Blue-tit tiff leads to loss of clutch?

On 15 May 2002 I wrote an item for the USENET newsgroup uk.rec.birdwatching headed "Blue tits fight in nest box", as follows.

Tonight (Wednesday) had good light so I plugged in to my new nest-box colour camera. I soon saw, while the box was vacated, that two eggs had hatched (I'm fairly sure there were no chicks yesterday, though the light was not so good.)

The box is just outside the window so I can see what is going on outside it as well as inside. I could see a bird incubating and one hanging outside looking in. Each time it leant in, the resident bird stretched out its neck towards the entrance, without moving from the nest cup. The movement looked unfriendly, somehow. I wished I had a microphone in there to hear what they were "saying".

I am not sure whether the outside bird flew off and returned, but suddenly it entered the nest-box. There was then a furious fight, lasting several minutes. During it I captured eight 40Kb JPEG pictures which are listed here

I worried that this fight was going to damage the two chicks and/or the remaining seven eggs. Perhaps, I wondered, I ought to interrupt by taking the lid off the box, or something. But eventually one bird broke free and was chased out of the box, leaving the two chicks to sort themselves out. They seemed to me to be OK. One of the remaining eggs now had an obvious crack. It is visible in the last, post-scrap, JPEG.

Nothing so exciting happened that evening while the light was still good enough to watch. The other collection of five JPEGs shows an adult at peace having returned to quiet brooding, and the two chicks gaping for more food.

If the nest-box programs are going to be this engrossing I shall have to get a better camera for next year, and stereo sound!

The fight images from my nest-box video camera are here; the peaceful post-fight images are here.

To read the whole of the above discussion thread, courtesy of Google, see here.

Then later, on 26 May 2002, I wrote:

Last weekend I became aware that only one parent was visiting the nest box and although the chicks were naked and with eyes still closed they were left on their own a lot of the time. Through Sunday they were abandoned altogether. I could see a large blue-bottle-type fly prospecting around the chicks.

Since I was removing small green caterpillars from my gooseberry bushes I took the nest box down, warmed the four chicks by reflecting sunlight into it and tried to feed them the caterpillars. Although I had some limited success, and was rewarded by the presentation of a few faecal sacs to remove, the chicks were very weak and feeding was difficult. Especially getting the chicks to crane and gape for long enough to aim a caterpillar. I also removed two dead chicks that may have attracted the fly.

I decided that it would not be fair to try to find someone to take the chicks on for raising. Had they had feathers and their eyes open it might have been a better prospect. I put the nest box back in position in the early evening.

When I got back from work on Monday the chicks were, as I expected, dead. There were already numbers of minute maggots starting the process of recycling them. I am left wondering if the fight between the adults, who I presume were the parents, caused one bird to desert and thus led to the demise of the chicks. And, of course, what led to the fight. Was it an errant male who had the blue-tit equivalent of lipstick on his collar?

Again, to read the whole of the above discussion thread, including a contribution from the late great ornithologist Chris Mead, courtesy of Google, see here.