Stressed bird moms
Stress may have its upside for parents. More hungry babies meant more stress hormones but also more fledglings for mother tree swallows, an international team reports online June 1 in Biology Letters. Overworked moms put more effort into parenting and raised more chicks successfully than small-brood moms did. Most previous tests with artificially big broods didn’t find overworked avian moms to be any more likely to have higher stress hormones. Those studies, however, didn’t track hormone changes in the same individuals. In the new study, mother birds’ hormone concentrations rose in the chick-enhanced nests. —Susan Milius
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