Parasitic Birds?! | Natural History Museum of Los Angeles

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Parasitic Birds?!

Unable to build a home of their own, pin-tailed whydahs leave their babies with strangers

Photo by Jeff Bray

Fledgling pin-tailed whydah (left) accompanying an adult scaly-breasted munia (right) at San Joaquin Marsh in Irvine, Orange County, California, 29 July 2014. Photo by Jeff Bray.

People don’t usually picture birds when they think of parasites. The word parasite conjures up thoughts of tapeworms, ticks, or — for the microbially inclined — malaria. But birds? We don’t usually hear about parasitism in this class of animals.

But backing up for a moment — what exactly is a parasite? It’s an organism that uses the resources of a different species, harming it in the process in some way. It could be drinking its blood, stealing its food, or crowding out its young — one way or another the parasite flourishes at the expense of its unwitting host. Nature abounds with examples of this, and many are not for the faint of heart. Whatever you do, don’t Google “botfly.”

Ornithology Collections Manager Kimball Garrett opens a drawer of pin-tailed whydah specimens in the NHMLA Collections.

But parasites aren’t all creeping, crawling things that get inside your body and steal your essence. Birds (as well as a few fish and insects) can be brood parasites, which means they lay their eggs in someone else’s nest. This is more sinister than it sounds. The hosts care for babies that don’t belong to them, and often their own young suffer as a result.

Native to sub-Saharan Africa, the pin-tailed whydah (Vidua macroura) is one of these parasites — an obligate brood parasite, to be exact. These birds don’t ever build their own nests; they rely completely on other birds to incubate their eggs and raise their young. In Africa, pin-tailed whydahs lay their eggs in the nests of waxbill birds (in the family Estrildidae). But now pin-tailed whydahs have found their way to Los Angeles, most likely via the pet trade, and are becoming increasingly common across California.

At first the odd whydah sighting was attributed to a recent escapee, but when bird watchers started seeing larger flocks of these birds, people increasingly realized it meant they were breeding.

But without African waxbills, how are they reproducing? After all, they can’t build nests.

Pasadena Audubon member and NHMLA volunteer John Garrett and Ornithology Collections Manager Kimball Garrett (no relation) recently solved this urban nature mystery. It turns out these introduced birds are parasitizing another introduced bird — scaly-breasted munias (Lonchura punctulata) from southeast Asia. A potential agricultural pest, munias too found their way here via the pet trade, only to wind up the unexpecting hosts of our introduced, parasitic whydahs.

To confirm this bird behavior, the team turned to local citizen scientists and resources like eBird to locate flocks of pin-tailed whydahs. Then it was a matter of birding detective work — staking out whydahs and watching their behavior. During fieldwork, John Garrett paid particular attention to female pin-tailed whydahs, noting if they entered other birds’ nests.

The first confirmation of this parasitic relationship came from photographer Jeff Bray, who documented a young whydah following adult munias around and being fed by its “adopted” parents.

Fledgling pin-tailed whydah being fed by an adult scaly-breasted munia at Riverdale Park, Anaheim, Orange County, California, 6 September 2014. Photo by Jeff Bray.

While this non-native parasitic relationship is unusual, it wasn’t entirely unexpected. Kimball Garrett and John Garrett suspected that pin-tailed whydahs might be using scaly-breasted munia nests because the latter build domed nests (as opposed to the “open cup” style) with a side entrance. Back home in Africa, pin-tailed whydahs’ host birds make domed nests, so these introduced birds are probably hunting for the most similar host they can find. Here in Southern California, munias provide some of the only domed nests around.

“It's still a novel relation since munias and whydahs don't overlap in their native ranges,” said John Garrett.

To further complicate the introduced bird landscape, orange-cheeked waxbills have started popping up in California, a known host of parasitic whydahs in their native Africa. Will the whydahs abandon their adopted hosts if enough waxbills establish a population around Los Angeles? Only time will tell.

“We need to keep doing field work and rely also on birders and other citizen scientists to keep us apprised of what is going on,” said Kimball Garrett.

 

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