Prothonotary Warbler

Prothonotary Warbler

Friday, 5 December 2014

What kind of bird is this.....are you sure?

I've been a little behind in posting this. It all started about a week ago, when I posted some shots of swans and geese taken in the fields of the former Dover Township, between Chatham and Lake St. Clair. A couple of shots showed what I determined to be a juvenile Ross's Goose. The photos weren't definitive, but in combination with what I saw in addition to the photos, I was convinced (and still am) that it was a Ross's Goose.

A former MNR colleague who specializes in, amongst other things, northern geese and swans, sent me a message making some comments on it. I wanted to get some additional photos to be more definitive, and indicated that I would be going out again to see what I could find.

This past Wednesday, December 3, I returned to the scene. However things had changed in the several days between visits. Once the corn fields were harvested, farmers set about to plow or disc them. So instead of the 15 or so fields I had seen on Nov 28 with swans and sometimes other assorted waterfowl. the choices were limited. I only saw 3 fields with swans, although one was in fine condition and had upwards of 1000 birds. This was right along Belle Rose Line, a bit east of St. Clair NWA.

I looked and looked over the swans, but did not see any small white goose.

It was quite windy, and small flocks of swans were arriving steadily while I watched.

But after awhile, I decided to see if there were other fields harbouring my target small white goose. So I moved on.

As mentioned, there were only a couple of other fields with swans, and even then only a few, so I didn't have any greater success at those fields.

But I did notice other white birds.....Snowy Owls.

One field alone had three Snowies, with yet a fourth only a few hundred metres away across the small creek. Yet another field well away from this concentration had another individual. All were sitting tight close to the ground. Perhaps the very windy conditions caused them to sit low and tight, and I likely missed others.

None of them were as close as I wanted them to be....they never are! While I was watching one individual, it got up and flew a short distance farther into the corn stubble, heading into the sun. I got a record shot, but the light was poor as was the angle of shooting from the car.

Eventually, I decided to meander on back to the main field of swans. The days are just too short! And there were even more birds arriving. Usually at the end of the day, swans that have been feeding in the fields return to the lake to spend the night. But presumably the 40-60 km/hour winds were keeping the lake surface a bit riled up, and so the swans were heading inland for the night.

I watched and watched, and was about to pack up and head for home. The sun had already set, as one can see from the slightly rosy hue on the swans in the previous photo.

And then a small group of swans arrived, with a small white goose with black wing tips out in front!

This is a fairly heavily cropped photo, and again, one can see the pink in the sky indicating the lateness of the afternoon. The fading light made it more challenging to get the photo I was hoping for. To keep the shutter speed to an acceptable level of 1/640 sec, I had to shoot wide open at about f/4 and with an ISO of either 800 or 1600, certainly higher than I normally like on this particular camera body (7D). But at least they landed more or less in front of me, so I got some more distant shots which I could, and did, crop.

Clearly this was a different bird than the juvenile bird I had seen the previous week. This clean white bird is obviously an adult. It is small enough for a Ross's Goose. There is no 'grinning' patch on the bill, although it may not be really obvious from these two photos. The bluish base of the bill also fits Ross's Goose. The only thing that doesn't fit well for Ross's is the longer beak and more sloped forehead than one would expect. It isn't always easy to get all the salient features well represented in a photo. Ideally one needs to study the bird from different angles, especially when the characteristics don't fit nicely.

I sent three of the photos to a former MNR colleague, who has a Ph. D involving waterfowl, especially geese, of the far north. He in turn sent it to another former MNR colleague, who is an excellent field biologist and birder. He also sent it to another Ph. D. researcher with the American Museum of Natural History, who specializes in Snow Geese of the northern latitudes. I also sent it to another former MNR colleague who did his Ph. D. in researching geese both in the northern latitudes and also on their wintering ground. Two of the aforementioned individuals spent many years as the waterfowl biologist with Moosonee District. So clearly all of these gentlemen had a lot of first hand experience with this species and any other goose species of the northern latitudes.

It took a couple of days to get the responses, hence this post is a little later arriving on my blog than I would normally plan.

Their responses were interesting. They ranged from:
-clearly a hybrid between Ross's Goose and Lesser Snow Goose
-definitely a Ross's Goose
-strongly would consider it being a Lesser Snow Goose

In the face of the varied opinions of these experts, and they are very much experts, it pointed out something that I've known for quite some time: viewing one or two photos, if they don't illustrate all the important and therefore clinching features, makes it difficult to be 100% certain of a bird's identity. One needs to study a bird first hand to really get a true feeling of how a bird behaves and how it looks from various angles.

So what do I conclude?

Being the only person to have seen this bird in real life and under better conditions that the two photos show, I do feel that it shows a lot of Ross's Goose characteristics: the very small size (less than half the size of a swan), the lack of a grinning patch and the bluish base to the bill all nicely fit Ross's Goose (I saw several white Snow Geese just yesterday at Ridgetown Sewage Lagoon, and they were definitely larger and the grinning patch was evident even from a distance). However, and herein lies the difficulty in declaring it a pure Ross's Goose, this bird also shows some characteristics that don't fit, primarily the longer bill and more sloped forehead. A 'good' Ross's Goose has a stubbier bill, and a more abrupt forehead, not a sloping one.

Therefore, this bird is almost guaranteed to have some Snow Goose genes in its heritage, but there is no way of telling how many generations one has to go back to determine when that happened. And it is possible that those genes came into the mix on more than one occasion. Snow Geese and Ross's Geese are known to hybridize, so overall it isn't surprising that this bird shows some traits of both.

So there you have it....I think one can safely say this bird is a hybrid.

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