Re: Dowitchers
Tue, 20 Oct 1998 09:45:54 -0700 (PDT)
From: Tom Condit
It is possible to distinguish them, but just barely.
Basically, you have to have the bird in your scope for several minutes so you can study it closely. Then it has to fly off at an angle that lets you see the tail and rump clearly.
Then you ponder for several minutes. Then you write "long-tailed dowitcher (???)" on your list.
There are, of course, people who can tell more readily than this. They're the same ones who can pick semi-palmated sandpipers out of flocks of westerns. As far as we mere mortals go, however ...
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Re: Dowitchers
Date: 20 Oct 98 10:23:10 -0700
From: Les Chibana
Tom Condit wrote:
Basically, you have to have the bird in your scope for several minutes so you can study it closely. Then it has to fly off at an angle that lets you see the tail and rump clearly. Then you ponder for several minutes. Then you write "long-tailed dowitcher (???)" on your list.
You can only use this ploy with juveniles that have not yet molted into winter plumage. If you try it with winter-plumaged birds, you might drop a level of your birding rank. I once noticed that I could actually sense that the bills on a few Short-billed Dowitchers were shorter than that of some Long-billed that I had seen a few days before, after I heard the SBDO call in their hollow "tu-tu-tu". It's a very scientific process.
By the way, these were West Bay dowitchers that I compared, East Bay birds may vary.... ;-)
Les Chibana, Palo Alto, CA
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Re: Dowitchers
Tue, 20 Oct 1998 13:59:18 -0700
From: Larry Tunstall
Most of you probably know the literature on this subject far better than I do. However, for those who may not have the latest guides, here's what they have to say:
American Bird Conservancy, All the Birds of North America (1997), Shorebirds Consultant Kimball Garrett: "Only useful mark [in winter] is barred tail, seen in flight. Width of barring varies, but any bird whose pale bars are wider than dark ones can be safely called a short-billed dowitcher." ... "Voice, rather than bill length, is the sure way to separate dowitchers." Short-billed: "Tu-tu-tu, mellow flight call." Long-billed: "Keek, thin, high-pitched flight call."
Donald & Lillian Stokes, Stokes Field Guide to Birds, Western Region: In winter, "Dowitchers best distinguished by voice." Short-billed: "Flight call is a medium-pitched repeated 'tututu.'" Long-billed: "Flight call is a high-pitched thin 'keeek,' sometimes given in a series." Habitat: Short-billed "winters on coastal mudflats" and "roosts in large groups. Long-billed "winters on freshwater ponds and marshes" and is "most common in standing freshwater situations, rather than on extensive tidal flats."
Sounds fairly straightforward. But then I read a more-extensive discussion in Howard Cogswell's Water Birds of California (1977). Speaking of nonbreeding plumage, he says:
Since only a minority of individuals can be distinguished by their extremely long or short bills, dowitchers in this feathering can usually not be identified to species in the field except by voice." He says that prior to a detailed study by Frank Pitelka in 1950, "the two species of dowitchers were often confused even in museums." When settled for the winter, the short-billed is "almost strictly a saltwater bird on the California coast. It is very gregarious, and flocks mass closely in flight and pack even more densely when waiting out the high tide on their roosts in marshy or open pools or on salt-pond dikes near the bay or lagoon. Voice: a mellow tu-tu-tu or kew-kew-kewp, usually uttered in series of up to six or so notes when taking flight, irregularly or singly at other times, and distinguishable from calls of the Long-billed by their lower pitch and more resonant quality.
During migration, however, each species is commonly found in the habitats favored by the other. Cogswell does say that "From Dec. through Feb. any dowitchers seen at inland points in California (except possibly Salton Sea) are almost certainly Long-bills. They are also then in coastal lowlands, and some even occasionally forage in salt water along with the Short-bills, as they do fairly commonly in spring and fall when on migration." He describes the Long-billed voice as "a sharp kip or keep more often uttered singly than is the lower-pitched call of the Short-billed, but also given in series frequently when alarmed; both species give soft, rather liquid calls when feeding."
Now, having absorbed all that, I come back to Tom's original comment. We mere mortals probably should just write "Dowitcher sp." and move on! Those who insist upon knowing the innermost secrets of the universe no doubt will persevere in more precise identification.
Happy birding,
Larry Tunstall
http://www.best.com/~folkbird/
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Re: Dowitchers
Date: 20 Oct 98 15:22:57 -0700
From: Les Chibana
Did any of the references mention that there are different races of Short-billed, too? We probably only see the western race, caurinus, in the Bay Area. Al Jaramillo, who has studied them and co-authored an ID paper about them in his former range (Canada) says that this race is also the most variable, and therefore, I assume, the hardest to separate from Long-billed.
A few years ago, Al mentioned comparing the wing extension to tail length, to which I believe Tom was alluding. At that time, he said that he hadn't seen it mentioned in any recent ID papers. The theory goes: if the wings extended noticeably beyond the tail, it's Short-billed; if there is no primary extension (primary tips extending beyond the tertials), then its Long-billed. He said that THIS FIELDMARK IS NOT WELL-TESTED, but felt that there might be something to it. If this is a good key, it should work for basic (winter) plumage birds. I don't know if his opinion about this has changed.
