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Why South-Facing Bird Houses are a Bad Idea

It can be difficult to choose the best site for your bird house, especially if you don’t happen to be an ornithologist. There are many factors to consider including the threat from predators and the danger of birds flying into the windows of your home. Now, new research has revealed that the direction in which your bird house faces could be crucial too.

Scientists at Lund University in Sweden have looked at how temperatures in a nesting box impact the development of the young birds within. The biologists experimentally increased nest temperatures to see how this would affect body temperature, growth and apparent survival in blue tit nestlings.

Baby Blue Tits Battling High Temperatures

Baby blue tits are able to maintain their regular body temperature even when nest box temperatures reach 50 degrees C or above. But the researchers found that the nestlings pay a high price for the effort they exert to regulate their body temperature. The birds who have battled high temperatures exhibit restricted growth when compared to those who benefitted from a cooler environment.

The study’s findings are likely to apply to other small species of hole-nesting birds. The research team have, therefore, recommended that nesting boxes are not positioned so as to be south-facing and exposed to the sun. A spot in the shade would be a much better choice. South facing locations are the hottest and so present problems for the birds.

Nesting Boxes and Climate Change

The effects of climate change are making the issue of overheating nesting boxes an increasing problem. Indeed, the various extreme weather events that we are experiencing are all seriously impacting birds. Their food sources are often disrupted and their migration patterns disturbed. Birds are being forced into a fight for survival in the face of abnormally mild winters, abnormally early springs, ridiculously late snow fall and high winds.

The First Study of its Kind

According to the Swedish researchers, their study represents the first of its kind. The team warmed up the nest environment inside the box for a week by placing human hand warmers under the nesting material. They continuously measured the temperature in the nest box, the nestlings' body temperature and their body weight. The birds are so good at maintaining their own body temperatures that the biologists believe natural selection has favoured birds with this ability.

It could be a good idea to relocate any south facing bird houses in your garden which do not benefit from shade, even if blue tits do not visit your garden. It is highly likely that most species will be impacted by excessive heat in their nesting environment and so you can help the birds by choosing the right spot for your box.


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