Heat Waves Harm Bird Reproduction in Farms, Research Shows

Bird populations in North America are rapidly decreasing. Climate change, among various factors affecting these birds, plays a noteworthy role, often interacting with other stressors like habitat loss. Researchers from the University of California, Davis, discovered that extreme temperatures affect avian reproduction differently based on the bird’s habitat.

Published in the journal Science, the study reveals how climate change, when combined with habitat loss, can impact bird reproduction throughout the United States.

The research discovered that extreme high temperatures have a pronounced negative effect on bird reproductive success in agricultural settings. Birds nesting near farmlands experienced a 50% reduction in the likelihood of successfully fledging at least one chick when temperatures soared. In contrast, forests appeared to offer a protective shield against high temperatures, thanks to their shaded areas, which boosted nesting success.

The Role of Canopy Cover in Mitigating Heat Effects on Bird Reproduction

Katherine Lauck, a co-lead author and a Ph.D. candidate in ecology at UC Davis, noted, “The impact of heat is more severe for birds nesting in agricultural environments than for those in forested ones, indicating that canopy cover likely serves as a crucial climate refuge for birds adaptable to various habitats.”

When assessing the influence of heat waves on nesting success in urban regions, the researchers observed a milder negative impact compared to agriculture. This difference is likely due to nests being frequently located in city parks and residential areas with abundant tree cover.

Lauck added, “This suggests that locations like backyard and parks may offer essential bird habitats that are somewhat more resilient to climate extremes in the future.”

In an extensive dataset analysis, Associate Professor Daniel Karp of the Department of Wildlife, Fish and Conservation Biology initiated a project with his students during the COVID-19 pandemic. They conducted this analysis using data from NestWatch, a project established by Cornell University’s Laboratory of Ornithology, where individuals nationwide monitor bird nests in their vicinity and use an app to document information about bird species, nest locations, egg quantities, chick activity, and more.

“What sets this dataset apart is its ability to provide insights into bird reproduction on a large geographic scale,” explained Karp. “This data allowed us to start unraveling the combined impacts of climate change and habitat loss on numerous North American bird species.”

The research team examined over 152,000 nesting records, encompassing almost 60 bird species nesting in a variety of environments, including farms, forests, grasslands, and urban areas, spanning 23 years from 1998 to 2020.

Increased hazards

Additionally, the scientists investigated the species that were most susceptible to heat waves in agricultural settings. The detrimental effects were evident in a wide range of bird species under examination. Among them, western bluebirds and tree swallows, both frequently found on farms, displayed substantial decreases in nesting success when temperatures surged in agricultural regions.

“We observe these significant effects in common and adaptable bird species, which are typically considered more resilient to changes in land use and climate,” Lauck elaborated.

Endangered birds and those that construct exposed-cup nests, lacking any form of shelter, showed even greater susceptibility to heat waves in farming areas when compared to typical species and those that build their nests in tree cavities and nest boxes.

“The nearly 50% decline in nesting success we observed, on average, jumps to 70% when we consider species of heightened conservation concern,” Karp noted. “This implies that species already experiencing declines may face even more challenges in raising their young in the future as heat waves become more frequent and as more land is converted to agriculture.”

Future Projections and Potential Solutions

The study also provided insight into future scenarios. According to their models, by the year 2100, nesting success in agricultural regions is projected to decrease by an additional 5% on average if current greenhouse gas emissions continue.

The research suggests that reducing emissions and promoting thermal refuges, such as planting or preserving areas of natural vegetation, are likely to be critical for bird conservation. Maintaining shaded areas may also be necessary to support bird populations in urban and agricultural settings.

“Farmers often install nest boxes to attract birds to their farms and assist in controlling insect pests. It might be a sensible idea to position these boxes in shaded locations,” Karp proposed. “They might also consider planting hedgerows and conserving patches of native vegetation to offer shade and help birds cope with rising temperatures. These interventions could be pivotal for the well-being of birds in the future.”

The study’s co-authors also included Alison Ke, Daniel Paredes, Kees Hood, and Thomas Phillips from the UC Davis Department of Wildlife, Fish and Conservation Biology, along with Elissa Olimpi from Virginia Tech and Bill Anderegg from the University of Utah.

Read the original article: Phys Org

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