Every year we need to clean out the bird boxes around the park. The reason is that the nest will be a great home for fleas and parasites. They will infect the young birds that hatch the following year. This might kill most of the chicks.
What we do at Falls of Clyde is empty the boxes as well as we can and do some maintenance. What that includes is checking if the box is falling down or how rotten it might be. We were not able to get into some of the older boxes so we also spent some time opening them up and making them easier to clean out for the years to come.
It is best to do this in October, November or even December which is after the breeding season. In Scotland you are not allowed to remove a nest box outside the months of August through to January since you will disturb the birds.
In one of our nest boxes we found four skeletons and one unhatched egg. We could not decide from what species of bird they came from but they were definitely chicks. There could be many reasons for the death of these pour creatures. Maybe the parents died. Maybe the fleas and parasites got to them. It is really hard to tell. However, it is quite normal for some eggs not to hatch and for chicks to die. Blue and great tits lay up to 14 eggs so that they will have enough chicks if some of them died.
We also check what type of nest was build in there. Different birds has different ways of making their nests. The wren for example will fill the nest box to the top and make a little hole by the entrance. We wrote down if the nest box had been used and what material was used in it. Next year we will be able to see whether birds nest in the same box or one of the others.
You should empty out your nest boxes too. The best way to do it is to use boiling water. The water will kill fleas and parasites. Avoid using insecticides or flea powder. Also, you can put the nest and skeletons (if you have any) in the compost bin. By doing this there is a greater chance of new birds moving in the coming spring. I suggest you wear gloves when doing this. Again, the nest can house fleas, ticks and lice.
When the box has dried out properly, you could put a little bit of hay or saw dust in the bottom of your nest box before you put it up again. This will be a good roosting spot for birds but also a fine base for the new nest. It can also be a good hiding spot for wood mice and other mammals.
If you find unhatched eggs inside you have to destroy them.
Carina Marcussen – Volunteer Assistant Ranger, Scottish Wildlife Trust
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