If doing with multiple people. The ducks do despawn when harvested, but respawn in about 5 seconds.
As a visible level 44 Paladin, approaching the final dead duck, Quacker Lemmy, inevitably proved fatal (too much aggro). But a little invisibility, courtesy of a Totem of the Great Chameleon purchased from a Broker, made all the difference.
Role playing a level 42 character with intelligence as a primary attribute, and using a Saliraptor, I jumped over the mountain range from the north east and then along the west canyon wall until I could drop down on the final dead duck and collect it without any aggro at all.
Steps
Find the lost clockwork duck, Quacker Lin.
Quacker Lin was found at ( -1099, 166, 584 ) Copy/waypoint -1099, 166, 584. Near the climbable wall to Shiculiant in Recluse Hollow.
Find the lost clockwork duck, Quacker Stan.
Quacker Stan was found at ( -1327, 95, 849 ) Copy/waypoint -1327, 95, 849. Near Torn Ear Springs.
Find the lost clockwork duck, Quacker Mort.
Quacker Mort was found at ( -1188, 68, 1256 ) Copy/waypoint -1188, 68, 1256. Behind Kerafyrm's Crater.
Find the lost clockwork duck, Quacker Lemmy.
Quacker Lemmy was found at ( -419, 74, 1664 ) Copy/waypoint -419, 74, 1664. This is at the far back of the Steamfont Wetlands area.
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. Near the climbable wall to Shiculiant in Recluse Hollow.
. Behind Kerafyrm's Crater.