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ID-FRONTIERS for April 27-30, 2008
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Subject: Sabine's Gull molt
From: Joseph Morlan <jmorlan(AT)GMAIL.COM>
Date: 29 Apr 2008 8:37am
Last week I was teaching gulls in my Ornithology class and was confused by
the account of Sabine's Gull molt in "Gulls of the Americas" by Howell &
Dunn.
Page 338 discusses a "typically complete" PF (preformative) molt. If it's
complete, then why not call it PB1 (prebasic 1)?
Under Second Cycle the book discusses a PB2 molt. How can there logically
be a PB2 molt unless there is also a PB1 molt?
--
Joseph Morlan, Pacifica, CA 94044 jmorlan (at) ccsf.edu
Birding Classes start Apr 1 in SF http://fog.ccsf.edu/~jmorlan/
California Bird Records Committee http://www.wfo-cbrc.org/cbrc/
Join or Leave BIRDWG01: http://listserv.arizona.edu/cgi-bin/wa?SUBED1=birdwg01
Archives: http://listserv.arizona.edu/archives/birdwg01.html
[ << | >> | ^^ ]
Subject: Re: Sabine's Gull molt
From: Peter Pyle <ppyle(AT)BIRDPOP.ORG>
Date: 29 Apr 2008 11:18am
Hi Joe and all -
Under the revised terminology of Howell et al. 2003 (Condor
105:635-653) the "first prebasic molt" (PB1) is now considered to be
the molt into juvenal plumage, which occurs at the natal site
(synonymous with "prejuvenal molt"). Formerly, various molts were
considered the PB1, including what we now call the preformative molt
(most species), the first-prealternate molt (some species that lack
preformative molts), or the second prebasic molt (some hawks,
seabirds, and a few other taxa that lack first-cycle molts al
together). This did not reflect evolutionary homologies among birds,
which is what Humphrey and Parkes were trying to achieve with their
nomenclature. The revisions of Howell et al. (2003) have greatly
improved first-cycle H-P terminology from an evolutionary standpoint
and have made it much easier to train students in the use of molt for
ageing and identification.
The preformative molt varies across species from absent to partial to
incomplete to complete, depending on the life-history strategies of
the species, and not as much on phylogenetics. Only a small
proportion of species have evolved complete preformative molts,
including species that are small and do not need substantial energy
to replace all feathers (hummingbirds, Bushtit, etc.) and certain
opportunists that can find enough resources during their first year
to undergo a complete molt (starlings, doves). Most waterbirds that
undergo complete preformative molts are small and highly migratory
species that spend the first boreal winter in the southern
hemisphere, where austral-summer resources and foraging day-lengths
are sufficient to undergo more complete molting. These include some
sandpipers, some terns, and Sabine's Gull. In many species, the molt
can vary from incomplete to complete among individuals. Thus,
completeness cannot be used to define these molts, and they are still
preformative molts when compared to related or ancestral species. If
you called the preformative molt in these waterbirds the PB1, just
because they are complete, then you would be comparing them with
preformative molts in related species (e.g., other sandpipers, terns,
and gulls) and homology would be lost.
Molt is not a user-friendly subject but once you look at it from an
evolutionary perspective, as Humphrey and Parkes originally promoted,
it becomes a lot clearer. Hope this helps.
Peter
At 08:35 AM 4/29/2008, Joseph Morlan wrote:
>Last week I was teaching gulls in my Ornithology class and was confused by
>the account of Sabine's Gull molt in "Gulls of the Americas" by Howell &
>Dunn.
>
>Page 338 discusses a "typically complete" PF (preformative) molt. If it's
>complete, then why not call it PB1 (prebasic 1)?
>
>Under Second Cycle the book discusses a PB2 molt. How can there logically
>be a PB2 molt unless there is also a PB1 molt?