Longer wing length is supposed to imply a longer distance migrant, by the way.
All of the other visual field marks, pertain to non-basic plumages: alternate (breeding) plumage adults and juvenal plumage hatch year birds (i.e., before 1st winter molt). Regarding the tail patterns, Joe Morlan once deduced:
Since Long-billed consistently has wider dark bars on the tail; and since Short-billed is variable in this character, then any dowitcher with narrow dark bars must be a Short-billed, but one with wide dark bars could be either. This should work for all plumages including winter.Care must be used to distinguish the barring on the tail from that on the uppertail coverts which may be even more variable.
I believe that Joe is on this list, and may care to comment or amend this.
Les Chibana
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Re: Dowitchers
Tue, 20 Oct 1998 15:53:34
From: Graham J Etherington
Hi all,
If your dowitcher is still in juvenile plumage, then rather than look at the (rather subjective) bill length, or width of black to white banding on the tail, you should just look at the tertials. If they are 'tiger-striped' then it's a Short-billed, if they are plain (usually with some pale edges) then it's a Long-billed. When birding in the Bay-area, Short-billed is they 'default dowitcher' for me, i.e. it's a Short-billed unless I can prove otherwise. I also find that Short-billed tend to be paler grey on the breast and more spotted on the flanks in winter, whereas Long-billed tend to be darker grey and more barred on the flanks. Also, at least when compared directly with east coast Short-billed Dowitchers of the race 'griseus', Long-billed have a more 'humpbacked' appearance.
Hope this is of help.
All the best,
Graham Etherington
UC Berkeley
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Dowitchers again
Tue, 20 Oct 1998 17:43:31 -0700 (PDT)
From: Tom Condit
When the first dowitchers show up, a few still have traces of breeding plumage. Then we hit our other big local problem: the Pacfic race of short-billed dowitcher (Limnodromus griseus caurinus) has a breeding plumage which looks a whole lot like that of the long-billed dowitcher. I am morally certain that I've distinguished between them a couple of times, but it's very hard.
There's a detailed (8-page) description of the dowitcher problem by Claudia Wilds in Kenn Kaufman, Advanced Birding (Peterson Guides). Lots of drawings of plumage, tails, etc., by Kaufman, with a text by Wilds which limns the difficulties in interpretation very well (but also makes it clear that it's possible to distinguish the two) (sometimes).
Tom Condit
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Re: Dowitchers
Tue, 20 Oct 1998 17:57:58 -0700 (PDT)
From: Tom Condit
At 03:22 PM 10/20/1998 -0700, Les Chibana wrote:
[snip]
Regarding the tail patterns, Joe Morlan once deduced:Since Long-billed consistently has wider dark bars on the tail; and since Short-billed is variable in this character, then any dowitcher with narrow dark bars must be a Short-billed, but one with wide dark bars could be either. This should work for all plumages including winter.
This tail pattern problem is what I was referring to, and why the (???) is most common after any tentative long-billed identification. Claudia Wilds says:
If you can decide that the light bars are much narrower than the dark bars, you are looking at a Long-billed. If you are sure the light bars are wider than the dark bars, you have a Short-billed. In between, this character is not safe to use.
(Wilds, by the way, is field identification editor for Birding.)
Tom Condit
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Virginia Rail at Friendship Park, Richmond
Tue, 20 Oct 1998 18:51:10 -0700
From: Steve Hayashi
Today at the marsh to the east of Shimada Friendship Park in Richmond, Dorothy Furseth and I had great looks at two Virginia Rails.
Steve Hayashi
Re: Dowitchers
Tue, 20 Oct 1998 22:14:25 PDT
From: Joseph Morlan
On Tue, 20 Oct 1998 17:57:58 -0700 (PDT), Tom Condit (quoting Claudia Wilds) wrote:
If you can decide that the light bars are much narrower than the dark bars, you are looking at a Long-billed. If you are sure the light bars are wider than the dark bars, you have a Short-billed. In between, this character is not safe to use.
This may work on the East coast, but on the West coast with the race caurinus, the tail bars are too variable for this to be reliable.
(Wilds, by the way, is field identification editor for Birding.)
Actually Claudia Wilds is dead. A tragic loss.
Here is an extract of an analysis of a claimed Long-billed Dowitcher from Australia I was asked to evaluate. The bird turned out to actually be a Short-billed Dowitcher based on measurements, although it had a mostly dark tail. Perhaps some of this may be of use:
---------------------snip----------------------------
As pointed out in the submission, the bird is entirely in basic plumage. However, dorsal photographs appear to show two generations of feathers. Some first-year dowitchers undergo a partial pre-alternate molt in which the new alternate feathers are basic-like. This is particularly true of individuals which do not migrate all the way back to their breeding grounds. Long-billed Dowitchers in such plumage usually retain some juvenile rectrices. Short-billed Dowitchers replace all rectrices in their post-juvenile molt while Long-billed Dowitchers do not (Pitelka, pg 5-7). The fresh appearing adult rectrices combined with the upperpart pattern suggest that this bird might be a second calendar-year Short-billed Dowitcher. However the unusual appearance of this bird including the apparently fresh adult-type remiges, may best be explained by the fact that it is in the wrong hemisphere and it's just weird.In any event there are no juvenile or alternate feathers which might give a clue to identification. Much has been made of the tail-pattern. Unfortunately the pattern on this individual is not useful for identification. Long-billed always has broad dark bars and narrow white ones while Short-billed is highly variable in this trait. Thus a bird with a mostly white tail (narrow dark and broad white bands) can be confidently identified as Short-billed, but the reverse is not true.
