November and December are always exciting times on Bird
Island as many of our study species being to hatch. In mid-November the
northern geeps began hatching, followed shortly by the gentoos.
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A pintail nest, only the second I have seen and the hardest nest to find on BI! |
Then in December the skuas were hatching closely followed by
the macs and mollies in the middle of the month. The final species to hatch at
this time were the southern geeps at the end of the month.
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Skua chick |
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Mac chick |
It is great to see all the life around the island and whilst
some species are faring better than others at this stage at least there are no
breeding crashes like there was for the
gentoos last season! Of course it is not just the birds that are progressing, the
seal pups are growing up well and enjoying being left alone around the beaches
by their mums who are going out to feed.
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A puppy trying to investigate inside a log! |
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"Who are you? Intruding on our puppy party!" |
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They are very curious at this stage, and tough little guys! |
Not all species are at the young stage though, the wanderers
take so long to raise a chick that they don’t actually lay their eggs until
mid-December and won’t hatch until March. Alongside this whilst most chicks
have fledged there are still a few stranglers left by the end of the month and
these won’t take their first flight until January, by which time all of this
years’ eggs will have been laid! (This is why wanals only breed once every 2
years, they don’t have the time/energy to lay an egg and raise a chick so close
after their previous chick has fledged.)
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A wanal not yet quite ready to fledge |
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'Superhero wanal' - so called because of the mask look on the face - practicing to fly |
But amongst all this excitement and regular studying of all
these species this December marked a very special survey for us. Last year we
had the
all island giant petrel census, but this year we had the all island
white-chinned petrel census!
White-chins are burrow nesting seabirds and are about the
size of a magpie but shaped like an albatross! This breeding habit makes them
more difficult to survey than giant petrels who could simply be counted every
time one was seen. In fact counting a few thousand giant petrels above ground
is much simpler than counting a few magnitudes more of underground white-chins!
So a different method is required.
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White-chins are hard to get photos of, so having to re-use a couple from a blog last year... |
Instead of trying to count all burrows, a near impossible
task that would take months, we instead set up quadrats in areas that represent
the surrounding habitat and terrain and counted the number of burrows within the
quadrat alone; therefore we don't actually have to count all burrows on the island, so long as we are representative of the island as a whole the numbers can be extrapolated. Each burrow is checked for occupancy in order to determine
the ratio of active to inactive burrows.
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...but when the photos are this good I can't help it! |
Whilst using this quadrat method makes the survey feasible
it is still a long-haul survey. We conducted 495 individual quadrats,
representing the habitats across the entire island, across 12 days of work (15th-24th,
27th and 31st December). Usually a quadrat would take 4
people to survey, two taking measurements of the habitat (tussock height, seal
presence, incline, orientation, tussock cover) with the other two counting and
assessing burrows. Repeating this process 495 times takes a lot of effort but
it was a lot of fun – except when sticking our heads in the tussock during
hayfever season makes us suffer through some of it!
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Measuring the habitat (Photo courtesy of Carrie) |
This census was one of the biggest I have ever conducted and
it went incredibly well, white-chins are potentially becoming my favourite
species, their call is something I will always remember, particularly as it is
the sound I go to sleep with – they are nesting in the tussock behind base as
well – and they have a very striking look despite being almost all black. They
can be quite curious birds and I am very happy to have worked so much with a
species that is not usually studied this way (all island census’ for any
species only occur every 5 or 10 years depending on the species, except wanals
which are an annual survey).
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A white-chin lands mid-survey... |
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...and just hangs around to see what we are doing! :) |