Monday, 26 August 2013

Bulwer's Petrel - the same the World over?

I don't do much seawatching anymore, a few good boat trips spoiled it for me. A couple of years ago I spent a few days on, or rather a few miles off, Madeira getting to grips with some of the Western Palearctic's rarer and more local species. As I had hoped, Bulwer's Petrel Bulweria bulwerii were numerous and often close. They weren't too easy to photograph, they moved fast and the boat rolled on the swell, but at least they kept coming past and, by blasting off hundreds of shots, I got a few half decent images.

Tubenoses which breed in low to mid latitudes tend to be quite restricted in their breeding sites, Bulwer's isn't. Of the 'big five' Madeira tubenose specialities, two species, Zino's Petrel Pterodroma madeira and Desertas Petrel P.(feae) deserta, are extremely rare and breed only on one island each; while three, Bulwer's Petrel, White-faced Storm-petrel Pelagodroma marina and Madeiran (or Band-rumped) Storm-petrel Oceanodroma¹ castro, are both fairly numerous and are found in both the Atlantic and the Pacific.

Of course I know things are a little more complicated than that; Madeiran Storm-petrel in the strict sense only breeds in the Madeiran and Canarian archipelagos, the other taxa in the complex being variously regarded as subspecies or species.  White-faced Storm-petrel (with up to six subspecies) breeds on islands in the North and South Atlantic and also from southern Australia to the western Pacific.

Bulwer's Petrel is found breeding in tropical and sub-tropical zones across The World's oceans from the eastern Atlantic to the central and western Pacific and the western Indian Ocean (it may also breed in the South Atlantic on St. Helena). However, unlike the two Storm-petrels, there are no recognised subspecies. Bulwer's Petrels from Hawaii and the seas off Taiwan appear to be identical from those from Madeira and the Canaries - there appear to be no plumage or size differences that I can detect from specimens. Other than Jouanin's Petrel Bulweria fallax, which, when lumping was the fashion, was sometimes thought to be conspecific with Bulwer's (in fact it's much bigger and a different shape), I don't think Bulwer's has ever had any subspecies. The monotypic multi-ocean distribution of Bulwer's Petrel is, in fact, so unusual for a (sub)tropical tubenose that only Wedge-tailed Shearwater Puffinus² pacificus shows a similar pattern, although in this case it does not occur in the Atlantic.

I'm not aware of any research into the genetics of these populations though I suspect the results would be interesting.

Many thanks to Caterina Fagundes and Hugo Romano of Madeira Windbirds for some quite splendid boat trips, I can't recommend them too highly.

 ¹ It has been suggested that this species (species group) differs so much from 'typical' Oceanodroma that it may be better placed in it's own genus Thalobata.

 ² Like the other large shearwaters, probably better placed in a separate genus Ardenna.

Friday, 16 August 2013

Getting distracted again

13th-15th August - Topsham

The days are long and so are the gaps between posts. I could make excuses about pressures of work but the truth is I've been taking a bit of a break. There doesn't seem to be much happening bird-wise locally (maybe I'm not looking hard enough) so I find my attention wandering. As a five minute break from my desk, I like to take a walk down the garden with my macro lens/tripod set-up. There's nearly always something of interest. So, at the risk of disappointing those expecting photos of gulls, sketches of birds or even an update on my Tubenose work, here are some more insect photos. All taken in my back garden in the last few days - the technical details (if anyone's interested) are: Nikon D200, Sigma 180mm macro, Uniloc tripod and Manfrotto ball head, no flash, just long exposure, mirror lock-up, cable release and wait for the wind to drop.

First here's a bug, Deraeocoris ruber, family Miridae. I've photographed this species a few times and it varies a lot in colour; this is a paler individual, some are quite blackish - mostly males according to Southwood & Leston (1959). Both adults and young are predators of aphids and other small insects.

The next two shots show a Hoverfly, a Eumerus sp. There are four British species (Stubbs and Falk, 2002; Ball and Morris, 2013); it's not E.sabulonum as that has a reddish base to the abdomen, also I think E.ornatus can be ruled out as the ocellar triangle is not far forward enough. This leaves E.funeralis, which has a distinct bare patch on the underside of the hind femur, and E.strigatus, which doesn't. I suspect this is strigatus but can't be certain with these views.

Now for some flies with somewhat less savoury lifestyles, Tachinids, all identified, with varying degrees of confidence using Belshaw (1993) and Tschorsnig and Herting (1994). First we have Voria ruralis, I see this in some numbers locally in late summer - when I look. It parasitises moth larvae, mostly Plusiinae - Silver Y, Burnished Brass and Dark Spectacle are mentioned.

The next two photos show another fairly common Tachinid,  Eriothrix rufomaculata. The reddish patches on the sides of the abdomen (just visible through the wing) are typical, though not diagnostic, this was keyed using Belshaw (1993). This also appears to parasitise moth larvae, although it's usual host is surprisingly unknown given that it's so common.

This last fly is a new one for me, using Belshaw it keyed out as Gastrolepta anthracina, I checked reliably identified photos (e.g. and, a little surprisingly, they seem to match. I'll put it down as a probable and check with those who know. This doesn't seem to be a common species - though it's hard to tell with such an under recorded group - and mainly found in coastal southern England; the host species appear to be beetles.



Belshaw, R. 1993. Tachinid flies. Diptera: Tachinidae. Handbooks for the identification of British Insects. Royal Entomological Society of London 10, Part 4a(i).
Southwood, T.R.E. & Leston, D. 1959, Land and Water Bugs of The British Isles. Warne, London.
Tschorsnig, H.P. and B. Herting. 1994. Die Raupenfliegen (Diptera: Tachinidae) Mitteleuropas: Bestimmungstabellen und Angaben zur Verbreitung und Ökologie der einzelnen Arten. Stutt. Beitr. Naturk. (A) 506, 170 pp.