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An Eawag researcher has shown that birds have had to adapt to the fact that climate change has had an influence on their food supply.
Not all insects have the same nutritional value for birds.
AFP
In our latitudes, climate change has an influence on the food supply of brooding insectivorous birds: “the insect buffet (terrestrial and aquatic) opens earlier, is no longer as diverse and half as abundant”. This is the conclusion reached by ornithologist, Ryan Shipley, of the Swiss Federal Institute of Aquatic Science and Technology (Eawag).
To arrive at this result, the researcher “examined how the abundance of insects and the breeding period of various species of migratory songbirds have evolved over 25 years in the northeastern United States in relation to climate change” , explains Eawag.
The choice of this region is explained by the access to a large amount of data and long-term observations (from 1989 to 2014). The climate data showed “as with us, a rise in temperatures in early spring. As expected, the emergence of insects takes place earlier, as does the flowering period. In the spring, aquatic insects emerge on average one week, and terrestrial insects almost two weeks earlier than in the 1990s”. details Ryan Shipley.
“For aquatic insects, the data further shows that their numbers increase much faster in April than before but decrease drastically in May. The period when the supply of aquatic insects is rich has therefore shortened and moved forward in the breeding season,” he adds.
Superfoods
The problem is that not all insects are created equal. “Aquatic insects are of higher quality than terrestrial insects, they are, so to speak, the superfoods of many birds. Their omega 3 fatty acid content is several times higher than that of terrestrial insects”.
As the ornithologist explains, “Child birds that ingest more of these precious fats grow faster and can leave the nest more quickly – an extra chance of survival as they are always at risk of being eaten by predators”.
Birds have adapted to these changes. Some species begin to brood earlier: in 25 years, the brooding period of observed bird species has advanced by 3 to 7 days. From now on, “it will be necessary to better study whether and to what extent the various species of birds can adapt to climate change and to the supply of food”, concludes the researcher.
Although Ryan Shipley’s results cannot be applied to other regions, “it is quite possible that the development of insects and the brooding period have also shifted and separated in central Europe”, specifies Eawag, which points out that these results “clearly show that life aquatic is of crucial importance to life on land. Aquatic and terrestrial ecosystems react to climate change and influence each other”.
(comm/aze)