Band-rumped Storm Petrel ID

The Possibilities and the Challenges.

by Dani

Separating Leach´s from Band-rumped Storm Petrels (the Madeiran Petrel in ‘old money’) has always been one of the greatest challenges for the seawatcher.

As with many other seabirds, these Storm Petrels  aren´t as easy to study in detail as are gulls or shorebirds. And that means distant birds, seen briefly or in poor conditions, as from a moving boat in rough seas, are sometimes best  left unidentified.

Having said that, it´s true that the basics of their ID are already well-known, and covered in all field guides, especially so in the excellent Multimedia ID Guide by Bob Flood and Ashley Fisher.  So you could think a bird shown in a good photograph should be easy to identify. However, it´s not always the case. Not even for the experienced seabirder.  And especially if such important things as flight manner or structure can´t be evaluated, like in photos.  Sometimes, even separating it from a Wilson´s or a European is tricky. See it for yourself…

Here are 3 Photos…

What do you think are the species? (feel free to guess it on the comments section)

PHOTO ONE

Photo © Marcel Gil

PHOTO TWO

And this one?

Photo © Juan Sagardia

PHOTO 3

What about this bird, facing away? Band-rumped? Wilson´s? Or an atypical Leach´s?

Photo © Luke Seitz

OK then… You´ve done your pelagics. You´ve studied the guides and the birds in the field. You started feeling a little bit confident on the ID of these 2 species…

Until recently, all of a sudden, and as if this wasn´t difficult enough, things got even more complicated.

Thanks to the pioneering studies of several highly skilled birders and ornithologists, including those by Magnus Robb and Killian Mullarney/The Sound Approach (see their fabulous “Petrels Night and Day” book for more information), the Band-rumped Storm Petrel complex in the North Atlantic has preliminary been divided into 4 taxa. Mainly based on differences in vocalisations on the breeding grounds and on different breeding timings (summer breeders and winter breeders), as well as on biometrics and moult. So now, according to them, we have:

Grant´s Storm Petrel:  Widespread winter breeder

Madeiran Storm Petrel: Summer breeder from the Canaries and Madeira

Monteiro´s Storm Petrel: Very rare summer breeder from the Azores

Cape Verde Storm Petrel: Winter breeder from the Cape Verdes

However, most of the criteria considered for their separation is of little use to the field observer. Although several subtle plumage features have been suggested as more indicative of certain taxa. For example, Monteiro´s  is supposed to have a deeper tail fork, and more prominent carpal bars than the others. But…

There´s a big problem that shouldn´t be forgotten for at-sea identification: VARIATION.

As  Flood and Fisher indicate, no consistent plumage features have been found to assist on the at-sea identification of the various proposed forms.

Our own observations, mainly off the Canaries, confirm this. We´ve seen birds from presumably the same population showing features associated with birds from all other populations! We think variation within the same populations is the explanation… Of special interest is that, amongst presumably summer breeders (“Madeirans”), off Lanzarote, we´ve seen, roughly speaking, 2 types, including one that resembles Monteiro´s ! This has also been noted off Madeira by H.Shirihai, B.Flood et al.

a – Summer breeding, Monteiro´s-like birds: Birds with quite deeply forked tail (apparent from all angles and positions), pointed wings and prominent pale carpal  birds. We think these birds are definitely not Monteiro´s, of course. But they look superficially like them at sea. And this would make identification of out-of range Monteiro´s impossible, on current knowledge

Photo © Juan Sagardía: Presumed summer breeder, “Madeiran”, with deeply forked tail, pointed wings and well-marked upperwing covert bars. Similar to newly described “Monteiro´s” , from the Azores, but note the above bird was photographed in the Canaries, thus identified as a variation of “Madeiran”

b – Summer breeding, “classic”, almost European Storm-petrel-like birds. Birds with shallow or no tail fork and square-ended tails, (but note that the degree of fork can change depending on angle/position) – being more accentuated when the bird faces away), relatively blunt wing tips, broad wings and quite faint upperwing covert bars.

Photo © Juan Sagardía: Presumed summer breeder “Madeiran” , from late May off Lanzarote, with almost square-ended tail, poor marked upperwing covert bars, relatively blunt wing tip, and small amount of typically U-shaped white on the uppertail coverts. Compare it with the bird above.

Photo © Daniel López-Velasco: Presumed adult summer breeder, photographed in early September off Lanzarote. Note again square-ended tail and dull bars of this bird.

Moult would be then the only visible field feature that could help, sometimes, to divide the complex into 2 wide categories: “Summer” breeders and “Winter “breeders. On actual knowledge, this is in my opinion the best approach.

Steve Howell´s studies on moulting birds off North Carolina are very interesting and help shed some light on the issue.

However, It must be stressed that at certain times of the year, birds on certain states of moult, can´t even be ascribed to one of the 2 main categories. And this is because there can be some overlap amongst different age groups of the different forms.

