ZOOS across North America are moving their birds indoors and away from people and wildlife as they try to protect them from the highly contagious and potentially deadly avian influenza.

Penguins may be the only birds visitors to many zoos can see right now, because they already are kept inside and usually protected behind glass in their exhibits, making it harder for the bird flu to reach them.

Nearly 23 million chickens and turkeys have already been killed across the United States to limit the spread of the virus, and zoos are working hard to prevent any of their birds from meeting the same fate. It would be especially upsetting for zoos to have to kill any of the endangered or threatened species in their care.

“It would be extremely devastating,” said Maria Franke, manager of welfare science at Toronto Zoo, which has less than two dozen Loggerhead Shrike songbirds that it’s breeding with the hope of reintroducing them into the wild.

“We take amazing care and the welfare and well being of our animals is the utmost importance. There’s a lot of staff that has close connections with the animals that they care for here at the zoo.”

Toronto Zoo workers are adding roofs to some outdoor bird exhibits and double-checking the mesh surrounding enclosures to ensure it will keep wild birds out.

Birds shed the virus through their droppings and nasal discharge. Experts say it can be spread through contaminated equipment, clothing, boots and vehicles carrying supplies. Research has shown that small birds that squeeze into zoo exhibits or buildings can also spread the flu, and that mice can even track it inside.

So far, no outbreaks have been reported at zoos, but there have been wild birds found dead that had the flu.

When bird flu cases are found in poultry, officials order the entire flock to be killed because the virus is so contagious. However, the U.S. Department of Agriculture has indicated that zoos might be able to avoid that by isolating infected birds and possibly euthanizing a small number of them.

Among the precautions zoos are taking is to keep birds in smaller groups so that if a case is found, only a few would be affected.

Kansas City Zoo CEO Sean Putney said he’s heard a few complaints from visitors, but most people seem OK with not getting to see some birds. “I think our guests understand that we have what’s in the best interests of the animals in mind when we make these decisions even though they can’t get to see them,” Putney said.

(SD-Agencies)