Climate change impact on larger, migratory birds more worrisome: Study

New Delhi: A new study has found climate change to have more worrisome effects on larger birds and migratory birds than on smaller, sedentary species.

Researchers on this international study assessed changes in the annual production of young by female breeders in 201 populations of 104 bird species covering all continents between 1970 and 2019 and found that climatic changes affect offspring production through compounded effects on ecological and life history traits of species.

They have published their findings in the journal Proceedings of the National Academy of Sciences (PNAS).

Overall, they said in the study, average offspring production has declined in recent decades, with 56.7 per cent of the populations showing a declining trend and 43.3 per cent exhibiting an increase. However, considerable differences were found among species and populations.

The researchers found that migratory and larger-bodied species experienced reduced offspring production with increasing temperatures during the chick-rearing period, whereas smaller-bodied, sedentary species tended to produce more offspring.

"The study suggested that the body mass is one of the key factors for the adaptability towards climate change, in which the larger body-sized species are struggling to synchronise with weather anomalies compared to the small and sedentary species," said J. Pandiyan, Assistant Professor, Department of Zoology and Wildlife Biology, Anbanathapuram Vahaira Charities College, Tamil Nadu.

Further, multi-brooded species showed increased breeding success with increasing temperatures, whereas rising temperatures were unrelated to reproductive success in single-brooded species, the researchers said.

The study also found that the egg laying process has decreased with the preponing of egg laying mechanisms among the bird species.

The study explained that the clutch size (number of eggs per nest) and success (fledgling and nestling) are positively influenced by various ecological factors.

However, the offspring production, clutch size, nest success, date of first egg, egg laying process are examined towards various ecological factors in which the temperature influenced the offspring production, clutch size and nest success.

"The global warning and the elements causing climate change should be measured, monitored and managed properly to save the species, which are facing vulnerability otherwise, existence of biodiversity especially intolerable species would be extinct from the world due to human life style," said Pandiyan.

However, Pandiyan said, the study did not deeply investigate the bird population in the Asiatic region, including those in India. The migratory species birds are using diversity of habitat in India as a vital stop over sites or refuel sites during their migration, he said, and therefore, the status of migratory birds in India must be studied.

"We have to explore their life history in relation to the ecological factors to sustain their population in India," said Pandiyan.