The trough allowed the female great Tits do not save energy winter nights

Regular feeding allows the female great Tits to spend more energy for heating during the winter nights. This is the conclusion reached by researchers after analyzing the body temperature of these birds in forest areas with the feeders without them. While the males maintain the same body temperature at night regardless of feeding. As I assume the authors of the article to Biology Letters, the reason for this difference may lie in the hierarchy. Dominant males can easily find enough food to stay warm on a winter night, and females in the absence of feeders has to be strict to save resources.

In winter, of small passerine birds have a hard time. The days are short, which limits the time for searching food, and cold nights require to expend a lot of energy to heat the body. One of the most common ways to save energy resources is to temporarily lower the body temperature by a few degrees during the winter nights. Unfortunately, this strategy has its price and may increase the vulnerability of birds to predators, decrease their quality of sleep and disrupt intracellular processes.

Regular fertilizing with people significantly increases the chances of wintering birds to survive. However, it is unclear how it affects their approach to waste of resources. One study showed that regular feeding common blue Tits (Cyanistes caeruleus) do not reduce the body temperature during the winter nights. However, it was not with wild birds, and to individuals living in a cage.

A team of ornithologists headed by Johan Nilsson (Johan F. Nilsson) from the Lund University decided to find out how feeding affects energy strategy of wild birds. The research focused on great Tits (Parus major). This is one of the most numerous wintering birds of Europe and are regular visitors to the feeders.

In the winter of 2016-2017 years, scientists have placed on one end of the forest in southern Sweden eleven feeders and regularly filled up in them a stock of sunflower seeds and peanuts. At the other end of the forest there was no trough. In the middle of winter, researchers caught 82 tit from both forest areas, assessed their ages and gender, and then implanted them under the skin of the neck heat-sensitive transponder. It was easy, because birds prefer to sleep in artificial nest boxes.

A few weeks later ornithologists have used implanted sensors to remotely determine the temperature of the body sleeping Tits. In total they spent 152 measurements as to the area with feeders and where they were not.

It turned out that when regular feeding female great Tits during the winter nights, maintained a higher body temperature. However, on the energy strategy of males is the presence of feeders does not affect: their body temperature was the same as at the forest feeders and where they were not.

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