Most literature on Yellow-legged Gull identification is about separation from Herring Gull. This bird is obviously too dark for smithsonianus, argenteus, and argentatus Herring Gulls. The upper parts are dark enough to suggest a pale Lesser Black-backed Gull Larus fuscus graellsii. The bird is slightly smaller than smithsonianus placing it on the small end of the size scale for Larus cachinnans michahellis, the most abundant race of Yellow-legged Gull in Europe. The identification challenge here is Yellow-legged Gull vs. Lesser Black-backed Gull.
For those familiar with Lesser Black-backed Gull the head shape should appear different. In relaxed position the head is flat topped with a short steep forehead and a squared nape (photos 1 ,2, 3 &4). This gives the head a squared look. Viewed from behind the head is broad (photos 5 & 6). Lesser Black-backed Gull usually has a more domed head and an overall look of diminutiveness relative to body. The head was immaculate white on Feb. 5 as all Yellow-legged Gulls should be by this time. When the bird was first found on Oct. 24 it had a small cap of very fine pale gray streaks neatly confined to the forehead, forward half of crown and forward part of ear coverts. The rear of head and nape were unmarked pure white. By late November the head streaking had been reduced by 90% and was restricted to some gray lines in the lores and on the forehead near the base of the bill. There was a gap in sightings until Dec. 26 by which time the head was gleaming pure white. I do not know if graellsii can have a white head in December. Limited personal experience (<50 individuals) and the literature suggests that adult graellsii usually have head streaking until early February.
The bill is bright yellow with a bright red gony spot much as Lesser Black-backed Gull. The bill is parallel sided with the culmen dropping steeply toward the tip giving an blunt ended look (photos 1, 2, 7 & 15). Lesser Black-backed Gull often has a longer down curve to the culmen creating a less blunt and less parallel sided bill (Garner 1997). Yellow-legged Gull characteristically has parallel sided, blunt tipped bills (Gruber 1995, Garner 1997).
Body and Wing Shape
Side by side comparisons with a 4th winter Lesser Black-backed Gull were possible on several occasions during October and November 1996. The Yellow-legged Gull was larger than the Lesser Black-backed Gull, closer to the size of Herring Gull. More importantly the body shape was different. The Yellow-legged Gull usually appeared to be fuller chested with legs set at a wider stance. In flight the wings were broader based, more Herring Gull shaped and unlike the long narrow winged look of Lesser Black-backed Gull.
The mantle color was a little paler than a pale graellsii. In bright sunlight it could look very pale, so as to be inconspicuous among adult Herring Gulls. Shades of gray are difficult to capture on film. The scanned photos accompanying this note are slightly darker than it was in life - on my computer monitor! Individual monitor variation is to be expected. Be careful when comparing mantle with Herring Gulls in the same photo. Note that comparisons lead to a different impression of darkness with each photo.
The size and shape of the wing tip is captured nicely in (photo 8). The large squared off hand of black is probably quite similar in size and shape to Lesser Black-backed Gull. However, rarely if ever, does Lesser Black-backed Gull show such a striking contrast between the black tip and the gray of the upper side and particulary with the paleness of the under side. Garner (1997) says 'the striking contrast between the black of the primaries and the grey of the upperwing is more obvious' on Yellow-legged Gull. On Lesser Black-backed Gull the black wing tip usually blends into the gray of upper side. The one white window in P10 is typical of Lesser Black-backed Gull and many Yellow-legged Gulls. The black bar in the outer web of P4 is characteristic of Yellow-legged Gull but is also found on Lesser Black-backed Gull.
Legs and feet deep bright yellow, obvious at considerable distance. The thick and fleshy orbital ring was colored crimson red. Iris clear yellowish.
Subspecies and Origin
This bird is smaller and darker than a typical michahellis. The form of Yellow-legged Gull that fits best is Larus cachinnans atlantis. It breeds on the Atlantic islands of Azores, Madeira and the Canary Islands. Gruber (1995) describes them as smaller than michahellis and darker, only a shade lighter than the lightest individuals of graellsii. The Azores are one third of the way across the Atlantic Ocean from the Portuguese coast, thus a mere 1600 miles or so south east of St. John's, NF. Early statements suggesting that they are sedentary have been challenged in recent years. The first North American specimen from Magdelan Is., Quebec on Aug. 18, 1983 closely resembles atlantis.
Shrouded in the mystery of the subspecies of Yellow-legged Gulls in north west Portugal is a form that is smaller and as dark or darker than michahellis (Garner 1997). Whether this is atlantis or another form of Yellow-legged Gull is yet to be determined.
Gruber, D. 1995. Die Kennziechen und das Vorkommen der Weisskopfmöwe Larus cachinnans in Europa. Limicola 9: 121 - 165.
Garner, M. 1997. Identification of Yellow-legged Gulls in Britain. British Birds 90: 25 - 62.
NBHC ID-FRONTIERS Frontiers of Field Identification or Dave Fifield or Bruce Mactavish
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