>
>--
>Joseph Morlan, Pacifica, CA 94044 jmorlan (at) ccsf.edu
>Birding Classes start Apr 1 in SF http://fog.ccsf.edu/~jmorlan/
>California Bird Records Committee http://www.wfo-cbrc.org/cbrc/
>
>
>Join or Leave BIRDWG01: http://listserv.arizona.edu/cgi-bin/wa?SUBED1=birdwg01
>
>Archives: http://listserv.arizona.edu/archives/birdwg01.html
Join or Leave BIRDWG01: http://listserv.arizona.edu/cgi-bin/wa?SUBED1=birdwg01
Archives: http://listserv.arizona.edu/archives/birdwg01.html
[ << | >> | ^^ ]
Subject: Re: Sabine's Gull molt
From: Laurent Raty <l.raty(AT)SKYNET.BE>
Date: 29 Apr 2008 7:13pm
Hi Peter,
But Sabine's molt strategy is not simply characterised by an increase in
the amount of feathers molted during their preformative molts. After
their complete preformative molt, unlike any other gull species, they
stay on a 'reversed' cycle, with partial molts in autumn and complete
molts in spring.
Under Humphrey & Parkes' terminology, as far as I understand it, a
complete molt occurring once every cycle should always be termed
prebasic (independently of other phenomena in the bird cycle such as
season or breeding, that may influence the brightness of the plumage it
produces). The possible partial molts between them should be called
prealternate. Prebasic molts (and the basic plumages acquired through
them) are explicitly assumed to be homologous across all bird species;
prealternate molts are presumed to have been 'added' between them.
How does this apply to Sabine's Gull? Does this make their dark-hooded
summer plumage a basic plumage, not homologous to the dark-hooded summer
plumage of, say, a Black-headed Gull?
Best,
Laurent -
Peter Pyle wrote:
> Hi Joe and all -
>
> Under the revised terminology of Howell et al. 2003 (Condor
> 105:635-653) the "first prebasic molt" (PB1) is now considered to be
> the molt into juvenal plumage, which occurs at the natal site
> (synonymous with "prejuvenal molt"). Formerly, various molts were
> considered the PB1, including what we now call the preformative molt
> (most species), the first-prealternate molt (some species that lack
> preformative molts), or the second prebasic molt (some hawks,
> seabirds, and a few other taxa that lack first-cycle molts al
> together). This did not reflect evolutionary homologies among birds,
> which is what Humphrey and Parkes were trying to achieve with their
> nomenclature. The revisions of Howell et al. (2003) have greatly
> improved first-cycle H-P terminology from an evolutionary standpoint
> and have made it much easier to train students in the use of molt
> for ageing and identification.
>
> The preformative molt varies across species from absent to partial to
> incomplete to complete, depending on the life-history strategies of
> the species, and not as much on phylogenetics. Only a small
> proportion of species have evolved complete preformative molts,
> including species that are small and do not need substantial energy
> to replace all feathers (hummingbirds, Bushtit, etc.) and certain
> opportunists that can find enough resources during their first year
> to undergo a complete molt (starlings, doves). Most waterbirds that
> undergo complete preformative molts are small and highly migratory
> species that spend the first boreal winter in the southern
> hemisphere, where austral-summer resources and foraging day-lengths
> are sufficient to undergo more complete molting. These include some
> sandpipers, some terns, and Sabine's Gull. In many species, the molt
> can vary from incomplete to complete among individuals. Thus,
> completeness cannot be used to define these molts, and they are still
> preformative molts when compared to related or ancestral species. If
> you called the preformative molt in these waterbirds the PB1, just
> because they are complete, then you would be comparing them with
> preformative molts in related species (e.g., other sandpipers, terns,
> and gulls) and homology would be lost.
>
> Molt is not a user-friendly subject but once you look at it from an
> evolutionary perspective, as Humphrey and Parkes originally promoted,
> it becomes a lot clearer. Hope this helps.
>
> Peter
>
> At 08:35 AM 4/29/2008, Joseph Morlan wrote:
>> Last week I was teaching gulls in my Ornithology class and was
>> confused by the account of Sabine's Gull molt in "Gulls of the
>> Americas" by Howell & Dunn.
>>
>> Page 338 discusses a "typically complete" PF (preformative) molt.
>> If it's complete, then why not call it PB1 (prebasic 1)?
>>
>> Under Second Cycle the book discusses a PB2 molt. How can there
>> logically be a PB2 molt unless there is also a PB1 molt?
