Tuesday 1 March 2016

He Who Shall Not Be Named (in Newfoundland)

Identifying a gull as a Thayer's Gull in Newfoundland is not taken lightly. Finding a bonafide bird on this island that passes all the tests happens maybe a few times per decade. In the meantime, hundreds of gulls are seen that are thought to be Thayer's but fail to satisfy the strict criteria. This leads to a lot of frustration and many people (myself included!!) have thought they've found one only to be rejected.

Truth is that our criteria for a "real" Thayer's Gull is much more stringent than the rest of the continent. We get thousands of Kumlien's Gulls every winter and with their immense variation there are always a few that could easily pass as Thayer's in other provinces/states. But not here. And I tend to agree with these strict rules.

To really be happy with a Thayer's in Newfoundland, it has to go a few steps beyond the minimal requirements for that species and a few steps beyond the most extreme Kumlien's Gull.

That's what we're up against in Newfoundland. So today when Ed and I were scanning through a pure flock of 800+ Kumlien's Gulls I was excited to see one that popped out to both of us. It had a noticeably darker mantle and the primaries seemed significantly darker than ANY of the hundreds of Kumlien's. Having seen many Thayer's candidates over the years I knew we had to get photos to really be sure of anything, but something felt right about this bird right from the start. That gut feeling that you know you're finally looking at the real deal.

Can you find it in this flock? Answer at bottom of post:

Greenish base to bill rules out Herring Gull

Pale underside to primaries also rules out Herring Gull.

I've never seen a Kumlien's/Iceland gull that had a dark leading edge to P9 such as this bird

Hard to visualize in any of these photos, but another feature to look out for:
the white tongue extends down from the proximal end of the primary and merges with the white mirror (mirror = white circle on distal primary that is often surrounded by black)

The bird sticks out from the rest of the flock by the dark primaries, and more importantly, the slightly dark mantle!
While trying to refind the bird a few times we saw several dark-primaried Kumlien's Gulls that made us stop and think. But this bird has a darker mantle which no other bird has.

Now, three Kumlien's Gulls to help explain the main differences:

This bird from January 2015 was a promising candidate at first. Nice and dark primaries, with an apparent dark iris.

But in flight it was obvious it was "just" a Kumlien's Iceland Gull

A good example of the variation in Kumlien's Gull from Dec 2015. The closer bird has obviously darker primaries with a darkish iris.

Again, in flight it is missing the important clinching features of a Thayer's Gull

Another gull with dark primaries and apparent dark mantle in Jan 2016.

But again, fails to meet the spread wing criteria.

Eventually, with persistent observation you come across a bird that just feels like "the bird" upon first glance despite being notoriously difficult to identify.
A self-found Thayer's in Newfoundland is a major milestone for me in gull-watching!
It even got a thumb's up from the local gull guru (i.e. Bruce Mactavish) :)