[eloshwg] Re: Ageing quiz/ molt esoterica

  • From: "Christopher Hill" <dmarc-noreply@xxxxxxxxxxxxx> ("Chill")
  • To: "eloshwg@xxxxxxxxxxxxx" <eloshwg@xxxxxxxxxxxxx>
  • Date: Mon, 28 Feb 2022 16:25:06 +0000

Hi all,
There’s more detail here than probably any of you want, but I’m spelling out my thought process because I want to get this right and if I’m wrong (for like the third time!) I hope you’ll point it out.  I think compared to people with greater all-species banding experience I may be a bit slow with this stuff.
I’m reporting back (with long delay!) about the photos I sent recently, where the bird in question (and two other birds with almost identical patterns that I didn’t show) had replaced all flight feathers except one or two secondaries in each wing (but probably did not replace the primary coverts).  As I told Amy Kearns, I’ve now been wrong at least twice on them (since I kept changing my mind) but Amy, with some excellent documentation of a bird she captured and photographed. both as a fall HY and a spring SY, along with my carefully reading of the Birds of the World account, have changed my outlook: I now think all my birds are SY.  
I did not know that in their first prebasic molt our local shrikes could replace so many remiges.  My impression from handling them was that almost all SY birds here in SC replace the secondary coverts and some tertials, maybe an inner secondary or two, and that’s generally it. See the drawing labeled “E” in the scanned figure from Pyle below.  But it turns out it’s common for LOSH to replace primaries too in the first prebasic, according to the BOW account, referenced to Miller 1928 and Miller 1931.  I appended the section of the BOW account on prebasic molt at the bottom of this post.  Given my (wrong) understanding I was thinking that the number of [secondaries plus primaries] replaced looked like this:
HY birds: 3,3,2,3,1,3,,3,2,2,1,5,2AHY birds: 19,19,19,19,19,19,19,19My photographed birds: 18, 18, 17

So I thought my birds were more likely adults that came up a little short.  But if the real number of molted flight feathers for HY birds is more like 8, 3, 10, 11, it’s now easier to see my birds fitting in as SY birds, especially since at least some of them have what appear to be retained old (Juvenal) primary coverts.
I don’t know how I missed extensive primary replacement if it’s happening in “our” birds here.  The BOW account implies that primary replacement varies by populations - in some places 85% of young birds replace some primaries, in others only 5%.  I still feel like we’re in the 5% range even though our southern resident birds have a long time to molt.  I have photographs of the spread wing of every bird we capture, so I could go back and look at all of them but I’m not going to do that right now.
Anyway, thanks very much Amy Kearns and Susan Craig for the feedback and helping me learn a little more about these birds.
Chris

On Feb 15, 2022, at 5:01 PM, Kearns, Amy <AKearns@xxxxxxxxxx> wrote:

CAUTION: This email originated from outside your organization. Exercise caution when opening attachments or clicking links, especially from unknown senders.

That’s neat and I haven’t seen one like that before. I would probably call it a “more advanced” SY but will love to hear what people with more expertise think about it.

Amy Kearns
Assistant Ornithologist
Indiana Division of Fish & Wildlife562 DNR Rd Mitchell IN 47446
akearns@xxxxxxxxxx
(812) 849-4586 ext. 223 (office)(812) 844-3042 (cell)www.dnr.IN.gov * Please let us know about the quality of our service by taking this brief customer survey.
On Feb 15, 2022, at 4:13 PM, Christopher Hill <dmarc-noreply@xxxxxxxxxxxxx> wrote:


I think the folded wings show what to me is the key.  This bird has a retained S3 in the right wing, much browner than the rest of the flight feathers, clearly a different generation feather from the rest of the wing.  The primary coverts also appear brown and worn.  On the left wing it has retained S3 and S4.

So the question becomes: is it more likely for an adult to fail to completely replace flight feathers, leaving S3 and S4 as retained older feathers (this is what Pyle says we should “look for” and he also mentions the possibility of an adult retaining old primary coverts).

OR is this a young (SY) bird that, in addiation to the usual tertials and secondary coverts, has replaced all its primaries and all but one or two of its secondaries, but retained a juvenal secondary and juvenal primary coverts?

Chris

Prebasic I molt occurs late Mar–late Nov (Palmer 1898, Miller 1928a). Begins shortly after all Juvenile flight feathers are fully grown (rectrices last to complete growth at 40 d [Lohrer 1974]), i.e., about 20 d after fledging. Incomplete molt includes all body plumage and usually all rectrices, some inner secondaries, and some outer primaries (Miller Miller 1928a, Miller 1931c). It is noteworthy that congeric Northern Shrike does not replace any flight feathers during this molt; Loggerhead Shrikes are more migratory than Northern Shrikes. Body molt begins slowly with marginal upper- and underwing coverts near middle of wing, progressing distally, proximally, and posteriorly. Subsequent body molt begins about 1 mo later on upper back and breast, progressing both anteriorly and posteriorly. Then the upper greater- and median secondary coverts are replaced. At about this time, some to all rectrices and some outer primaries may be replaced; rectrices typically replaced from central pair (R1) outward (Palmer 1898, Miller 1928a); however, some birds may replace R1 and outermost (R6) pairs at about same time followed by intervening pairs, i.e., R1–R6–r2–R3–R4–R5 (Miller 1928a). About 20% of birds replace no rectrices; these birds also fail to replace remiges. Primary molt usually begins with P5, P6, or P7 and progresses outward to P10. Rarely, especially in resident southern populations, birds may replace all primaries or all except P1–P2. Among subspecies, 15–95% of birds may not replace any primaries; about two-thirds of birds that replace no primaries also do not replace any rectrices or other remiges (Miller 1931c). Alula is replaced at same time as outer primaries; however, all Juvenile greater-primary coverts are almost always retained; rarely a few outer ones are replaced. Despite feather wear, the buff tips of inner greater-primary coverts usually are apparent until replaced during Definitive Prebasic molt at about 1 yr of age, i.e., this is a very reliable indicator of age (along with contrast in wear and color between inner and outer primaries). Slightly after onset of rectrix molt, secondary molt begins with S8, followed by S7 and S9 in no apparent order. Secondary molt may continue distally to replace S6, S6–S5, or S6–S4 (rarely S3). Birds may replace no secondaries or as many as 7. As with primary molt, southern populations tend to replace more secondaries than northern populations. Secondaries are usually last flight feathers to finish growing, especially in birds replacing ≥ 1 of S4–S6.

JPEG image

JPEG image

Other related posts:

  1. Home
  2. eloshwg
  3. Archive
  4. 02-2022