HKBWS Forum 香港觀鳥會討論區 - Powered by Discuz! Board

Subject: [Eagles] Imperial Eagle - 白肩鵰 (Juvenile)- [Print This Page]

Author: Andy-li Time: 8/11/2009 18:25 Subject: Imperial Eagle - 白肩鵰 (Juvenile)-

2-11-2009 MP

Thanks for viewing..

Author: kfmak Time: 8/11/2009 20:37

Excellent!

Author: Andy-li Time: 9/11/2009 01:56

Thanks, kongfan...

Author: thein83 Time: 9/11/2009 06:51

準

Author: DanielCKChan Time: 9/11/2009 23:26

My favorite!

Author: Andy-li Time: 10/11/2009 19:21

Quote:

Original posted by DanielCKChan at 9/11/2009 23:26
My favorite!

Daniel...go..go..go..

Author: lmichael Time: 11/11/2009 10:17

Lovely photos - but this is not a juvenile.

There are at least 2 ages of feathers on this bird (perhaps 3) which would make it at least 2 or more likely 3 years old - large eagles like this often don't have a complete moult every year - a juvenile would have all fresh feathers.

Mike Leven

Author: Andy-li Time: 12/11/2009 02:44

Quote:

Original posted by lmichael at 11/11/2009 10:17
Lovely photos - but this is not a juvenile.

There are at least 2 ages of feathers on this bird (perhaps 3) which would make it at least 2 or more likely 3 years old - large eagles like this often don ...

But I have looked over relevant books, point out this feather color is a juvenile Imperial Eagle. ( Really a little confused )

anyway, Mike..Thank you for your suggestions

This pic take on 4/11, is it sub-adult?

Image Attachment: DSC_8068a.jpg (12/11/2009 02:44, 165.03 KB) / Download count 487
http://hkbws.org.hk/BBS/attachment.php?aid=4686

Author: 觀鳥新丁 Time: 12/11/2009 07:28

FANTASTIC///////////

Author: ajohn Time: 12/11/2009 10:13

You are correct that juvenile Imperial Eagle is pale buff. Many of the feathers on this bird are juvenile feathers, giving the overall pale appearance.
As Mike points out, there is very obvious moult contrast on this bird. It is clear that some of the body feathers have been replaced by dark feathers typical of adult Imperial Eagle, and the typical adult pattern of pale nape contrasting with darker breast is apparent on some of the photos. There is also obvious contrast on the wings and tail between fresh new feathers and old worn feathers (note especially how worn the central tail feathers are).
A juvenile eagle at this time of year would show entirely fresh feathers (no more than a few months old) with no moult contrast. As Mike mentions, these feathers are gradually replaced over a number of years into adult-type plumage. Birds in their 2nd and 3rd year (as this bird) will therefore show a mixture of adult and juvenile features. The moult contrast is usually apparent in the field, often at reasonable distance - look for the difference in length between old and new wing feathers, and for any missing feathers in the wings.

I hope this clarifies the situation, which is not well explained in many field guides (these can be misleading by suggesting birds are either 'juvenile' or 'adult', without considering intermediate plumages). I suspec this is why you are confused by Mike's respaonse. These are a great set of photos which show very well how this transition from juvenile to adult occurs.

Author: Andy-li Time: 12/11/2009 13:13

John,Thank you for your comments

You let me understand this Eagle more..

Author: ajohn Time: 12/11/2009 15:46

I forgot to mention before. The second bird also shows a mixture of juvenile and adult feathers, but with relatively more adult feathers than the first. This bird will therefore be older than the first bird - probably in its 4th year. (The term sub-adult is actually a bit vague and can refer to any bird that has not yet gained full adult plumage)

Comparison of plumage details in a series of good photos like these would be useful in assessing the number of individual eagles present in HK over the course of the winter, so keep posting them!

Author: Andy-li Time: 12/11/2009 18:44

Jhon, Thanks again...

Welcome to HKBWS Forum 香港觀鳥會討論區 (http://hkbws.org.hk/BBS/)