Date: 3/14/17 10:03 am From: Will RIsser <wlrisser...> Subject: [obol] many hawks at Ft. Rock
Inspired by Kim Boddie's reports on OBOL of hawk censuses in the Christmas Valley and Ft. Rock areas, Jan and I have been going there in winter for the last three years. The first winter we counted 68 rough-legged hawks in a four-mile stretch along Ft. Rock Road. The hawks concentrate in the hay fields.
I went again on Sunday and Monday. In two half-days, I had 18 encounters with ferruginous hawks, including one dark-phase adult. A few of these may have been the same bird. I had 17 encounters with rough-legs, including two dark-phase adults. A few of these may have been the same bird. The rough-legs have started to migrate and numbers are down.
I had 9 unique encounters with golden eagles.
A pair of prairie falcons was courting on the rock of Ft. Rock.
I was confused by an adult male rough-leg that had an all-white head and a black belly. It was unlike any painting in Sibley or the National Geographic field guide. Research in Ralph S. Palmer's (ed.) Handbook of North American Birds clarified this. In the article on rough-legs (by Palmer himself), he states that in adult males the head varies from nearly unmarked white through a long gradient of increasing width of dark. The belly may be all white to blotchy to solid dark. He notes that there is tremendous individual variation in the deposition of melanin in the male rough-leg and that "the various areas apparently vary independently so that each bird may be regarded as a kind of mosaic, although there are some common patterns." The field guides that I used didn't mention this.
If you are interested in more information, please contact me privately.