More vocal copying by American Goldfinch, Purple Finch, and Ovenbird

After listening carefully to Pine Siskins this year to pick out the calls of other species (see my earlier post) I have run across several other mimics. In early June in Arlington, Massachusetts I heard a remarkable American Goldfinch song that incorporated several phrases of a Song Sparrow song along with Northern Flicker and I suspect other species were being copied but I couldn't pick them out. This is the first time I've heard an American Goldfinch that included copies of other species in its song, and these were very clear and obvious copies, but as Dan Lane pointed out in comments on my previous Siskin post American Goldfinch seems to be exceptional – the one American member of the genus that does not copy. Apparently they do, at least occasionally.

In western Massachusetts in late June 2009 I heard a male Purple Finch giving its territorial song. This territorial song began with a bright warble like a typical Purple Finch song, then continued into a longer and more varied section – a jumble of short song phrases and copies of other species. I was able to pick out copies of American Robin, Tufted Titmouse, Eastern Towhee, and Hairy Woodpecker, and again I suspect there were more. In this case the copying has been previously reported in the literature, with the BNA account mentioning Barn Swallow, American Goldfinch, Eastern Towhee, and Brown-headed Cowbird.

Several years ago I noticed a few copies in the flight song of an Ovenbird, and I've heard a few others since then. Over several days in late June 2009 I was able to hear many flight songs from one Ovenbird in Colton, New York, which included copies of Red-eyed Vireo song phrase, Robin tut note, and a Purple Finch song phrase. There are very few recordings of the flight song (since it is given at such long intervals) but one on the Stokes Guide to Bird Songs: Eastern includes a lot of mimicry. Listening carefully to that I can hear a snippet of Winter Wren song, the trill of Eastern Towhee song, Red-eyed Vireo song phrase, and ending with White-eyed Vireo song. It's such a jumble of calls that (like the Siskin song) it's very hard to pull out all the copies, so I suspect there are others, and this whole performance – other than the few typical Ovenbird song phrases in the middle – might be copies. This is another instance of vocal copying that has never been reported before, as far as I know. The BNA account for Ovenbird makes no mention of it.

It's interesting that both the Purple Finch and Ovenbird use copies in these sort of extended or auxiliary songs, and not in the more frequently heard "typical" songs.

I should point out a very interesting new blog by Nathan Pieplow about bird vocalizations, with a comment on the Pine Siskin issue here, and lots of other good stuff. And another blog about bird voices by Paul Driver, with a recent post about Mimicry here.

References:

McGraw, Kevin J. and Alex L. Middleton. 2009. American Goldfinch (Carduelis tristis), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/080

Van Horn, M. A. and T.M. Donovan. 1994. Ovenbird (Seiurus aurocapilla), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/088

Wootton, J. Timothy. 1996. Purple Finch (Carpodacus purpureus), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/208

Promising new window film may prevent bird collisions

The most recent research by Dr. Daniel Klem, who has been studying the problem of bird/window collisions since the 1990s, has just been published in the June 2009 Wilson Bulletin. It is available, along with lots of other bird/window resources, at his website here.

Klem tested the effectiveness of various window treatments confirming, for example, that single decals on a window are not effective at preventing bird collisions, and that the non-reflective Collidescape film is nearly 100% effective at preventing collisions. Several different UV-absorbing films were tested with small to moderate success.

Beginning in 2007 Klem tested a new film developed in collaboration with Dr. Tony Port, a chemist at CPFilms. This film has vertical strips that reflect UV wavelengths alternating with vertical stripes that absorb UV wavelengths. The UV reflection and the alternating pattern seems to be very effective at deterring birds – only a few birds collided with the windows treated with this film, and none of those collisions were fatal. The real promise of this film lies in the fact that it appears clear to humans, and should be relatively easy to apply to existing windows!

Hopefully the company, CPFilms, can be convinced that there is a market for this window film, and start producing it commercially. I can think of dozens of windows that I would put it on.

Klem, Daniel, Jr. 2009. Preventing Bird-Window Collisions. The Wilson Journal of Ornithology 121:314 –321

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.

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.

