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Sunday, February 24, 2008

Audubon's (type) Warbler New Photos & Sound Files

Earlier this week Adam Byrne and I attempted to photograph and record the putative Audubon's Warbler in Lowell, without luck. In the frigid single digit temperatures of the early morning, we merely got fleeting glimpses at the bird in the treetops, and failed to record it. Today (24 Feb) however, we waited until mid-day before we arrived, and we were well-rewarded for it. At 2:23PM the bird came into the feeders while Adam, Curtis Dykstra, Bob Tarte, and 3 Lansing area birders watched. The bird was hyperactive and difficult to photograph, but it did allow these much awaited photos:If you look carefully, you can see that at least one mantle feather has a grayish (not brownish) fringe and very thick black center. It's probable that this represents a newly-grown alternate feather amongst a backdrop of older feathers (molted last fall). The prealternate molt in this species may occur from Dec-Mar according to Pyle. It may also be that the thicker black motling in the forward and rear flanks represent new feathers as well, but I will defer to anyone who knows this species better than I.Note the flecking on the undertail coverts and yellow on the crown, two features not observed before this day. Copyright Curtis Dykstra 2008. Here you can see the suggestion of an eyeline behind the eye, something which is visible in the field as well.

After much effort to record this frustratingly quiet bird, today I finally got one chip note on tape using my Saul Mineroff starting recording package- at the time the bird was distant and there was a lot of background noise, but using Raven Lite software I was able to generate this sound spectrogram of the chip note I recorded (click on photo for larger versions):You can recognize the chip as the inverted "V" shaped mark in the lower left corner, between 4 and 6 kHz. For comparison, here are the sound spectograms of the Stokes eastern Myrtle chip note and Stokes western Audubon's chip note. First, Myrtle:Second, Audubon's:I am not an expert in sound spectrogram analysis, but we can start to look for patterns regardless. First, frequency range: the Myrtle recording from Stokes centers in the 3-6 kHz range, while the Audubon's recording is similar, but seems to show several parallel lines, perhaps harmonics (anyone who understands this better than I, your clarification is solicited!), which creep into the frequencies higher than 7 kHz. I assume this accounts for the "scratchier" tone of Audubon's chip note. The Lowell bird's sound spectrogram lacks the parallel lines (perhaps due to low recording quality?), and seems to occur in a narrower range of frequencies.

Second, the shape of the "inverted V". That of the Lowell bird seems closer to the Audubon's recording in that the right (descending) half of the V is nearly vertical, while in the Myrtle recording it is more angled.

Third, the thickness of the line. The Lowell bird is clearly in closer to the Audubon's recording in this regard- a very thin line, rather than the wider line of Myrtle. Perhaps this is how the qualities our ears and brains utilize to so easily distinguish these species in the field are represented in the spectrogram.

This analysis is certainly preliminary, but as I've indicated before, in the field this bird sounds much more like the Audubon's chip than the Myrtle's chip. The spectrogram here appears to show many similarities to that of Audubon's, and some key differences with Myrtle. Comments or observations on these musings would be very welcome here.

Sunday, February 17, 2008

Audubon's Warbler (?) in Michigan

A week ago I noticed this photo of a Yellow-rumped Warbler from a backyard near Grand Rapids, MI. I immediately noticed the yellow throat and suspected it may be an Audubon's Yellow-rump, not the familiar Myrtle which is the normal form here. Today I finally was able to make an effort to see this bird, and I was rewarded with the following photos. There are only 2 accepted records of Audubon's Warbler in Michigan. Although most of the time this bird looked very plain-faced, there was at times a very slight suggestion of an outline to the auricular, something perhaps suggestive of a Myrtle X Audubon's intergrade. I would really appreciate the thoughts of those familiar with this species in all its forms.
My field notes mention a faint pale spot on the supraloral as well as a rearward and upward extending pale mark from the top eye arc, and that the throat appeared not to have a rearward extension coming up behind the auricular.
From most angles, the throat appeared uniformly yellow, concolorous with the flank spot, but the brief views I had seemed to suggest some whitish admixture of color along its anterior and lateral borders.

My field notes also mention the suggestion of a pale eyeline posterior to the eye, extending a very short distance rearward.
Copyright Bob Tarte 2007. In this photo, the face appears extremely plain.
Copyright Bob Tarte 2007. Here the exposure is slightly different, creating the appearance of a more contrasty head pattern.
Copyright Bob Tarte 2007.
Copyright Bob Tarte 2007. Here the pale supraloral and rear top eye arc extension can be seen, although they appear more pronounced here than in many of my views in the field today.
This map shows the location of the bird from today. It is certainly on a winter territory and should be present for several more weeks should it survive. The left arrow shows the residence at which the bird is very infrequently seen at a suet feeder. Today I first located the bird at the right arrow- about 1/4 mile east of the property in a band of woodland between Fulton (M-21) and the Grand River. The plot is either state or county owned according to Bob Tarte, the homeowner, and he felt birders could park on the roadside without much trouble. Traffic is fast here, however, so be careful. NOTE: be sure to wear rubber boots as the snow is deep and wet here!

Directions: Take I-96 to the Lowell exit and go north into downtown Lowell. Turn left at M-21 (Fulton) and go about 3-4 miles west of town. After crossing Cumberland, look for a blue house with a red barn on the south (left) side of the street, address 10696 (difficult to see the numbers near the front door frame). The homeowner and finder of the bird is Bob Tarte, who can be reached at 897-9202 if you want to ask him whether the bird is being seen. It is seen between zero and a few times per day at the suet feeder directly behind the house, and on the green lawn chair beneath it. However, there have been periods up to a week or more where it isn't seen here, and you should be prepared to walk east along the river listening for mixed species flocks. I found it all by itself (no other Yellow-rumps), only loosely associating with titmice, chickadees, creepers, and nuthatches. It was very high in the treetop, and was only attracted down by use of an iPod and Audubon's Warbler chip notes. Had I not had the iPod and speakers I certainly would not have been able to get a respectable look at this bird.