Madeiran Storm-petrel: first for Britain

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Bob Flood

On the evening of 28 July 2007 I was on board MV Sapphire south of Scilly with four other birders, Alan Hannington and John Higginson from Scilly, Tony James from Newcastle, and Ken Adelsten Jensen from Norway. The skipper was Joe Pender who also has an interest in seabirds. The south-westerly wind had picked up from force 3 when we left harbour to force 5 and was strengthening. There was 100% cloud cover but precipitation from that afternoon had all but ceased, although there was some sea spray that was a problem if looking into the wind. Light and other conditions were good looking down wind. We were drifting and chumming watching European Storm-petrels heading in from down wind, searching for a Wilson’s Storm-petrel.

At about 18.55 I was located port side of the cabin looking down wind. Through binoculars I saw a long-winged black-brown storm-petrel rise over the crest of a wave heading directly towards the boat. Immediate impressions said it was not a Wilson’s. Compared to Wilson’s it was larger, the arm relative to the hand was longer, and the wings were not flattened but were held in a shallow m-shaped bow. Neither did those first moments resonate with Leach’s, in particular because the jizz and flight behaviour was steady and methodical rather than tern-like. Madeiran flashed into the mind. I shouted to the other birders, “Get on this storm-petrel!”

However and despite these very first impressions, my next stage of thinking over the following 10 seconds or so was akin to trying to force a square peg into a round hole trying to make this storm-petrel a Wilson’s. I guess this was because a Madeiran off Scilly was just too incredible to believe. Also, in these early stages of interpretation, there was some correspondence between Wilson’s and our Madeiran, albeit weak, like relatively straight trailing edge to the wing and purposeful travelling flight behaviour. And of course we were expecting to see Wilson’s. Conversely, Leach’s was never a candidate.

About 30 metres away from the boat the storm-petrel banked to its right though continued to approach but now was methodically quartering the sea surface. I could see an upperwing covert bar but it did not reach the leading edge (Leach’s reaches the leading edge) and was not strong as on a typical Leach’s. The white rump was broader than long (Leach’s is longer than broad) extending to the lateral undertail-coverts (unlike Leach’s) and was still clearly visible when the storm-petrel banked away showing its underside (Leach’s white rump is then obscured). The ‘band rump’ seemingly always was visible as the storm-petrel manoeuvred around (unlike Leach’s). The tail was short and the rear carriage looked particularly short relative to the wing span, whereas the rear carriage of Wilson’s looks relatively long even when feet are retracted eliminating toe projection. There was no toe projection beyond the end of the tail (Wilson’s mainly has a very obvious toe projection). By now I was trying to accept that this storm-petrel had to be a Madeiran, but could it really be?! I was aware that the only British record involved one found dead at Milford Haven, Hampshire in November 1911 (Category B). If this was a Madeiran, then to all intents and purposes it was a first for Britain (Category A)!

The Madeiran-like storm-petrel was approaching close to the stern and I expected it to pass the stern and head into the slick off starboard side and feed. Instead it banked to its left and flew a course parallel to the port side at about 12 metres off. We had front row seats. Now I could see the unique thickish bill that always looks too thick for a storm-petrel (much thinner in Leach’s and Wilson’s). The body was chunky (relatively slim in Leach’s and Wilson’s). The leading edge of the wing was mildly angular at the carpal joint and the trailing edge was gently angular (both sharply angular in Leach’s and the trailing edge in Wilson’s is all but straight). The arm was broad (narrow in Leach’s). The wing tips were moderately blunt (very pointed in Leach’s and Wilson’s).

The underwings were evenly hued black-brown with the body all black-brown, and these plumage features, amongst many other plumage and structural features, eliminated both species of Fregetta storm-petrel, White-bellied and Black-bellied, where underwing coverts are largely white as is the belly (normally with a dark central stripe in Black-bellied). European Storm-petrels alongside the Madeiran simply were dwarfed.

The jizz was consistently methodical, almost predictable, like a European Nightjar, not buoyant and sometimes unpredictable as Leach’s, or hirundine-like as with Wilson’s, or like a small bat as with European. It rose up to three metres above the sea surface on several occasions (very rare in Wilson’s and European that almost always keep within a metre of the sea surface).

Having noted all relevant structural and plumage features, and flight behaviour, and deliberated albeit briefly over other possible storm-petrel species, I was now confident enough to call, “It’s a Madeiran!” The Madeiran continued on its methodical way past the bow and then, banking to its left, away from the boat and was lost to sight. The whole event lasted about one minute. The exact location was ‘049 51.741 N, 006 08.781 W’ or approximately 7.5 miles south-east of St Mary’s Quay.

Identification was clear-cut and categorical given the close pass and excellent views with all key field identification features seen, and so celebrations immediately began. However, we did not have an experienced photographer on board and none of us amateur photographers had a camera at hand keeping them bagged because of sea spray. The lack of photographic evidence was niggling at the back of my mind. After about 50 minutes revelry had peaked and we had mostly fallen quiet as the facts sunk in.

