Food overlap of birds, bats and dragonflies disadvantageous in the decline of insects

According to a new Finnish study, different groups of insectivores compete for the same type of food. Researchers from the University of Turku, Finland, and the Finnish Museum of Natural History have made a discovery by comparing birds, bats and dragonflies that eat food in the same area in southwestern Finland. These very distantly related predators consumed the same groups of insects, such as flies, mosquitoes, and other diptera. The findings shed new light on the decline in insect populations, because a substantial portion of insectivores may actually be in greater danger than previously believed.

According to the study, a common food source for birds, bats, and dragonflies are chironomids. These mosquito-like mosquitoes consume nothing as adults and can be found in large masses on the surfaces of lakes and other water systems. In Finland alone, there are up to 800 species of chironomids. Chironomids are a very rich and diverse family, and many insectivores have got their flavor. If a major group of insects like this one dies, the cascading effect on nature and humans can be considerable.

“This is exactly what causes a deeper concern. If many predators consume more or less the same food, the decline of chironomids, for example, could lead to an unprecedented echocatastrophe,” explains university professor Eero Vesterinen of the Department of Biology. of the University of Turku.

Basis in in-depth research on the eating habits of insectivores

Eero Vesterinen, who designed the study, has been studying interspecific interaction for over a decade, focusing on food chains, or more specifically food webs.

“I compared the material I had collected over the years with the studies I had published, and I noticed an exciting pattern. It seemed that even if the predators that prey on insects were in different parts of the animal kingdom, and therefore did not share the same story. evolutionary, there are clear similarities in their diet. “

A more precise analysis was conducted on the insectivores collected from the same area so that the available prey taxa were comparable. The insectivores from southwestern Finland selected for the study were the European flycatcher, northern bat, brown long-eared bat, Daubenton’s bat, whiskered bat, Brandt’s bat, black darter, common spreadwing, Northern bluet, spearhead bluet, crescent bluet, and bluet.

“It is surprising how similar the dietary composition was among invertebrates, such as dragonflies and vertebrates in the study. These results also raise concerns about what would happen if the small dipterans that all of our focal predators collect decreased,” says Senior Researcher Kari Kaunisto of the study. University of Turku Biodiversity Unit.

“Most of all bats in the world are insectivores and our previous studies have already revealed many significant details about their diet,” says Thomas Lilley, researcher at the Academy of the Finnish Museum of Natural History.

The mass decline of insects resonates extensively on the food chain and ecosystem

The mass decline of insects has received extensive coverage in recent years, and several reports based on long-term observations have been published on the subject. In some places, the insect population has plummeted to below 50% and news around the world reports similar events.

“The situation could be worse than previously estimated, if the results of the new study can be generalized cross-continental. Our study appears to have produced diverse and elaborate data that help us focus our future research on the cascade effect of the phenomenon. highest in the food chain, “says Vesterinen.