Following this sighting of two birds together, and after a brief discussion with others this evening. I thought it might be interesting to look at some of the photos of the Franklin's Gull(s).
Comparison of the side-on bird from John's photo today suggests that this is a a different bird from that photographed by lyatming on 9th April
http://www.hkbws.org.hk/BBS/view ... &extra=page%3D1 (compare especially the pattern of white in the wing tip). Of course, lyatming's bird could be the front-on bird in John's photo.
Looking back to earlier photos, I get the impression that there may be a difference between the bird on 29/11/15 (
http://www.hkbws.org.hk/BBS/view ... &extra=page%3D1) and 12/12/15 (
http://www.hkbws.org.hk/BBS/view ... &extra=page%3D1)
In particular, from flight shots the 6th outermost primary seems to have a black tip in late November but an obvious white tip with a black subterminal band in December. I also have the impression that the December bird is slightly more extensively black in the primary coverts, and slightly blacker also on the head. The February bird (
http://www.hkbws.org.hk/BBS/view ... &extra=page%3D1) overall looks close to that from December.
Finally, there is an obvious difference in the extent of white in the closed wing between the February record (obvious white spots) and the April record (virtually no white). This may be related to wear, but if so the wear seems to have taken place much faster in the two months from February and April than in the two months from December to February (very little change).
So, I wonder how many individuals have actually been involved in the sightings this winter. We have assumed it is the same bird returning at infrequent and irregular periods, but could there have been different individuals over the course of the winter?
