(http://31.media.tumblr.com/tumblr_m74nw3lF3x1qeoinio1_500.jpg)
(http://www.hdrhq.de/images/gallery/hdrhq_bfme2_wk_conzeptarts/pic004.jpg)
(http://forums.revora.net/uploads/monthly_04_2009/post-17768-1239606421.jpg)
Those are actually purely decoration. One of the few things. I didn't came up with any specific meaning for them. It was more a means to distinguish the elite banner from the standard banner.
They are pretty nice decoration. Anyway, I had some different view on them after I have seen first time that non canon (correct me if I am wrong) shiled of Faramir:
(http://img13.deviantart.net/b25a/i/2013/280/9/a/faramir_s_shield_by_ever_so_excited-d6phyux.png)
I think that those "birds" present two simetrical parts of Elendil's crown. :)
Anyway, very fitting for Arnor. ;)
P.S. Why did you divide you answer on my post? :P
I got confused. :D
Regards,
CragLord