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A new long-term study finds that male acorn woodpeckers breeding polygamously in duos or trios of males actually fathered more offspring than males breeding alone with a single female, contrary to conventional thinking among biologists that monogamous males necessarily produce more offspring than those in polygamous groups. For females, polygamy is less of a slam dunk but co-breeding duos left behind the same number of offspring as the birds that coupled up, while female trios left behind fewer offspring than either group.