tolerant, common species successfully colonize these extreme environments during the short summer season.