Response to high ambient temperatures in short-distance and
trans-Saharan migratory species
Abstract
In consideration of current global climate change, ecophysiological
research on wild birds has increased its emphasis on approaches related
to thermal tolerance. Many studies have investigated how desert
specialists are adapted physiologically to the hot and xeric conditions
they live in. Our aim was to test whether migratory passerines from
temperate areas also have physiological adaptations to cope with heat
stress and whether such adaptations may be related to habitat or
migration distance. Using video recording and flow-through respirometry,
we measured temperatures of panting onset (TPANT) of 113 individuals of
14 different species, exposed to increasing ambient temperature. Our
study species differed in size, migration type (short-distance migrants
vs. trans-Saharan migrants) and habitat preferences (woodland, farmland,
reeds). We found that trans-Saharan migrants started panting at higher
ambient temperatures (TA) than short-distance migrants of similar size,
but no difference between species from different habitats. This finding
suggests that migrants facing a desert crossing may have adaptations to
decrease the risk of dehydration while maintaining body temperature
below the critical range. According to this, we suggest that there may
be selection on traits related to the modulation of respiratory water
loss in birds that cross the Sahara Desert during migration. Flexibility
in these traits will be of crucial importance in a warmer future.