Nest Boxes

Nest boxes

Sorry, a bit of an essay! (and a soapbox :))

The few of you that have walked the woods with me will know that I dislike nest boxes! So, you may be surprised to find that I do use them. I have two pieces of woodland, the smaller one, despite being ancient semi natural woodland, has very few dead or decaying trees with natural nest holes, so I have nest boxes up. The larger one has a lot of suitable nest sites, so I don’t use them. However, see below for a new experiment in artificial nest sites.

First, why do I dislike them? To start with, they are ugly, they spoil the look of any natural wood. But, of course, that in itself is not a reason to not use them if there’s a need. It’s that last bit that makes me urge people to think carefully; is there actually a need? what species need them? and if there is a need, what negative outcomes are there and can we mitigate the downside? Every action we take in conservation will have a negative knock-on effect; how well we mitigate against them will determine the value of our intervention.

We’ve just spent the winter feeding the birds and making sure there’s an unnatural number of blue tits and great tits around. They will now be starting to nest and using up all the nesting sites they can find and will be devouring and feeding their young on vast amounts of invertebrate larva that will consequently never reach adulthood. In April and May our severely depleted migrants, such as redstarts and pied flycatchers, will be arriving and there will be very few good nest sites and reduced numbers of invertebrate food sources. Basically, we have stacked the cards against the already stressed migrants.

If we want to enjoy birds at the feeder over winter (let’s be totally honest here, that’s for our pleasure, not for conservation) we need to find ways to mitigate against the inflated numbers of resident birds. As far as food is concerned the only way to do that is to continue feeding throughout the nesting season. Even that has a negative outcome in as much as it means even more blue tit and great tit young survive!

When it comes to nest boxes the easiest way to make sure there are still sites available for the migrants is to block the entrance holes until the migrants arrive. I block about 50% with a short piece of hazel branch then remove that in early April.

Now, my experiment: although there are a lot of good natural nesting sites in the larger wood, it is unlikely to be at a natural ‘ancient wood’ level and I would like to make it easier for migrants such as pied flycatchers to find sites when they arrive. I don’t want obviously visible nest boxes in a very natural wood so I’m trying out a new nesting site method. In standing dead wood I have bored a 90mm hole to a depth of about 200mm. I have then fastened a metal and thin ply cover with a hole over the top. In a year or so the ply will fade to grey and the nest site will be far less visible. I’ll report on how well it’s worked later in the season!