Thursday, May 14, 2009

Identification of Belding's Savannah Sparrow

In early March 2009 it was my pleasure to spend a few days in California at the San Diego Bird Festival. On my first morning in San Diego I headed straight out to the Tijuana River National Estuarine Research Reserve hoping to spend a few hours studying Savannah Sparrows (who wouldn't, right?). I had seen some Belding's Savannah Sparrows in March 2008 in Orange County, California, and realized that the treatment of this endangered subspecies in my field guide was not very good, so I was anxious to learn more.

I succeeded in seeing dozens of the resident Belding's, with many birds singing and territorial around the marsh. I also saw quite a few of the migratory northern subspecies of Savannah Sparrows (ranging from grayish to brownish) in weedy areas around the margins of the marsh.

The image below compares two of my photos showing the most obvious differences between the subspecies. Compared to northern birds, Belding's has:
  • longer and thicker bill with curved culmen
  • darker and much thicker streaks on the underside
  • darker streaks on the upperside and coarser and darker markings on the face
  • Belding's never (as far as I could see) raises a crest, while the northern birds often look slightly crested and show a distinct peak on the rear crown
Belding's (left) and Northern-type Savannah Sparrows. Photos 5 and 8 March 2009, San Diego, CA 
 copyright David Sibley (digiscoped with Nikon Coolpix 4300 handheld to Swarovski telescope)

Differences in behavior, habitat, and molt were also fairly obvious, and should be very helpful for identification (but bill and plumage features should be checked to confirm). 
  • Belding's in early March were singing and territorial, chasing each other across the marsh, while the northern birds were in small, loose flocks moving together widely across dry grassy and weedy areas around the marsh
  • Belding's flight was low and weak, with round body and fluttering wingbeats, reminding me of Sharp-tailed Sparrow, unlike the stronger, higher, more "bounding" and undulating flight of northern Savannahs
  • in early March the Belding's were all in clean fresh plumage, while the northern birds were molting and scruffy with missing feathers all over the head and body
I could not hear any difference in the song of Belding's compared to Savannah Sparrows from farther north.

I was struck by how much stockier and larger-billed the Belding's looked in comparison to the northern subspecies, in many ways intermediate between northern and "Large-billed" Savannah Sparrows. Apparently some populations intermediate between Belding's and northern birds are resident farther north along the California coast, but alongside the migratory northern subspecies the Belding's Savannah Sparrows in southern California seem quite distinctive.

Wednesday, May 13, 2009

Vocal copying by Pine Siskins

[10 July 2009 - update added at end]

In July 1990 I spent several weeks birding in west-central British Columbia, where Pine Siskins were one of the most conspicuous birds, and I became convinced that Pine Siskins were copying the sounds of other species of birds and incorporating these sounds into their songs. I was able to identify American Robin (squeal call), Evening Grosbeak (“krrr” call), Warbling Vireo (scold call and a song phrase), White-winged Crossbill (flight call and trill), and even House Sparrow (calls).

Since then I’ve heard this in many other places, and come to expect it whenever I hear siskins singing. From late March to early April 2009 I had the opportunity to listen to several individuals repeatedly in my yard in Concord, Massachusetts, and I was able to identify the following 14 species in the siskins’ songs:

Evening Grosbeak “krrr” call

American Robin, flight squeal and single “pup” call

Eastern Bluebird, rattling flight call

Eastern Towhee, “chewink”

Black-capped Chickadee, a single “dee” note

Northern Flicker, “kew” call

Hairy or other woodpecker, “wika” call

Dark-eyed Junco, soft “tew-tew-tew” call

Eastern Phoebe, song phrase and chase call

Blue-headed Vireo, two syllables of scolding call

Red-eyed Vireo, scold call

Song Sparrow, “jimp” call

Ruby-crowned Kinglet, two-syllabled whistled song phrase

Common Redpoll, flight call

These sounds can be very challenging to pick out, since the song moves along so rapidly that the bird is already singing other sounds while your brain struggles to process and identify the previous sound. The Evening Grosbeak call is commonly used and distinctive enough to stand out each time, but other calls like the Eastern Bluebird rattle simply blend in with the staccato jumble of sounds.

In my yard the same sounds were used repeatedly day after day, so as I became familiar with them I was better able to pick them out, and started to notice other copied sounds. I could not distinguish individual siskins, so I don’t know how many sounds were shared among birds, but the fact that the Evening Grosbeak call and American Robin call were heard virtually every time I listened carefully (and were heard years earlier in BC as well) suggests that most or all siskins use these calls, and probably share a lot of other sounds as well.

If you’d like to hear some of this, check out the recording catalog number 133352 at Cornell's Macauley Library, July 2, 2007, recorded in Newfoundland by Geoffrey Keller. [You’ll have to Search audio for Pine Siskin, and then find this recording]

The bird starts singing at about the 40 second mark, and between 47 and 56 seconds imitates Common Redpoll, Evening Grosbeak, Hairy Woodpecker, Dark-eyed Junco, American Tree Sparrow and American Robin (and probably others). Notice the clear sing-song notes of American Tree Sparrow at about 55 seconds, with the abrupt “pup” of American Robin following immediately after.

Amazingly, this vocal copying seems to have been almost completely overlooked. In Bent’s life histories (online here) copying of Evening Grosbeak and (in a captive bird) Common Redpoll and Canary, are mentioned. A study of vocal copying by Lawrence’s and Lesser goldfinches (Remsen et al, 1982, pdf here) specifically says that the song of Pine Siskin does not include any copied sounds, and the Birds of North America account makes no mention of it.

Presumably the sounds that are learned are simply the ones that are common in the siskins’ environment, so siskins from the western mountains must learn some sounds that are not heard in the east, and vice versa. Another Macauley Library recording from California (catalog number 120288) includes copies of Lesser Goldfinch flight calls, among others. Given how much siskins wander, it would make a really interesting exercise to listen for copied sounds that are “out-of-range”. Hearing, for example, Eastern Towhee in British Columbia or Lesser Goldfinch in Massachusetts would give you some idea of how far that individual siskin has traveled.

Update - in early June 2009 I spent a week at The Nature Conservancy's Pine Butte Guest Ranch near Choteau Montana, and was able to hear several Pine Siskins singing. I was able to hear copies of the vocalizations of seven species there. In addition to the now-expected calls of American Robin, Dark-eyed Junco, Common Redpoll, and Evening Grosbeak, the Montana siskins copied Western Tanager call, Mountain Chickadee dee note, and a Cassin's Vireo song phrase. Clearly these birds had learned their calls in the west, and would stand out in the east. So the challenge remains – to find a siskin that has traveled cross the continent, and recognize it based on the sounds it has learned.