Re: American Oystercatcher(?)


David Trissel
 

OK, I’ve had time to compile the many submissions (actually only one) of Jehl Scale ratings on the bird. Due to confidentiality, I am not going to disclose the author without his permission, but I wanted to close the loop and let everyone know what the experts are saying.

First, the Jehl scale:

---------------
Jehl considered birds with character scores from 0-9 Black, 10-29 hybrids, and 30-38 American.
Upper tail coverts		0	black, as in bachmani
				1	black, a few white mottlings
				2	nearly equally black and white
				3	white, a few black mottlings
				4	white, as in palliatus

Tail				0	black, as in bachmani
				1	mainly black, trace of white at base of vanes
				2	basal quarter of rectrices white
				3	basal third of rectrices white
				4	basal half of rectrices white, as in palliatus

Chest				0	black, with black chest band extending smoothly onto mid-belly, as in bachmani
				1	black chest band extending onto upper third of belly
				2	black chest band extending onto upper quarter of belly
				3	black chest band bordered by ragged edge on upper breast
				4	black chest band sharply delimited from white of upper chest, as in palliatus

Belly				0	blackish, as in bachmani
				1	blackish, with traces of white on a few feathers
				2	blackish, white area around crissum
				3	three quarters black, one quarter white
				4	nearly equally black and white
				5	three quarters white, one quarter black
				6	entirely white, as in palliatus

Under tail coverts		0	entirely black, as in bachmani
				1	mainly black with slight white mottling
				2	nearly equally black and white
				3	mainly white
				4	entirely white, as in palliatus

Thighs				0	entirely black, as in bachmani
				1	black with grayish underdown, not noticable externally
				2	puffs of grayish down noticeable
				3	mainly white
				4	entirely white, as in palliatus
	
Greater secondary coverts 	0	lacking, as in bachmani
   (width of white edging	1	less than 2 mm
   in folded wing)		2	2-5 mm
				3	6-15 mm
				4	more than 15 mm

Extent of white wing stripe	0	lacking, as in bachmani
				1	white markings confined to inner half of secondaries
				2	white markings extend to outer secondaries, but not onto primaries
				3	white present on some or all of inner five primaries
				4	white present on at least one of primaries 6-10

Underwing coverts		0	entirely black, as in bachmani
				1	mainly black, some white mottling
				2	nearly equally black and white
				3	mainly white
				4	white, as in palliatus
	
Axillars			0	black, as in bachmani
				1	mainly black, some white mottling
				2	nearly equally black and white
				3	mainly white
				4	white, as in palliatus	
———————

Now, the ratings received on the July 9 bird:

Upper tail coverts	(1-2)	
				1	black, a few white mottlings
				2	nearly equally black and white

Tail			(1)	
				1	mainly black, trace of white at base of vanes
Chest			(3)	
				3	black chest band bordered by ragged edge on upper breast

Belly			(6)	
				6	entirely white, as in palliatus
Under tail coverts	(3)	
				3	mainly white

Thighs			(4)	
				4	entirely white, as in palliatus
Greater secondary coverts (3)	
   (width of white edging	
   in folded wing)		
				3	6-15 mm
				
Extent of white wing stripe (1)	
				1	white markings confined to inner half of secondaries
				
Underwing coverts	(3)	
				3	mainly white
				
Axillars		(4)	
				4	white, as in palliatus	

	Total = 29 or 30
That puts the bird squarely in … well, I don’t know. 29 is considered a hybrid and 30 is considered an American.

In discussion with others, all admittedly NOT experts, there is possibly some white specks on the outer secondaries and/or primaries. If that is true, then the rating jumps up well into the American range.

At this point, you could stop and draw your own conclusion and not read any further. The pictures are very good and the Jehl Scale can be used to rate this bird along the lines of the above.

— Everything below here are just my notes on what I have learned in doing this exercise —

I’m embarrassed to say that I have looked at far too many American Oystercatcher photos on eBird over the last few days. Of the 29,763 photos in eBird (just American Oystercatcher), the vast majority are of the “normal” Haematopus palliatus. I was most interested in the “fazari” subspecies which is most likely to show up in California. So, narrowing down to just Mexico, there are 544 photos. Narrowing it further to the west Mexico (Nayarit, Sinaloa, Sonora, Baja and Baja Sur), you get down to 84, 69, 127, 73, and 52 photos respectively. So, about 400 photos.

