Oenanthe isabellina – Tinwen Isabella – vagrant
Kim Gowney (KGP), Trevor Price (TJP) and myself had booked to stay on Skokholm for our first time, taking advantage of a four-night short break from 23rd-27th September 1997. We joined Graham Thompson and Theresa Purcell,, Graham’s mother and two non-birding visitors for the last “occupied” week of 1997.
During our first full walk around the island on Wednesday 24th, we arrived at the lighthouse at around 11am. After a quick check there, KPG and I walked ahead of TJP, away from the lighthouse through an area known as Horse’s Bottom. I pointed out a particularly pale northern wheatear, Oenanthe oenanthe, to KPG, remarking something like “that’s about as pale as a northern wheatear gets”, with reference to queries from KPG on the field identification of Isabelline wheatear. We had seen several northern wheatears that day, but none as pale as this one.
A few steps further on and another wheatear appeared to the right of the path, and as soon as I looked at it through my bins I urged KPG to look too. Initial impressions were of a bird which was very pale sandy brown, looked long-legged and rotund, and had little contrast between the upper- and underparts. This really was interesting! TJP soon joined us and we watched the bird for a few more minutes before it was lost from view. We were collectively confident it was an Isabelline, but we obviously needed more views. KPG volunteered to fetch GT (and some reference material to check the features) whilst TJP and I continued to search for the bird.
KPG and GT soon joined us, and about an hour after the first sighting (it was a very long hour . . .) we relocated the bird back where we had first seen it. We then watched it at ranges down to 20m for about 40 minutes, during which time we noted all of the main separating features from Northern, apart from the underwing (but boy did we try!). At this point we were 100% confident we had in front of us Pembrokeshire’s first Isabelline wheater, although GT was a little more cautious, having not seen the species before (we were all acutely away of the difficulty of identifying this species).
We returned to the wheelhouse for lunch and I showed GT some photos of Isabelline wheated in British Birds and he was now convinced we had the definite article (the photo of the Cork bird in 1992 looked exactly like ours).
The bird remained faithful to the same area over the next three days and we were able to enjoy it performing very well, in the company of several northern wheatears, during this time. The bird was still present and “settled” on the late afternoon of 26th September, but could not be relocated, despite searching, on 27th September. The bird was photographed.
The following notes are a summary of my original field notes, based upon approximately four and a half hours watching over three days. All comparisons are made against northern wheater (NW), several of which were often within a few metres of the Isabelline (none of these were considered to be of the Greenland race, althoughone was very pale, as mentioned above).
Structure/posture: Appeared slightly larger, with longer legs and more pot-bellied than NW. Tail did not touch ground when bolt upright (often difficult to asses in windy conditions when the bird crouched more, or when not on a flat surface which was the norm – usually on small mounds!)
Bare parts: Bill all dark, slightly longer and deeper than NW. The bill seemed more “obvious” because of the pale face. Legs long and dark, and eye all dark.
Head pattern: The chin and throat were sandy brown, with perhaps the chin slightly whiter (photo 1 shows a paler submoustachial area which was not noticeable in most light conditions). The lores (the darkest feature of the head), and to some extent the ear coverts (which appeared the darkst/most contrasted feature when viewed head on) were darker than the rest of the head, but there was no eye stripe. The supercilium, which joined across the base of the bill, was usually more distinct in front of the eye (especially in brighter conditions), but in most light conditions was poorly defined. Overall, the supercilium was not as contrasting as NM and was not stronger gehind the eye as was the case will all the other NWs I saw. A paler, thin eye ring was seen on the closts views. The crown and nape were a pale sandy brown colour. In some views, when the bird was very upright, the crown appeared very flat.
Upperparts: The upperparts were a pale sandy brown colour, concolorous with the nape. They contrasted little with the wings or underparts (a feature shown by all NWs examined during our stay)
Underparts: The underparts were a uniformly sandy brown colour, with the vent and undertail whiter. All other NWs seen were a warmer peachy colour across the breast and none were as pale, or as uniform, as the Isabelline.
Tail and rump: The tail was distinctive, showing clearly more blackish colour (the tail was not as dark black as NW, more blackish-brown) and less of an inverted “T” than any NW I have ever seen. The blackish-brown on the tail sides was clearly more extensive, and the blackish brown central feathers, although more extensive than the outers, showed slightly less than NW giving a much reduced “T” but an overall darker tail. In many flight views and especially from the side, the “T” was far less noticeable than in NW. When perched it was difficult to make out any “T” pattern at all. Each tail feather had a pale tip. The lower rump and upper-tail coverts were white, but not as extensive as NW and hence accentuated the overall darker tail.
Wings: The greater, median and lesser coverts were broadly fringed a uniform pale sandy brown colour with darker centres, but due to the width of the fringe it was the pale colour which was evident and did not contrast with the upperparts (occasionally the darker centres to the median coverts were more noticeable). The alula was blackish and was often (but not always) visible, standing out on the pale wing and contrasting with the pale flanks. The tertials were brown with a broad sandy brown fringe, the secondaries similarly so but the fringes were broader, and the way they were bunched together formed a distinct pale panel in the winger (made larger by the lowest fringes of the longest tertial). The primaries were dark brown with distinct thin pale tips, and seven (initially through to be six) primary tips were visible beyoned the tertials on the closed wing. The exposed primaries were slightly longer than the length of the tertials on the closed wing. Two/three buff-fringed, dark-centred, greater primary coverts could be seen extending down below the greater coverts. The underwing was a most difficult feature to asses, and it wasn’t until the third day that I was finally convinced that the Isabelline had a distinctly paler underwing than NW, an impression I only confirmed after have a good view of a NW’s dark udnerwing (GT had seen the feature earlier and was happy it was pale, with a slightly darker row of secondary converts).
Habits: Generally behaved much as a NW, hopping and running across the ground (mostly a grassy areas of Manx shearwater burrows). It would often perch on the highest available mound on full view, taking short flights. Occasionally it would fly up to 200m away but always returned to the same small area.
Call: On the final day I heard the bird call several times, usually when chasing off a NW or alarmed by my presence. I would describe it as a “chack”, very simily to NW but softer to my ear.
This record has been accepted by the British Birds Rarities Committee and, assuming the bird on Bardsey Island a few days previously is accepted, becomes the second for Wales and the 14th for Britain and Ireland.
Pembrokeshire Bird Report 1997