Nesting season 2001
Broad Street, Guildford, UK.
Page five.
4th May 2001.Today, we have nine eggs and a happily brooding bird. Here are a selection of recent pictures. There has been one egg a day for each of the last nine days. Brooding is estimated to take two weeks (14 days) so we expect a hatching party on the 18th May 2001. It will then take a further 19 or 20 days to fledging, so the birds will fly on 6th or 7th June 2001.
Nine eggs
quietly sitting
watchfully brooding
showing straw to the camera
inspecting detritus in the entrance
forming the nest cup
In the picture immediately above, the bird is forming the nest cup by rolling around on the eggs, and rolling the eggs in the forming cup. This activity is repeated at regular intervals. So far there has been little evidence of egg-turning. The eggs have to be turned to ensure uniform warmth and development.
Our bird continues to import nest material, straw, hair, feathers, and soft stuff. She enters the box at speed, then flies up and down to the camera a half-dozen times, before relinquishing her hold on the contents of her beak. She doesn't place the new material carefully; it gets worked in in the normal course of her movements, rotating on the nest cup and the eggs, and wriggling and turning the eggs.
7th May 2001. Eggs are being laid in box 2. Today there are four.
four eggs in box 2
8th May 2001. A beautiful sunny spring day. The microphone in box 1 developed a fault so, while the bird was foraging, the box was demounted and the microphone fixed. The following pictures were taken of the nine eggs.
Nest box 1 with nine eggs
A close-up of the nine eggs
We can see here that the markings on the eggs in box 1 are more vivid than the markings on the eggs in box 2. The textbooks tell us that this is possibly because the bird in box 1 is younger than the bird in box 2.
The oak tree leaves are bursting today. The birds time their hatching to coincide with a plentiful supply of caterpillars that live on young, freshly unfurled, oak leaves. As the oak leaves develop, the tannin ("an astringent vegetable substance" - SOED) content increases and this is not liked by the caterpillars. So the caterpillars are timed to develop with the young, tannin-free, oak leaves, and the developing birds are fed developing caterpillars. Thus, the birds time their egg laying so that the young are developing during the peak caterpillar supply. If you are ever in the countryside and you see bursting oak leaves, think "bluetit eggs about to hatch".
Oak-leaf burst, 8th May 2001.
10th May 2001. Today there are 7 eggs in nest box 2. However, on close inspection we see that an egg at the right on the top row seems to be cracked, so that albumen has leaked out...
A cracked egg in Box 2
11th May 2001. Sure enough, when we looked in today, a day later, there are only six eggs. Our bird has surgically removed the cracked seventh egg.
12th May 2001. Today the bird has laid a replacement seventh egg, and started to brood.
13th May 2001. (Sunday). Although the bird which is brooding in box 1 is active, in and out all day, leaving the eggs for up to 10 minutes at a time, and bringing in quantities of straw, we have not seen the bird in Box 2 leave her brooding at all. She seems to be a very much more placid and broody bird. Today we saw our Box 1 male deliver a caterpillar to the sitting female for the first time. There was none of the exaggerated fluttering on the part of the female, of the kind observed in previous years.
14th May 2001. We have been unable to determine how many eggs there are, in total, in box 2. There are at least seven; we think that the bird never got around to laying the eighth egg, having lost one and having thus "output" a total of eight eggs. The weather has turned cooler after several days of 25+C temperatures.
15th May 2001. Box 1 eggs may hatch any time from tomorrow onwards. Box 2 eggs will probably be about a week later. We have still not observed the Box 2 brooding bird depart for a feed, neither have we seen her mate bring in any food.
16th May 2001. No hatching today. This is not too surprising, as the box 1 bird (unlike the box 2 bird), has been very lackadaisical about keeping her eggs warm. Anthropomorphising, these birds have character. I empathise with the box 1 bird, who is unable to sit on her eggs for more than about 20 minutes at a stretch, without going out for a fly-around, chat with the mates, call of nature, feed, "cup of tea", or what have you.
The weather has degenerated into bursts of very heavy showers. Birds do not seem to mind, or take any notice of, wet weather. One can hear the sound of the rain on the bird box, just above the inbuilt microphone. Sometimes the individual drops make a noise like hailstones, and sometimes, as today, the rain is intense, but with smaller droplets that make a whooshing sound.
The male bird has been feeding our restless character from time to time today, but even this "waiting on her wing and foot" activity has not suppressed her propensity for going walkabout.
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There are many pictures of the kind of activity now proceeding, on the pages from earlier years. Please see the links on the page "Old birdsite" below.
Old birdsite http://www.ee.surrey.ac.uk/Personal/D.Jefferies/bird/birdsite.html
Lifeforms pictures http://www.eryptick.net/lifeforms.htm
Email dj@eryptick.net
diary continues......