Grebes are remarkably beautiful birds, but it is not just their beauty that attracts attention. They have a wide repertoire of visual and vocal signals, (well, less on the vocal than the visual) and it is their courtship behaviour that attracts most attention.
A more unusual behaviour begins two to three days before eggs hatch and will continue for up to a week after hatching. The behaviour occurs most often when mates are swapping incubation duties with each other and it is only after eggs have hatched that the reason for the behaviour becomes apparent.
The bird leaving the nest will stand up in the nest bowl, move backwards to the edge of the nest, stretch out its wings and shake itself vigorously.
As it happens, this last week I was armed with my son’s camera when the grebe on nest 3 did its shake thing and sure enough, out popped two grebe chicks, one of which can just be seen diving head first over the back edge of the nest (bottom left).
Photo: John Darby
It took nine minutes for both chicks to climb back onto the nest and then onto the back of the adult on the nest.
The interesting aspect to all of this is the anticipatory behaviour of the birds to the impending hatching of eggs.
My guess is that it is triggered by the sound of a chick peeping inside the egg one to two days prior to hatching.
I muse over all of this because I would have thought that the cue would have been a tactile one and that there would be no need for a practice run before the chicks were hatched.
So nest 3 has hatched two of its three eggs, the first on the September 28 and the second on September 30.
Nest 1 is due on October 8 and pairs are still prospecting rafts 2 and 4.
I remain apprehensive as to the outcomes of this breeding season. In the 2015-16 season, we had seven nests with eggs by the beginning of October!
- John Darby
Photo: Grebe nesting, Lake Wanaka (29/9/17). Photo: John Darby
• Grebe Diary 2017 (No1) by John Darby Posted: 26 Sep 2017
• Grebe Diary 2017 (No2) by John Darby Posted: 30 Sep 2017
Click to read the Wanaka Sun online
Enlarge screen by double-clicking on the page
View all earlier editions of the Wanaka Sun here