More on identification of Greenland White-fronts

Coincidentally, just days after my last post about the two White-fronted Geese in Concord, two White-fronted Geese showed up in Amherst, Massachusetts (about 60 miles west of Concord, but not the same birds) that appear to be one Greenland and one North American type. James Smith has some discussion and really nice photos on his blog, and he's allowed me to post some of the photos here. 

Two Greater White-fronted Geese - 23 November 2008, Amherst, MA. Photos copyright James P. Smith, used by permission. Click for higher resolution (660 kB). In this montage the upper image shows the apparent North American bird with the Greenland-type on the left. I've resized and pasted in another photo of the Greenland type below for comparison.

This provides a great comparison of the two birds, very well-photographed, in similar light and from similar angles. The Greenland-type bird shows the following differences from the North American-type:

• neck, head and bill larger and bulkier than the North American-type
• neck and head more uniform and darker brownish
  
• scapulars with slightly narrower and less contrasting pale edges
• white border on flank feathers narrower
• pale tips on median and greater coverts narrower and less contrasting, not bright white
• pale edges on tertials slightly narrower and less white

These are all the same differences that I noticed on the two birds in Concord, and that have been described before as identification features for Greenland White-fronts in Europe. One other feature deserves mention:

• bill bright orange (and James says the color is accurate and this bird was truly very orange-billed) which may be useful even though we know how unreliable bill color can be, and the other bird happens to be a fairly obviously pink-billed individual, providing a strong contrast. One thing I noticed on the Concord birds, and again here, is that the North American bird has a fairly obvious whitish tip on the bill, while the Greenland bird does not.

And on 24 November, Taylor Yeager posted photos of another apparent Greenland White-front (scroll through the gallery to see several images of this bird), this one in Sharon, MA about 30 miles south of Concord. This bird doesn't look quite as heavy-billed as the other two, but it still looks fairly thick-necked, the bill is bright orange, and it has the dark head, narrow and low-contrast feather edges on the back, virtually no white on the wing coverts, very narrow white flank stripe, and extensive black on the belly between the legs. I'm comfortable calling this a Greenland White-front also. 

This would all seem to lead to confidence in identifying Greenland White-fronts, and I think we're getting there. But when I browse photos of White-fronts from other areas they show a bewildering range of variation. Identifying Greenland White-fronts will require excellent views and a careful assessment of all the different identifying features, preferably with direct comparison to other White-fronts, and a healthy dose of caution.

Another photo of the two birds in Amherst: Greenland-type in front showing the much larger and bulkier bill and head, and thicker neck, in comparison with the more delicate features of the North American-type bird behind. Photo by James P. Smith, used by permission. 23 November 2008, Amherst, MA.

Finally, one further mystery: It's not at all clear how we can tell that the smaller bird in Amherst is a North American White-front rather than a Eurasian bird. I don't think I've ever seen a discussion of that identification issue, but Eurasian White-fronts show up rarely in Iceland, and could easily wander into North America from there or from Siberia, so it is a potential vagrant to North America. All I can dig up in a cursory search is that Eurasian birds are consistently pink-billed, and may average smaller-billed, and may average less white on the wing covert and tertial edges, but those things are all vague, subjective, and variable. So while I've called the smaller bird in James Smith's photos a North American-type, I can't actually rule out the possibility that it is a Eurasian bird. Any comments or suggestions welcome. 

Identification tips for Greenland Greater White-fronted Goose

The Greenland Greater White-fronted Goose (Anser frontalis flavirostris) is known to be a rare visitor to northeastern North America, but I have never been satisfied with a reliable, objective way of distinguishing it from the North American subspecies of Greater White-fronted Goose, also a rare visitor to the northeast.

Bill color is the most frequently-mentioned field mark – supposedly orange on Greenland birds and pinkish on North American – but this has been refuted multiple times (see Kenn Kaufmann's note in Birding 1994, my blog post here). I suspect this is a mark that works in Europe, where local White-fronts are reliably pink-billed, but not in North America, where lots of the local birds look more or less orange-billed.

Over the last few weeks a single adult White-fronted Goose has been frequenting farm fields near my home in Concord, Massachusetts, and about a week ago it was joined by a second bird (well... "joined" is an overstatement since they pay no attention to each other and keep apart in the big flock of Canada Geese). 

