A professor has taken to ringing owls on his mobile phone. What is most remarkable is that they return his calls in a project that could revolutionise surveys of wild bird populations.

Great horned owl: The study is sticking with owls because calls at night are cheaper

Researchers at the Massachusetts Institute of Technology near Boston report today that the phones can help keep more accurate counts of owls.

When Eben Goodale wants to count the birds, he places a call that triggers phones in the forest to play, via speakers, pre-recorded owl calls, such as hoots and whistles.

Territorial owls raise their heads and approach what they think may be an intruder. If they respond with a hoot, the phones transmit the sound back to the "owl project" website.

Goodale and Dale Joachim, who describe the research today in the journal Biology Letters, believe that they have shown that mobiles are an effective way to listen in to how birds are doing in the wild, and the diversity of the area.

"If you play a chickadee call, other birds will approach the phone, and call themselves. If you walk around the forest, squirrels might call first, then birds chime in," said Goodale, who is now working in Sri Lanka.

For now they are sticking with owls, which call at night when phone time is cheapest. One use has been to track great horned owls in Louisiana and their effects on local swallow tailed kite populations. In the new study, they show that Barred Owls and the Eastern screech owl are also happy to take a call on the mobile.

Traditionally, bird surveys rely on people standing in the woods, playing a CD of bird calls, and taking note of the birds they hear responding. It can be labour intensive and inexact.

The researchers now plan to compare a survey conducted with 65 phones with one that relies on CD recordings used by 250 volunteers from the Audubon Society in Maine to see if the mobiles do as well. The advantage is that the new method allows ornithologists to dial up birds anywhere on the planet, and to cover a large area at the same time.

There could be other uses of the technology.

There have been anecdotal claims that some species of birds left southern Louisiana and Mississippi in August 2005, perhaps because they sensed the devastation that was about to be visited upon the area by Hurricane Katrina. A system that can remotely monitor animals in their habitats could help confirm or refute such stories.

Only the scientists get to call the owls using the mobile network. After all, too many crank calls would ruffle their feathers.