The list includes several species that occur in central Ontario, mostly as migrants.

Avian flu is caused by wild birds and is transmitted to people via poultry.

"Avian flu has an unprecedented ability to infect humans directly from poultry," the U.S. Department of Agriculture warned.

According to Tom Roffe of the U.S. Fish and Wildlife Service, wild birds carry and transmit avian flu readily "by lots of pathways."

Birds at highest risk of carrying avian flu include greater scaup, pintail, lesser snow goose, sandhill crane, horned grebe, tundra swan and several kinds of shorebirds.

An 'early-detection program' is in place to detect avian flu in wild birds.

So far, more than 100,000 have been tested.

"It is very clear that wild birds carry avian flu and transmit it to poultry," Roffe says.

Hunters might be at risk, because they hunt pintails and other waterfowl in the high-risk group.

"Hunters would be notified of potential risks," the USDA says.

Towns and cities are bird oases, new data confirms. According to Paige Warren of Arizona State University, birds are often more abundant in built-up areas compared with rural areas.

"The overall abundance of birds is often greater in towns and cities compared with the surrounding areas," she said.

"More species of native birds prefer to live in urban areas."

The researchers found that birds overwhelmingly prefer to live in wealthier neighbourhoods.

Upper-income areas have twice as many bird species as do middle- or lower-income sites, the studies show.

"You would think that parks in lower-income areas would be bird magnets, but that is not the case, even though they have the oldest trees," the researchers said.

Urbanites are urged to plant native vegetation in their gardens if they want to attract local birds.

Not surprisingly, bird diversity and numbers are lowest in the noisiest parts of towns and cities, as a general rule.

Buzzing of mosquitoes is an annoying sound to most people. But, it is music to the ears of other mosquitoes, research shows. Mosquitoes find the sound of mosquito buzzing to be "alluring", researchers conclude.

According to recent studies, mosquitoes change their flight tones when approached by other mosquitoes. That means that buzzing is a type of signalling.

Tests show that special buzzing occurs when a male mosquito is approached by a female, and vice versa.

But, same-sex mosquitoes, when approaching each other, emit offensive buzzes that are acutely dissimilar, warning each other to keep their distance.

In addition, mosquito buzzing often has local 'dialects'.

Each species tends to have a different wing shape and wing-beat frequency, so every species has its own buzz pitch.

Such differences are usually not noticed by humans, who are more concerned with keeping the pesky insects away.