[obol] Re: Why you need the bodies

From: Bob Archer <rabican1@xxxxxxxxx>
To: OBOL <obol@xxxxxxxxxxxxx>
Date: Fri, 17 Dec 2021 08:48:23 -0800

First off if you want to get to this level, or into this torture chamber,
of field ornothology you need to get the book Lars posted from, both
volumes. .Also remember these volumes were/are at the very cutting edge of
what we know about molt, aging and sexing NA birds, so there may be and are
many errors.  If you want more info, check out the references they used.
Not sure when these will be updated.

http://www.slatecreekpress.com/

Hermit Thrush is the one illustrated, mentioned in the description of Fig
238.

In field ornithology, emarginated means the  leading edge of the flight
feather is sort of shaved down towards the tip a bit creating what looks
like a shelf.

Notched means the trailing edge of feather is shaved down towards the tip
creating a shelf kind of thing.

On a folded wing, the leading edges are the ones visible.

In NORTH AMERICA, primaries are numbered from inner to outer, so 1-10 in
most birds.  In many birds you cannot see 10, so on thrushes you are really
seeing 1-9.  I think Europe has adopted this system but you do run into
different numbering systems from time to time.

On thrushes P10 is really about as long as the coverts, so that measurement
of the length of P10 compared to the length of the pp coverts can help in
aging, but you need to have the bird in hand I would think.  Remember these
books are for banders.

pp refers to the plural of primary (primaries)  ss would mean secondaries.

The difference in length of the actual primaries that form the wing
determine the shape of the wing, so you can measure the length of
P8 compared to P6 and get an average distance so  p8 - p6 =  4-5 means the
length difference between the two feathers is 4-5 mm.  You can't see that
measurement in the field of course, but it does impact the shape of the
wing.  Swainson Hawks , for example, have different  comparative lengths in
their primaries than say a Red-tail, which gives their wing a pointed look.

So P9  >  P6 means the outer primary is longer than the 4 th one in.

I think I can see the emargination or lack thereof on a folded wing of a
thrush.  Need to practice a bunch.  Which goes to show there are always fun
things to look for  even in the common birds.

Any corrections welcomed.

Bob Archer

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On Thu, Dec 16, 2021 at 9:01 PM Paul T. Sullivan <paultsullivan@xxxxxxxxxxxx>
wrote:

I’m still trying to understand the diagram Lars posted.  (See below)
Reading Lars post of 7:59 AM explaining emargination as a constriction of
the margin of P6, and then the statement that Swainson’s thrush has an
unemarginated (straight-edged) P6, I’m led to conclude that the diagram
represents a Hermit Thrush.

So my path was:  define emarginated, then find P6, then figure out which
species has which form of P6, then figure out which species is
illustrated.  Phew!

Why couldn’t you say that up front?

If you’re trying to inform, don’t start in the middle.  Start at the
beginning.

Thanks,

Paul Sullivan

*From:* Paul T. Sullivan [mailto:paultsullivan@xxxxxxxxxxxx]
*Sent:* Thursday, December 16, 2021 3:21 AM
*To:* OBOL <obol@xxxxxxxxxxxxx>
*Subject:* [obol] Why you need the bodies

Lars, Somebody,

You can’t just post this and expect anyone to understand it.  You need to
EXPLAIN it!

Which species is illustrated?

What does emarginated mean?

Explain the numbering of primary feathers.

What does “pp covs – p10   5-4 mm” mean?

What does “p8 – p6   5-6 mm” mean?

What does “p9 <p6” mean?

This kind of post to OBOL does not illuminate the discussion of Catharus
thrushes.

Teach us, rather than snow us under.

Thanks,

Paul Sullivan

*Oregon*

*Date:* 12/16 12:39 AM
*From:* larspernorgren <larspernorgren...>
*Subject:* [obol] Why you need the bodies
[image:
https://aba.org/wp-content/plugins/birdnews/attachments/1639644243-20211216_003615.jpg]
------------------------------

Someone took a photo on November 9,2020 that showed this lack of
emmargination on a perched SWTH, l believe in their yard in Corvallis. Sent
from my Verizon, Samsung Galaxy smartphone

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References:
- [obol] Re: Why you need the bodies
  - From: Paul T. Sullivan

[obol] Re: Why you need the bodies

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