cold resilience winter birds perch, resilient in the snowy ecosystem

cold resilience winter birds perch snowy ecosystem adaptation bird behavior migration thermoregulation snow camouflage foraging survival weather extreme temperatures avian physiology heat conservation feather insulation roosting metabolic adaptations coldtolerant species territories hardy roosts icy conditions snowfall wintering grounds strategies hibernation diurnal patterns plumage habitat acclimation subzero cover thermal regulation coldhardiness ecology freeze tolerance