Some observations:

1. H. palliatus fazari definitely have “hybrid” characteristics that look like Black Oystercatcher genes are mixed in there. Now, whether those are “ancient” hybrid genes from back when Black and American were closer or if they are “new” hybrid genes is debatable. For this discussion, we will accept that Haematopus palliatus fazari is American Oystercatcher. Regardless, on H. p. fazari, you’ll see a ragged line between black and white on the chest and the black extends lower towards the belly than in H. palliatus. You’ll also see less white on the upper wings and some slight mottling on the front edge of the underwing coverts. The upper tail coverts are a mix of black and white.

2. Nearly all of the photos of west Mexico appear to be H. p. fazari. The extent of white wing stripe almost never appears on the primaries (so far I found one in Baja and one in Nayarit that had a small white mark on a primary). The white appears to be restricted to the upper wing coverts and, as a rule, is not on the secondaries or primaries. So, if that is true, nearly all fazari would get a Jehl score of 1  for that characteristic. NOTE: I found a Sonora photo of 11 in flight together and not one of those birds shows any white in the primaries.

3. Underwing coverts - H. p. fazari, almost as a rule, appear to have some brown mottling on the leading edge of the underwing coverts. But, even some otherwise “pure” H. palliatus (NY, CT, MA) show a little brown on that leading edge. NOTE: I found a New York photo of 5 in flight together and at least 3 of them have that same characteristic. 

4. I think the biggest marks against the July 9 bird being an American are the upper tail coverts and the tail. If those two characteristics alone were the determining characteristics, I think you’d have to conclude this is a hybrid. Otherwise, I think one would be hard-pressed to say the other characteristics do not fall well into the fazari range.

5. In looking at the photos of the July 9 bird, the May 13 bird, and the April 8 bird, the July 9 bird is the “cleanest” of the three and has the best photos of the main Jehl scale characteristics. The April 8 bird is VERY similar and has just a little more black extending in a V shape further down the chest, but otherwise looks nearly identical to the July 9 bird.

I would love to hear what others think. I welcome a lively and constructive discussion. 

Sincerely,

David Trissel
San Diego, CA


On Jul 9, 2021, at 5:13 PM, David Trissel <dtrisse1@...> wrote:

Here’s a link to a Flickr album with Mandy Etpison’s photos: https://www.flickr.com/photos/62366066@N02/shares/37cUc2

David Trissel
San Diego, CA

On Jul 9, 2021, at 4:13 PM, David Trissel <dtrisse1@...> wrote:

OK, since it’s the summer doldrums and we have nothing better to do anyway, let’s have some fun with the Oystercatcher found this morning by John Dumlao and then subsequently photographed by a few folks. The bird was originally found at 6:23-ish at the Point La Jolla Seawatch spot, standing on the rocks below. It flew south past Children’s pool and landed about a 1/3 mile south of there out on a point where it stuck around for 30 minutes until a guy and his dogs went out on the rocky point and chased it off. It flew south but then returned to the flat rocks below the cliffs, again about 1/3 mile south of Children’s.

 I don’t know if Mandy Etpison’s photos attached below will come through (this group email system tends to strip them) but they are spectacular. If they get stripped I’ll see if I can get and post a link to them.

DAB DAB checklist with good flight shots: https://ebird.org/checklist/S91488528

John Dumlao checklist with one flight shot: https://ebird.org/checklist/S91496254 

My checklist with description and distant and far less professional pics here: https://ebird.org/checklist/S91494335

For those of you (like me) that are interested in the Jehl Scale and how American Oystercatchers are rated by the experts, here it is: https://fog.ccsf.edu/~jmorlan/jehl.txt

I’m not an experienced at rating American Oystercatchers, so I’ll only weigh in with my two cents in a follow-up email.

Enjoy!

David Trissel
San Diego, CA


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