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Carrion Crow vs. subspecies of Large-billed Crow

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Old Friday 3rd April 2020, 06:47   #1
Otarujef
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Question Carrion Crow vs. subspecies of Large-billed Crow

Place: Naebo Park, Otaru, Hokkaido, Japan
Date: August 4, 2019
Time: 9 am
Weather: clear, nice.


Hi Everyone!

I have 2 photos here,
which are examples of a fairly regular conundrum I have.
Usually the Frankenstein forehead of the Large-billed Crow
as well as the beak size (ssp. japonensis, here in Hokkaido),
are traits that makes it distinguishable from the Carrion Crow.

Crow #2 (7839) in the photos, appears as expected to be a Carrion crow,
but Crow #1 (4717) in the photos is where I am stuck.
Other photos in my collections are similar shaped head
of a Carrion with an even larger bill.

Could the questionable crow be a juvenile Large-billed (japonensis) or an other subspecies,
such as mandschuricus (finding itself in Kamtchatka and it is said now possibly into Hokkaido)???

Thanks greatly for any clarity!

Jeff
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Name:	crow 2-_DSC7839.jpg
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ID:	722921  
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Old Friday 3rd April 2020, 06:50   #2
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here is the LB crow subspecies for comparison

Corvus macrorhynchos mandschuricus with thanks from Patrick Blakes site.
my other photos are similar to this one.

Jeff
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Old Friday 3rd April 2020, 08:50   #3
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It's time we found some websites with good info on this matter. I thought i read some english Korean page about it but I can't find it anymore.
I think we can safely say that Carrion Crow is fairly uniform but Large-billed can vary widely from steep foreheaded clear-cut-case to nearing Carrion Crow in shape and size.
A few comparative sites i found only really describe the extremes.
https://carasblog.net/hasibosohasibuto.php


I thought it might have to do with the length of the feathers on the bill base
Carrion Crow: > than half bill size
Large-billed Crow: < than half bill size
but I think that feature is easily dismissed.

At the moment I don;t know anymore, and i'm judging mostly by gut...which is not much to go by

please help us out here : )!

thanks
Gerben
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Old Friday 3rd April 2020, 11:59   #4
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Thumbs up Thanks for that

Gerben,

Thanks for the interesting read! :thumbs up:
All seems to be confused again,
LOL.

Different aspects of the Carrion and LB,
seem to be able to appear as the other at times.

Interesting that the head skeleton of the LB is the same
whether the feathers are fluffed up or laid down,
but the appearance is night and day.
LOL LOOK! I'm a Carrion, NOW I am a Large-billed!
....never considered seeing it in that way before.

It does seem that when calling,
The positioning is different,
especially the LB tail feather
moving inward.

The bill, forehead, walk, call sound.....
I thought were unique hints to determine the difference,
but now I don't know either, except to watch that tail!
and wait for more input here on this thread hopefully.

Jeff
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Old Friday 3rd April 2020, 12:47   #5
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Arrow some links and PDFs about Carrion and Large-billed Crows

Here are some items that might help add to the confusion or give additional hints if read closely:

Vocal variation and future splits of the Large-billed Crow complex:
https://www.xeno-canto.org/article/109

one range map of Large-billed Crow (mandshuricus):
https://avibase.bsc-eoc.org/species....ec=map&ssver=1

Thread discussion on the myriad of subspecies of Large-billed Crows:
https://www.birdforum.net/showthread.php?t=146179

And some interesting PDFs on crow variations
in the attachments. With great thanks to those that wrote them.

Jeff
Attached Files
File Type: pdf 19649_00010915.pdf (397.1 KB, 2 views)
File Type: pdf 19658_ECE3-8-10057.pdf (844.1 KB, 2 views)
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