Early nesting ducks are at risk from climate and land-use changes

Every year, approximately 10 million waterfowl migrate northward to their breeding grounds in the Prairie Pothole Region of North America. However, this landscape is rapidly changing due to shifting weather patterns and agricultural practices, which have drastically transformed the native grasslands that waterfowl have relied on for thousands of years. As a result, some waterfowl species are thriving, while others face decline. A new study led by a research team from Penn State University suggests that the timing of nesting plays a crucial role in determining the winners and losers in this region.

Professor Frances Buderman elaborated on the diverse habitats within the region where waterfowl make their nests. These habitats range from idle grassland, cropland, and even over water. Professor Buderman noted a particular challenge for early nesting ducks: “When early nesting ducks arrive in the Prairie Pothole Region, many fields are covered in debris left from the previous fall’s harvest, mainly stubble from cereal grains. Although this habitat looks inviting, the eventual replanting of these fields, as opposed to leaving them fallow, makes the ducks more vulnerable to predators and often results in their nests being destroyed by agricultural activities such as tilling and planting.”

The U.S. Fish and Wildlife Service and the Canadian Wildlife Service have been monitoring the spring population abundances of North American waterfowl since 1955. Their Waterfowl Breeding Population and Habitat Survey has yielded one of the largest datasets on vertebrate populations globally.

The ducks in this region are typically adapted to nest in mixed-grass prairie. With the surge of agriculture replacing this wild habitat, the birds are left in a state of confusion. 

“Last year’s stubble looks good to them from the air, but in reality, it does not offer the same advantages and protections that the grass does,” said Professor Buderman. “Over time, on a large scale, this association with cropland can lead to lower reproductive success and declining population numbers for early nesting ducks that breed in the region.”

In prior research, Buderman’s group focused on the northern pintail ducks, a species experiencing a decline since the 1980s. They discovered that these ducks’ tendency to nest in agricultural fields acted as an “ecological trap,” leading to a decrease in the pintail population the following year, a direct outcome of demographic processes like reproduction and survival.

With this in mind, the researchers set out to understand if the northern pintail’s response was unique, potentially explaining the diverging trends in abundance among waterfowl in the region. Their findings, published in the Journal of Animal Ecology, reveal that the timing of nesting is crucial in determining the effect of nesting in cropland on demographic processes. Early nesting ducks exhibited the most significant negative demographic responses to agricultural fields.

“Early nesting ducks that don’t nest in cropland, and diving ducks such as canvasbacks, nest over water and are not likely to be impacted by this trap,” noted Buderman. “Climate change, which may allow farmers to till and plant earlier in the spring, could make matters worse. An earlier spring warm-up could also lead to a mismatch between nesting activities and food availability.”

How the research was conducted

The researchers’ first step involved estimating the impact of climate and land-use changes on habitat selection and population dynamics for the nine species of ducks native to the region. This method allowed the researchers to recognize the response patterns of each species and to identify cases where certain species opted for conditions that were detrimental to their population dynamics. For example, the northern pintail has a preference for cropland.

The results of the analysis, however, painted a complex picture. The northern pintail, American wigeon, and blue-winged teal, in particular, often showcased extreme responses to habitat changes. But it’s crucial to note, as Buderman points out, that these responses were not uniform. “Each of the species we studied reacted a bit differently to changes in climate and land-use,” she said.

Such variability underlines a nuanced complexity in managing these habitats at the community level. The researchers observed species-level differences in demographic and habitat-selection responses to climate and land-use change, which adds layers of complication to community-level habitat management. 

“Our work highlights the importance of multi-species monitoring and community-level analysis, even among closely related species,” said Professor Buderman. “This underscores the need for a comprehensive approach in conservation efforts, taking into account the unique responses of each species to climatic and land-use shifts, thereby ensuring the preservation of biodiversity in the face of changing environmental landscapes.”

How climate change impacts nesting ducks

Climate change has far-reaching effects on a wide range of species, and nesting ducks are not immune to these impacts. As global temperatures rise and weather patterns become more unpredictable, the ecosystems that ducks and other waterfowl depend on for nesting are undergoing significant changes.

Here’s a closer look at how climate change affects nesting ducks:

Shifts in Timing

Warming temperatures can lead to earlier springs, which may cause a shift in the timing of nesting for some duck species. This earlier nesting could potentially lead to mismatches between the timing of duckling hatching and the availability of their food sources, which can in turn affect survival rates.

Habitat Changes

Climate change can significantly alter waterfowl habitats. Rising temperatures and changes in precipitation can lead to droughts, floods, or the drying up of wetlands, which ducks rely on for nesting. In addition, sea level rise can lead to the loss of coastal habitats used by some duck species.

Increased Predation

Changes in climate can also affect predator populations. For example, milder winters could lead to increased survival and reproduction of predators like foxes and raccoons, which can have a negative impact on duck nest survival.

Changes in Food Availability

Changes in weather patterns can affect the timing and abundance of food sources that ducks rely on. For instance, a late frost could kill off insects that ducklings feed on, and changes in precipitation can affect the availability of aquatic plants that adult ducks eat.

Increased Disease Risk

Warmer temperatures can also contribute to the spread of diseases that affect waterfowl, such as avian influenza and botulism.

Migration Disruption 

Changes in temperature and weather patterns can disrupt traditional migration routes and timings for ducks. This can lead to ducks arriving at their breeding grounds either too early or too late, which can impact their ability to successfully nest and raise offspring.

Overall, climate change presents a serious challenge for nesting ducks and other wildlife. It’s vital that conservation efforts take into account these climate-related threats and work towards strategies that help protect and preserve vital waterfowl habitats. This includes preserving wetlands, managing land use effectively, and working on global efforts to mitigate climate change.

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