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Climate change alters bird clutches

A worldwide study with the participation of the University of Veterinary Medicine Vienna shows: Climate change has far-reaching consequences and also affects the offspring of birds - in very different ways.

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Climate change influences the timing of reproduction in many bird species, but little is known about the impact on annual reproductive output. A recently published global study with the participation of the Vetmeduni now provides important new data based on a meta-analysis.

Broods become smaller on average

The research team examined long-term breeding data for the period from 1970 to 2019. A total of 201 populations of 104 bird species with 745,962 clutches on all continents were included in the study. On average, the number of offspring decreased over the last decades, but the researchers found significant differences between individual species and populations: 56.7% of the populations (significant at 17.4%) produced fewer offspring, whereas 43.3% (significant at 10.4%) had larger broods.

Some species benefit from climate change

"The results show that climatic changes influence offspring production," says co-author Marcin Tobółka from the Konrad Lorenz Institute of Ethology at Vetmeduni. In detail, the analyses indicate that rising temperatures have a negative effect especially on migratory, larger species, while sedentary species with smaller bodies might benefit from a warmer climate.

Declining number of birds is not due to smaller clutches

Since the trend towards smaller clutches is not very pronounced and is also inconsistent, the researchers assume that the rapid decline in bird populations worldwide is only to a small extent due to changes in the number of young.


The article „The effect of climate change on avian offspring production: A global meta-analysis“ by Lucyna Halupkaa, Marcin Tobółka, Konrad Halupkagg et al. was published in „PNAS“.

Scientific article