40-B-2018 Rusty Blackbird

STATUS
Pending
HOW MANY OBSERVED?
1 - adult, sex uncertain
DATE SIGHTING OCCURRED
DATE REPORT PREPARED
REPORTER
Jon Curd
OTHER OBSERVERS
Jon Curd (discovered bird)
Cheryl Huizinga (arrived a little over an hour later after initial discovery)
RL Rowland (about 4 hours after initial discovery and with me, Jim James, & Cheryl)
Jim James (same as above, ~4 hours later)
LOCALITY OF OBSERVATION
Blacks Creek Birding Preserve, Ada County
SE side of reservoir, right alongside the shoreline.
HABITAT WHERE THE BIRD WAS OBSERVED
Muddy edge of the reservoir, with lots of "smart weed" intermixed along the water's edge.
SIGHTING DURATION, CONDITIONS, and EQUIPMENT USED
Initially seen for about 15 minutes; then again about 4 hours later, with 3 others, for about 15 minutes again. Cloudy skies, one brief period of sunshine. Lower 40's and fairly calm wind conditions. Bird was at close range, often within 10 yards.
Binoculars: Vortex Talon, 10X42
Camera: Digital Panasonic Lumix, 25-400 lens
Spotting scope: (bird was too close to utilize)
DID YOU TAKE NOTES?
No, not at all
DID YOU CONSULT A FIELD GUIDE OR OTHER REFERENCE WORK?
Yes, during the observation
Yes, later the same day
WHICH GUIDE(S) OR REFERENCE(S): DID YOU CONSULT?
Sibley's "Guide to Birds" (2000)
iBird Pro, North America (electronic bird app, original 2008, but updated on a regular basis)
eBird photo gallery
DESCRIPTION OF THE BIRD(s)
Definitely in the blackbird family (Genus: Euphagus). Very pale eye, set in a dark eye-patch was very striking. Very buffy and distinct eyebrow. Top of head, just below the black of the eye area, and back were all fairly rusty colored. Throat, breast and upper belly were a buffy color, similar to the eyebrow. There was some occasional black mottling mixed in with the buffy chest/belly. The primaries, tail and lower belly were mostly black, but edged with rust on the primaries and paler edging on the rump and vent areas. The rump was fairly covered by the folded wings and appeared to be dark.
BEHAVIOR OF THE BIRD(s)
Vocalization was an often repeated, fairly harsh, "check" call. After the initial observation/photo period, I walked about 30 yards away and pulled up my iBird Pro app and listened to the call note of rusty blackbird; the bird immediately flew from its location to me, landing just a few yards away. I observed it gleaning some sort of food source from the smart weed and alternated walking along the muddy edge and occasionally picking things from the mud. On the second observation period, it did fly off and do a large circle and landed back again along the waters edge. I failed to note flight pattern, but seemed typical of blackbirds. During the initial observation period, there was a female red-winged blackbird moving around with the subject bird, but it was feeding alone later when I observed it with the additional 3 persons, in the same general vicinity.
HOW AND WHEN DID YOU POSITIVELY IDENTIFY THE BIRD, AND WHAT CLINCHED THE IDENTIFICATION FOR YOU?
At my first sighting I just assumed juvenile or molting Brewer's blackbird, but I was so struck by the overall paleness/rusty color of the bird, that I followed it and took many photos, starting to suspect Rusty blackbird. Shortly after the encounter, I returned to my vehicle and consulted Sibley's guide and was fairly certain at that point. I put a quick note out on Facebook (Idaho Rare Birds & Discussion group) and got several positive/affirmative comments back from some of Idaho's renown Ornithologists.
HOW DID YOU ELIMINATE SIMILAR SPECIES? WHAT WERE THEY?
The only really similar blackbird, with a pale eye, was Brewer's blackbird. Sibley's shows no rusty edging on the primaries, or the rump and vent areas on Brewer's, nor the buffy and rusty colors present on this bird.
WHAT IS YOUR EXPERIENCE WITH THIS (AND SIMILAR) SPECIES?
Only once prior in basic plumage (Salt Lake area, Dec. 2016). Often seen in breeding plumage in Alaska over a 25 year period.
DESCRIBE YOUR GENERAL BIRDING EXPERIENCE
~40 years of birding; much of it on a semi-serious level.
ADDITIONAL INFORMATION (If any)
Cheryl Huizinga also obtained many photos and a video of the bird and would be happy to share them with the committee. Here is the link to her checklist: https://ebird.org/view/checklist/S49589051
After checking several other reference later, I'm still on the fence as to whether a male or female. A juvenile lacks the pale eye (Sibley), so it is an adult bird. The plumage seems to align almost perfectly with a female: much buffier and rustier than the male, with much less black intermixed into the breast, belly and back, and a much more pronounced eyebrow. The only thing lacking is the gray rump. I've included several photos of the rear of the bird, but as far as I can tell, the rump is fairly dark to black, but I can't be positive. I'm hoping the committee can ascertain the sex with certainty.
WERE PHOTO(S), VIDEO, AND/OR AUDIO OBTAINED FROM THIS SIGHTING?
Photo
SUPPORTING IMAGES