>>
>> -- Joseph Morlan, Pacifica, CA 94044 jmorlan (at) ccsf.edu
>> Birding Classes start Apr 1 in SF http://fog.ccsf.edu/~jmorlan/
>> California Bird Records Committee http://www.wfo-cbrc.org/cbrc/
Join or Leave BIRDWG01: http://listserv.arizona.edu/cgi-bin/wa?SUBED1=birdwg01
Archives: http://listserv.arizona.edu/archives/birdwg01.html
[ << | >> | ^^ ]
Subject: Re: House Wren subspecies
From: Joseph Morlan <jmorlan(AT)GMAIL.COM>
Date: 30 Apr 2008 9:20am
FWIW I decided to dig into the literature.
T. parkmanii was originally described by Audubon (1841). His original
description focuses mostly on the length and curvature of the bill:
http://www.abirdshome.com/Audubon/VolII/00210.html
In "A Revision of the North American House Wrens," Oberholser described
parkmanii thus:
SUBSPECIFIC CHARACTERS.—Similar to Troglodytes domesticus baldwini, but
much paler, and sometimes more grayish above; sides and flanks paler,
rather more rufescent; remainder of lower surface lighter, more buffy.
https://kb.osu.edu/dspace/bitstream/1811/2678/1/V34N02_086.pdf
Neither of these authors make an issue about the extent or prominence of
back barring.
However Ridgway and Bent both describe parkmanii as slightly larger, but
paler and grayer with the back and scapulars more distinctly barred with
dusky. Ridgway's description appears to be the first reference to back
barring as a feature distinguishing parkmanii from nominate aedon. However
it is given last in the list of distinguishing features.
Handbook of Birds of the World says parkmanii is "larger, paler and grayer"
than nominate. It makes no mention of any differences in back barring.
My guess is that back barring varies in both races.
On Sat, 26 Apr 2008 17:29:17 -0500, Ross Silcock <silcock(AT)ROSSSILCOCK.COM>
wrote:
>I haven't seen any responses to this interesting question- did I miss them
>(it)?
>
>Ross
>
>Ross Silcock
>P.O. Box 57
>Tabor, IA 51653
>New Zealand Land and Pelagic Bird Tours
>http://www.rosssilcock.com
>
>
>----- Original Message -----
>From: "Ian A. McLaren" <I.A.McLaren(AT)DAL.CA>
>To: <BIRDWG01(AT)LISTSERV.ARIZONA.EDU>
>Sent: Thursday, April 17, 2008 3:33 PM
>Subject: [BIRDWG01] House Wren subspecies
>
>
>> All:
>>
>> I'm confused (not infrequent). Pyle gives "western" subspecies _parkmanii_
>> as
>> "back feathers usually with dusky barring" and "eastern" _aedon_ as "back
>> feathers usually unmarked" and this echoes Phillips' statements. Yet
>> illustrations in both Nat. Geogr. and Sibley Guide seem to show the
>> opposite.
>>
>> Am I missing something?
>>
>> Cheers, Ian M.
>>
>> Ian McLaren
>> Biology Department
>> Dalhousie University
>> Halifax, NS Canada B3H 4J1
>>
>>
>> Join or Leave BIRDWG01:
>> http://listserv.arizona.edu/cgi-bin/wa?SUBED1=birdwg01
>>
>> Archives: http://listserv.arizona.edu/archives/birdwg01.html
>>
>
>
>Join or Leave BIRDWG01: http://listserv.arizona.edu/cgi-bin/wa?SUBED1=birdwg01
>
>Archives: http://listserv.arizona.edu/archives/birdwg01.html
--
Joseph Morlan, Pacifica, CA 94044 jmorlan (at) ccsf.edu
Birding Classes start Apr 1 in SF http://fog.ccsf.edu/~jmorlan/
California Bird Records Committee http://www.wfo-cbrc.org/cbrc/
Join or Leave BIRDWG01: http://listserv.arizona.edu/cgi-bin/wa?SUBED1=birdwg01
Archives: http://listserv.arizona.edu/archives/birdwg01.html
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