January 24, 2018, American
Ornithological Society
Biologists have known for a long
time that animals living in colder climates tend to have larger bodies,
supposedly as an adaptation to reduce heat loss. However, understanding how
temperature affects animals has gained new importance thanks to climate change.
A new study from The Auk: Ornithological Advances uses European House
Sparrows, which have spread into a variety of climates in Australia and New
Zealand since their introduction in the mid-19th century, to show that this
trend in birds might actually be due to the effects of high temperatures during
development—raising new alarms about how populations might be affected by
global warming.
Macquarie University's Samuel
Andrew and his colleagues captured and measured approximately 40 adult House
Sparrows at each of 30 locations across Australia and New Zealand. They found
that maximum temperatures during the summer, when the birds breed, were a
better predictor of adult body
size at each location than winter minimum temperatures. This adds
support to the idea that excessive heat during development may affect birds'
growth throughout their lives, raising concerns that increasing summer temperatures due
to climate change could
drive down the average adult body size, with potential effects on the birds'
fitness.
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