mjm@oliven.olivetti.com (Michael Mammoser) (12/14/89)
In article <14739@shamash.cdc.com>, gls@hare.udev.cdc.com (gl sprandel x4707) writes: > > Re: Chicken hawk > Note: Size is not a very good diagnostic for determining > coopers versus sharp shinned. > I've seem hand held birds a few times and there is a even size gradient > from male sharpie, to female sharpie, to male coopers to female. > (and then on up to goshawk) > Thus after looking at male sharpies for a while, if you see a larger > bird you might think coopers but its more likely a female sharpie. > Shape of tail does not work that well during migration during the fall > since they may set it differently in heavy migration. > What do you all use as a field mark for coopers/vs sharp shinned ? As was mentioned in a previous posting, identifying Cooper's from Sharp-Shinned Hawk is probably the most difficult raptor ID problem. One should undoubtedly use a number of field marks rather than rely on just a single one. It may not be possible to identify every bird that you see. There is no documented overlap in size between Cooper's and Sharp-Shinned Hawk, although female sharpies may "approach" the size of male coops. Size may be a useful field mark for birds at the extreme of the range. People living in the southwest should be aware that the mexican race of Sharp-Shinned Hawk is larger than the north american race and the western race of Cooper's is smaller than the eastern. Birds in this area may overlap in wing chord size, but do not in weight or overall length. I agree that tail shape may be misleading when the bird is fanning its tail, but when folded, I believe that tail shape is an excellent field mark. Cooper's have tail feathers that are successively shorter from the inside feathers to the outside, and the shape of the feather tips is rounded, which gives the Cooper's a more rounded overall look to the tail. Sharp-Shinned have tail feathers of nearly equal length, and the shape of the outer feathers is more square, giving the tail an overall square look. Also, Cooper's Hawks have an extensive white terminal band on the tail that generally abuts the first dark tail band, while Sharp-Shinned have a thin (or absent) white terminal band that generally abuts the grayish/brown base color of the tail some distance from the first dark tail band. Of course, wear in the tail feathers can obscure this mark to varying degrees. I once observed an immature Cooper's Hawk whose tail was so worn that it had no white terminal band at all. Cooper's Hawks have proportionally larger heads and longer necks. They also tend to hold their wings more perpendicular to the body while soaring. This gives the impression in Cooper's, when they are flying, that the head sticks out further beyond the leading edge of the wing. Perched Cooper's Hawks have a tendency to raise the feathers on the back of the neck and head, giving the back of the head a squared-off look. Supposedly, this behavior has never been reported in Sharp-Shinned Hawks. The eyes of both species are very nearly equal in size and, with the larger head of the Cooper's and its tendency to raise its hackles, its eyes look smaller with respect to the head size. The eyes also appear to be placed more forward in the side of the head. The crown of the adult Cooper's Hawk is somewhat darker than the back, separated by a pale nape, which produces a sharp line of contrast at the junction of the nape and crown. The adult Sharp-Shinned Hawk has a crown nearly equal in color to the back, without a pale nape and no apparent contrast. The streaking on the undersides of immature Cooper's Hawks is finer and darker than immature Sharp-Shinned. Also, the streaking on Cooper's diminishes on the belly, while that on Sharp-Shinned remains dense. An excellent article on identifying accipiters was published in Birding magazine a few years ago and details the above mentioned field marks. I don't know what month or year it was, but it was in volume XVI, number 6. I believe that it is easier to see field marks on perched birds rather than those that are flying. Soaring birds tend to be too far away to make out most diagnostic field marks and birds that aren't soaring are generally in view for only a short time. I sure don't envy hawk counters who usually have to make an ID on soaring accipiters during migration. However, the more birds that you look at, the better you will get. There is no substitution for experience. Mike
grp@unify.uucp (Greg Pasquariello) (12/16/89)
In article <52342@oliveb.olivetti.com> mjm@oliven.olivetti.com (Michael Mammoser) writes: > > >In article <14739@shamash.cdc.com>, gls@hare.udev.cdc.com (gl sprandel x4707) writes: >> >> Re: Chicken hawk >> Note: Size is not a very good diagnostic for determining >> coopers versus sharp shinned. > > As was mentioned in a previous posting, identifying Cooper's >from Sharp-Shinned Hawk is probably the most difficult raptor ID >problem. One should undoubtedly use a number of field marks rather >than rely on just a single one. It may not be possible to identify >every bird that you see. Excellent list of field marks deleted. The only thing that I would add is that Cooper's are generally somewhat heavier than sharpies, thus they have a greater wingload. This in turn causes them to have a heavier flap than the sharp shin, which can often be used to seperate them a extreme distances. > > I believe that it is easier to see field marks on perched >birds rather than those that are flying. Soaring birds tend to be >too far away to make out most diagnostic field marks and birds that >aren't soaring are generally in view for only a short time. I sure >don't envy hawk counters who usually have to make an ID on soaring >accipiters during migration. However, the more birds that you look >at, the better you will get. There is no substitution for experience. > >Mike One of the other species to be aware of when trying to seperate acciptiers, is the Marsh Hawk. Although not an Accipiter, it has a similar shape when seen soaring high overhead, as they often do while migrating in the east. The key here is to recognize the long wings that seem to give the bird a stretched out look. Many times I have looked at a soaring accipiter and thought "now what the heck is that?", only to have it become a Marsh Hawk. -Greg -- ------------------------------------------------------------------------------- Greg Pasquariello (916) 920-9092 grp@unify.UUCP Unify Corporation ...!{csusac, pyramid}!unify!grp