Skip to content

[LBI 2012] Going Solo (with apologies to Roald Dahl)

October 14, 2012

[This is the second in a series of posts – essentially diary entries – on fieldwork on Little Barrier Island, New Zealand. Internet access was unavailable on the island, so I am publishing them one-per-day now that I am back on the mainland.]

19/09/2012

A thing is different to what I expected. We are walking the Hihi monitoring lines solo, not in pairs. How this made it past OSH, I am unaware.

Each of us is equipped with compass, maps, instructions for each Hihi transect, 30m tape measure, track-marking ribbon, first aid kit, laser rangefinder, and datasheets, and sent up a line. Each line has between 11 and 20 monitoring stations, at which we count Hihi, Tui and Saddleback, and record presence of any other species we see.

The walking is tough. Lines are marked only with blue tape, and have not been walked in a year. Treefalls result in very difficult sections, as there are LARGE trees here which, when they fall, can take out a half dozen other large trees with them. Where the route follows an obvious path, such as a stream-bed, there may be no blue tape for reasonable sections.

We were trained in distance sampling this morning. The underlying theory is pretty simple: that birds are randomly distributed and the chance of detection decreases with distance from the observer in the horizontal 2D plane. The vertical distance is not modelled, which strikes me as odd for species which actively move in 3 dimensions.

The model also assumes 100% observation rate for birds on the sampling point, and that birds’ locations are not influenced by the observer. In practice, this means we have to sneak quietly towards the points as soon as they become visible, watching the point the whole time, because in reality the point is the place birds are most likely to be scared away from. So any estimates of density will indicate minimum plausible density.

All told, I did not see many birds today. I took distance measurements on even fewer: one Hihi, one Saddleback. But I heard many: Fantail, Kaka, Kereru, Kakariki, NI Robin, Whitehead, Bellbird, Tui, Saddleback, Stitchbird… Saddleback are now ruined forever by the advice that their call is like a motorbike starting up. Hooray.

My informants were right to caution me about the steepness of the terrain here. On the more-trafficked paths, you can find sections with a rope running down them – because it is too steep to walk safely. On the less-trafficked paths, ‘walking’ is frequently replaced by ‘sideways brachiating’. Fortunately, there are plenty of trees to brachiate on.

We shall all leave this place as massively-toned superpersons, or utterly broken.

Advertisements

From → Scientist

Leave a Comment

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: