Date: 11/3/17 5:01 pm
From: Jay Withgott <withgott...>
Subject: [obol] thoughts on the Newport Costa's Hummingbird

Hi all --

Andy Frank and I were fortunate enough to be birding the Newport area Wednesday when we ran into Russ Namitz, who told us of Eric Horvath's COSTA'S HUMMINGBIRD. We headed over and, along with Eric and Mike Wheeler, viewed and photographed the hummingbird. Our thanks to Russ and to Eric!

I was thrown a bit, however, by the bird's song, which sounded a great deal like an Anna's Hummingbird song. It seemed softer and somewhat different, but overall quite similar to Anna's and certainly very different than the typical up & down slurred whistle/scream of a Costa's perched song or dive-song.

There was nothing in the bird's appearance to suggest hybridization; it looked like a pure Costa's. So below are my thoughts and speculations, based on what I heard, with references to relevant research. But I'll stress that I only SAW the bird vocalizing once, and that I failed to get a recording. So I would urge others to see if they can get a recording of the bird singing and make this available on eBird, xeno canto, or elsewhere.


Three things to know at the start:
(1) These closely related sister species differ in that Anna's has a structurally very complex song while Costa's has a relatively simple song.
(2) Hummingbirds are known to learn their songs, but it is possible that learning occurs in some species and not others.
(3) Eric believes his adult male bird to be the same individual that was present at the site, in immature plumage, this past winter.


So here are the possibilities as I see them:

Q1 -- Is the scratchy complex song this bird uttered in fact a normal but rarely heard part of Costa's repertoire?
A1 -- Possibly. An old paper (Woods 1927; see below) states that young male Costa's, before attaining their gorgets, "begin practicing on these whistled notes ... with results that sometimes rather resemble the song of the Anna's Hummingbird, though much fainter and less sustained." And another paper (Wells et al 1978) cites researcher Gary Stiles in stating that "young males of C. costae apparently sing more frequently [than adults], as well as use a more complex song. The song of these first-year birds approaches the complexity of male C. anna songs." I have found no recordings of these immature male songs, but one of the 28 recordings of Costa's Hummingbirds on xeno canto (www.xeno-canto.org/203734) contains two seconds' worth of "chattering calls during a rapid shuttle display" that precede the typical song that sound a little bit like what I heard from Eric's bird. ... So perhaps Eric's bird has retained an immature-type practice song, or was uttering an adult chattering ca
ll not well described in the literature.

Q2 -- Could Eric's bird be a hybrid?
A2 -- Take a look at the photos in peoples' eBird checklists and decide for yourself, but to our eyes the bird appeared to be a pure Costa's with no obvious evidence of mixed parentage. The Wells et al (1978) paper documents in great detail 11 individuals thought to be Anna's x Costa's hybrids. These birds sang Anna's songs, and their appearance, while intermediate, was closer to Costa's than to Anna's. So given this, I'm not sure we can totally rule out the possibility that Eric's bird could be an outlier of a hybrid that looks especially much like a Costa's, or that it might be a 3/4 Costa's backcross ... but I suspect that's unlikely and that one would want to find some suggestive physical evidence of hybridization before proposing this.

Q3 -- Could Eric's bird be a pure Costa's that learned an Anna's song while it was an immature this past winter, surrounded by Anna's singing in Eric's South Beach neighborhood?
A3 -- I'm attracted to this explanation. As Dr. Claudio Mello of OHSU explained in his talk this fall at the Oregon Birding Association meeting, hummingbirds are one of the groups in which song learning occurs (as opposed to songs being innate and hard-wired). Anna's has been experimentally demonstrated to learn its songs. A paper on songs of Costa's Hummingbird (Williams & Houtman 2008) suggests that not all hummingbird species may be learners, however, and predicts that species with simple songs (like Costa's) are more likely to be innate singers, not learners -- but as far as I can tell, this is not yet known for sure.


Finally, I note that back on 12-13 May, 2004, Tim Janzen, David Mandell, and I observed a bird at Sawyer Park in Bend that we felt was a Costa's x Anna's hybrid. Tim got video footage of this bird as it sang. Its morphology was intermediate between the two species, and it was singing a song that, according to Tim's OBOL posting of the time, "was very reminiscent of an Anna's Hummingbird, except that the song seemed somewhat softer and shorter than a typical Anna's Hummingbird song."


For all these reasons, it could be useful to have an audio recording of Eric's hummingbird singing. I also welcome information from others with more experience with Costa's Hummingbirds or further knowledge of any of the issues above.


Jay Withgott
Portland


CITATIONS:

Wells, S., R.A. Bradley, & L.F. Baptista. 1978. Hybridization in Calypte hummingbirds. Auk 95: 537-549.

Williams, B.R., & A.M. Houtman. 2008. Song of Costa's Hummingbird (Calypte costae). Auk 125: 663-669.

Woods, R.S. 1927. The hummingbirds of California. Auk 44: 297-318.

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