Friday, January 9, 2009
The White-throated Sparrow was one of the many birds counted as part of the Carlisle annual Christmas Bird Count (CBC). There were some unusual birds in this year’s count but I chose the White-throated Sparrow because it is a bird that all of us could easily learn by either its distinctive appearance or its memorable song. For a long time I didn’t realize how many different sparrows there are, and when the light finally dawned I still thought they would probably be too similar to one another for a novice to distinguish. Not so. The White-throated Sparrow is my break-through bird.
Name: The White-throated Sparrow is Zonotrichia albicollis where the species name is from the Latin albus meaning white and collum meaning neck. The common name is more accurate than the scientific name since the white patch at the throat does not extend all the way around the neck. It is like a very short bib – way too short to keep the spaghetti sauce off your sweater.
When and where seen: Susan Emmons and Steve Spang, who were counting birds in an area around the middle of the town, spotted White-throated Sparrows on Bedford Road near the daylily farm and others near the Clark farm on Concord Street. They (the birds – not Susan and Steve) were near the ground and hanging out in low shrubbery. The Sibley Guide to Bird Behavior says that White-throated Sparrows are agile enough to forage a little bit further from cover than less agile fliers. When foraging in the open they form small flocks and rely on the “many eyes” method to detect predators – the theory being that at least one bird in the flock will see the predator soon enough for the whole flock to fly back to cover.
Word for the day: “Lores” is the term for the tiny feathers between a bird’s eye and its bill. They are prominent in the White-throated Sparrow because they are bright yellow.
Distinguishing characteristics: The White-throated Sparrow has two color morphs, one with brown and tan stripes on the head and the other with black and white stripes. The easiest one to recognize is the black and white striped one where the stripe contrast is stronger and the yellow of the lores is brighter. The two morphs are governed by the genetic code for feather color and are not related to age or gender. The combination of the head stripes, the yellow lores, and the white throat make this sparrow distinctive.
Song: On June 2, 2008, you may have heard a bird singing “Bye, Bo Diddley, Diddley, Diddley” (pronouncing Diddley as if it had three syllables). This would have been a White-throated Sparrow that likes rock and roll and was up to date on the news. On other days the very obvious rhythm of the song can be recalled by the more traditional mnemonic “Old Sam Peabody, Peabody, Peabody” or as some prefer “Oh sweet Canada, Canada, Canada”. If you have trouble remembering and distinguishing bird songs, as I do, this is an easy one to master. It has little or no pitch variation and is a high pure whistle.
Choosing a mate: Some birds detect the presence of others of their species by the number of syllables in a song. White-throated Sparrows are among those that use the pitch and the rhythm of the song. But that only gets them into the dating scene. They still need to choose an individual. They seem to have been trained in the school of “opposites attract” because they show a strong preference for mates belonging to the other morph. The bright bold white-striped morph chooses the duller, drabber tan-striped morph and vice versa. Some White-throats who prefer super-extreme-ultra-opposites mate with Dark-eyed Juncos. This is rare, and I assume the offspring are infertile, or I’ll have to find a new definition of “species” which up to now has been “a group of organisms that are capable of interbreeding to produce fertile offspring.”
Carlisle CBC numbers: White-throated Sparrows breed and nest mostly in latitudes north of here and winter over in the more southerly Atlantic states and Gulf states. Some years more birds migrate further south than in other years. This means that the CBC numbers for Carlisle show a lot of fluctuations. This year only nine were counted, and seven last year, while in 2006 there were 64. The biggest count (from Ken Harte’s records going back to 1975) was 92 in the year 2000. From 1990 to 1999 there were no more than 11 in a given year.
Manomet Center for Conservation Sciences: The Manomet Center for Conservation Sciences, just south of Plymouth, has 42 years of bird-banding experience. For a variety of reasons, their numbers for White-throated Sparrows can’t be compared with the Carlisle CBC numbers. In the last ten years, they have counted anywhere from 89 to 302 White-throated Sparrows in a given year. Ten years of count data is available online (http://www.manomet.org/programs/landbirds/observatory/) if you want to check out other species.
References: The Sibley Guide to Birds and The Sibley Guide to Bird Life and Behavior, both by David Allen Sibley; Cornell Lab of Ornithology at www.birds.cornell.edu (search for white-throated sparrow) .
Did anyone make a New Year resolution to write an article (or two … or more) this year for the Biodiversity Corner? It’s not too late and you’d be very welcome. The topic doesn’t have to be something rare – just something that was seen in the wild in Carlisle. Send your ideas, your nature photos, or the whole column to Kay Fairweather at 392 School Street, Carlisle MA 01741 or to firstname.lastname@example.org
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