Help!!!

[Elizabeth B]

If incubation hasn't started, the eggs can be left for a long time. In 2002 there was a fight over Box 2 when there were 8 eggs in it (but incubation hadn't started), then there was a gap of nearly three weeks before another female laid 3 eggs and started incubating. Six eggs hatched, so some of them must have been from the first clutch.

I would think eight hours might be too long if incubation had already started - but would she have stayed away so long if this was the case? I really don't know - but I'd be interested to hear how things go.

[Jenny W]

If she hasn't started incubating (which I guess she hasn't - if she had 6 eggs on the 1st she would have 9 by today so could be yet to lay another 3/4) then pretty much the only time she will spend in the box during the day is when she is actually laying an egg, the rest of the time she will be out feeding.

When incubating she should be there most of the time, but again, don't worry if she stays away for a while, they have to come off the eggs to feed at intervals.

[Elizabeth B]

We've been watching nest boxes via cameras since 2001, and have records for 11 bluetit nests - this is the first year we've seen as many as 12 eggs, and this beat the previous record of 11 eggs (seen only once). On three occasion there were 8, two occasions each for 9 and 10 and one occasion each for 5 and 7 eggs.

My Collins Guide to nests, eggs etc says there are usually 7-12 eggs, sometimes 5 to 16. I wonder if it varies according to habitat?

[Digit]

I wonder how many out of 12 will fledge?
The largest number of fledglings that I have seen is 7!

Roy.

[Elizabeth B]

Our highest number is ten bluetits fledged from 11 eggs, and eight from 10 eggs.

All the figures since 2001 can be seen on the Overview page of our website - mainly bluetits, but some great tits too.

[Jenny W]

The largest clutch ever seen in our scheme is 14, but this was only once. However, they will regularly (seen in several boxes each year) have 13. The fledging rate for Blue Tits last year was 5.3 chicks, which is close to the long term mean (although I can't remember what the long term mean is sorry!)

Clutch size does depend on habitat, Blue Tits in particular will lay larger clutches in prime Oak woodland habitat and generally smaller ones in more marginal habitat. I would think that fledging success follows a similar trend on the basis that more food would be available in prime habitat than more marginal areas.

[Elizabeth B]

There are some interesting figures on the BTO website. (It's fifty years since I studied statistics - can anyone explain things like this: 9.06 ± 2.14 (2 - 16) N = 2875)?

Breeding and Survival

Egg Size: 16 x 12 mm Egg Weight: 1.1 g (of which 6 % is shell)

Number of Nest Records: 4000
Clutch Size: 8 - 10 eggs 9.06 ± 2.14 (2 - 16) N = 2875

Incubation: 13- 15 days 13.88 ± 1.31 (12 - 16) N = 2875 by the: Female
Fledging: 18 - 21days 19.28 ± 2.16 (15 - 22.5) N = 4391 as: Altricial, downy

Source: British Trust for Ornithology (2005) Nest Record Scheme data

More here:

BTO BirdFacts - Blue Tit

[derek71]

After all the worried moments we have a nest that has 9 growing blue tits in....