The movement patterns of waterfowl, including ducks, swans and geese, may affect the spread of highly pathogenic avian influenza in bird populations, according to a new study from the University of Georgia.
Researchers found that birds travel much shorter distances in areas with human activity, likely because those landscapes have plenty of food, water and shelter.
When birds stay in one place, disease doesn't spread as much. But it could also mean more intense hotspots of disease outbreaks in concentrated areas.
By understanding the movement patterns of waterfowl outside of typical migration periods, scientists could better predict where bird flu, or H5N1, might spread next.
"Birds are like us. They're always responding to what's around them, whether that's food availability or disturbance from people or other animals," said Claire Teitelbaum , assistant unit leader with the U.S. Geological Survey's Georgia Cooperative Fish and Wildlife Research Unit, lead author of the study and an adjunct assistant professor in the Warnell School of Forestry and Natural Resources . "We can take the environment, predict how much we think birds are moving and then use that to predict where avian flu is going to go."
Waterfowl stay put in areas with diverse habitats, human influence
The researchers analyzed 20 years of data containing movement information from more than 4,600 total waterfowl spanning 26 species in the Northern Hemisphere. The scientists tracked how far the waterfowl moved over time during breeding and winter seasons, when birds "commute" regularly between areas used for resting and eating.
The distance of these so-called commutes, which took place outside of their regular seasonal migrations, appeared to depend on the birds' environment. Birds in uniform areas, such as vast expanses of grasslands or farmlands, traveled six times farther to acquire food or a safe location to rest compared to birds in more diverse landscapes.
The waterfowl in those more varied landscapes, which ranged from wetlands to urban green spaces, often didn't need to travel more than a mile around their "home" to meet all or most of their daily needs.
"If we provide enough diverse attractive habitats, these animals may want to stick around," Teitelbaum said. "Like humans, if you live in a suburban neighborhood where it's just single-family homes for miles and miles, you're going to have to drive miles and miles out of that area to get to work or shop. If you live in an urban center, you have everything you need right there."
Locations with a significant human population also played a role, as they were more likely to have protected green spaces with water sources or cover. Human activity could also mean literal blocks that prevent bird movement, such as roads or fences.
Birds in these regions traveled about one-third of the distance of birds residing in sparser areas.
Different seasons could play role in bird flu spread outside of seasonal migrations
While yearly migrations are a major factor in the spread of H5N1, the present study aimed to understand how flight during breeding and winter seasons may add to transmission.
The researchers found that during winter months, movements were over twice as far when compared to travel during the breeding season. Waterfowl often had to fly farther in their daily routines to secure food or places to sleep, potentially carrying the virus with them.
In addition to studying these daily movements, the researchers found the same patterns when studying birds' weekly movement distances. That's key, Teitelbaum explained, as one week is also the incubation period for the virus.
Breeding season could present its own challenges. During this time, birds were less likely to travel far distances, instead remaining close to their nests. Although that can limit wider spread, it also could increase the risk for localized hotspots of the virus.
"If we want to keep the flu from spreading, we might want to see what we can do to keep the birds in one place, but there's that flipside. Outbreaks happen when birds are in high density, so we might have increased transmission locally," she said. "That's the underpinning: How can we link the distances that birds are moving to the distances that flu is moving?"
This study was published in Ecology Letters.