At about 19.45 I was amazed to see the Madeiran approaching the boat for a second time. We were treated to an almost carbon copy performance and an opportunity to run through once again all key field identification features. This time I yelled to the skipper Joe Pender to take photos and he had time to run into the cabin, turn on his camera and take a photograph (which see). This fine record shot shows enough of the features mentioned above to be identifiable as a Madeiran Storm-petrel. The exact location of the second sighting was ‘049 51.590 N, 006 07.422 W’ or approximately 8.4 miles south-east of St Mary’s Quay.

The Madeiran was clad in what looked like very fresh plumage like a fresh juvenile or recently moulted immature or adult bird, and certainly was not in wing moult. Different populations of Madeiran Storm-petrel in the Atlantic breed at different times of the year, some time sharing burrows on the Azores with each having non-overlapping breeding and dispersal periods, and hence different moult timings. Thus, the state of plumage of our Madeiran does not obviously point to the age or origin of the bird.

Finally, it was extremely helpful though quite astonishing that this sighting occurred just two weeks after publication of our article in British Birds that deals with identification of ‘black-and-white’ storm-petrels of the North Atlantic (Flood and Thomas 2007) and completion of our DVD on flight behaviour of these storm-petrels (Flood and Fisher 2007).

Vessel MV Sapphire is about 16 metres in length and six metres across the beam, eye-level is about four metres above the sea surface, and angle of view is shallow making it; (a) relatively easy to see bill shape and proportions, underwing-coverts and axillary feathers, the extent of white on undertail-coverts and rear flanks, and the belly, and, if we had not been so close to the bird, (b) relatively difficult to see travelling wing shape, tail shape and toe projection, wing-covert bars, white on rump and uppertail-coverts, and moult and wear of remiges and rectrices.

Jizz Like a European Nightjar Caprimulgus europaeus. Chunky-bodied and heavy-billed, warm-toned black-brown; in flight methodical and predictable, overall rather plain.

Body length and wing span Medium-sized appearing much larger than accompanying European Storm-petrels, with comments from other observers including “its like a small shearwater”, but taking into account size illusion between storm-petrel species at sea I would estimate the body length and wing span ratios for European Storm-petrel versus our Madeiran Storm-petrel to be in the region of the known ratios 1.27 and 1.17 respectively

Structure This bird was not in moult thus there were no moult related issues that affected structure. Wing shape Long, broad arms, blunt-ended wing-tips, most of the time held straight out so leading and trailing edges were only moderately angular at the carpal joint. Head on profile Slightly bowed in shallow-M, arms medium length, hands long. Tail Shape Shallow fork but appeared square-ended when fanned as the bird manoeuvred. Toe projection None. Body build Chunky. Bill shape and proportions Thick, bulky, and heavily hooked, unlike other storm-petrel species.

Plumage Eye-level above sea surface was about three metres thus angle of view was shallow (also see ‘Vessel’). General colour and colour tones Warm-toned black-brown and overall rather plain-looking. Upperwing covert bars At range, quite uniform dark upperwings with fairly indistinct covert bars. Close-up, greater coverts formed dull bars that stopped short of the leading edge. Underwing coverts and axillary feathers Evenly hued black-brown Rump, uppertail- and undertail-coverts and rear flanks Narrow, rectangular, broader than long, extended to lateral undertail-coverts and rear flanks, seemingly always visible. Belly All-dark.  Bill Black. Eyes Black. Legs Not seen.

Flight behaviour In travelling flight steady and buoyant with short runs of shallow wing beats, low banking turns, small shearwater-like glides, occasionally rising to three metres above sea surface in these manoeuvres. When searching for food progressing by weaving a regular horizontal zigzag and quartering areas of the sea surface.

Madeiran Storm-petrel

Above Madeiran Storm-petrel Oceanodroma castro c8.4 miles south-east of St Mary’s quay, Isles of Scilly (Joe Pender). The combination of structure and visible plumage shown in this image are unique to Madeiran. Note the long outstretched wings, considerable length of the arm relative to the hand, leading edge mildly angular at the carpal joint and trailing edge gently angular, wing tips moderately blunt, a short tail relative to the wing span, a ‘band rump’ extending to the lateral undertail-coverts still clearly visible when banking revealing the underside (as in this photo), and all dark underwings and body. Also note the Madeiran is about three metres above the sea surface. The photograph is a fine record shot that clearly shows several key field features that combined are diagnostic of Madeiran Storm-petrel.

Madeiran Sketch
Sketch By Tony James.


Elimination of other species Comparisons are between our Madeiran and other possible storm-petrel species.

European Storm-petrel Hydrobates pelagicus European is much smaller and those present were dwarfed by our Madeiran. Knowledge of size illusion between storm-petrel species at sea prevented wild comparisons such as ‘twice as big’ and the known relative wingspan and body length of 1.17 and 1.27 respectively felt correct. European flies like a bat with weak fluttery flight compared to the stronger, methodical, Nightjar-like flight of our Madeiran. European has short arms and hands and blunt-ended wings that always are strongly angular at the carpal joint on both leading and trailing edges, whereas the wings of our Madeiran were long with arms broad and medium length and hand long, with wings held out quite straight so that leading and trailing edges were only moderately angular. European tail is short and gently rounded whereas the tail of our Madeiran had a shallow fork. European has a compact short body whereas our Madeiran was long and chunky. European bill is short, slim, and only slightly hooked whereas our Madeiran had a bulky bill that was heavily hooked. European exhibits a pale upperwing covert pencil line, whereas our Madeiran showed covert bars. European has white underwing covert panels, whereas the underwing of our Madeiran was evenly hued black-brown.

