We have 2 blue tit hens sharing and incubating 18 eggs in a nestbox with a camera. Does this happen very often

Hi

occasionally a male Blue Tit pairs with two females in different nests - VERY occasionally as far as we know they share a nest.

Probably a proportion of ( the strongest / loudest) of each brood will survive to fledge.

S

Thanks for the information. It sounds a fairly rare occurrence then. I have been taking some videos to archive but nothing hatched so far. I don't think the outcome will be good and I hope that they don't all hatch as that is a lot of chicks to look after and feed even if there are three parents. I also think that food will be scarce because of the cold weather. We have been putting out food for the parents but it probably won't be suitable for chicks.

Thanks, I'd better change the current ones. They may be a tad over 20 days. I also have a fat cylinder with various ingredients including dried meal worms so I will put that out as well.
Mike

Thanks Wendy, I will give them a try.
Mike

Forgot to add that I keep mine in the fridge, their box in polythene bag for hygiene, slows down life cycle & stops them smelling !  Buy small quantities & use quickly if not used to dealing with them!

This has been the case in our nest box this year. 
Two female blue tits, incubating around 16 eggs, one sitting on top of other, occasionally being fed by a male.  Looks very uncomfortable.