The momma's boy, not the early bird, gets the worm in zebra finch families. But there are no daddy's girls.
Zebra finch mothers preferentially feed sons more than daughters. But fathers don't appear to play favorites.
"If a female has paired up with a particularly sexy male, it's in her interests to make sure her sons are well cared for, because the odds are that they'll grow up to be just as successful as their dad. So her genes are more likely to be passed to the next generation," said Ian Hartley of Lancaster University, co-author of the study, in a press release.
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"Females put a lot of energy into producing and incubating eggs; the males don't. But males put their energies into attracting or defending females. These different costs of reproduction – and the need to save some energy for future breeding attempts – have knock-on effects to how the mother and father invest in their offspring," said Hartley.
To determine which chicks were getting fed, Hartley and her colleagues analyzed video images of around 9,000 'feeding events' at 28 zebra finch (Taeniopygia guttata) nests. For both genders, as begging got louder and more intense, the chicks got more food. But at comparable intense levels of begging, male chicks were fed more often by the mother. Father finches didn't show any preference.
Before this study, researchers hadn't realized that finch parents could even determine the gender of their chicks. Scientists had assumed that the bird's parents couldn't tell the chicks apart until they developed adult plumage.
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"We don't know how they know, but it could be that because they can see ultraviolet light, they can see things in their chicks that we can't. Or maybe male and female chicks make different calls when they beg for food," said Hartley.
The results are published in Behavioral Ecology and Sociobiology.
IMAGES 1 and 2: Juvenile zebra finches in a nest. (Wikimedia Commons)
Tags: Animal Behavior, Animals, Pet Birds, Wild Birds
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