Shetland 21, part 3: pipits and ditches

On 5th October we visited Channerwick on the east coast of Mainland Shetland. It is a superb-looking site, with enough sheltered cover to attract migrants, but not too much as to make finding them a daunting task. Two notable things happened here. Firstly, we saw and heard Olive-backed Pipit; secondly, I put our car in a ditch as I reversed out of the site. Let’s look at both those incidents, starting with the one that has generated the most conversation. Sadly, it is not the pipit.

It was a simple, though embarrassing, misjudgment. I wasn’t even the only person to ditch their car that day, as Penny Clarke put her car in exactly the same ditch that same afternoon. Fortunately, Andy and Dave dealt with the delay without fuss or drama. They went birding whilst I called for the tow truck. Below, the resuce, with help from the tow-truck and a group of visiting birders. Thank you, to all of these people:

At times like these, it is good to know that I have friends who will quietly support me at difficult moments, who will not send pictures of my handiwork to everyone they know or say “mind the ditch” every single time that I park for the duration of the trip. Unfortunately, those friends were not with me. So the next day when I bump into Sue and Roger Wyatt from Oxfordshire, Roger greets me with the words “Who put the car in the ditch then? Ian Lewington sent me a picture!” Later the same day, Andy receives a picture of our car in the ditch from Terry Sherlock and Wayne Paes in Oxford, who ask for an explanation of how it got there. Word was well and truely out. Oh, how those long autumn evenings flew by.

Now, back to the pipit. An Olive-backed Pipit had been reported at Channerwick, but we were pleased to see that we had the site to ourselves when we arrived. We would find the bird ourselves. Andy stayed near the sycamores and tree cover, Dave headed south towards the shore, I checked the burn and the fields opposite:

Dave found the pipit in the scrub and rough fields to the south. It was elusive and only gave flight views initially, before showing beautifully to Dave and Andy. By the time I joined them I had more distant views, but twice heard the flight call. Below, Olive-backed Pipit, photo by Andy:

On 8th October we headed north to Unst, arriving at one of our favourite sites, the small woodland of Halligarth, at 8:15am. As we walked down towards the gate to the wood, I heard and simultaneously saw, a pipit flying towards us with an explosive high-pitched flight call. I called out “interesting pipit coming over” and we, and two other birders, watched the pipit drop into the canopy of the wood. Had I been visiting my patch in the Lye Valley, Oxford, I would have added Tree Pipit to my checklist and moved on, happy with a good find. But this being Shetland, in October, there is a temptation to reach for other, rarer options. So, on the basis of hearing a single flight call, which I thought similar to the Olive-backed Pipit we heard at Channerwick, I called “Olive-backed Pipit?” We needed to see, or at least hear, the bird again.

We watched from outside the wood, got a glimpse of the bird fly out and then disappear into the sycamore canopy once again. There then followed about half an hour without sight or sound of the pipit. The two other birders we had met outside of the wood then flushed the pipit from the rough fields to the south of the wood. We all saw and heard the bird fly past the wood to perch on distant wires, before dropping into a cattle field to feed. After this fly-by, none of us felt confident to identify the bird on call alone, but it was either a Tree or an Olive-backed Pipit. One of the birders we had met played recordings of the flight call of both species on his phone. Tree Pipit sounded much more similar to our bird, a fatter, more buzzy call, slightly lower-pitched than the thin, high-pitched flight call of Olive-backed Pipit. But we were also aware that there can be an overlap between the two species’ flight calls.

Dave and I decided to re-find the bird in the field and I would try to get a recording of the flight call on my phone. This worked a treat. The flight calls are at 11 and 14 seconds. The wood at Helligarth can be seen in the background:

We got some distant photos of the bird perched on a wall a little while later, but little could be seen on the back of the camera, so we parked the ID of this pipit until the evening when we could review the evidence at our accommodation. In the meantime, the two other birders we met had put the news out that an Olive-backed Pipit was present at Halligarth. By now, we weren’t quite so sure.

This is the sonogram of the key moments. The faint purple haze below 2kHz through the recording is wind noise, with a loud gust at the 3-second mark, which creates the faint vertical purple column between the pipit flight calls:

Examination of the sonogram taken from the video (for tech-geeks, a .MOV file converted to .WAV file and then processed using Audacity) shows a number of things:

Firstly, the frequency of the pipit’s flight call. Although not completely diagnostic (see this technical article by Avesrares here) Tree Pipit flight calls rarely exceed 8kHz. I would say the flight calls we recorded barely exceed 7 kHz. The Avesrares article shows Olive-backed Pipit flight calls peaking at about 8.5-9kHz, significantly higher-pitched than our bird.

Secondly, the mooing of cows is at a very low frequency, somewhere between 1 and 4 kHz. Incredibly, Dave’s broad Bolton accent is at a lower frequency than a cow moo, below 0.5kHz, though the two are rarely confused in the field. The sonogram also captures Dave’s reaction time between hearing the flight call and calling out “there it is!” The flight call ends at the 2s mark. Dave’s voice begins at about the 2.5-second point, quick work Dave.

So, to cut a long story short, we saw and heard a Tree Pipit. But now we know exactly why and more importantly, why it was not an Olive-backed Pipit. This was an educational pipit and we all felt more informed for it. However, distinguishing this species pair on flight call alone is not always straightforward. If an Olive-backed Pipit flies over your head calling, you need to hope it is one with a call at the more obvious end of the spectrum – the higher-pitched, thinner and less buzzy, the better! Take a listen to these examples from xeno-canto:

Many thanks to Mick Cunningham for his thoughts and input on our pipit calls too.

Next: goodies from the east, despite the winds.