Majority of wild bird migration has yet to arrive in Iowa
A duck walks in a partially submerged soybean field near Iowa City in 2015. (The Gazette)
Wild ducks that are the primary carriers of the highly contagious bird flu are migrating through Iowa in greater numbers this month, said Adam Janke, wildlife extension specialist at Iowa State University.
There are about 20 different species of ducks numbering in the hundreds of thousands that pass through Iowa on their way to breeding grounds in the northern United States and Canada, he said. Different species may arrive at different times, but now is when there is the greatest overlap and the most ducks pass at once.
“We are reaching a peak for duck migration,” said Janke, who studies bird migrations. “We’re probably in this overlap area where there happens to be a lot of species right now.”
The overlap period can last about a month, he said.
Related: Pelicans stop in Iowa City on their migration north
Ducks, geese and other waterfowl are well-known carriers of bird flu
Ducks, geese and other waterfowl are well-known carriers of bird flu and may show no symptoms of infection, according to the US Centers for Disease Control and Prevention. Bird flu is often fatal to domestic poultry, including turkeys and chickens raised for meat and eggs.
Versions of the virus have been identified in 16 commercial and backyard flocks in Iowa since March 1. The most recent confirmation was from a commercial flock of turkeys in Hardin County.
The total number of birds that have been culled this year due to the virus in Iowa is more than 13 million, according to data from the US Department of Agriculture. The death toll of domestic birds during the last major outbreak in the state in 2015 was more than 32 million.
Half of the state’s virus detections have occurred in the past week, and Iowa Agriculture Secretary Mike Naig recently said the situation could get worse.
No documented human cases in Iowa this year
There have been no documented infections of humans from wild birds this year, state agriculture officials said, and meat and eggs from infected birds are being destroyed.
Geese accounted for most of the 25 infected wild birds found in Iowa, along with a duck and a red-tailed hawk, the USDA reports. But most of the migrating geese have already come and gone, Janke said.
These geese often continue north when ponds and lakes thaw, feeding on leftover grain from agricultural fields as they go. Research has shown that geese that arrive earlier in their northern breeding grounds have a better chance of breeding.
There are more than 100 species of wild birds that commonly migrate through Iowa, and “the vast majority are yet to come,” Janke said. Some of those who arrive last migrate from South America.
Infected waterfowl spend their winters in the southern United States. Nationally, they account for most detections of highly pathogenic avian influenza in wild birds, but other infected birds include bald eagles, vultures, hawks and owls.
The virus has been detected in 12 Iowa counties so far, with Buena Vista accounting for four of the outbreaks.
State agriculture officials said their goal is to cull infected herds within 24 hours of detection to stem the spread of the virus because site-to-site infections were a problem in 2015. They found no evidence that any of the sites infected so far were the result of transmission from another infected site.
Naig said the threat of infection from wild birds could persist for another two months.
This article first appeared in the Iowa Capital Dispatch.