Fregetta Stormpetrel, Oman 050808 (1 Viewer)

[gerdwichers8]

Hello,

This involves a bird, seen in two instances. Perhaps two different birds. First observation revealed a Wilson's Storm-Petrel together with an other Storm-petrel which showed a white belly while bouncing the sea. Sea bein rough, no extended observaton is available for many(especially) SP's. 10-15 minutes later (after searching for about 10minutes) the bird was found back, very close to the shore. Persian Shearwater and again Wilson's Storm-petrel for comparision.
Immediate certainty about Fregetta sp. obtained (White belly, big mac compared to Wilson's, broad winged, heavy chested/bodied, second observation white underwing prominent and 'black' appearance)
Tried to convince myself this being Black Bellied. In both instances the bird showed an all white belly with no hint of any black stripe.
Secons instance confirmed this to be so. Being a bit disappointed not to find any belly stripe, I found dark flanks.
These are supposed to be diagnostic for White-bellied Stormpetrel, a bird new to the country.
Are these dark flanks never so found in Black-bellied(in combination with lack of a black belly stripe or any hints what so ever)
These greater underwingcoverts, are they commonly found being 'tern' grey, instead of 'dusky' brown, and is this a true colour, or would it be a result of a dark remex?
Thanx.

 

[Jan-Paul Charteris]

I'm not too sure, looked at quite a few photos of each species and can't see dusky or dark flanks in Black-bellied or White bellied... have got zero experience of either myself though

Jan

 

[gerdwichers8]

Hello Jan

Yes, I know, these dark flanked birds fail to appear to my PC screen as well. Did any posible googling to find any.
Some sites mention dark phase and intermediate phase White-bellied SP though. In literature I only find in Scofield and Onley a bird being intermediate.
Dark phase BB still have an open flank with white underwingcoverts but heavy dark belly stripe.
Pale phase BB would not show dark flanks.
I am not sure though; taxonomically both sp. seem to cause a mess, and I am not pure enough a guy with 100's of both species to speak myself out in confidence.

grtinxs

 

[StuartReeves]

Hi Gerd,

Have you seen the recent paper on Storm Petrel ID in the North Atlantic in British Birds? I'm not sure it will solve your problem, but it does cover Black-bellied and White-bellied to a certain extent.

Stuart

 

[gerdwichers8]

Hi Gerd,

Have you seen the recent paper on Storm Petrel ID in the North Atlantic in British Birds? I'm not sure it will solve your problem, but it does cover Black-bellied and White-bellied to a certain extent.

Stuart

This is a very nice article for me indeed. I read that this article is in Volume 100, July 2007?
I owe 100 volumes of British Birds interactive but... volume 100 does not open with my copy. Perhaps I bought it too soon? Ill give m a call.

 

[gerdwichers8]

Uncertainty at subspecific level causes specific problems

Hello

The article is nice indeed but in this case, not of much help. In it, white bellied Fregetta's , are mentioned generally not to be identified for sure. Black-bellied Stormpetrel may have a white bellied morph (F.t.melanoleuca ))at Tristan da Cunha and Gough and identification of it has yet to be established.There is one record of White-bellied S-P recorded in BWPi but that case is not documented very well and it may not be enough to exclude Black-bellied Stormpetrel .
I tried to get more sources and found Shirihai's "Complete guide to Antarctic wildlife". He holds the same position as the others (e.g Scofield and Onley) ;1 image of white bellied Storm-petrel sp. in the Net (http://www.deanar.btinternet.co.uk/seabirds/petrels/wbstormpetrel.htm) and two unidentified white bellied S-P's in Shirihai's.
Apart from Scofield and Onley in illustration (and literature), no illustrations, nor immages where found in the case of white bellied and dark flanked Fregettta's . Shirihai's texts are clarifying.
Conform Scofield and Onley it is stated that a tiny number of White-bellied is extensively black-bellied. . The darker birds will show the central abdomen mostly still paler. This feature is in both intermediate (only the flanks) and dark (almost entirely) contrary Black-bellied Storm-Petrel so found.In both these cases, dark feathers are found at the sides of the body: the flanks; rather than across the middle of the belly
Unconform the subject bird, both sources illustrate or mention in text "variable dusky blotches and streaks to body sides". The subject had uniform dark bodysides but fading to either side; sharply seperated from the underwingcoverts; difuse towards the white underbody and belly and the underwingcoverts. The greater underwing coverts where not dusky but appeared 'tern'grey.
These darker birds mainly originate from Lord Howe I., east of Australia, where "sizeable percentage are of intermediate appearance"