Saturday 19 March 2016

How Crossbills Feed

Crossbills use their specially adapted bills to pry open cones and extract the seeds. They always use their lower mandible such that it points towards the axis/centre of the cone. This means that only part of the seeds can be reached easily depending on the birds position or if the cone can't be removed from the tree and turned around.

Check out how this bird pries open the cone scale with its bill. Click on the picture to see a much bigger version :)

In the next picture you'll see that the same bird has its LOWER mandible pointed towards its LEFT. 
Review the above photo and you'll see that the lower mandible is pointing towards the axis of the cone.

But only 50% of crossbills have their bills crossed in this way. The other half have their bills in the opposite orientation. This bird has its lower mandible pointing towards its RIGHT:

Studies have shown that there is an equal frequency of left-to-right mandible crossings within the crossbill populations. This minimizes overlap in the use of cones and maximizes foraging efficiency.

This adult male is a lefty:

While this adult male is a righty:

Crossbills are an exciting species to observe. They descend upon spruce trees in chattering flocks of a dozen or more, and are often very approachable while they busily pry the seeds out of the cones creating a light flurry of little winged spruce seeds that float to the ground around you.

There is often a wide array of colours visible in a single flock from bright yellow young males to the deep pinks and roses of adult males. The young males can be a blend of yellow and red, while the females are rather greenish-yellow. Juveniles tend to have bolder streaking on the flanks.

Check out this close-up video of a WWCR feeding on a cone to get an idea of how they pry open those cones!

Another interesting tidbit about White-winged Crossbills is that they breed very early in the year to take advantage of maximal cone supplies. With the high numbers of crossbills in Newfoundland this winter I've been expecting to see breeding evidence. So far I haven't found any signs yet - maybe someone will beat me to it?

Compare these two maps of White-winged Crossbill sightings from winter 2014-2015:

And winter 2015 - 2016:

Thursday 17 March 2016

Three Common Gulls in St. John's

Although we didn't quite realize it until this week, there have been three Common Gulls (the European sub-species of Mew Gull) in St. John's this winter. There have only ever been two seen at any one time this winter. The recent closure of the Pier 17 sewer outflow, has made it more difficult to keep track of our local Common Gull population.

Last winter there were 3-4 Common Gulls over-wintering in St. John's. Four individuals were actually photographed together in late March last year, but there's a chance that one of them was a migrant considering that Ring-billed Gulls start trickling back by late March.

These kinds of facts are only of interest to the few hard core gull watchers in town. But here are the 3 Common Gulls of winter 2015-2016 to demonstrate the variation and have a place to look back to when comparing with future sightings.

To start, this is the banded Common Gull. It was banded in St. John's in the winter of 2011/2012 as a second winter bird. That means it hatched in 2010, so it is now in its 6th winter (i.e. 7th calendar year of life).

It has a fairly distinct ring near the tip of its bill.

In flight, we can see a large mirror in both P9 & P10, as well as a small mirror in P8. This mirror crosses the shaft but doesn't quite meet the outer edge of P8.

Bird #2:
The second bird has a similar wing tip pattern, but has significantly brighter yellow legs with no band on its leg.

Bird #2: has a large mirror in both P9 & P10, as well as a small mirror in P8. This mirror DOES NOT cross the shaft so it is limited to the inner half of the feather. There is also a complete dark band across the distal end of P5.

Bird #3:
 Also has bright yellow legs, but not nearly as distinct of a ring near the tip of the bill.

In flight it has no mirror on P8.

Bird #2 has been seen as far away as Kelligrews, a distance of almost 30km from Quidi Vidi lake.

Saturday 12 March 2016

Winter Birds of Lumsden

I arrived in Lumsden this morning 10 minutes before official sunrise, after sleeping less than 1km from the towns outer limit. My main goal was to see the elusive Fieldfare that had been here for over a month! I knew it would be a hard bird to get based on the experiences of others.

As expected there were a lot of birds in town. Mostly redpolls, with at least 80 at one of the local feeders. They gave some easy entertainment while waiting for the Fieldfare to show its face.

There are two sub-species of Common Redpoll. The more Southern (and more expected) flammea, and the more Northern rostrata sub-species (which breeds on Baffin Island & Greenland). Jean Irons has a good summary of these sub-species here.

This flammea Common Redpoll demonstrates the pink breast and forehead, although it is a little more exuberant than the average. 

Compare that pink colour with the blood-red forehead of this rostrata Common Redpoll:

The difference in forehead colour isn't the only unique thing about this sub-species. It is notably larger, and has a darker complexion over much of its body. To me, it seems like the underlying colour is more brown versus the white of the flammea redpolls.

True to form, the Fieldfare was extremely wary and only showed its face for a total of 2 minutes despite an all out 6+ hour manhunt.

Check out this video of a River Otter skating across a frozen bay:

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) :)