It's not easy to distinguish between original predator kill sign and scavenging.
Earlier this spring, Eliane Lagnaz sent us photos of just such an instance near Waipu in Northland. She had noticed a pair of paradise ducks, sounding vigorously, and spotted the entrance to their nest. Three weeks later, when she returned to the area, there was no sign of the birds but she saw a native swamp harrier fly up from the nest area. Eliane investigated and describes what she found.
"On inspection, I found two predated eggs, one dry, the other with fluids attached to the egg shell. In addition to the entrance hole to the nest there was now a second hole through the reeds at the top."
There is no way of knowing what animal actually attacked the nest and whether or not the bird was scavenging the remains of a pre-existing kill, perhaps that of a rat or mustelid.
This example is a useful reminder that kill sign is not always a reliable clue on its own and to look for other sign to back up killer identification. It is also interesting to note that some native species are natural predators, although they are generally protected under the Wildlife Act, whilst introduced predators are not.
See Eliane's other photos on our new possible scavenging examples page.