Wednesday, July 6, 2016

Pelagic off Olhão

(all photos are clickable to enhance)
Yesterday morning, 5th of July, we went out on a boat with Passeios Ria Formosa (Fuzeta), this time departing from next to the Real Marina Hotel in Olhão and headed for the waters off Culatra Island. There was an overcast in the beginning, therefore not a hot morning, calm sea and hardly any noticeable wind. The light improved along the trip. Despite not getting any fishing vessel within reachable distance, it turned out to be a very successful trip.

Great Shearwater (Ardenna gravis) with Cory's Shearwaters (Calonectris borealis) off Culatra Island, 05-Jul-2016.

For more than one hour we were basically surrounded by a huge pod of over 100 Short-beaked Common Dolphins (Delphinus delphis) and also well over 100 Cory's Shearwaters (Calonectris borealis) among which we coud also identify and photograph at least three Scopoli's Shearwaters (Calonectris diomedea) a species (or still a subspecies, depending on systematic - but have a look here). There are only a hand full of records of this taxon in the Algarve so far anyhow and as far as I know none of them documented by photos. On the other hand, Scopoli's mainly breeds in the Mediterranean and winters in the South Atlantic, so occurance in Algarvian waters during non-breeding season at least makes sense. Identification in the field is often not straight forward (good views or better, photos of the underwing neccessary) and therefore the few Scopoli's among the majority of Cory's go easily unidentified.

Scopoli's Shearwater (Calonectris diomedea) off Culatra Island (Olhão) 05-Jul-2016. Note 
the white extending into the wing tip (web of primaries).

After searching for quite a while, we also spotted two Sooty Shearwaters (Ardenna griseus) and finally a single Great Shearwater (Ardenna gravis) - both giving great and close views and this is only the very beginning of the season for both species.

Great Shearwater (Ardenna gravis) with Cory's Shearwater (Calonectris borealis) in the background.
Off Culatra Island, 05-Jul-2016.

Cory's Shearwater (Calonectris borealis). Off Culatra Island, 05-Jul-2016.

We also encountered Storm Petrels, among them Wilson's SP and European SP - perhaps three or four Ind. of each species, but did not get the best views, because without the birds foraging (next to a fishing boat pulling in the net, for instance) but only travelling, even photographing them is not an easy task. However, we managed at least record shots and thought to have found also one "Band-rumped Storm Petrel". The now potentially 4 species in this species-complex (compare Robb et al., 2008) were previously all lumped as Madeiran Storm Petrel (Oceanodroma castro or Hydrobates castro). Systematic here is not uniform and field-ID within the "Band-rumped SP -complex" is very difficult if not impossible, but have a look  here). Interesting is that also the recently published "Atlas of Marine birds in Portugal" (in Portuguese) shows the occurence of this species in Algarvian waters.
However, after reviewing the ID and getting expert opinions, it turned out to be "just" a Wilson's SP flying with feet retracted and therefore completely lacking feet projection over the tail, one of the most usefull fetaures to ID Wilson's in the field. The Storm Petrel in question also shows a too short arm and too weak bill to be a possible "Band-rumped". We will keep looking....

Wilson's Storm Petrel (Oceanites oceanicus) off Culatra Island (Olhão) 05-Jul-2016.

The following five photos show a potential "Band-rumped Storm Petrel" we saw during the trip. But for the reasons explained above, it turned out to be another Wilson's Storm Petrel in the end.

Expert opinion on the above Storm Petrel by Bob Flood is here:

In my opinion, this is a Wilson's Storm-petrel. It has a small squarish head and slim bill (Band-rumped has bulkier head and deeper bill, even the smaller forms). The arms are short and broad, hands medium length, and wing tips pointed (Band-rumps have medium-length arms, long hands, while some forms do have fairly pointed wing tips). The leading edge of the wing is moderately angular, but the trailing edge is fairly straight in most shots (typically angular in Band-rumps). I don't think the tail is really forked; this may be an impression given by a toe projection. It has a long caudal projection (rear carriage behind wing, longer than Band-rumps). The head, body and tail are fairly sleek (unlike Band-rumps). The white 'rump patch' folds over to the underside and joins the thigh patches (depth greater than N Atlantic Band-rumps). The upperwing ulnar bars are variable in intensity in Wilson's and we see quite a few with dullish bars, as this bird (affected by wear and bleaching). Second-year and older Wilson's start moult by early June, but juveniles do not start the complete preformative moult until at least mid July, most later, so presumably this is a juvenile (plumage looks pretty fresh). By the way, it always helps if you describe flight behaviour, because this can be very important in storm-petrel ID.
Hope this is of use.

Robert L. Flood DSc, PhD, BSc (1st Hons)
Twitter: @Scillypelagics

Naturally we saw many Northern Gannets and also had one immature Pomarine Skua (Stercorarius pomarinus) flying over.

New dates for Pelagics have been scheduled on my website here. Available dates are: July, 22nd; August, 2nd; August 12th; August 25th; September 6th; September 30th; October, 13th. We can organize a pelagic at any time between June and October/November when the participation of min. 4 people is assured.

 Pomarine Skua (Stercorarius pomarinus) pale morph juvenile flying over. C. 3 miles off Culatra Island, 5th of July 2016.

Fresh juvenile Audouin's Gull (Ichthyaetus audouinii) in Ria Formosa, next to Olhão on the way back in. In the background: Caspian Tern, Sandwich Terns and an adult Yellow-legged Gull. July, 5th, 2016.

Fresh juvenile Audouin's Gull (Ichthyaetus audouinii) in Ria Formosa, next to Olhão on the way back in. In the background: Caspian Tern, Sandwich Terns and an adult Yellow-legged Gull. July, 5th, 2016.

And the Caspian Tern (Hydroprogne caspia) turned out to be color-ringed. Red: FY2. Still looking for the program...

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