(Headphones recommended for video clips)
A constant flow of Common Scoter contact calls (between 1 and 2khz), with the sound of their wingbeats at a higher frequency as the flock passes over the recorder (positioned in a plantpot in a village garden)
As I've written about extensively here, I've been running nocturnal migration (nocmig) recorders at several local sites for a couple of years now, and I'm just in the process of analysing nightly recordings from the latter end of March (when we were away in the States). I was going through a few Flamborough files last night, and all was relatively predictable, until I got to about 2334hrs on the 28th March....
Redwings, church bells striking midnight, and Common Scoters (complete with close-up 'honks')
As I clicked each 30-second frame, the flocks became clearer, longer, and more intense, with many involving (lower) female calls, strange, frequency-spanning honks (which I've only heard occasionally before, from very close recordings), and loud wingbeats (involving birds low over the recorder); throw in lots of background Redwings and a few for-context church bells, and there are some lovely, evocative sound clips.
So how many were involved? Who the hell knows, but I can say that, conservatively, there were 84 discrete flocks (more if applying a looser definition), and a minimum of 4,839 individual calls.... absolute scoter bedlam, lasting on and off - mostly on - for hours, and unusually until very late: the flow was at its strongest between midnight and 0200hrs, and continued until 0320hrs.
Scoters and their low, rapid wingbeats - see video clips for full effect
I've had 'good' nights for scoters before, when flock counts are into double figures and call counts into the hundreds, but this was outrageous, and unprecedented. Influencing factors include the time of year (peak scoter migration time), low cloud, favourable winds, and a weak weather front (including a light shower, when scoters on the spectrogram briefly dry up) that perhaps served to channel them perfectly over Flamborough village and out over the sea.
Judging flock size is a crapshoot of course (I tokenistically note down the minimum number of birds in a flock, but appreciate the inaccuracy of this approach), but there were many particularly large groups during this huge movement - some, for example, lasting for several minutes and containing many hundreds of calls. It's fair to assume then, there were, well, a lot of scoters bombing over the village rooftops that night.
Low-flying Redwing with Scoter friends
Was their any duplication involved, i.e. birds making repeated flights over the recorder? Possibly, but very unlikely; of all species, scoters are notably committed to gunning directly across the English landmass and straight out over the North Sea, and they'd have no good reason to not do so on the night involved.
Given the time, I could very likely increase the count by analysing the main periods via an extended listening session - on the occasions I've done so before, there are always registrations that can be heard, but not seen - but don't hold your breath; it's a ridiculously busy time and I've a huge virtual in-tray of nocmig to sift through....
Otherwise, it was a good (but not outstanding) night - a very healthy 485 Redwing registrations, Snipe, Teal, Wigeon, Curlew, Dunlin, Common and Black-headed Gulls - but it was all about one species.
Full counts from this and other recent nights on Trektellen soon, and a full March summary to follow shortly.
Comparisons with other nearby sites
Two of my other nocmig sites are situated nearby - Buckton (just 5km NW), and Filey North Cliff (15km NW, over Filey Bay). Having just analysed their spectrograms from the same night, it seems something special did indeed transpire at Flamborough,with Buckton logging 22 flocks and 643 calls (roughly a quarter and a sixth of Flamborough's results respectively), and Filey logging 14 flocks and 389 calls (a seventh and a tenth respectively). Clearly several factors conspired to deliver far more over Flamborough village, with weather conditions very likely playing a significant part.
Stop press.... I've just noticed the following tweet from Tom Lowe, posted on the night in question. Kind of says it all.....