Coping mechanisms of alpine and arctic breeding birds: extreme weather and limitations to reproductive resilience

As ground nesting homeotherms, alpine and arctic birds mustmeet similar physiological requirements for breeding as otherbirds, but must do so in more extreme conditions. Annual springsnowfall and timing of snow melt can vary by up to 1 month anddaily temperatures near the ground surface vary from below freezingto over 45°C in alpine and arctic habitats. Species breedingin these environments have various behavioral, physiological,and morphological adaptations to cope with energetically demandingconditions. We review the ways birds cope with harsh and variableweather, and present data from long term field studies of ptarmiganto examine effects of spring weather on reproduction. In variablebut normal spring conditions, timing of breeding was not influencedby snow melt, snow depth or daily temperatures in the alpine,as breeding did not commence until conditions were generallyfavorable. Arctic ptarmigan tended to vary breeding onset inresponse to spring conditions. Generally, birds breeding inalpine and arctic habitats suffer a seasonal reproductive disadvantagecompared to birds at lower latitudes or elevations because thebreeding window is short and in late years, nest failure maybe high with little opportunity for renesting. Coping mechanismsmay only be effective below a threshold of climactic extremes.Despite strong resilience in fecundity parameters, when snowmeltis extremely delayed breeding success is greatly reduced. Alpineand arctic birds will be further challenged as they attemptto cope with anticipated increases in the frequency and severityof weather events (climate variability), as well as generalclimate warming.