See the state of moult of the following birds, presumably of the 2 different populations, from the Canaries:

1-Presumed winter breeder (Grant´s)

Photo © Juan Sagardía: Mid primary moult in late May indicate this bird is most likely a bird from the wintering population (Grant´s). The visible tail fork and large ammount of white on the rump are more marked than what´s usually associated with this form.

Photo © Juan Sagardía: Presumed winter breeder (Grant´s). Same bird as above, see how colour and appearance can change depending on the bird´s posture.

Photo © Carlos Martín. A very fresh looking bird seen in September off Lanzarote, presumably, given the date and state of plumage, an adult from the winter population. Fresh juveniles from the summer population shouldn´t, in theory, fledge until late October.

2-Presumed summer breeders (Madeiran)

Photo © Juan Sagardia: Presumed summer breeder, from early june. Note fresh plumage and no wing moult, typical of summer breeders on that date. A second cycle winter breeder could presumably look like this too, but considering all birds studied at the same time, at the same place, and with the same wing condition, we think they were most likely summer breeders.

Photo © Daniel López-Velasco. Another presumed adult from the summer population, seen in September off Lanzarote.

3-Summer/Winter breeders

Several very worn birds, with no signs of moult, were seen in Lanzarote last September. Shape and wear of primaries would probably indicate they are juvenile. Could these birds be worn first cycle Winter breeders?

Second prebasic moult of summer breeders should, in theory, start by July.  Thus, these birds, with no visible wing moult, shouldn´t belong to that population. But can some first cycle summer breeders start it later…? More work is needed in order to answer this, and other questions related to these fascinating Storm-Petrels.

Photo © Carlos Martín. Note the very worn primaries of this bird, with no signs of moult, photographed in September. Could it be a first cycle winter breeder? And can a retarded first cycle summer breeder be ruled out?

Over to you. Did you have a go at identifying the ‘mystery petrels’ ONE, TWO and THREE?

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13 Responses to Band-rumped Storm Petrel ID

  1. The first two photos are very interesting but will need more time than is available at the moment to study them, so as to give a better comment with more basis to it. Photo 3 seems more like Leach’s for me, although not the typical bird…tail (and obviously legs, although some Wilson’s do not show extention) are wrong for Wilson’s, much better for Madeiran but also some Leach’s (also due to the angle). Wing pattern definitely more Leach’s, I’ve seen Madeiran several times last year and they look more smoothly marked, more gradual on the coverts. Rump better for Leach’s. I wouldn’t exlude Madeiran totally obviously, having only one single photo in dark light conditions and because of that strange angle, but I’d definitely rule out Wilson’s, wing shape also wrong for the latter.

    Silvio Davison

  2. Martin Garner says:

    MG here: Seems a lack of keenness- understandably perhaps – to have a try at the 3 petrels in Dani’s post. So I will have a go. He hasn’t told me so I know as much as anyone… I think I see?????

    Photo one Madeiran Petrel
    Photo two Wilson’s Petrel
    Photo three Leach’s Petrel

    But not 100% sure and may well be wrong!
    What do you think?

  3. Adam Hartley says:

    OK, prompted by MG’s Facebook posting I’ve taken a look and find that I agree with Martin.
    1. Madeiran: not much of a forked tail & width of white rump greater than length
    2. Wilson’s: you can just see the projecting feet
    3. Leach’s: not much width to the white rump though can’t really see the fork at that angle.

  4. Hugh Delaney says:

    1. Wilson’s
    2. Madeiran
    3. Leach’s
    Hopefully i’ve at least one right!
    regards
    Hugh

  5. Pim Wolf says:

    ok, I’ll bite..

    1. Madeiran
    2. Madeiran
    3. probably Leach

    hoping that you will have better pics of these birds to go with the answers 😉

    pim

  6. 1. Madeiran
    2. Leach
    3. Leach
    Saludos
    Juan Sagardía

  7. Brett Richards says:

    1. Madeiran
    2. Leach’s
    3. Leach’s

    Cheers

    Brett

  8. 1. Band-rumped
    2. Band-rumped? (based on the upperwing covert bar extending nearly to carpal joint, Wilson’s would presumably appear more restricted and brighter, though it looks small headed and thin billed?)
    3. Band-rumped? (very blackish, lack of dark through middle of rump, lack of deeply forked tail, though still showing some features suggestive of Leach’s)

  9. Ricardo hevia says:

    Hola

    1.madeiran
    2.Leach
    3.leach
    Saludos a todos
    Ricardo Hevia

  10. Pingback: Mystery Storm-Petrels: Solutions | Birding Frontiers

  11. Maarten Platteeuw says:

    To me:
    1. Castro
    2. Leucorhoa
    3.leucorhoa?

    Maarten Platteeuw

    • Martin Garner says:

      hi Maarten answer is a bit higher up, with explanations from Dani- not all straightforward!

      • Hi Martin, Just getting in to the Thalobata-complex so perhaps! 1. T. ‘granti’ Dark plumage overall including dull carpal bar. 2. Leucorhoa. There IS foot projection. Hit the photo with brightness and contrast in Word. 3. T. monteiroi. Tiger striped carpal bar and faint rump centre divide. Not forgetting location, location, loca…..

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