La Jolla oystercatcher: "pure" or hybrid?


lehman.paul@verizon.net
 

As has been alluded to only slightly to date, the American-type Oystercatcher in the La Jolla area the past few days and then also back in earlier April (may or may not be the same bird) is currently the subject of some debate over its "purity." Some birds that look partly or mostly like American Oystercatchers in CA and nw. Baja are hybrids. Some are "acceptable" Americans. The way one attempts to figure out where to somewhat artificially "slice the pie" is to use the "Jehl scale," named after Joe Jehl (Dan's dad). A number of characters are scored on the basis of the amount of dark or white present, and then the total score means it's an OK American if over some number (30+), and hybrid if under that number (<30). But again, this is a somewhat artificial designation. Some of the characters one scores are the breast band sharpness, thighs, rump, undertail coverts, underwing, and wing-stripe length and thickness. Using photos taken of the early April bird by Pawlicki and Sadowski, a couple folks came up with a Jehl score of 27-28, thus calling it a hybrid, whereas somebody else came up with about a 31, just inside the allowable American camp. So, this bird is a close call, but it seems as though if called an American, it should be with quotation marks around it--"American" Oystercatcher--at least given the current state of discussion.

This morning, another Olive-sided Flycatcher to add to the good county-wide spring total was at the main Dairy Mart Pond.

--Paul Lehman, San Diego


Joe Morlan
 

Another angle on the Jehl scoring scale and its implications here:

http://creagrus.home.montereybay.com/CAbirdsAMOY.html


On Fri, 14 May 2021 15:01:57 -0700, "lehman.paul@verizon.net via groups.io"
<lehman.paul=verizon.net@groups.io> wrote:

As has been alluded to only slightly to date, the American-type
Oystercatcher in the La Jolla area the past few days and then also back
in earlier April (may or may not be the same bird) is currently the
subject of some debate over its "purity." Some birds that look partly or
mostly like American Oystercatchers in CA and nw. Baja are hybrids. Some
are "acceptable" Americans. The way one attempts to figure out where to
somewhat artificially "slice the pie" is to use the "Jehl scale," named
after Joe Jehl (Dan's dad). A number of characters are scored on the
basis of the amount of dark or white present, and then the total score
means it's an OK American if over some number (30+), and hybrid if under
that number (<30). But again, this is a somewhat artificial designation.
Some of the characters one scores are the breast band sharpness, thighs,
rump, undertail coverts, underwing, and wing-stripe length and
thickness. Using photos taken of the early April bird by Pawlicki and
Sadowski, a couple folks came up with a Jehl score of 27-28, thus
calling it a hybrid, whereas somebody else came up with about a 31, just
inside the allowable American camp. So, this bird is a close call, but
it seems as though if called an American, it should be with quotation
marks around it--"American" Oystercatcher--at least given the current
state of discussion.

This morning, another Olive-sided Flycatcher to add to the good
county-wide spring total was at the main Dairy Mart Pond.

--Paul Lehman, San Diego





--
Joseph Morlan, Pacifica, CA