[obol] Re: Baskett Slough shrike question
- From: Bob Archer <rabican1@xxxxxxxxx>
- To: OBOL <obol@xxxxxxxxxxxxx>
- Date: Thu, 26 Mar 2015 08:18:37 -0700
It usually takes more than just one id point to call a shrike. And I look
for those things that Dave mentioned. Pale tips to coverts and the extent
of the white patch on base of primaries should be noted and maybe rump
color as well. I thought it interesting in comparing Pam's pictures of an
adult Northern to the Loggerhead, another sort-of-helpful-but-be-careful
trait can be observed. Loggerheads tend to stick close to the ground and
in small shrubs, Northerns like to sit up high on phone poles and tops of
trees. All depends on what they are hunting , so just a fun thing..
Pam captured this behavior.
Bob Archer
PDX
On Wed, Mar 25, 2015 at 11:44 PM, David Irons <llsdirons@xxxxxxx> wrote:
> Hi Linda,
>
> In my opinion, bill length is a useless field mark unless you have
> Loggerhead and Northern Shrikes side-by-side for comparison. In over 40
> years of birding I don't think I've ever seen Northern and Loggerhead
> Shrike in the same day, let alone close enough together for a direct
> comparison.
>
> Sibley points to throat/breast contrast as a useful field mark (I am
> assuming this is where you found this field mark). Again, I think this is a
> useless field mark. I have a number of photos of adult Loggerhead Shrikes
> from various places and times of year (April, June, May and November). None
> of them shows any discernible contrast between the throat and breast and
> I've never used this to ID a Loggerhead Shrike in the field.
>
> There are essentially three things that I look for on an out-of-range or
> out-of-season Loggerhead.
>
> 1. Darkness of the upperparts -- They always look considerably darker gray
> above than Northern Shrike, particularly on the crown and mantle. Even
> adult Northerns are pretty pale pearly gray above, whereas Loggerheads are
> a darker rain-cloud gray that contrasts with the much whiter underparts.
>
> 2. Width of the black mask -- As a general rule, Loggerheads have a deeper
> black mask than Northerns. Note that young (hatch-year) Loggerheads have a
> narrower mask than adults.
>
> 3. Does the black in the face wrap over the top of the bill -- This is
> absolutely the best field mark for separating these two species. On
> Loggerheads the black in the face wraps up over the top of the bill and on
> Northern it doesn't.
>
> Here is something else to think about. The preformative molt of Loggerhead
> Shrike is more extensive than it is in Northern and results in a
> first-winter/early spring appearance that is virtually identical to that of
> an adult. Aside from their juvenile plumage (first set of feathers out of
> the nest) Loggerheads don't really have what might be referred to as an
> "immature" plumage. The preformative molt occurs on the breeding grounds
> before fall migration, so by the time say November rolls around all
> Loggerhead Shrikes will look adult-like, with fairly clean whitish to pale
> gray underparts and no obvious barring below. Their prealternate molt (late
> winter/early spring) is comparatively limited, so first-winter birds will
> not change much in appearance in their first spring.
>
> Most of the Northern Shrikes that winter in Oregon are immatures. I see
> maybe one in ten wintering birds that is an adult. First-winter Northerns
> are rather dingy and brownish-gray. This look results from fine brown
> vermiculations on the underparts. When they arrive in fall they will look
> quite brown and barred below. Their preformative molt is less extensive
> than Loggerhead, thus first-winter birds look more like juveniles than
> adults. Then, they have a more extensive prealternate molt in late winter
> early spring. Thus, immature Northerns overwintering in Oregon are likely
> to start looking more like adults in the days just before they leave for
> more northerly breeding grounds.
>
> I have photos of both species if anyone wants to see those, I can send
> them privately. If I get the time, I will put together a gallery.
>
> Dave Irons
> Portland, OR
>
> > Date: Wed, 25 Mar 2015 22:16:46 -0700
> > From: linda@xxxxxxxx
> > To: OBOL@xxxxxxxxxxxxx
> > Subject: [obol] Baskett Slough shrike question
>
> >
> > Forgive me if this has been discussed, but why is this a Loggerhead
> > rather than a Northern Shrike? I have not seen the bird but only Pam
> > Otley's photos. The mask appears narrow to me and the throat does not
> > contrast with the breast, at least in her photos. I can't tell that the
> > bill is short. ??? Please educate me.
> >
> > Linda Fink
> > --
> > http://lindafink.blogspot.com/
> > http://lindafink-birdnotes.blogspot.com/
> >
> >
> >
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> >
>
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