With their cheery green feathers and red beaks, rose-ringed parakeets might seem like a welcome addition to cities. But this invasive species, which has infiltrated urban areas around the world, is keeping native birds away from their food.
Researchers studied the effects of rose-ringed parakeets at 41 gardens in and around London. At each site, they set up a feeding station with sunflower seeds and peanuts. Then the team recorded the behaviour of visiting birds, including how long they stayed at the feeder and whether they ate anything, under different sets of conditions.
Sometimes a caged parakeet was present, or an audio recording of a parakeet call was playing, or both. As a control, the researchers also tested the effects of having a caged native woodpecker present, a woodpecker call playing, or simply an empty cage.
The study authors observed 10,893 bird visits to the sites and identified 18 native species. Most of the birds were blue tits or great tits. At sites in the parakeet’s range, fewer native birds visited the feeder if a caged parakeet was present; they also spent less time eating and more time acting vigilant. Woodpeckers deterred visitors too, but not as much as the parakeets did.
The researchers found similar trends at sites outside the parakeet’s range. But even fewer of the visiting birds ate at the feeders with parakeets, perhaps because they weren’t as used to the invasive birds.
The results are probably conservative, the authors add, because feeders are often swarmed by entire flocks of rose-ringed parakeets. Native birds that stay away from those food sources may suffer from lower energy levels, and their numbers could eventually drop.
To protect them, people may need to figure out ways to let native birds eat at the feeders — but keep parakeets out.
Source: Peck, H.L. et al. 2014. Experimental evidence of impacts of an invasive parakeet on foraging behavior of native birds. Behavioral Ecology doi: 10.1093/beheco/aru025.