Wilson’s Storm-petrel Oceanites oceanicus Wilson’s is smaller and indeed we had seen fair numbers of them off Scilly in the forerunning two months so the larger size of our Madeiran when it first arrived was immediately apparent. Wilson’s jizz and flight behaviour is well characterised by the hirundine simile so different from the methodical, Nightjar-like flight of our Madeiran. The wingspan of our Madeiran immediately was visibly longer than Wilson’s based on recent observations of Wilson’s. Wilson’s compared to our Madeiran has shorter wings and is more angular at the carpal joint on the leading edge and straighter on the trailing edge. The head on profile of Wilson’s shows wings straight and stiff, arms short, hands medium length, whereas the wings of our Madeiran were slightly bowed in a shallow-M, arms medium length, and hands long. Wilson’s tail is medium length, slightly concave with rounded corners, whereas the tail of our Madeiran had a shallow fork. The rear carriage of Wilson’s looks quite long relative to the wing span, but the rear carriage of our Madeiran looked particularly short compared to the wing span. Wilson’s has long spindly legs that normally project beyond the tail in travelling flight, unlike our Madeiran. Wilson’s has an evenly proportioned body whereas our Madeiran was chunky. Wilson’s bill is medium length and only slightly hooked, whereas our Madeiran had a bulky bill that was heavily hooked. Wilson’s normally has obvious and broad upperwing covert bars that start short of leading edge and extend to body, which are far more obvious than the covert bars on our Madeiran.

Leach’s Storm-petrel Oceanodroma leucorhoa Our Madeiran flew with methodical, Nightjar-like flight whereas Leach’s flies with buoyant and graceful, deep, languid wingbeats, and may make unpredictable speed and direction changes, darting, vertical leaping, and bounding ahead. Leach’s wings are long and quite narrow with decidedly pointed wing-tips, and leading and trailing edges are strongly angular, whereas our Madeiran had long wings held outstretched so that leading and trailing edges were only moderately angular, and the wing tips were blunt. Our Madeiran looked longer winged than Leach’s because mainly it held its wings outstretched, whereas Leach’s tends to hold its wings swept back. The tail of Leach’s is deeply forked and scooped, whereas the tail of our Madeiran had a shallow fork. Leach’s body is rather long and slim, whereas our Madeiran had a chunky body. Leach’s bill is relatively long, slender, and only slightly hooked, whereas our Madeiran had a bulky bill that was heavily hooked. The upperwing covert bars of Leach’s normally are striking stretching across the wing coverts to the leading edge, whereas our Madeiran had duller covert bars that ended short of the leading edge. Leach’s white patch on the rump is dull and not gleaming white, barely extends to undertail-coverts and rear flanks, is longer than it is broad, and is hard to observe at sea especially when the bird banks away, whereas our Madeiran had a narrow, rectangular white patch, broader than it was long, that extended to the lateral undertail-coverts and rear flanks, and seemingly was always visible even when the bird banked away.

Black-bellied Storm-petrel Fregetta tropica and White-bellied Storm-petrel F. grallaria. Fregetta storm-petrels are fat and compact, whereas our Madeiran was quite long bodied but chunky. Fregetta storm-petrels fly like an exhibition skateborder and tend to skim close to the sea surface, whereas our Madeiran flew with methodical, Nightjar-like flight occasionally rising to three metres above the sea surface. Fregetta wing shape is broad with short arms, strongly curved leading and straight trailing edges, tapering to pointed wing-tips, whereas our Madeiran had long, broad arms, blunt-ended wing-tips, with wings held straight out so leading and trailing edges were only moderately angular. Fregetta head on profile shows wings slightly bowed in a shallow-M with arms short, hands long, whereas our Madeiran also had wings slightly bowed, but arms were medium length and hands were long. Fregetta tail shape is short and square-ended, whereas our Madeiran was shortish but with a shallow fork. Fregetta bill shape is short, broad-based, and finely hooked, whereas the bill of our Madeiran was bulky and quite heavily hooked. Fregetta upperwing covert bars vary slightly between species but in both cases normally are less conspicuous than exhibited by our Madeiran. Fregetta underwings have obvious white covert panels, some outer greater underwing-coverts dark-centred with white fringes, whereas our Madeiran underwing was evenly hued black-brown. Both Fregetta species show extensive amounts of white on the belly, though the pattern varies, however, our Madeiran had an all dark belly.

References
Flood, RL and Thomas, B (2007) ‘Identification of ‘black-and-white’ storm-petrels of the North Atlantic’, British Birds, 100: 407-442.
Flood, RL and Fisher EA (2007) Flight Behaviour of ‘black-and-white’ storm-petrels of the North Atlantic, DVD, privately published via WWW.Scillypelagics.com