I recently purchased a house sparrow terrace nest box. The box has been up for just 2 weeks and we have blue tits nest building in the box. Is this common with the hole diameter being bigger for the sparrow. I have also noticed that the nest building only occurs in the morning, we then don't see the birds all day. Now i have noticed they are using 2 of the 3 holes to the comparments of the sparrow terrace to build 2 nests is this usual building 2 nests thanks
ANY ADVICE PLEASE
Hi Madness
Although the ideal entrance hole diameter for blue tits is 25mm, they can set up home in holes with a larger entrance hole even though they would then run the risk of being evicted by birds larger than themselves. Choosing a nest with a larger entrance hole often happens if there is a shortage of nesting sites, and so they take a larger hole rather than no hole at all. This may well be the case here, as your sparrow terrace only went up a couple of weeks ago.
In normal circumstances birds choose one nest site and build one nest (well, exceptions like wrens do exist, but more of their habits elsewhere). If there are a number of similar or identical nest holes very close together, the birds may become confused and start to build in two or more of the holes by mistake. There is a well-documented case of a robin from some years ago, which chose a bank of open ended pipes as its nest site, and ended up starting several nests as it got confused which pipe it had chosen, and even laid eggs into two separate nests. Let's hope that your tits eventually pick on one box and stick to it.