It may seem like birds have the freedom to fly wherever they like, but researchers at the University of Missouri have discovered that what’s on the ground can determine where a bird flies.
Dylan Kesler, assistant professor in fisheries and wildlife at MU’s School of Natural Resources, said movement of individual members of a species can teach scientists everything from how smaller populations exist to how they interact with other species. With that knowledge, foresters and urban planners improve bird habitats and maintain strong, healthy populations.
“Movement determines where individual birds procreate,” Kesler said. “How they spread across the landscape affects who meets whom, which in turn dictates how genes are spread.”
Kesler’s research involves radio-tagging juvenile red-bellied, red-cockaded and black-backed woodpeckers to track their movements. Kesler chose to study the red-bellied woodpecker because the bird lives in the same area year-round and is very loyal to specific sites. The tags, which are designed to fall off after four months, allow researchers to track the birds’ daily flights using radiotelemetry and GPS technology.
In the first systematic analysis of how these birds fly, feed and fight predators, Kesler confirmed what conservationists have suspected since the 1990s – that birds make landscape-influenced flight decisions along paths where they can immediately dive into tree cover to escape predators and readily find food.
Kesler has found that non-migrating resident birds tend to travel over forest “corridors,” which are areas protected by trees and used by wildlife to travel. Birds choose to travel over forests because they can make an easier escape from predators as well as find food.
Man-made features, such as roads and gaps in forested lands caused by agriculture or rivers, can restrict birds to certain areas. When forests are removed, bird populations become isolated and disconnected, which can lead to inbreeding and weaker, more disease-prone birds.
This summer and fall, Kesler and his team hope to see if the woodpeckers return to their originating home site after searching for food or if they sleep in any place that is convenient. The earlier research suggested that the woodpeckers flew almost two miles away, where they stayed for several hours, before they returned to their permanent home base. It appears that birds mapped the landscape and evaluated their breeding options through these repeated forays and explorations, Kesler said.
The research team hopes to discover more about natal dispersal, the time interval between when a bird moves from where it is hatched to an area where it will breed. Very little is known about what influences natal dispersal.
“In many territorial resident birds, natal dispersal is the only time an individual bird makes a substantial movement from one location to another,” Kesler said. “Natal dispersal is, therefore, integral to gene flow among populations, colonizing vacant habitat, inbreeding avoidance and maintaining optimal population densities.”
This year’s work builds upon research Kesler has been conducting since 2005 on three species of woodpeckers and two Pacific island kingfishers. Results will be published this fall in conservation-oriented science journals. Results from Kesler’s previous research about dispersal appeared in the nation’s top ornithological journal, The Auk, and another paper will soon be published in Behavioral Ecology.