'Typical' avian predator sign

[Dave Houston]

Jo Duck out on Great Barrier has a dead pateke that appears to have died from an avian attack but doesn't resemble the usual harrier sign.  Can anyone give descriptions of "typical" falcon, pukeko and black-backed gull predator sign?

[Dave Houston]

Laurence Barea of Hamilton was quick off the mark with this reply ...

Hi, I have looked at many carcasses that have been killed by a range of falcon species and hawks here and overseas, including harriers. One thing that separates falcon sign from all other hawks is bruising and other trauma to the tissues around the vertebrae at the base of the skull (the head of smaller birds is often removed). This results from the instinctive behaviour of all falcons to bite and twist at this location immediately after capturing their prey. Falcons have a tooth like projection on their upper mandible that slots into a recess in the lower mandible. To go with this they also have a very strong bite. Thus, they are able to kill prey larger than themselves quickly. Mustelids also kill prey by biting the back of the head / neck area and this might confound predator identity.
 
Both hawks and falcons pluck much (not all) of the feathers from the birds they catch. They often leave diagnostic sign on feather shafts. When plucking feathers, they often leave a kink in the main shaft of the feather that results from the bite and pulling action. This is often visible on larger feathers e.g., flight feathers and upper wing coverts. It is not always obvious. However, if you grasp the ends of the feather between your finger tips and bend the shaft carefully, a plucked feather often bends / kinks at the bite mark much more easily than a non plucked feather. Close examination may indicate parallel marks left by the ridges either side of the mandible.
 
A combination of both sign might help identify the predator as a raptor / falcon. Do you have photos?

Hope this helps.
 
Laurence Barea
Terrestrial Ecologist
Technical Support Supervisor - Biodiversity
Department of Conservation
Waikato Conservancy
Private Bag 3072
Hamilton
New Zealand

[Leovb]

It would be very interesting to see photo's of the carcass. If possible please put them on the forum?
Could you also give a common english or scientific name for the Patake?
Thanks, Leo

[Bruce McKinlay]

Pateke is brown teal

[Dave Houston]

There's a paper recently published in Notornis about new prey items being recorded in bush falcon diet, but most usfeully it has a photograph of prey remains that is captioned -  "Characteristic notches can clearly be seen on the sternum (and other bones) where the falcons have fed on the carcass."

Hyde, Noel and Seaton, Richard - A new prey species for the New Zealand bush falcon (Falco novaeseelandiae), Notornis, 2008, Vol. 55: 40-41

[Leovb]

Thank you mr. Mckinlay, it makes it better to understand.