Slaty-backed Gull
SLATY-BACKED GULL
Larus schistisagus
Laridae Family
L 635 mm (25")
migrant, rare
Bird # 400 - March 2013
This bird was first spotted and photographed by Sylvia. The Philippine ducks we were watching flew up into the air and when they landed they brought a gull with them. It was quite a surprise since we had already looked at all the birds in the pond. There was no gull the first time we scanned the pond. Sylvia exclaimed, "There is a gull!" Then it stayed for a short time, enough for a bunch of photos. It quickly flew off. We went back several times after and did not see it again. Truly a chance encounter. This bird is a rare visitor to the Philippines. As most immature gulls are difficult to ID, several experts were consulted by Arne Jensen of WBCP to confirm the ID.
Philip Round: I think you are correct. The bird, with all-black tail and excessively "bleached-appearing" upperparts, and (apparently) massive build looks like a 1w Slaty-backed to me.
Klaus Malling Olsen (translated from Danish): As usual when it come to large immature gulls, the response can be more than one: I favor Slaty-backed Gull, because of the shape of the bird, the uniform black beak and the apparent complete dark tail. That the greater covers above are unusual worn, is something you observe among most of the East Asian gulls. Vega would typically have had a much broader light color basis at the root of the tail and a lighter colored beak; furthermore less flat head profile and therefore a less ”brutal-looking” beak. However the worn feathers may contribute to this impression considerably. Heuglin´s Gull, which is born later in calendar year, would probable not have had so extreme worn wing covers as well as having a light colored bases of the beak. So the characters seen on the pictures in combination say Slaty-backed Gull.
Arne Jensen: In parallel I checked pictures at the net and my opinion is a 2nd Year (1st winter) Slaty-backed Gull as well. Although we don't have the formal rarity committee in place, I use to seek the consensus of least four specialist persons when it comes to "difficult" to id species. It would be good to get the final opinion of Desmond and Rob on the Slaty backed G.
Robert Hutchinson: The tail is dark all the way to the base, this seems a good feature to separate Slaty-backed Gull from Vega Gull, I checked many online photos and it seems a consistent feature. Vega usually seems to show a pale, sometimes barred tail bases. American Herring Gull would also show the all dark tail. Since the rump and upper-tail feathers of all species become bleached and paler by the stage of its plumage development, my previous ascertain that the paler rump supported Vega Gull is probably not relevant. Studies of photos online show huge variation in this feature.The dark bill likewise doesn’t seem a useful feature, both Slaty-backed and Vega it seems can retain this into their 1st summer. According to Nial Moores the solid secondary bar, contrasting with the pale flash on the inner primaries is typical of Slaty-backed. It doesn’t separate the birds from Vega but does help eliminate other such as aimyrensis and Galucous-winged. The heavily bleached upperparts seem fine for birds of this age and study of on-line photos suggests this bleaching often makes the greater coverts very pale like this bird so my previous concerns that the bird should show darker markings are not relevant. The dark brown primaries confirm that this is not Glaucous-winged Gull. The smudgy black patterning on the scapulars seems closest to Slaty-backed, Vega should show better defined black markings in most cases. I find the structure too hard to judge with no other gulls for comparison but would be happy to follow Phil and Klaus’s experience on that. It seems that all plumage features fall within the range of 1st Winter Slaty-backed Gull with the all-dark tail as a key feature, and a combination of other features eliminating other possibilities. I’m happy with this as a 1st Winter Slaty-backed Gull.
Read MoreLarus schistisagus
Laridae Family
L 635 mm (25")
migrant, rare
Bird # 400 - March 2013
This bird was first spotted and photographed by Sylvia. The Philippine ducks we were watching flew up into the air and when they landed they brought a gull with them. It was quite a surprise since we had already looked at all the birds in the pond. There was no gull the first time we scanned the pond. Sylvia exclaimed, "There is a gull!" Then it stayed for a short time, enough for a bunch of photos. It quickly flew off. We went back several times after and did not see it again. Truly a chance encounter. This bird is a rare visitor to the Philippines. As most immature gulls are difficult to ID, several experts were consulted by Arne Jensen of WBCP to confirm the ID.
Philip Round: I think you are correct. The bird, with all-black tail and excessively "bleached-appearing" upperparts, and (apparently) massive build looks like a 1w Slaty-backed to me.
Klaus Malling Olsen (translated from Danish): As usual when it come to large immature gulls, the response can be more than one: I favor Slaty-backed Gull, because of the shape of the bird, the uniform black beak and the apparent complete dark tail. That the greater covers above are unusual worn, is something you observe among most of the East Asian gulls. Vega would typically have had a much broader light color basis at the root of the tail and a lighter colored beak; furthermore less flat head profile and therefore a less ”brutal-looking” beak. However the worn feathers may contribute to this impression considerably. Heuglin´s Gull, which is born later in calendar year, would probable not have had so extreme worn wing covers as well as having a light colored bases of the beak. So the characters seen on the pictures in combination say Slaty-backed Gull.
Arne Jensen: In parallel I checked pictures at the net and my opinion is a 2nd Year (1st winter) Slaty-backed Gull as well. Although we don't have the formal rarity committee in place, I use to seek the consensus of least four specialist persons when it comes to "difficult" to id species. It would be good to get the final opinion of Desmond and Rob on the Slaty backed G.
Robert Hutchinson: The tail is dark all the way to the base, this seems a good feature to separate Slaty-backed Gull from Vega Gull, I checked many online photos and it seems a consistent feature. Vega usually seems to show a pale, sometimes barred tail bases. American Herring Gull would also show the all dark tail. Since the rump and upper-tail feathers of all species become bleached and paler by the stage of its plumage development, my previous ascertain that the paler rump supported Vega Gull is probably not relevant. Studies of photos online show huge variation in this feature.The dark bill likewise doesn’t seem a useful feature, both Slaty-backed and Vega it seems can retain this into their 1st summer. According to Nial Moores the solid secondary bar, contrasting with the pale flash on the inner primaries is typical of Slaty-backed. It doesn’t separate the birds from Vega but does help eliminate other such as aimyrensis and Galucous-winged. The heavily bleached upperparts seem fine for birds of this age and study of on-line photos suggests this bleaching often makes the greater coverts very pale like this bird so my previous concerns that the bird should show darker markings are not relevant. The dark brown primaries confirm that this is not Glaucous-winged Gull. The smudgy black patterning on the scapulars seems closest to Slaty-backed, Vega should show better defined black markings in most cases. I find the structure too hard to judge with no other gulls for comparison but would be happy to follow Phil and Klaus’s experience on that. It seems that all plumage features fall within the range of 1st Winter Slaty-backed Gull with the all-dark tail as a key feature, and a combination of other features eliminating other possibilities. I’m happy with this as a 1st Winter Slaty-backed Gull.
SLATY-BACKED GULL Larus schistisagus Bgy. Gabu, Laoag, Ilocos Norte
