Some of the most invasive birds in North America are also some of our favorite. Shimmery starlings engage in mind-blowing murmurations, but they also decimate agricultural fields and kick bluebirds and other cavity-nesting birds out of their homes. The invasive house sparrow outcompetes other birds so effectively, it's become the most common bird in the world. Now, Joanna Klein at The New York Times reports another beautiful bird, the pin-tailed whydah, is on the verge of launching a new invasion into the U.S.
The flashy whydah, Vidua macroura, is a native of sub-Saharan Africa. Males have a bright orange beak, a black and white pattern, and grow long black tails during breeding season. Their distinctive plumage has made them popular in the exotic pet trade, which is what brought them to Puerto Rico and Orange County.
While having a beautiful bird might not seem like much of a problem, the whydah is one of only about 100 parasitic birds in the world. Whydahs are brood parasites, meaning they lay their eggs in another bird’s nest and leave that species to raise the baby, reports Klein. In some cases, the parasitic nestlings outcompete their foster siblings or are much larger than the host species, causing their "parents" to expend extra resources feeding them.
“These birds don’t look like a virus or bacteria, but they have the same impact,” evolutionary ecologist Mark Hauber tells Klein. “It’s basically like a virus jumping from a pig to a human or a bat to some domestic animal.”
For a study released in The Condor: Ornthilogical Applications, Hauber and his colleagues tried to figure out where the pin-tailed whydah may spread next. According to a press release, the researchers looked at whydah sightings in the Global Biodiversity Information Facility, identified potential habitats, and looked at the presence of known host species to predict where the whydahs might end up. They found that southern California, southern Texas, south Florida, Jamaica and Hawaii could all experience whydah invasions.
Because the whydah can piggyback on the nesting work of birds with which it shares no evolutionary history, researchers worry it may use both native and other non-native species to establish a population in the wild. While birds in and from sub-Saharan Africa know how to identify whydah chicks, species unfamiliar with whydahs wouldn't have this advantage, and the whydah might begin to exploit a whole new group of host birds.
And it's not the first time a brood parasite has disrupted the local ecosystem. Over the last century, the brown-headed cowbird, a native bird, has moved into eastern North America due to urbanization and forest fragmentation. Several species unable to cope with a brood parasite have suffered because of it; the cowbird is one of the primary factors in pushing the Kirtland’s warbler to the edge of extinction.
“This study shows how humans are not just transplanting individual species but entire ecological networks, where here an invasive bird species will likely be able to expand in the Americas due to a previous introduction of its host species," says James Russell in the press release. Russell, a conservation biologist at the University of Auckland not involved in the study, adds that "the study predicts the introduced species will most strongly invade already vulnerable island ecosystems, where it could potentially begin parasitizing native bird species, which would be a very novel form of invasive species impact.”