The sixth labor of Herakles (AKA Hercules) is dealing with the Stymphalian birds. They were birds were man eaters with beaks of bronze and metallic feathers they can launch like arrows. Herckles destroys or drives them off and they are encountered later by the Argonauts.

SOURCE: http://en.wikipedia.org/wiki/Stymphalian_birds

THE ORNITHES STYMPHALIDES (or Stymphalian Birds)  were a flock of man-eating birds which haunted Lake Stymphalis in Arkadia. Herakles’ destroyed them as his sixth labour, employing first a rattle to rouse them from the thick vegetation of the lake, then shooting them down one by one with bow and arrow or a sling.

…

The Stymphalides were sometimes identified with the arrow-shooting Ornithes Areioi (Birds of Ares) encountered by the Argonauts in the Black Sea.

SOURCE: http://www.theoi.com/Ther/OrnithesStymphalides.html

If you search for Symphalian birds, you will find pictures of ancient Greek pottery, Roman mosaics, and lots of modern interpretations. Deviant Art has quite a few examples.

One artist describes the birds as having poisonous dung. Knowing the way that much ancient mythology was cleaned up for presentation in the Victorian Era, I can believe this. However, I have not yet found a source to back this idea.

Here is my efforts to stat them as per AD&D.

NAME: Stymphalian Birds
FREQUENCY: Rare to Very Rare
NO. APPEARING: 3-30
ARMOR CLASS: 6
MOVE: 3″/18″
HIT DICE: 1
% IN LAIR: 60%
TREASURE TYPE: D
NO. OF ATTACKS: 2
DAMAGE/ATTACK: 1-4/1-6
SPECIAL ATTACKS: Launch feathers as arrows
SPECIAL DEFENSES: Metallic Feathers
MAGIC RESISTANCE: Standard
INTELLIGENCE: Low
ALIGNMENT: N
SIZE: S
PSIONIC ABILITY: N/A
Attack/Defense Modes: N/A
LEVEL/X.P. VALUE: (Added in MM2, also in FF):
CLIMATE/TERRAIN: They nest in trees surrounded by swamps and marshes.

 Swords & Wizardry (So I can use them in my hex for the OSR Tenkar’s Landing Crowdsourced Sandbox Setting.)

Hit Dice: 1
Armor Class: 6/[13]
Attacks: 2
Saving Throw: 16
Special: Launch bronze feathers as arrows.
Move: 3/18 (when flying)
Alignment: Neutrality
Challenge Level/XP: 2/30