On Thursday, 27 March 2003, Dan Singer and I visited the collection at the California Academy of Sciences to analyze their Nutting's and Ash-throated Flycatcher holdings. The CAS has 23 specimens of Nutting's, but only four (CAS #s 76757, 72031, 63995, and 42261) were collected in mid-winter. All were of the subspecies Myiarchus nuttingi inquietus. Peter Pyle and Steve Howell were at the Academy and assisted us briefly with the specimens and helped answer some questions.
Wing Formula
First we analyzed wing-formula. All had more-or-less similar wing formulas as follows:
10 <<< 9 < 8 = 7 > 6 >> 5 >>> 4 > 3
P10 is short, p8 is usually the longest with p7 and p6 almost equal or slightly shorter, then a noticeable gap between p6 and p5 and a larger gap between p5 and p4. Ash-throated flycatcher skins showed a similar wing formula. One difference is the position of p9. On Nutting's p9 falls noticeably short of p8 while on Ash-throated p9 is closer to p8. Unfortunately the position of p9 is not visible on any photos of the Santa Cruz bird. It can be seen on the photo of the Arizona bird on the cover of "Field Notes" for the 1997-98 Winter Season. Emargination was present on p9 through p5 on both species. CAS #76757 shown at right.
Primary Projection
Nutting's seemed to show a shorter primary projection than Ash-throated. However, the difference was not always pronounced or obvious. Steve Howell advised against assessing this character using skins prepared by W.W. Brown, because the feathers are reported to have been pulled unnaturally in those specimens. See photos of rump below.
Secondary Pattern
The Nutting's consistently showed a more extensive rust and yellow pattern on the secondaries than did Ash-throated. The pattern on s1 was similar on both species, although some Ash-throated has less rust than others. Only one Nutting's showed a secondary pattern similar to photos of the Santa Cruz bird. It is CAS #72031 collected by W. Rook at Puerto Escondido, Oaxaca on 9 November 1964. Photo below, right. However, that specimen has a notably longer, thinner bill than the other Nutting's and its tail pattern was more consistent with Ash-throated Flycatcher. We feel the specimen was probably misidentified and made a note so indicating on the label.
Bill Shape
The bills of the Nutting's (except for CAS #72031 noted above and shown to the right) were consistently shorter and thicker than those of Ash-throated. In my opinion, this was one of the more striking differences visible in the specimens.
Chest Pattern
Most Ash-throated showed a pale or whitish area between the gray breast and yellow underparts. This rather subtle character was absent on all of the Nutting's (except for CAS #72031 noted above where it was very evident).
Nape Pattern
Most Ash-throated showed a more obvious contrast between gray nape and brownish crown. This contrast was absent or faint on Nutting's (See photos below). Ash-throated also showed more gray in the lores and sometimes across the forehead, but some had head patterns similar to Nutting's.
Rump Color
Most Ash-throated showed a colder brown color to the rump compared to the warmer reddish color on most of the Nutting's. We did not attempt to quantify this further, but did take photos that show the difference. Nutting's left; Ash-throated right.
Tail Pattern
Both species are quite variable. In general Nutting's has the dark on the outer web cross the feather shaft all the way up the feather while on Nutting's it crosses the shaft only toward the tip of the feather. Again CAS #72031 was an exception with a more Ash-throated like tail pattern.
Conclusions
Lanyon's statement about the difference in the amount of rust on s1 is not supported by our specimen research. The secondary pattern shown by the Santa Cruz bird seemed more consistent with Ash-throated Flycatcher. However, it was also consistent with Lanyon's descriptions of Nutting's and perhaps a larger collection of Nutting's would show more variation.
In my opinion, the size and shape of the bill of the Santa Cruz bird is consistent with Nutting's, and not Ash-throated. The chest pattern, nape pattern, and rump color seemed to me to be better for Nutting's, but it is difficult to draw firm conclusions from the specimens we examined.
The most compelling argument for Nutting's remains the voice.
Acknowledgments
Thanks go to Dr. Douglas J. Long for allowing us access to specimens in his care and to Steve Howell and Peter Pyle for assistance with the specimens.