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Crafty Brood Parasites – Some Zebra Finches Lay Eggs in Neighbors’ Nests

Posted by: Frank Indiviglio in Baby Birds, Bird Behavior, Bird Breeding, Bird Research or Recent News September 30, 2010 1 Comment 5267 Views

Male Zebra FinchCowbirds, cuckoos and whydahs are well known brood parasites, meaning that females deposit eggs in the nests of other bird species and leave them to the care of their unsuspecting foster parents.  Finch owners may be surprised to learn that some female Zebra Finches also use this reproductive strategy – but with a special twist.

Cheating…Zebra Finch Style

Researchers at Bavaria’s Max Planck Institute for Ornithology (the former stomping grounds of the legendary animal behaviorist Konrad Lorenz) have discovered that certain female Zebra Finches specialize in taking advantage of their neighbors’ nests. 

Unlike cuckoos and other brood parasites, which lay eggs in the nests of unrelated birds (please see photo of a Reed Warbler feeding a Cuckoo chick), Zebra Finch females parasitize their own species.  Also unique is the fact that, in addition to the foster eggs, the “cheating” Zebra Finch moms also raise a separate clutch of eggs themselves (cowbirds and others typically raise no eggs of their own).

Stealth Required

Warbler feeding Cuckoo in her nestUtilizing genetic techniques, the ornithologists at Max Planck were able to determine that 1 in 5 Zebra Finch nests contained eggs that were not produced by the female sitting on the nest.

Only a small number of females resorted to parasitism, but they seem to be very skilled at it.  Females seeking to use another’s nest must watch their victims carefully – if they lay before the foster female does, she will abandon the nest; wait too long, however, and the foster female will begin incubating her own eggs and leave little opportunity for additions to the clutch.  Most parasitic females laid their eggs after the first or second egg was produced by the foster mom.

Evolution in Progress?

We may be seeing evolution at work – female finches that dole out their eggs wind up producing the same number of fledglings (in their own and foster nests) as do females that reproduce in the more usual manner.  Depending upon whether or not this trend continues or changes, brood parasitism may become the norm for Zebra Finches, or it may disappear altogether.

Further Reading

The Zebra Finch has been dubbed the “Lab Mouse of the Bird World”; read more about its important contributions in The Unknown Side of the Zebra Finch.

Pin Tailed Whydahs as brood parasites in Uganda.

 

 
Male Zebra Finch image referenced from wikipedia and originally posted by Peripitus
Warbler feeding cuckoo image referenced from wikipedia and originally posted by H Olsen

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I believe that I was born with an intense interest in animals, as neither I nor any of my family can recall a time when I was not fascinated by creatures large and small. One might imagine this to be an unfortunate set of circumstances for a person born and raised in the Bronx, but, in actuality, quite the opposite was true. Most importantly, my family encouraged both my interest and the extensive menagerie that sprung from it. My mother and grandmother somehow found ways to cope with the skunks, flying squirrels, octopus, caimans and countless other odd creatures that routinely arrived un-announced at our front door. Assisting in hand-feeding hatchling praying mantises and in eradicating hoards of mosquitoes (I once thought I had discovered “fresh-water brine shrimp” and stocked my tanks with thousands of mosquito larvae!) became second nature to them. My mother went on to become a serious naturalist, and has helped thousands learn about wildlife in her 16 years as a volunteer at the Bronx Zoo. My grandfather actively conspired in my zoo-buildings efforts, regularly appearing with chipmunks, boa constrictors, turtles rescued from the Fulton Fish Market and, especially, unusual marine creatures. It was his passion for seahorses that led me to write a book about them years later. Thank you very much, for a complete biography of my experience click here.
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