Wanaka Sun column by retired zoologist John Darby
Grebe Diary 4. October 8, 2017
Nest 1 was calculated to hatch her eggs on October 8. As of this last Sunday the chicks have yet to appear. I am confident that she will oblige in the next day or so. There is just a single pair still prospecting and it looks like I might have to find other things to write about unless the birds suddenly become enthusiastic.
I would be speculating if I were to dare to provide a reason for the very late start and the paucity of interested breeders. Part of my frustration, as it is with many others in the science community, is the lack of any useful baseline data on the lake that has been part of any long term study. Lake Wanaka, as is the case with almost all lakes, is not a flat piece of water that remains the same throughout the seasons and from year to year. In just this year alone, it has been at its lowest since 2010 and that alone would influence productivity and nutrient levels, but by how much and what it changes is pretty much unknown.
Photo: Albatross and chick (1969 - Taiaroa Heads) by John Darby
Long-term studies or longitudinal studies provide valuable insights into biological systems, perhaps none more so than the Dunedin study of those born in 1972 in Dunedin. But the Dunedin study was not the first longitudinal study in Otago, or New Zealand for that matter. That honour goes to the late Dr Lance Richdale, a school teacher who studied both Royal Albatross and the Yellow-eyed Penguin on Otago Peninsula. But he did not do what at that time (1930’s) was the regulation one to two year study; he carried on the study for over 15 years.
I was recently browsing a book he published in 1952 (Post-egg Period in Albatrosses. pp166) and noted that he had dedicated the work to Margaret Morse Nice, an American ornithologist who died in 1974 age 91. Margaret Nice was a trained biologist and while bringing up a family of five decided to study the biology of the song sparrow. It was a remarkable study, for it morphed into following some 60 pairs of birds, their loves, lives, losses and territories for over 12 years. To be continued.
- John Darby
Grebe Diary 5. October 15, 2017
I left you last week with an image of a Royal Albatross on the diary page. It is a photo I took in 1969 at Taiaroa Heads and was of a bird that had been banded by Dr Lance Richdale in the mid 1950’s. Richdale you will recall initiated long term studies on both albatross and yellow-eyed penguin.
We might just be moving into a long-term study on grebes. Certainly it is the longest one of any species of bird on Lake Wanaka, but it falls far short of the type of study most ornithologists engage in these days. Its greatest shortcoming is that we are not practically able to mark this species of bird so that we know exactly who he or she is.
We usually mark birds using numbered or coloured bands on their legs (penguins on their flippers) and in most instances we do that just before the bird leaves the nest or when it is a juvenile. Doing it then ensures that we know exactly where it was banded and how old it was when banded.
Grebes have their legs in water for almost all of their life making it almost impossible to read bands. Additionally, when adults leave nests with their chicks, the chicks weigh between 20-30 grams and may take up to 3 months or more to become independent of their parents as juveniles and thus big enough to tag.
An alternative is to use R.F.I.T. (radio frequency identity tags), but I really don’t want to go down that road, particularly when we take into consideration the cost of remote electronic readers on every nest, tags, and the huge effort needed to record and manage data.
I will clarify where I am coming from with all of this next time round, but in the meantime, nest 1 has hatched all three eggs and this last Friday I noted a total of 7 unemployed birds, 3 pairs and a singleton prospecting nest sites, and as usual squabbling over who found it first!
Cover photo “Grumpy Grebes” by Heather Macleod.
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