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There just aren’t enough palm tree homes to go around. Invasive ring-necked parakeets have prompted a rapid decline in Israel’s native hoopoe population, probably because of their aggressive takeover of nesting cavities in palm trees.

Reuven Yosef at Ben Gurion University, Israel, and colleagues followed densities of hoopoes in four palmeries in rural areas over a period of 10 years. In the two that were invaded by parakeets in 2000 and 2006, the team found a significant decline in hoopoe population density. By contrast, in the two palmeries without parakeets the hoopoe density remained unchanged.

These invasive parakeets usually nest in existing tree cavities. But in Israel they were observed digging new cavities, which suggests there is a lack of nesting sites. Parakeets start breeding earlier in the season than hoopoes do, and may use up all nesting sites before hoopoes can get to them, the team says.

Cavity competition

The results add to growing evidence of competition for suitable nesting cavities between ring-necked parakeets (Psittacula krameri) and native birds, including nuthatches, starlings and great tits. They may even be affecting bats.

Originally from Africa and South Asia, parakeets have spread globally, probably after individuals kept as pets escaped or were released into the wild. They are now a permanent fixture in cities like London.

But hoopoes in Europe are safe for now. “Currently, almost the entire European population of ring-necked parakeets is breeding in urban areas, whereas the hoopoes are generally not entering cities,” says Liviu Pârâu at Heidelberg University, Germany.

“The authors describe a local situation in Israel which cannot be generalised,” says Michael Wink at Heidelberg University. He says that in his experience there is no lack of nest holes and no apparent competition with native species in Germany, for example.

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