FORSYTH — Reports of more Georgians finding dead songbirds at feeders and tests pointing to salmonella as the major culprit have Georgia Wildlife Resources Division biologists urging care and diligence in feeder upkeep.

Salmonella, a bacteria with hundreds of strains, naturally occurs in many birds and is transmitted by contact with feces. The disease can sicken and kill birds under certain condition, often if they are weakened by stress or other factors or if they receive a large dose of the infectious bacteria.

It is not clear why there has been an apparent surge in avian salmonella deaths this winter in many Southern states, although increased numbers of birds at feeders — including larger flocks of pine siskins — raise the risk of transmission.

Because salmonella can be transmitted to humans, those who find dead birds should use plastic gloves and dispose of the birds in double plastic bags.

In addition to dead birds that obviously were not killed by a predator or by hitting a window, sick birds can indicate problems at feeders.

Birds suffering from salmonella may be lethargic and unusually easy to approach. Their eyes are often closed or puffy, and their feathers fluffed out.

Owners might consider buying new seed, though there has been no evidence that tainted seed contributed to the flare-up.

Two companies, Scotts Co. LLC (www.scotts.com/smg) and Burkmann Feeds (www.burkmannfeeds.com), voluntarily recalled some bird seed products because of salmonella concerns.

Salmonella strains from dead birds examined at the Southeastern Cooperative Wildlife Disease Study in Athens did not match those from the Blakely peanut plant at the center of the human salmonella outbreak, according to Kevin Keel, supervisor of diagnostic services at the state-federal cooperative.

Southeastern Cooperative Wildlife Disease Study biologists are trying to map the geographic extent of the outbreak and determine the strains of salmonella involved. Keel said this year has been "particularly severe," but such large outbreaks are not unprecedented. Smaller, more localized outbreaks are seen throughout the Southeast each year and are often associated with backyard bird feeders.

Proper care of bird feeders and birdbaths means occasionally cleaning them with the 10-percent bleach solution, disposing of seeds or hulls that accumulate beneath feeders, and keeping seed dry. People should use plastic or rubber gloves, if possible, while cleaning feeders and disposing of hulls, and thoroughly wash their hands afterward, as well as after adding seed.

Birds concentrate at feeders in winter and early spring, increasing the incidence of diseases being transmitted.