image: North temperate species, like this Hermit Thrush, often raise four or more young, compared with the typical two young raised by tropical species. This material relates to a paper that appeared in the Aug. 28, 2015, issue of Science, published by AAAS. The paper, by T.E. Martin at US Geological Survey in Missoula, Mont., and colleagues was titled, "Age-related mortality explains life history strategies of tropical and temperate songbirds." view more
Credit: Photo by Thomas E. Martin