16 November 2007
I've been working at the RSPB as a wildlife adviser since October 2005. I have been a keen naturalist all of my life with a particular interest in birds, insects and animal behaviour. I have a background in Environmental Biology and Environmental Impact Assessment and regularly contribute to bird surveys. Other interests I have include wildlife gardening and birding as well as keeping track with important issues such as climate change and renewable energy.
Sent in by Emily Messer, Yorkshire
There is one bird which is known to hibernate throughout the winter - the common poorwill. This small relative of the nightjar is found in western states of the USA such as California and New Mexico where it inhabits open areas of low vegetation and rocky outcrops.
As a nocturnal hunter of insects, the poorwill would struggle to find enough food to survive during the cold winters. When faced with harsh weather and little food, this unique bird hides away in rocky crevices and hibernates through the winter, emerging in spring when the temperature has risen and more insects are active.
Here in the UK, bats, dormice and hedgehogs are most commonly associated with hibernation. Birds, instead of hibernating, use migration to avoid adverse conditions. Our summer visitors such as the swallow head south to warmer climes whilst many birds that breed further north, such as the redwing, head to the UK to spend the winter as it is comparatively mild. Colonial roosting is another way to conserve energy and body heat. The wren has been documented to share a nest box overnight with up to 60 other wrens!
Although birds in the UK do not hibernate, one species uses a similar strategy to cope with periods of cold weather and low food availability. Young swifts go into a state of 'torpor' which is where the body temperature and metabolism is greatly reduced in order to save energy. The energy saved by reducing activity in this way allows these birds to survive for short periods of time until conditions improve.
Torpor is a commonly used survival strategy in a number of bird families across the world such as the hummingbirds, nightjars and swifts. Much of the research on torpor in birds has been conducted in North America where many of the species can be found in a torpid state during cold spells. Torpor is usually only a short term solution to allow birds to survive cold nights.
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