[Elizabeth Bigg]

We received an interesting feedback on our website this morning:

Our box is also connected to our VCR and I spend hours looking at the progress of our birds. We do however seem to have something different from the norm. We appear to have two females incubating approx. 17/20 eggs! The male comes in offering tit bits to whichever bird is available. Sometimes both want to sit on the eggs which I think should hatch at the end of the week. Do we have something unusual here? I would be very grateful for any information.

We have never heard of anything like this - but is there anyone out there with any info?

[Elizabeth Bigg]

I have succeeded in finding the address of Christopher Perrins, author of "British Tits", and I have emailed this question to him. He is a Professor at the Edward Grey Institute of Field Ornithology at the University of Oxford!

[steve_nova]

Very intriguing Elizabeth, I'm interested to hear if this has been noted before.

[Elizabeth Bigg]

This is Chris Perrins' reply:

Highly unusual, but not unheard of. Usually, the two females will not
tolerate each other and enlarged clutches are result of one laying a whole
or part clutch and the second chucking her out and laying her own on top. We
have also had mixed clutches involving Great, Blue, Marsh and Coal, but
always only one female ends up incubating (indeed sometimes we only know
that it has happened when we find we have a mixed brood at the end! The two
females soldiering on together is very rare.
A clutch of 20 by a single female would also be extremely
unusual -8-12 is more usual range; so I think that you can be pretty certain
that both females have contributed to the clutch - of course if you ever saw
the clutch increase by two a day you could be even more certain since they
only lay an egg every 24 hours.
ChristopherPerrins

[Nina P]

Dear Elizabeth,
I have found in poultry that broody hens will not tolerate another using her nest but if the other hen is a sister or mother then the chances are a little higher some tolerance can be obtained. It certainly sounds very interesting and I really do hope they will be very successful in their rearing all of the clutch! I would be very interested to know if at the end they really brought it off without coming to blows!

[Elizabeth Bigg]

Originally Posted by Nina P

Dear Elizabeth,
I have found in poultry that broody hens will not tolerate another using her nest but if the other hen is a sister or mother then the chances are a little higher some tolerance can be obtained. It certainly sounds very interesting and I really do hope they will be very successful in their rearing all of the clutch! I would be very interested to know if at the end they really brought it off without coming to blows!

I'll see if I can "enrol" the person who sent the feedback, then she can keep us up-to-date herself.

[Michael Frankis]

Sounds to me what you have is a ménagerie à trois

[christineredgate]

It will be good if all the eggs hatch Elizabeth,the nesting box is going to be pretty crowded!!

[rogerk]

Originally Posted by christineredgat

It will be good if all the eggs hatch Elizabeth,the nesting box is going to be pretty crowded!!

I've seen 'lonely' Great Tits taking up some of the feeding duties of a Bluetit nest. Apparently this can occur when the Great Tit has lost its mate due to predation etc. This can also be apparent in other Tit species, as Mr Perrin has pointed out. But as for sitting, it's new to me!