nestling song sparrow, just after banding and measuring. Researchers at UC Davis are studying the song sparrows to see how and why climate change could affect a species across its ages and stages. (Credit: K. E. Dybala/UC Davis)

Aug. 12, 2013 — What's good for adults is not always best for the young, and vice versa. At least that is the case with song sparrows and how they experience the effects of climate change, according to two recent studies by scientists at the University of California, Davis, and Point Blue Conservation Science.

Both studies show the importance of considering the various stages and ages of individuals in a species — from babies to juveniles to adults — to best predict not only how climate change could affect a species as a whole, but also why.

"To learn how climate change is expected to affect an individual population, you have to look at demography," said lead author Kristen Dybala, a postdoctoral scholar in the UC Davis Department of Wildlife, Fish and Conservation Biology. "If you don't break it down by these different stages, you get a different understanding that may be misleading, or worse, that's just wrong."

For example, in the study published in print today in the journalGlobal Change Biology, climate change had opposite projected effects for adult and juvenile song sparrows in central coastal California. The researchers found, not surprisingly, that adult survival was sensitive to cold winter weather.

"Even though we rarely see freezing temperatures on the coast of California, it was clear that an adult bird's chances of survival were lowest in the coldest winters," said co-author Tom Gardali, Pacific Coast and Central Valley Group director of Point Blue Conservation Science.

They expected a similar response from the young. However, warmer, drier winters translated to less food for the juvenile sparrows during the following summer.

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