These two individuals, in their details, are really strikingly different, and the differences all lead me to the conclusion that the new arrival is a Greenland bird, and the other a North American bird. On 19 November I was able to get some photos of the Greenland-type bird, and I've annotated a photo here with the differences between it and the North American-type bird. The differences are listed simply from front to rear, not in order of importance. (I'll try to get some photos of the other bird to post here for comparison).

Presumed Greenland Greater White-fronted Goose, 19 November 2008, Concord, MA. Photo by David Sibley

1. bill color slightly more orange, with yellow base (vs. orange with pale pink base on the other bird); but this is very very difficult to judge and essentially worthless as a field mark (see my post from last fall about judging bill color).
   
2. whole head nearly uniform dark brownish, sometimes looking paler on the cheeks but still with solidly dark crown above the eyes (vs. paler gray-brown head and neck with narrow dark crown stripe and contrasting dark border along white front). This is highly dependent on lighting, and would be difficult to judge on a lone bird, but the Greenland-type bird does look consistently darker, and may show a contrasting dark hind-neck that the other bird doesn't, but I need to check that in more lighting conditions.
   
3. neck strikingly thick and heavy, no thinner than the head (vs. neck slender, obviously narrower than the head and looking graceful and slim). This is one of the most obvious differences on these two individuals.
4. margins of mantle and scapular feathers pale brownish, not strongly contrasting (vs. margins whitish, more strongly contrasting).
5. white border on flank feathers narrower and not extending as far forward (vs. broader and longer)
6. pale tips on median coverts narrow and not white, relatively inconspicuous (vs. broader, whitish, conspicuous)
7. greater coverts without pale edges, and with narrow and inconspicuous whitish tips (vs. obvious narrow white edges and broad white tips forming a conspicuous narrow white band across edge of folded wing). This is another obvious difference between these two individuals.
8. black smudges all over the small feathers of the belly between the legs and extending well behind the legs (vs. this area virtually all white). This is separate from the irregular black bands before the legs and up onto the flanks, which are marked similarly in both birds.
9. white tips on the tail feathers seem to be narrower on the Greenland-type, but this is very difficult to see in the field.

Overall the Greenland-type bird appears bulkier, heavy-billed and thick-necked, and darker, without the elegant white fringes that are prominent on the rear upperparts of the North American-type.

Here's another photo of the Greenland-type bird, showing the heavy orange bill, dark and thick neck, and the lack of contrasting edges on the feathers across the shoulders. But none of that is very helpful in a single photo without another bird for comparison, nor is it likely to be very helpful on a single bird in the field. 

I know that some of these things have been described before, and they are still pretty subjective, and it's not safe to generalize from a single individual, but if this is a typical Greenland White-front, then I feel more hopeful about identifying the subspecies.

notes:

Martin Reid's website has some other discussion, photos, and lots references

Sungrebe – New for North America!

Stunning news from Bosque del Apache NWR in New Mexico: a female Sungrebe was photographed there on 13 November 2008, those photos here. It was correctly identified on 17 November from the photos, then refound and photographed more on 18 November. This is not only a new species for North America, but a whole new family.

A map of the species' whole range can be seen here at InfoNatura (scroll down for the detailed map).

Of course, birders are already debating whether this is a wild, naturally-occcurring bird or an escape from captivity. On one hand, it's a secretive species that is rarely seen flying, with no known history of vagrancy or even real seasonal movements, making the prospect of one appearing nearly 1000 miles northwest of the closest known population seem very unlikely. On the other hand, it's not kept in any zoos, and doesn't seem like the kind of species that would be illegally transported by an individual, which makes the escapee theory unlikely also.

Tipping the balance in favor of natural occurrence, in my opinion, is that in South America Sungrebes are apparently quick to occupy ephemeral wetlands, even when those are isolated many miles from any other suitable Sungrebe habitat. So clearly they are capable of long-distance flight, and wander enough to discover recently-created habitat. Perhaps, like rails, or Masked Ducks, they are capable of amazing feats of vagrancy.

Unless there is some clear evidence of captivity, I would consider this a wild bird. Incredible!

Update 19 November: Jerry Oldenettel has more details and will be updating the bird's status on his website here; and apparently the original photos were taken 13 November, and identified on the 17th, so the bird has been present at least six days.