The lack of insects has reduced the breeding success of urban great Tits

Hungarian ornithologists have confirmed that due to the lack of insects living in cities great Tits cope with deducing of posterity worse than the forest species. In his article for the Journal of Animal Ecology , they describe the results of the experiment with the feeding of the great tit during the breeding season. It turned out that the success of forest nesting pairs does not depend on whether they receive food from humans. But the city’s tit could bring numerous and healthy offspring only provided extra feeding.

Cities around the world grow rapidly, taking the place of natural ecosystems. To adapt to the new conditions can only a few wild species. Birds cope with the colonization of cities better than other animals, but even they face a number of difficulties. For example, the breeding success of urban populations of great Tits (Parus major) than their forest relatives.

Ornithologists believe that the main reason for this is the lack of insects. Species diversity and abundance of this group in cities is lower than outside, especially in the caterpillars of Lepidoptera is the most important component of the diet of the Chicks of passerine birds. Nevertheless, the available data so far were not enough to definitely confirm this theory.

In search of reliable evidence, a team of scientists under the leadership of Seresa Gabor (Gabor Seress) from the Pannon University conducted an experiment on supplementary feeding of great Tits. The researchers chose 52 couples, some of which were nesting in the Hungarian city of Veszprem, and some — in the woods three kilometers from it.

On the third day after the first chick’s Tits in both groups have started to supply mealworms, which were placed in small plastic containers near the nest. This additional feed covers 40-50 percent of the needs of the offspring. Once the first chick has reached the age of fifteen days, the feeding was stopped. To assess the effect of it, the ornithologists have identified the control group, who had to bring up Chicks without human help.

Observations confirmed that great Tits living in cities face a shortage of feed in the breeding of offspring. The city pairs in the control group survived less Chicks than in the forest, and the survivors were not so large. All forest couples cope with the feeding of the Chicks equally well, regardless of whether they received fertilizer or not.

The greatest interest to ornithologists were attracted to the results shown by the city Tits, who received meal worms. These pairs of Chicks were 15 percent larger and survived better than their neighbors from the control group. Moreover, feeding has allowed the city Tits to achieve almost the same reproductive success, which showed the forest.

The results of the study prove conclusively that it is the lack of insects limits the survival rate of Chicks in urban birds. Other possible factors, such as the concern as well as light and noise pollution play a smaller role. The authors note that urban forestry could improve the food base of great Tits, however, to the success of their breeding was the same as in wild relatives, the insects must grow at least two and a half times.

Modern city sometimes become too inhospitable for even the most undemanding species of birds. For example, Moscow residents are increasingly complaining about the disappearance of sparrows. Ornithologists confirm: the number of these birds is really reduced. The reason for this was urban improvement — for example, the permanent mowing the lawn, which deprives the sparrows feed in the form of insects and seeds of weeds.

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