As San Francisco's cherry-headed conure population grows, Bittner will find it harder to keep tabs on individuals. The flock now has 85 birds, and is increasing each year. It is even listed as an attraction in some city tour guides.
Bakersfield's Rose-ringed Parakeets
In other cities parakeet colonies can be much bigger. In Bakersfield, California, there are over 1,000 rose-ringed Psittacula krameri, or ring-necked, parakeets. Native to the Indian subcontinent and sub-Saharan Africa, the species probably first gained a foothold in Bakersfield after a hurricane-force storm destroyed an aviary in 1977. Alison Sheehey, from California State University Bakersfield, has studied the birds since 1998. She believes their success is due largely to the manmade nature of their surroundings.
"Many urban plants are from tropical to subtropical climates. This established a habitat for the birds long before they took up residence. There are also plenty of backyard fruit and nut trees that keep them well fed," she said.
The popularity of garden bird-feeders is another important factor, and Sheehey says this "smorgasbord of parakeet delights" means the birds are unlikely to leave the city.
Sheehey says it's difficult to gauge the impact of parakeets on native fauna. Nevertheless, she has witnessed altercations with other birds.
"I have seen them battling with European starlings Sturnus vulgaris and acorn woodpeckers Melanerpes formicivorus over nest cavities," she said. "The parakeets won every time."
Sheehey has also encountered fickle behavior among these supposedly monogamous birds.
"One day while watching a nesting flock I observed a male tell his spouse he was going out. He looked back, and seeing she was gone, made a wide circle and came back to a neighboring tree. The good-looking little hen next-door came out, they flirted and, well, you know what happened next."
In London, England, rose-ringed parakeets have been present for some 30 years. Until recently the population expanded slowly reaching 1,500 birds in 1996. But by 2002 the number had soared to 7,000.
Some scientists believe this is an example of the Allee effect, where an introduced species keeps a low profile for a long period before suddenly exploding in numbers. This happens when enough potential mates are around for them to find each other.
But whatever the reason for the increase, it's possible the birds could lose their popular appeal if they stray beyond city limits.
In the fall of 2002, a rose-ringed parakeet flock stripped a vineyard of its crop at Painshill Park in Cobham, near the outskirts of London.
"It would have been a really fantastic year," said Teige O'Brien, Painshill Park's development manager. "But we ended up with just 500 bottles of red wine. The parakeets seem to be immune to scarecrows, things that go bang and all the other bird-scaring devices. I suspect this is going to be an annual problem."
The Royal Society for the Protection of Birds, Europe's largest wildlife conservation charity, is aware of such fears.
However, spokesman Andre Farrar added: "Any introduced species could cause a problem many years down the line. But the parakeets will carry on enchanting London's bird-loving gardeners."
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Nationalgeographic.com Bird-Watching Sites:
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From the National Geographic Store:
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Additional Information from Related Web Sites:
American Bird Center
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Fish and Wildlife Service Bird Web Site
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Environmental Protection Agency: Bird Conservation
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