Ducks that nest early are at increased risk due to climate change and land use

Every year, about 10 million waterfowl fly north to their breeding grounds in the prairie pothole region of North America, but the landscape that welcomes them has changed. Weather and agricultural practices have dramatically transformed the pothole-strewn native grasslands that waterfowl have used for thousands of years.

These changes have resulted in the proliferation of some waterfowl species while others decline. Nesting date is a major factor in determining winners and losers in the Prairie Potholes, according to a new study by a Penn State-led research team.

The waterfowl nest in a variety of habitats in the region, including unused grasslands, croplands and over water, according to team leader Frances Buderman, assistant professor of quantitative wildlife ecology.

“But when the early-nesting ducks arrive in the pothole region of the prairies, many fields are covered in debris left over from the previous fall’s harvest, mostly grain stubble,” she said. declared. “While this habitat looks inviting, the eventual replanting of these fields, rather than leaving them fallow, makes the ducks more vulnerable to predators and often results in the destruction of their nests by agricultural activities such as plowing and planting. “

The United States Fish and Wildlife Service and the Canadian Wildlife Service have monitored the abundance of spring populations of North American waterfowl using the Waterfowl Breeding Population and Habitat Survey since 1955, producing one of the largest sets data on the world’s vertebrate populations.

These ducks are adapted to nesting in mixed grasslands, and since that wild habitat has largely been replaced by agriculture in the pothole region of the prairies, the birds are confused, Buderman explained.

The Prairie Pothole region, which spans the Great Plains of the northern United States and Canada, is the most important breeding ground for many duck species on the continent. Credit: Penn State/Creative Commons

“Last year’s stubble looks nice to them from the air, but in reality, it doesn’t offer the same benefits and protections as grass,” she said. “Over time, on a large scale, this association with cropland can lead to lower breeding success and fewer populations of early-nesting ducks breeding in the area.”

In previous research, Buderman’s research group at the College of Agricultural Sciences focused on the northern pintail, a species that had been in decline since the 1980s. They identified the propensity of pintails to nest in agricultural fields as a ” ecological trap” because the number of pintails the following year – a product of demographic processes, such as reproduction and survival – declined with increasing use of cultivated land.

However, the researchers questioned whether the pintail response was unique, perhaps providing an explanation for the divergent abundance trends among waterfowl in the region.

In conclusions published on 24 April in the Journal of Animal Ecology, Buderman and colleagues report that the timing of nesting is a key factor in determining the effect of nesting in cropland on demographic processes. Early-nesting ducks had the strongest negative demographic responses to agricultural fields.

“That’s not to say that all early-nesting waterfowl are going to struggle,” Buderman said. “Early nesting ducks that do not nest in cropland and diving ducks such as Canvasbacks, nest over water and are not likely to be affected by this trap. Climate change, which could allow farmers to plow and sow earlier in the spring, could make matters worse. Earlier spring warming could also lead to a lag between nesting activities and food availability.

Researchers focused on nine species of ducks

To reach their conclusions, the researchers analyzed data from the Waterfowl Breeding Population and Habitat Survey from 1958 to 2011 and focused on nine species of ducks that have traditionally used the prairie pothole region. as breeding grounds: American Wigeon, Blue-winged Teal, American Teal, Gadwall, Mallard, Northern Pintail, Shoveler, Ruddy and Ruddy Duck.

Researchers estimated species-specific responses to climatic and land-use variables in the region, which changed from mixed grassland to cereal, oilseed, corn, wheat, sunflower and soybean fields.

They first estimated the effects of changes in climate and land use variables on habitat selection and population dynamics for the nine species, assessing species-specific responses to environmental changes. This allowed the researchers to see patterns in species-level responses and identify where species selected for variables detrimental to their population dynamics (such as Northern Pintail and cropland).

They found that northern pintails, American wigeons and green-winged teal often had extreme reactions to habitat changes, but not always in the same way, Buderman pointed out.

“Each of the species we studied responded a little differently to changes in climate and land use,” she said. “We observed species-level differences in demographic and habitat selection responses to climate change and land use, which would complicate habitat management at the community level. Our work highlights the importance of multi-species monitoring and analysis at the community level, even among closely related species.

Thanks to Penn State University for providing this news.