So, as the last post said, I’m back on the Scillies. Once again I came over to help out with an undergraduate field-course and was then left behind! Here are the undergrads, a thoroughly good bunch.
As I said in last year’s field diary, it’s a bit surreal being a demonstrator on this field course as it seems like only a couple of years since I myself was on the same field course as an undergrad.
The field course was a nice chance to take stock before starting my own work. While the students wandered the island conducting mini-behavioural experiments on the local wildlife (I am happy to say that one group enthusiastically chose shags!), I could settle back into island life and get into the right frame of mind for fieldwork.
There are shags about (also, Razorbills!), though everything seems to be in lower numbers than last year.
At the end of the field-course, I once again watched the Scillonian disappear over the horizon. Now I was left to my own devices. Rushing headlong into fieldwork would not be a wise decision though. I needed to be sure I knew exactly what I was doing before I started. How I would choose sites, how I would decide where to go each day, what my sampling protocol would be and how I would record data.
This year, I’m going to be videoing rafts of foraging shags around the island, in order to capture all the behaviour that goes on within these large groups. Since we can’t identify individual birds (even the colour ringed ones keep their legs underwater!) I attempt to avoid constantly recording the same birds by filming from several spatially distinct sites.
I ideally want to record data in each of these sites in a variety of tidal conditions. Is the tide ebbing or flooding? Is the tide at its fastest flow (half way between two tidal states) or slowest (right after high or low water)? Or is it in between?
Birds might also forage differently at different times of day, regardless of tide. I want to capture this potential variation with my sampling protocol if I can.
That is an awful lot of combinations of states to think about! Working out where I am going the next day could give me a serious headache. So I got a computer to do it for me. For those interested, here’s how it works:
- Firstly I got hold of a tide timetable
- I then wrote a script (using open source statistics package R) to interpolate between tidal states, at every hour. So for every hour I have the direction of the tide, the height of the tide and the stage of flow (according to the rule of twelfths).
- From this big table of tidal states, I can extract exactly what the tide is doing at each time of day that I am interested in, on every day.
- Finally I wrote another script, which extracts this information for whatever day it is tomorrow and then randomly generates a site number for me to visit. This script also checks this against what I’ve already done. The output looks like this:
So every night before fieldwork, I run the script and it tells me which sites to go to, and what tidal conditions I’ll be collecting data in. The script makes sure I won’t record a combination of site, time of day and tidal conditions that I’ve already done (for now!).
So soon I’ll begin my fieldwork. This weekend however, is world gig rowing championship here in the Scillies. Hundreds of gig rowers are arriving on the island, possibly causing it to sink slightly.
I had a moment of horror when I went to the shop yesterday to stock up before the crowds arrived and found it utterly bare. Luckily the shop was restocked when the next boat arrives, so I have safely stocked up for gigapocolypse.
For the next few days, the shops will be emptied, the pubs will run dry and the cash machine will run out of money! I’m also going to be sharing my bunker with a whole load of gig rowers. It could be interesting.
(Last year, gig weekend looked like this!: