Dear Chatters, tweeters and obolers:

The observations of Yellow-legged gulls, hybrids, and weird stuff mentioned
in birdchat has me salivating! Gull watching in North America is getting
seriously interesting. Another potential Kelp Gull, wow!
Yesterday I had the opportunity to go birding with Nial Moores a Brit
who has been living in Japan for four years, and doing a lot of birding
both there and in South Korea. It didn't take long to realize this guy
was both really sharp and a gull 'freak'. We went out around the Vancouver
area for a few hours looking for gulls. All we talked about was gulls,
gulls and more gulls, it was a joy.
We started out near Boundary Bay looking for the large flock that
roosts in the fields, this is the flock where I found a Slaty-backed a
couple of weeks back. We found the flock and located the Slaty-backed and
a couple of Westerns in with all of the Glacous-winged and hybrids. Once
he had studied the Slaty-backed Gull, he mentioned that the bird was
totally typical in every respect except the fact that it was in a field.
In Japan, Slaty-backed is seldom found away from rocky coasts! He noted that
the mantle colour was totally typical for Slaty-backed. Referring to
the recent paper by Mary Gustafson and Bruce Peterjohn (Birding XXVI:243-
249, 1994) that outlines the variation in mantle colour in Slaty-backed,
I qualified his statement by asking if he meant typical to mean average.
He replied, no typical because they don't vary in mantle colour! Now I
was confused. His experience looking at thousands upon thousands of
Slaty-backed Gull in the field was that they are quite standard in mantle
colour, at least in Japan and Korea. When he has found paler birds, upon
closer examination they have turned out to be dark Herring Gulls! In
Japan, they get several forms of Herring in winter, with vegae being the
most common. Fortunately, I had brought the article with me and showed it
to him. He was amazed and very incredulous. He disagreed with the statement
that vegae 'may be paler or darker than a pale Slaty-backed Gull' (caption
on figure 7. His observations are that vegae are always paler than slaty-
backed, darker Herring Gull types he has seen in Japan are birds from
further west (tamyrensis and mongolicus???). We studied the article, especi
ally figure 6 which shows the range in Slaty-backed. I noticed something
really odd. The two bird on the left, the dark ones have streaked heads,
the two on the right have pale heads. This implies that the two birds
on the left were taken in winter when they have less worn plumage than
the birds on the right. The primaries on Slaty-backed are black, so now
look at their colour in the photo. The two birds on the right have paler
primaries than the birds on the left, roughly paralleling the paleness
differences of the mantle. All of this suggests that the birds on the
right are paler due to wear, not due to variation in the mantle colour.
This would fit his interpretation of Slaty-backed mantle colour. The
article does show some variation in mantle colour of wild birds, but to
some extent this may be due to the angle of the birds in the photo. Have
a look at figure 4, the darkest bird appears to be most perpendicular
to the observer. The bird in front is turned somewhat toward the observer
, note that the sun is to the left. The tertials and hind scapulars look
paler on this bird, but likely because they are more perpendicular to
the rays of the sun. The two bird in the background are turned even more
perpendicular to the direction of the light and they look even paler. The
bird in figure 5 looks pale since the light is coming from behind the
photographer, check out the shadows.
I don't mean for this posting to be an attack on the paper, I think
it has been greatly useful in educating us about Slaty-backed Gulls. Yet,
Nial's comments suggest that something weird is going on. I have several
friends that have spent lots of time in Alaska and they mention that there
are lots of dark mantled birds they cannot identify up there, they have
thought that these birds may be hybrids (which has not been observed anywhere
as far as I know) with Herring Gull as they are paler than good slaty-backs.
Nial suggested that we may be overlooking other subspecies of Asian
Herring Gull here in North America and passing them off as Slaty-backs.
He noted that Mike Force's shot of a bird here in Vancouver (Figure 3) looked
rather un-slaty backed like. Could this be a different Herring Gull type?
Aparently the situation with Asian Herring Gulls is much more complex
than what is mentioned in Grant. This is the observation of Japanese and
Hong Kong birders, the Herring Gulls in Hong Kong have recently been
realized to be of a completely different subspecies than they had thought
before, I wish I had written down the exact details.

Well all of this has really 'rocked the foundations' of my gull watching
assumptions. Does this frighten me? No way, now I want to watch more gulls.
I hope that these comments may incite some good gull discussions.

good.birding

sorry to all of you e-mail fanatics that are on all three groups, I thought
it was relevant to the three of them.
Al Jaramillo
jaramill at sfu.ca
Vancouver, B.C.