The following article was written by Martin Calvert and originally printed in the RSPB Leeds Local Group Newsletter). It has been reproduced with his permission.
Thursday 28th May started off as a normal day to be spent checking the thriving population of blue and great tits in nestboxes in Gledhow Valley woods. It's a pleasurable task checking on the broods, ranging from newly hatched to ready to fledge groups of between two and twelve. There are occasional disappointments when broods are deserted but that's nature.
I hadn't checked the boxes in the wood beyond the new housing development for two weeks and I wasn't prepared for what I would find.
The first box I came to should have had a brood of blue tits approaching fledgling, but I feared the worst after noticing a triangular shaped hole at the side of the box where the box joined the back and side. Inside there was nothing, no nest, no blue tits, nothing. This was repeated at the next box, but at the third box, where the blue tit occupants should have fledged was a compete nest but no occupants. This suggested that the young blue tits had escaped through the entrance hole whilst the second triangular hole was forming.
The wood was full of birdsong, but the chip, chip of a great spotted woodpecker and the incessant chipping of young woodpeckers was constant. I soon discovered the nest hole and it didn't take a genius to work out that the predator of the nestbox occupants was down to Mr. Or Mrs. Great Spotted Woodpecker. At least nine broods in nine boxes disappeared in three weeks and eight more boxes were attacked without success for the woodpecker.
I actually arrived at a nestbox that had just been attacked. Inside was a lone shivering blue tit about eight days old, six siblings having been dragged out through a newly excavated hole. The adult blue tits were nearby so I resolved to shore up the box as soon as possible. I returned one hour later with wood, hammer and nails to find an empty box, the last young blue tit had gone.
After that, I reinforced six occupied vulnerable boxes in the vicinity of the woodpecker nest hole and all of these boxes survived to fledge blue and great tits. Just one more box fell victim to the woodpecker after that fateful afternoon, one that I hadn't shored up.
Nature continued to show it's savage side the next day when I came across that darling of the woodland, a magpie, pecking at something on the floor. Now remembering that the magpie is not responsible for decimating our local song birds (!!). I was most surprised to find a fledgling nuthatch on the floor looking decidedly unimpressed with life outside the nesthole. The young bird was happy to cling on to my hand. I guess it was his first day in the outside world. So what do you do to protect a young nuthatch from magpies and also a jay that had appeared on the scene. Both parent nuthatches were around and agitated, so I espied a nest hole in a silver birch, 2ft off the ground, with pieces of bark in the hole which could have been the original nest site, and placed the young bird inside. I left the fledgling calling from the nest hole and hoped that there was a place in the scheme of things for this particular young bird.
So, out of 70 nestboxes, at least 17 need replacing along with another eight that were due for replacement. Maybe reinforced concrete boxes are the answer if the woodpecker uses the same tactics next year. It hasn't happened on a big scale before and the last predation was by a woodpecker enlarging nestholes. After that every box was fitted with a metal entrance hole surround, and this, up to this year had been sufficient to deter any would be predators.
This year only 185 blue tits fledged from 24 successful boxes, compared to 272 from 34 last year. No great tits were predated and at least 13 broods of great tits fledged, with three more broods still in boxes at the time of writing. Last year 11 broods of great tits fledged.
So if you're in Gledhow Valley Woods and you see a lot of great its and a lack of blue tits, now you know why.