Band-rumped Petrel at Porthgwarra, Cornwall, 22nd October 2022
(The notes below are a copy of those sent to BBRC. The record has since been accepted and is the 4th for Cornwall and 5th for Britain. The first was found off Scilly on a Sapphire pelagic).
Notes:
The
seawatching season has been noticeably protracted this year. Warmer sea
temperature in the Approaches has seen above average numbers of Blue-fin Tuna
chasing bait fish and in turn, attracting high numbers of seabirds. Berry Head
and Lizard seawatchers have been setting county records this autumn with four
figure counts of Great Shearwater. On the 21st, Mark Darlaston reported a
decent seawatch from Berry Head, Devon. I forwarded the details to my WhattsApp
group and decided Porthgwarra next day was worth a punt.
Assembled
birders at Porthgwarra included just Graham Lawlor and myself! As normal, it
was slow start from first light; a few Arctic Skuas, a juv Common Tern, a Teal,
a Puffin. Then a juv Long-tailed Skua flew past at 08:37. Perhaps this was the
same bird from Berry Head. Things were looking up. A pulse of 24 Great Shearwaters
way past the Runnelstone went by. And that's where it ended. We decided to call it a
day, somewhat disappointed.
I
went home for the lunchtime game thinking the seawatch was over. No chance. An
expletive filled message from John Foster advised birders to get out
seawatching as huge numbers of Great Shearwater were moving past the Lizard. In
fact, the day-count there ended with a record breaking 10,235!
A
return to Gwennap Head mid afternoon caught the tail end of Great Shearwaters moving
through. The Porthgwarra day total ended at an impressive 864 birds, itself a high count.
With
a lull in Great Shearwaters passing, I concentrated on the Bay area between left
rock and the pinnacle. I picked up an obvious large storm-petrel about a third
of the way out (based on Runnelstone position). In a split second, I knew it
looked different. It wasn't the normal pondering, loafing and quick darting flight
of a Leach's. Instead, it was energetic, continuous, regular, fast, similar to
the quick flight of Bulwer's Petrel. I'd seen Band-rumped Petrel off Madeira in
June and I immediately shouted the words "Madeiran Petrel" to the six other
birders.
Description:
After
a minute or so of panic, everyone connected and enjoyed some four minutes of
views. Leach's was the benchmark species but nothing pointed in that direction.
As previously mentioned, the flight was so different. The fast movement,
regular high banking and shearing up to 2 or 3m on straight wings (shown well
in Martin's sketch and in one photo), similar to a Great Shearwater on the move
was always evident. It would double back on itself with a high banking movement
and then glide with slightly arched wings, presumably settle on the sea as we
lost it for several key seconds, only to reappear again with fast, energetic
and regular arcing flight. I couldn't see it feeding or settled on the water
due to the swell.
This
bird was clearly on the move (rather than a feeding bird). The wings appeared
long, straight and to my eye quite pointed. Tail was square ended with no feet
projection. To be fair, my 35x mag scope wouldn't have picked out feet
projection, but Paul Marshall zoomed up to 70x and saw no feet projection.
Others on higher mag also saw the squared tail. One photo does show a slight
"scoop" to the tail but this wasn't seen by me in the field.
Plumage
wise, the overall colour was uniform blackish brown with slightly paler
upperwing coverts, and indistinct carpal patch (ie. no obvious carpal bar). The
rump was white and extended down the sides to the under tail. The white
rump was obvious and continually on view. Underwing looked plain black with no
obvious markings.
 |
| Band-rumped Petrel, Pothgwarra,Oct 2022. All images courtesy N. Rogers. |
Nigel Rogers further commented:
"From the set of 9 photographs
provided, the following features can be seen:
*a clear white band over the rump (IMG 3897),
* the tail could look either slightly forked (fanned tail, when probably close to alighting on the sea, IMG 3899) or straight (e.g. See IMG 3915 and also IMG 3897),
* the white of the rump extended down the rump sides (IMG 3929, and the white areas down the rump sides probably accounts for the apparent white on the undertail coverts from behind, IMG 3933),
* the wings were long (very evident when shearing) and, in direct flight, the hand was broad with a pointed tip. The outline of the wings was a smooth, the rear edge appearing only slightly curved and with no sharp bend at the carpal joint on the forewing (IMG 3908, IMG 3909, IMG 3915, IMG 3929, IMG 3930),
* the wings were held slightly arched when gliding (IMG 3893, IMG 3933),
* when shearing, which it did frequently, its rather straight wings resembled a small shearwater (IMG 3915),
* the overall appearance in the images is uniform blackish brown (apart from white or paler poorly resolved areas on the rump and rump sides),
* all the above is consistent with Band-rumped Petrel and together eliminate Leach's Petrel. Of the features noted the consistent difference in wing shape (unaffected by issues of photographic resolution) from Leach's Petrel is very compelling evidence.
