A new 50-year study sheds light on the consequences of climate change on avian reproduction.

The reproductive output of 104 bird species around the world was examined in a new study published in the Proceedings of the National Academy of Sciences between 1970 and 2019. According to the study, larger and migratory birds seem to be more affected by a warming climate than smaller, sedentary species.

In an interview with Diana Yates, life sciences editor at the University of Illinois Urbana-Champaign, study co-author Jeffrey Hoover, an avian ecologist at the Illinois Natural History Survey, talks about the results.

Why is the review exceptional?
Over 100 species from over 200 bird populations on all continents were included in this study, and their potential effects on offspring production were examined in relation to warming and global climate change. For each of these bird populations, we looked at data from 15 to 49 breeding seasons to see if there were any changes in the average number of offspring produced per female per year as a result of changes in local temperatures and precipitation.

The study also looked into whether climate change could affect the production of offspring by interfering with the birds’ other characteristics, in addition to the effects of a warming climate on the reproductive output of individual species. Body mass, migration status, habitat requirements, human impacts on local landscapes, the protection and conservation status of sites, and the ability of the birds to raise two broods during a single breeding season are examples of such characteristics. The fleeting and spatial sizes of this work and the quantity of species and populations considered were great.

What were the fundamental discoveries?
Offspring production has generally decreased in recent decades across the 201 wild bird populations we studied. However, there is a great deal of variation between species and populations. Most migratory birds produced fewer offspring when local temperatures were raised during the chick-rearing phase of the breeding season, but many small and sedentary birds, which do not migrate, produced more.

Warming temperatures were likewise related to less posterity creation among somewhat huge birds. These changes were not necessarily brought about directly by climate change; rather, they were brought about by the effects of climate change on the life histories and ecological characteristics of species, which have an impact on the size of clutches and the percentage of nests that fail over time.

Jeff Hoover, an avian ecologist, and his colleagues investigated the potential effects of global warming on the reproductive output of birds worldwide. Credit: Fred Zwicky

What kinds of species have their reproductive output fluctuate over time?
Species with the biggest reductions in posterity creation included Montagu’s harriers and white storks, the two of which are enormous, transient birds; Vultures with beards, which are large and do not migrate; roseate terns, migratory birds of moderate size; martins of the common house, which are small and move around; and red-winged fairywrens, which are native to Australia, are small and do not migrate.

The Bulwer’s petrel, a medium-sized migratory bird, and the Eurasian sparrowhawk, a small migratory raptor, were two species that produced more offspring. together with collared flycatchers, protonotary warblers, and Eurasian wrynecks, all of which are small and migrate.

Some species, like the barn swallow, had more young in one location but fewer young elsewhere. This demonstrates that, despite the fact that the planet as a whole is warming, the effects of global warming on local weather and temperatures can vary significantly throughout a species’ breeding range.

Does this imply that species with large bodies and those that migrate are most at risk?
Huge-bodied species appeared to be especially defenseless against diminishments in posterity creation in the next fifty years. Environmental change-related warming probably exacerbated the issue for inactive species weighing more than 1.0 kilogram and transitory species weighing in excess of 50 grams. Bigger species might be less ready to adjust to a changing environment since they will generally carry on at a slower pace. They have smaller clutch sizes and take longer to mature and produce offspring.

A warming climate may result in mismatches between peak food resource availability and peak food demand for migratory species, such as when adults feed chicks and fledglings. Climate change could also have an impact on migratory species’ wintering grounds or the habitats they use while migrating.

How are the studied species adapting to changing climates?
Since 1994, we have been researching protonotary warblers in southern Illinois. Small and migratory, these warblers breed in forested wetlands and swamps. When local temperatures were higher, our study population saw an increase in the number of offspring it produced per female over time.

The females started laying eggs earlier in the season, increasing their chances of producing two broods of chicks in a single breeding season, resulting in this increase in reproductive output in warmer years. These warblers eat insects and breed in areas with a lot of insects. It would appear that the rise in local temperatures has not, at least not yet, resulted in a mismatch between peak insect supply and demand.

Did the findings surprise you in any way?
The main analysts merit such a lot of recognition for assembling this huge meta-investigation. It truly features the significance of directing long-haul, nitty-gritty segment investigations of wild populations of living beings. The results show how complicated nature is. While certain species might encounter direct impacts of an Earth-wide temperature boost, it is vital to perceive that a significant number of the hazards confronting species are the consequence of intricate cooperations between environmental change and the biological, life history, and social qualities of the species being thought of.

More information: Halupka, Lucyna, The effect of climate change on avian offspring production: A global meta-analysis, Proceedings of the National Academy of Sciences (2023). DOI: 10.1073/pnas.2208389120

Topic : Article