Migratory and seabird populations are declining due to climate change

Two independent studies published in June this year. by scientists from the United States and Australia have caused concern among environmentalists and ornithologists. They show that the population of migratory birds, as well as other winged species classified as food specialists, are facing a serious threat from severe storms and a general warming of the climate. Forecasts for the end of the 21st century. are not optimistic.

Skies over North America empty out

Researchers at the University of Illinois Urbana-Champaign have become the first to study the long-term effects of climate change on the abundance and diversity of North American birds. They found that a consistent increase in the number of days with temperatures above 25°C between 1980 and 2015 resulted in a 2.5 percent reduction in the total number of birds. and species depletion of 1.7 percent.

Extrapolating the observed changes and juxtaposing them with climate scientists’ predictions, the researchers presented a vision of a further reduction in the abundance and diversity of bird species by as much as 16 and 9 percent by 2099. The analysis showed that the biggest threat is to the so-called “new” market. ecological specialists, i.e., species that depend on specific habitats and food sources and adapt poorly to change, which include some migratory bird populations. While sparrows (generalists) do well in a variety of ecosystems, species such as the spotted owl and the woodpecker Leuconotopicus borealis , found only in the southeastern US, are very sensitive to climate change.

Migratory bird population under threat

The Illinois researchers also focused on species such as the whooping crane, which are among the food specialists and additionally migrate every year. It has emerged that migratory bird populations are even more severely affected by the impact of a warming climate changing food availability in breeding areas. Birds follow genetically encoded cycles in their migrations and have limited ability to adapt them to weather changes. Nor can they predict what conditions they will find at the end of their journey.

In particular, an increase in average daily temperature reduces the abundance of birds residing in the colder zones of North America and in regions that frequently experience drought. In contrast, the population of migratory birds classified as food generalists appears to be relatively least susceptible to climate change, finding new, more favorable habitats most easily.

Tropical cyclones – instant death

Climate change not only means higher temperatures that alter the supply of nutrients, but also more frequent and violent weather anomalies, such as tropical cyclones. In a study published in Communications Earth & Environment, Australian scientists focused on the environmental effect of the April 2023 storm Ilsa. passed over the west coast of the continent with winds reaching up to 300 km/h in gusts. The results proved devastating.

Of the three species of birds that inhabit Debout Island in the Timor Sea – the bonneted grosbeak, the white-bellied grosbeak, and the small frigate bird – as many as 80-90 percent. The population was killed almost immediately. According to observers who surveyed the island after the storm, most of the approximately 20,000 birds died on the spot without even attempting to escape. This observation partially contradicts earlier claims about the ability of seabirds to sense and respond to impending atmospheric threats. It seems that exceptionally strong cyclones can take birds by surprise and overpower them.

Although the aforementioned study is narrowed to a single island, its implications can be extended to the entire realm threatened by increasingly severe tropical storms. Approximately 11 cyclones occur over western Australia every year, systematically destroying coral reefs and bird breeding grounds.

Earlier, in 2017. An analysis of the impact of hurricanes on black tern mortality has been published on the PeerJ Life & Environment platform. It turned out that a population of migratory birds studied by Duke University encounters Category 4 and 5 storms every year on their migration routes over the Atlantic. Tired by their long flight, terns die in contact with the elements, and losses increase as cyclones become more frequent.

Scientists point out that seabirds have evolved under severe meteorological changes, and that individual species have so far successfully recovered from losses. In the current situation, where deaths are as high as 90 percent. local populations, there is a gender imbalance and greater susceptibility to disease. As a result, a few unfavorable years behind can lead to the complete extinction of endangered species!