Paul Marshall also commented as follows:
Band-rumped Petrel - Porthgwarra,
Saturday 22 October
Steve Rogers (finder), Graham
Lawlor, John Overfield, Martin Elliott, Nigel Rogers, Ray Archer
Steve called the bird at
approximately 15:50 and I was fortunate to get on to it almost immediately. It
was still left of the pinnacle and showing in good light. It was on view for
approximately four minutes at a distance of approximately 750 metres (judged on
being half way to Runnel Stone buoy).
My immediate impression was of a
large dark petrel. All manner of options flashed through my mind and for a
split second my initial, over excited thought was Bulwer’s Petrel due to the
size, overall dark appearance, long wings and initially no sign of a white
rump. However that was quickly dispelled when features began to fall into
place.
This year I’ve been fortunate
enough to see 100’s of European Storm Petrels, eight Leach’s Petrels and six
Wilson’s Petrels from land based seawatches off west Cornwall. It was clear
this wasn’t any of those.
European Storm Petrel could
instantly be dismissed on size alone and Wilson’s clearly didn’t fit. Leach’s
was the next obvious option but nothing about this bird suggested that species
either. The structure, plumage and flight action just didn’t add up.
It was evident that we were
watching a Band-rumped Petrel and Steve called it as one soon after getting my
first views of it.
The wings were long, with the arm
the same length, perhaps even slightly longer, than the hand. The angles
involved were subtle and shallow, never coming close to showing the obvious
carpal joint angle of Leach’s Petrel. When fully outstretched, which it seemed
to do a lot, they looked almost parallel, not unlike a shearwaters.
The flight action was unlike any
storm petrel I’ve seen. Between relatively short series of shallow wingbeats it
sheared constantly, not high arcs but a couple of metres from the surface.
Progress was steady and not erratic like Leach’s Petrel.
I zoomed into approximately 60x
on two occasions, to get a better idea of some of the plumage and structural
features. This allowed the following to be noted:
· Overall dark plumage, not brown
or black but somewhere in between, like the colour of dark chocolate.
· There was never any suggestion
of the almost two tone effect on the upperwing often shown by Leach’s Petrel.
They looked uniform in colour apart from a not very obvious covert bar.
Although present it was much more subtle than on any Leach’s Petrel I’ve seen.
Not only was it fainter but also appeared less well defined at the edges,
almost smudgy.
· The white rump was narrow. The
size and shape could almost be likened to a ringtail harrier. It never showed
the Leach’s Petrel like blaze of white. It was clear the white extended around
the sides of the rump, which reinforced the ringtail harrier like appearance,
and could be seen when the bird banked showing its underparts.
· The underwings appeared
entirely dark.
· The tail never looked forked
and I struggled to see much of impression of a notch, it just looked blunt
ended. This could be appreciated when not zoomed in but at 60x there was
without question no fork.
· There was no suggestion of feet
protruding beyond the tail, a feature I’ve seen on Wilson’s Petrels at this
site at a similar, albeit slightly closer, distance.
Martin
Elliott further commented:
The
following notes aren't that critical to the i.d. but at least give a fuller
picture of how I saw it:
BRSP
Porthgwarra, 22/10/22 additional notes
Although
one of the last to get on the bird I did use 60x zoom so a couple of further
observations may just complete the picture .
Moult-
This bird showed consistently pointed pp unlike any of the previous ( up to 6
but all bar 1 in early September) "BRSP" I've seen in Cornwall. This
is hardly surprising as it did not feed or deviate (apart from apparently
landing briefly in a trough) from the shearing progression described above, but
even so the wing-tip was quite sharp. I assume this could have been produced by
old retained p10 with at least p9 short/growing or shed?
Coupled
with this the tail also appeared to be in moult - although "square"
and certainly not forked it looked blunt or uneven, and this seems to be shown
by N Rogers's images. According to Howell and Dunn this should not be the case
for adults of either "Grant's" or castro (or Leach's?) at this
time of year,but I have no idea if this rules out any taxon in it's 2nd
calendar year!
Carpal-bar
- A fairly indistinct but even and moderate width pale carpal bar was visible
on the left wing but the whole "arm" looked paler than the pp on the
right. This was probably due to the angle of the bird to the diffuse sunlight
burning out or putting a slight sheen on the right inner wing and obscuring the
pattern.
The
flight, structure, and plumage - particularly the wrap-around white rump- all
fit BRSP rather than any other white-rumped petrel.
