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Summer 2005:
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.
The 2005 Breeding Season Results from the Nest Boxes in Gledhow Valley Woods
I've been maintaining the nest boxes in Gledhow Valley woods for 17 years. The scheme started off with 12 boxes in 1989 and has progressed to 83 boxes this year. The boxes are used predominantly by Great Tits and Blue Tits both for breeding and roosting.
Over the 17 years, 4344 birds have fledged from 627 nests in the boxes. The average number of fledglings and pairs of birds successfully using the boxes is as follows:
As can be seen from the table, the numbers vary from 5.3 to 8.5 for Blue Tits and for Great Tits, it is 4.8 to 8.0.
The numbers of pairs of Blue Tits using the boxes has remained fairly steady apart from a couple of boom years and an odd low year, but the Great Tit numbers have soared from 4 pairs in 1990 to 27 pairs in 2005.
2005 has been a season of great difficulty for the breeding Blue and Great Tits in Gledhow. The sizes of clutches laid seemed to be fairly normal, though I don't check the boxes until the birds are either sitting or feeding young so I don't particularly note clutch sizes. However, the numbers of birds fledging is well down compared to previous years with an average of only 5.3 per nest for Blue Tits and 4.9 for Great Tits. These figures don't include nests that failed before fledging.
Again, 2005 has had a record number of nests failing. This year, 12 pairs of Blue Tits deserted their broods and 6 pairs of Great Tits did likewise. One box contained 5 dead babies of varying ages, (2x14 days old, 1x9 day, 1x6 day and 1x4 day), implying that the pair must have tried to keep feeding despite regular deaths of their brood, but finally gave up.
The reason for this poor year was presumably a lack of suitable food available, probably due to wet and cold weather at crucial times in the breeding season. The massive deluge that caused widespread flooding in Leeds occurred in May and was probably a contributory factor.
The young birds were abandoned at any stage from hatchlings to 14 days old. (The birds fledge after about 20 days).
Brood sizes decreased as birds died regularly resulting in the small numbers fledging. Clutches of 9/10 eggs often produced only 2 or 3 fledglings. However, some pairs successfully fledged normal sizes with Blue Tits ranging from 2 to 8 and Great Tits from 2 to 7. Maybe there were some more experienced pairs that were better able to cope with the conditions. Again, these are still low maximums as in previous years, pairs regularly fledge 11/12 young.
Another factor which points to the difficulties the birds faced is the lack of second broods. Usually, there are a few pairs of Great Tits that raise a second brood, but I couldn't find any this year.
Some pairs are tidy nesters and as their offspring succumb, their bodies are removed from the nest cup to the rim of the nest. Other pairs leave the bodies in the cup where they get trampled by the remaining siblings. I found one nest this year that had been constructed on top of a dead adult Great Tit that had presumably died whilst roosting in the box sometime in the winter months. The feathers were in good condition on an emaciated body.
2005 can best be described using the nest boxes in my garden. There are 3 boxes, all of which were occupied this year.
Box 1, a pair of Blue Tits laid 7 eggs, of which 6 hatched and all survived to 7 days old. From then on, there were regular deaths to leave 3 birds that successfully fledged.
Box 2 contained a pair of Blue Tits that laid 10 eggs quite late in to the season. Only 2 hatched and despite surviving to 14 days old, were deserted and died.
Box 3 was occupied by a pair of Great Tits and 8 eggs were laid, 7 of which hatched. 2 birds died early on to leave 5 babies 8 days old. All was progressing nicely up until that point, when I noticed a lack of adults visiting the nest one day. The box is not far from the back door and every time it opened or shut, the babies could be heard begging for food, probably due to the vibrations caused by the door. At the end of the day, I was fairly certain that the nest had been deserted. Come the next day, a Sunday, I checked in the box and 2 birds had died overnight. I now had 3 abandoned Great Tits about 9 days old. Should I let nature take its course or should I attempt an adoption?
I have not tried before, but decided to billet the 3 with similar aged broods in the woods. After much checking of my records, I narrowed the possibilities down to just 2 suitable pairs of foster parents. Unfortunately, they were at opposite ends of the Woods, so it was a long trek with my ladders over my shoulder and nest containing 3 noisy Great Tits in my hands to nest box 76. By now, one of the three was fairly quiet compared to the other two.
Box 76 contained four 8 day old Great Tits, so I added two of the three (one noisy one and the quiet one) and left them to acquaint themselves with their adoptive family. The other destination was Box 59 much nearer to my house and this box contained a brood of four 7 day old Great Tits. To this was added the third deserted Great Tit and after a frantic couple of hours, it was finger crossing time.
I left them alone for a couple of days before I paid them a visit. To Box 76 first, to visit the two additions. The quiet one was now very quiet, having died and had been hauled out on to the rim. I removed him/her and noted a slightly larger individual Great Tit in the brood of five, all looking healthy.
Off to Box 59, where it was also easy to spot the incomer as he/she was bigger than his/her new siblings. All looked well. I checked both boxes in the next couple of weeks and there were no more corpses in Box 76 although one of the smaller ones in Box 59 succumbed before fledging.
So two out of the three orphans survived to fly to the outside world. Maybe they'll live long enough to be able to breed themselves in 2006. If they do, I hope the conditions are more favourable than they experienced in 2005.
To see how successful the nestboxes have been from the start of the scheme to the present day, please see the Nestbox Records for Gledhow Valley page. If you have any information, stories, pictures or memories you would like to contribute to this section of the web site, please contact us.
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