Bean Geese (7) - there they are, finally

Yesterday, Lützen Portengen found minimal 35 Taiga Beans in a flock of Tundra Beans near Udenhout, Brabant. This afternoon, I observed the group for more than two hours. Here some pics on which I will comment later.

Warning: these pictures also include several Tundra's, two orange-billed 1w Greater Whitefronted and other stuff! Have a look...

Two juvenile albifrons with orange bills. Are they F1 hybrids of a pair of rossicus x albifrons? I couldn't find their parents.

All Taiga Bean fabalis foraging in line, as they did the whole time at the edge of the big flock of rossicus.

Mix of rossicus and fabalis. 12 of the latter. Note the more slender structure and bowed necks of the birds from the Taiga!

Another part of the line of fabalis also mixed with most rossicus. The Taiga birds didn't move a lot.

Some just landed albifrons and rossicus in front of the massive group.

Some rossicus with two orange bills. Don't think it are fabalis. I followed these birds after landing and concluded that it were two males with type B bills!

Neckband from Germany.

Two fabalis, just one visible at left.

Alert at the background! Part of the line.

Alert male with a type A bill. Some more fabalis around, but not visible.

Interestingly, the little yellow-billed bird at the left was paired with a straight fabalis. That must be a female! The birds in the centre are more straight forward.

rossicus: 1w, ad male type B, ad, ad, ad

The same group.

Can you do it by yourself?

Bean geese (6) - an interesting pair on Shetland

Again some very interesting pictures of Shetland. Roger Riddington commented on these by e-mail:

On 1st February, a message went out on our grapevine about two Taiga Bean Geese, and that evening some pictures appeared on one of the Shetland birding blogs (http://www.shetlandbirding.blogspot.com/). See entry for 1st Feb (best to ignore some of the comments in the text).

I was intrigued by the pictures on the web since they seemed to show a rather skinny-billed bird that looked similar to the adult female Taiga in the group we corresponded about in December – whereas the other bird looked to have a bill structure more like Tundra. Anyway, a couple of days later I managed to get out of the office for a couple of hours and went to see them. In real life I was struck by two things – 1) that overall, in terms of overall size, body shape and structure etc, the two birds were pretty similar. I could see why people thought they were both the same form (and some people are of the view that they are both Tundras!). But through a telescope, the bill structure looked quite different, to me. The orange-billed bird has a much more slender bill, with a more or less entirely straight cutting edge to the upper mandible, a very slim, flat lower mandible, and I would say a bill depth at the base which is slightly but distinctly smaller than the second bird. The stripy-billed bird has a bill that is about the same length, but is deeper at the base, with a much deeper base to the lower mandible, and a very distinct curvature to the cutting edge of the upper mandible.

Based purely on bill structure, I felt that the ‘best fit’ solution was a petite female Taiga and a big male Tundra. But I can see that when you have two vagrant birds like this it is more often going to be the case that they are the same form. The similarities in overall shape and size was also confusing. I would hesitate to say that the two were ‘paired’ but they were certainly together the whole time I watched them – if anything, the stripy-billed one was slightly larger/heavier and perhaps spent a little more time alert – reinforcing my tentative view that it might be a male.

The light wasn’t great, so my pictures are again a bit grainy and distant – but if you felt able to comment I would be interested in your opinion.

All the best,

Roger

This is one of the bills you wouldn't expect on such a body! 

Hi Roger,

Thanks again for sending me these pictures. Your description is quite complete. The only thing I would say: yes, this is a pair of fabalis and the male has a type D bill. 10% of fabalis has this colouration.
It would be strange to seperate the birds into two species, since their is no known record of an hybrid pair of fabalis and rossicus (Heinicke in litt) and they behaved as a pair.

Except the bill, everything on this bird points to a classical, rather big Taiga Bean. Still, the variability of the billstructure in both rossicus and fabalis isn't described and depicted properly in the literature.
Thick lower mandibles like this male has, are very rare in fabalis. Pro fabalis is the concave culmen and the overlapping tip of the upper mandible. But such an deep and bowed base of the lower is
surprising. Note that the orange bills always look a bit more slender as the result of a kind of visual effect.

These pictures do stress my vision to have a databank once, with hundreds of heads 'en profile' of both species to depict their variability. For example, have a look at those pure fabalis flocks: http://www.birdphotos.dk/index.php?view=category&catid=910&page=3&catpage=1&option=com_joomgallery&Itemid=3&lang=en
Thanks, best regards,

Albert
 

Aging Bewicks Swans

Two years ago, I got an e-mail from Adri Clements about second winter Bewick's Swan.  Two years later, I have seen some birds he mentioned. Their plumage is slightly different from adults, since they have left some grey feathers in their neck and on their head. Also, the yellow part of the upper mandible is a bit paler. In good conditions, you can seperate them from adults. Unforntunately, I don't have pictures of second winters yet. But recognizing this plumage is important to measure the survival rate of the species. 

Still from 28 January 2012 -first winter

Another interesting thing is the difference in moult in first winter birds. They start moulting in December, beginning with the scapulars and underparts. Some birds still show an almost grey plumage at the end of the winter. Others have replaced up to 80% of the scapulars and most of feathers the belly and head. Have a look at this short video:

Iceland, Glaucous and Caspian Gulls - interesting feathers

Gulls have never been in the Dutch spotlights as they are right now. Since the influx of Iceland Gulls in Western Europe and the appereance of a possible American Herring (smithsonianus) in our country, Gullfeathers are hot!

Yesterday, Theo and I went to Den Oever, Noord-Holland to visit the candidate third-winter smithsonianus that is present for more than a week now. In this topic the bird is still in debate, but the opinions are a bit turned to the side of: close, but no sigar. Peter Adriaens has been studying a while on this taxon, and made clear that there are some  points against a good smithsonianus:

a. It does have 'straight, horizontal upper borders to the black pattern on both P6 and P7' (citation).
b. It doesn't have solid, black or darkbrown markings in the secondaries or adult-type secondaries.

Only the left wing is adult-type and could be used to interpret the pattern. (Albert de Jong)

In the field, the bird looked rather small. Is it still in the range of third winter smithsonianus or just an argentatus with a pattern we rarely see? If you like to read more about this interesting topic, note these pages on the ORG-site. Or have a look at these pictures.

Also, this giant white one was present in the same harbour.  The ID of this bird is without any doubt a second-winter hyperboreus. I think the Latin name tells something about the bird?

Larus hyperboreus - Glaucous Gull, 2w male (Albert de Jong)

After Den Oever, we visited the harbor Urk to look for the reported adult Glaucous Gull and the second winter Iceland Gull. Only the latter we found, and also four Caspian Gulls (two 1w, one 2w, one ad) and a Yellow-legged Gull. 

Cachinnans and argentatus

Larus cachinnans - Caspian Gull - adult

Larus cachinnans - Caspian Gull -2cy

The Iceland Gull shows brown shadings in the outer primaries. More birds with shadings (but without a dark hockeystick pattern towards the tips and a ghostmirror in p10) in the primaries have been reported and are presumed dark glaucoides rather than pale kumlieni. More about this interesting topic could be found here and on the blog of Chris Gibbins.