Otherwise there are no known reliable plumage characters which separate these two species in basic plumage. In North America field identification in basic plumage is determined only by call, and sometimes by a combination of habitat and range in areas where only one species is expected. Long-billed tends to be the more vocal of the two. The fact that your bird was silent upon release is somewhat more typical of Short-billed.
The breast pattern is unreliable and difficult to assess in the field. In general Long-billed is smoother and darker, and Short-billed is paler and more spotted, but many birds present an intermediate appearance (cf. plate 7, page 101 in Pitelka's monograph). I feel the small darker brown spots on the breast of the Barry Beach bird are suggestive of Short-billed, but would not rely on that for positive identification.
Measurements are the best criteria for identifying this bird. Jaramillo and I agree that these measurements point straight to Short-billed and eliminate Long-billed. Before getting down to cases, there appears to be a misconception that Long-billed is more likely to occur in Australia because of its longer distance migration. In fact Short-billed Dowitcher is the longer distance migrant and is the only one of the two which has been unequivocally recorded from southern South America. A specimen from Argentina which might be Long-billed needs to be reassessed. There are at least two records of Short-billed Dowitcher from Japan, although Long-billed is more common there. So there is precedent for Short-billed migrating down the wrong side of the Pacific Ocean. Once there, Short-billed is far more likely to migrate south of the equator.
.....
The reference to Pitelka above is Pitelka (Univ. Calif. Publ. Zool. 50:1-108, 1950)
Joseph Morlan, Pacifica, CA 94044
California Birding; Mystery Birds:
http://fog.ccsf.cc.ca.us/~jmorlan
California Bird Records Committee:
http://www.wfo-cbrc.org/cbrc
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Re: Dowitchers
Tue, 20 Oct 1998 22:38:14 PDT
From: Joseph Morlan
On 20 Oct 98 15:22:57 -0700, Les Chibana wrote:
A few years ago, Al mentioned comparing the wing extension to tail length, to which I believe Tom was alluding. At that time, he said that he hadn't seen it mentioned in any recent ID papers. The theory goes: if the wings extended noticeably beyond the tail, it's Short-billed; if there is no primary extension (primary tips extending beyond the tertials), then its Long-billed. He said that THIS FIELDMARK IS NOT WELL-TESTED, but felt that there might be something to it. If this is a good key, it should work for basic (winter) plumage birds. I don't know if his opinion about this has changed.
This mark was originally suggested by Ian Nisbet in his publication "Dowitchers in Great Britain and Ireland" published in British Birds but later discredited by D.I.M. Wallace in "Dowitcher identification: a brief review" also in British Birds. I don't have the original citations but both papers were reprinted in 1980 in Frontiers of Bird Identification edited by J.T.R. Sharrock.
However the situation in Britain deals only with hendersoni and griseus. Since caurinus is longer winged than the other two races then it might work a little better here on the West Coast than it does in the East or Midwest.
Joseph Morlan, Pacifica, CA 94044
California Birding; Mystery Birds:
http://fog.ccsf.cc.ca.us/~jmorlan
California Bird Records Committee:
http://www.wfo-cbrc.org/cbrc
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Re: Dowitchers
Tue, 20 Oct 1998 22:44:10 PDT
From: Joseph Morlan
On Tue, 20 Oct 1998 14:53:34, Graham J Etherington wrote:
When birding in the Bay-area, Short-billed is they 'default dowitcher' for me, i.e. it's a Short-billed unless I can prove otherwise.
In my experience, dowitcher ratios seem to have changed over the years in the East Bay. In the 70's and 80's I used to see almost exclusively Short-billed Dowitchers in winter on shoreline mudflats. However that started to change in the mid-80's and Long-bills started predominating at sites where Short-bills had been more common.
Recently Long-billed have outnumbered Short-billed at the Albany mudflats and in San Leandro Bay. And they are often more common at Alameda South Shore.
These are estuary situations with variable fresh water runoff that may account for the fluctuations, but difficulty of identification makes the actual situation hard to assess.
I think it may be safe to assume a dowitcher wintering in shallow rain pools inland are Long-billed, but on tidal mudflats I wouldn't assume they are all Short-billed.
Joseph Morlan, Pacifica, CA 94044
California Birding; Mystery Birds:
http://fog.ccsf.cc.ca.us/~jmorlan
California Bird Records Committee:
http://www.wfo-cbrc.org/cbrc