San Diego Wild Animal Park
Escondido, San Diego County, California
24 December 1998
The first sighting was of one of the very first birds to leave the roost. I did not immediately recognize it as a Zone-tail until I got my scope on it and saw the all feathered head and yellow cere, which showed up well in the morning light. However the bird glided straight off to the East and did not bank so I was unable to see any detail on the tail or underwings. Nevertheless I feel confident it was a Zone-tailed Hawk.
The second bird was much more cooperative and was seen under prolonged conditions in excellent light as it circled up with Turkey Vultures. It was decidedly smaller than adjacent Turkey Vultures. The yellow cere and the all black feathered head were evident. I was able to see the yellow feet, but when it dropped down into the eucalyptus, it lowered it's legs and I could see the long yellow legs as well
Both were all black on the body and closely resembled small Turkey Vultures. Both birds showed all black upperwings, unlike the more brownish cast to the wings of the Turkey Vulture. The underside of the long dark tail showed a single broad gray band. The upperside showed two broken white bands which were evident only when the bird banked.
Both birds flew with a tilting glide, similar to Turkey Vulture with their wings angled forward slightly. I thought they tilted less than the Turkey Vultures and they had fewer "fingers" or slotted primaries. The Zone-tailed Hawks showed only four "fingers" while the Turkey Vultures showed six.
The undersides of the wings were two-toned, with black wing linings and gray flight-feathers. However the gray did not seem to show the silvery reflective quality of the Turkey Vultures. Once in good light I was able to see faint barring on the flight-feathers, especially a dark subterminal bar on the remiges which did not show on the Turkey Vultures.
At least 45 Turkey Vultures came off the roost eventually and we were able to study the second bird several times with one of the kettles. The Zone-tailed showed a proportionally longer tail and narrower shorter wings, compared to the Turkey Vultures. Finally several ravens flying with the vulture kettle appeared to single-out the Zone-tailed for harassment.
Guy McCaskie saw these birds at the same location on December 11th. An account of his sighting was posted to the San Diego birders mailing list and is available online here. Additional information on these birds was supplied by Phil Unitt.
-- Joseph Morlan, Pacifica, CA 94044: firstname.lastname@example.org