Great Crested Grebes of Doubtful Parentage!

20th August. Rather windy today and not a single butterfly seen except the odd Small White in the sanctuary of the garden.

There were numbers of Swallow and House Martin and the odd Sand Martin feeding over the lake today. A handful of Swifts flew higher in the sky and a lone Common Tern was actively feeding. It was the great Crested Grebes that took the eye again on the smaller lake. On my return home and after finishing my chicken pie and chips I reached for the copy of The Grebes/Bird Families of the World. I must try and read this again more thoroughly. It was interesting to check out how some of the bird’s behaviour I have been watching over the weeks is recorded in the book. Since the juvenile numbers have dropped to two I had noticed that one each of the adult birds takes one of the juvenile birds to feed. This is mentioned in the book along with the fact that the family will often make a complete separation. (It seems that the adult birds strongly favour one particular juvenile). This separation hasn’t occurred with the local birds as they were resting closely together as a family this afternoon.

What really had me looking in the book however was that the photographer who I have met at the lake before was insisting that the three juvenile birds that I had assumed had been lost had been ‘fostered/adopted’ by the second pair of Great Crested Grebes on the larger lake. I thought this a bit odd, but didn’t argue. Sure enough the other pair of Great Crested Grebes have three juvenile birds with them and whilst I had thought they had not nested I must admit I have neglected that end of the patch lately. On reflection I think these three juveniles look a good way behind the other two in development, but maybe I need to take another look. Anyway my book seems to suggest that any such fostering would be unlikely as ‘because of the intolerance to foreign (I assume foreign to mean of different species, but no further explanation is given with regard to same species) chicks brood amalgamation is not likely to take place in grebes’. It does mention however an example of a Red Necked Grebe raising the young of a Great Crested Grebe and suggests that juveniles lost during combat may be accepted by other adults. Has anyone witnessed such behaviour in grebes? I have read elsewhere that it is thought that the R N Grebes have had their nest parasitized by the G C Grebes. I’d also be interested to know if anyone has seen any sign of this second pair nesting on the larger lake.
Anyway, it is good to report that five juvenile Great Crested Grebes appear to be doing well on the lake. Bearing in mind the behaviour I have read about I will take note as to how the group of three juveniles progress.