On the 27th of November, twenty one Master’s
students embarked upon a journey of endless self-discovery. It didn’t start well.
A chilly 4am start, some greatly resented Christmas songs, two seemingly
unnecessary forty-five minute comfort breaks and a flight briefing filmed
before we were born saw us dispensed onto an Island that is three miles long
and half a mile wide. Phone signal triumphantly discovered, we spent the first
day sleeping. A few (adventurous/keen/delirious) groups decided to actually
explore the island, which proved to be steep. Seals, however, were spotted and
enthusiasm for the week grew in direct correlation with 3G coverage.
Group One, aptly named after an Island bird, began their
second day with another pre-sunrise start. The Lundy Sparrow project was the
real reason we were here. The main event. The big cheese. Lucy and Alfredo (PhD
students/Sparrow Whisperers) met us at 7.15 (ok, 7.20) and we began with vigour
and determination to learn the mysterious ways of the bird ringer. Buoyant that
I knew what a tarsus was, it was brilliant to finally see where the data we had
been using had come from. Statistics with Sparrows had come full circle.
Lucy told us about the project – data sets that began in the
80s (probably around the same time as the flight briefing) and now formed a
complete census of the wild population of Lundy Sparrows. Each individual is
identifiable by a colour-specific leg ring. This code is linked to their DNA
(achieved through blood-sampling) and to a micro-chip under the skin. What is
more, their isolation means that there is no emigration or immigration into the
population – an entire pedigree has been constructed. This means every sparrow
can be related to its ancestors and the relationships amongst that population
are well known. The accuracy and volume of data available for research is
extremely rare for a wild population, making the Lundy Sparrows unique.
We learnt how measurements are taken to minimise error, how
birds were caught with mist netting and how much it hurt when a sparrow decides
it doesn’t like you or your fingers. Each individual, upon capture, had its
micro-chip scanned and its rings checked in order to confirm its identity.
Next, wing, tarsus, bill and bib measurements were taken and mass was recorded.
Sparrow mass fluctuates as energy reserves are used, so even birds caught
recently were re-weighed. As they worked, Lucy and Alfredo explained how the
measurements were supporting their current research. Male birds have a
collection of black breast feathers, known as a bib, which grows with age. As
this part of the bird is on display to others, Alfredo is looking into whether
this increase in size (and age) is related to male dominance and social status.
They also pointed to limitations with the measurements. A similar black band of
feathers around the eye in males, for example, is measured in length but not in
width or area. It is only recently that Lucy has realised that the width of
this band grows with age, as well as length. The dataset, therefore, is still developing
as more researchers become involved with the project.
The following days hid a lot of surprises in term of
exploration, field work and science! As the project was going on, we were asked
to collect data on parental care and social dominance in the house sparrow
population of Lundy. Thanks to all this previous knowledge and videos we were
able to draw overall conclusions. We went on to test three trade-offs. The first
hypothesis suggests that the more you care about your children the less chance
you have to survive. We were provided with videos of nest boxes of summer 2016 7
and 11 days after hatching. Based on observations about where the bird is
landing and how many time it stays at the nest-boxes, we collected data for
parental care analysis.
The second hypothesis focused on the social dominance of the
sparrow father. It predicts that good father are bad fighters. To investigate
the hierarchy of the Lundy house sparrow population we recorded all
interactions at a feeder, including threats or fight amongst birds and identify
the winner and the loser. Then we compared our results with those of the
parental care videos. Unfortunately, none of the father recorded in parental
care videos seem to appear on those of social dominance rank, which led to lack
of data for our analysis. This could be explain by 3 different points:
-
fathers who take care of the children are too
bad and don’t compete for food,
-
fathers died in between the record of those
different videos
-
our methodology was not the best and we should
have watched more videos
Also, we observed that apparently females win more fights
than males do. Which is surprising and make us think twice about the initial
question.
Another interesting part of the week was to asses the
effective population size of the house sparrow on the island thanks to
resighting. We had to go on the field with binoculars and chase sparrows and
identify them in their wild habitat thanks to the coloured rings. Resighting
combined with the previous mark-recapture method can give us good insights on
how big is our population, and the average estimate was approximately 330
individuals, which is pretty large for Lundy.
After all the hard work and amazing explorations our trip
came to an end. Lundy showed us its beauty but also the rain and foggy days.
Apart from science, Lundy has a bunch of heavy and mad historical stories!
Blogpost written by Elena Pearce & Floriane Coulmance Gayrard