In either
case these points do not lead me to disagree with the bird's identification as
a BRSP but given the later date it is tempting to wonder if this and other
recent records off west Cornwall are linked with the apparent warmer off-shore
waters and lingering Great Shearwaters etc. feeding on Anchovy shoals?
Earlier
records - mostly from the first week of September - were presumed most likely
refer to "returning" winter breeding "Grant's"
associating with a more general southward movement of Great and Sooty shears,
skuas etc.
Thanks
to Nigel Rogers for the photos, quite incredible considering the distance;
thanks to Martin Elliott for the artist impressions of the bird on the day and
to the other four observers: Paul Marshall, Graham Lawlor, Ray Archer and John
Overfield.
Steve
Rogers. October 2022.
 |
| Band-rumped Petrel, Porthgwarra, Oct 2022, artist impression by Martin Elliott. |
 |
| Band-rumped Petrel, flying away showing white rump, Porthgwarra, pics courtesy Nigel Rogers. |
Paul Marshall further commented on the timing of the sighting:
The peak seawatching season in west Cornwall for ‘warmer water’ species (large shearwaters and petrels) has traditionally finished by mid-September. So at first glance the third week of October might seem a rather late date for a record of Band-rumped Petrel off Britain.
However, in recent years there has been an increasing number of rarer seabirds seen later in September and into October. This year has proved to be exceptional even by recent standards.
From July to September, Cornwall and the Isles of Scilly enjoyed good numbers of seabirds. Large numbers of Atlantic Bluefin Tuna were present, a sure sign that sources of food were high. Amongst the numbers of large shearwaters there were nine reports of Fea’s-type Petrels and several Band-rumped Petrels. By late September there was no indication of anything particularly out of the ordinary going on.
The first sign that something was up was on 4 October when 4,500+ Great Shearwater were seen heading west past Peninnis on St Mary’s, Isles of Scilly. Over the course of the month it became clear that large flocks of Great Shearwaters were present between Devon and the Isles of Scilly. Numbers peaked on 22 October, with c10,0000 past the Lizard, a movement that included a Little Shearwater and a Band-rumped Petrel (thought to be different to the Porthgwarra bird due to timings of sightings).
The table below summarises the most notable seabird reports in west Cornwall and Devon during October 2022.
| | | |
| | St Marys, Isles of Scilly | 4,500+ past Peninnis in 1.5 hours |
| | | One on pelagic c10km off St Mary’s |
| | | 1,200+ from boat 24-30km south of Plymouth |
| | | One east of Wolf Rock on eastbound crossing |
| | | 2,000+ past Pendinnis Head |
| | | c10,0000 past in 2.5 hours |
| | | |
| | | |
| | | |
| | | |
| | St Agnes, Isles of Scilly | |
The last three figure count of Great Shearwaters was 570 past Porthgwarra on the 29 October. After this small numbers, mostly single figure counts, continued into November.
The nature of the Great Shearwater movements were different to the usual passage birds seen off Cornwall. These typically pass headlands either singularly or small groups over a prolonged period.
These movements were intense with many hundreds or thousands being seen over a short period of time. This suggests that these birds were part of one or more huge feeding flocks taking advantage of the good feeding. Given such numbers it is entirely realistic to expect other species (Fea’s-type Petrel, Band-rumped Petrel, Little Shearwater) to also be present.
There are two reasons why this is likely to have happened.
Sea temperature and food availability
The following graphic taken from [insert source] shows the sea temperature around Britain on [insert date]. The warm water plume extending north from the Bay of Biscay and covering Devon, Cornwall and the Isles of Scilly is clear. This warmer water has attracted baitfish, which in turn has attracted large numbers of Atlantic Bluefin Tuna and seabirds.
From early October a strong U-shaped jet stream became established. This created the conditions for several large, slow moving low pressure system to become established to the southwest of Britain. The result was a near constant and strong southeast to southwest, but predominately southerly airflow that extended from west of Iberia to southern Ireland.
From mid-October there were remarkably few days in west Cornwall where the average wind speed fell below 20mph and was frequently closer to 30mph.
The following graphic taken from ventusky.com shows the wind direction and speed on Friday 21 October and is fairly typical of the daily weather in west Cornwall from mid-October into November.
It seems reasonable to suggest that this strong headwind would not have encouraged seabirds to move south and west into more traditional areas. Particularly when you combine this with the good feeding opportunities evidently available in inshore waters around southwest Britain.
As the impacts of climate change have an increasing impact on sea temperatures and weather patterns it will be interesting to see whether such occurrences become a regular feature of autumn.
