The Red-tails are now 33 days old. If you watch closely and have a television with really good resolution you may notice that the nestlings have different eye color from their parents. The young hawks have almost yellowish eyes which gradually turn a reddish brown as they age. Changes in eye coloration is a common phenomenon in bird species. Cooper's Hawks and Sharp Shinned Hawk eyes start out yellow and turn orange and then blood red over a period of years. Osprey eyes go the opposite direction going from red as juveniles to yellow as adults. Crow eyes start out blue and turn darker. Scientists do not completely understand the evolutionary significance of these changes but it is believe to be related to help birds determine that age of potential mates.
On Tuesday I had the opportunity to visit another of our urban raptor nests. I banded nestling peregrine falcons on the Interstate 5 Bridge. Falcons have nested at this site since 2001. At one time they actually nested right on top of the giant cement blocks that raise and lower the bridge. Their nest would go up and down every time the bridge was raised and lowered. In recent years we worked with ODOT to give them a nest box in a less hazardous location. Peregrines do not build stick nests but rather hollow out a "scrape" in sand and gravel that accumulate on ledges.
Adult Peregrine on Interstate Bridge by Dave Helzer
17 Day Old Peregrines on Interstate Bridge by Bob Sallinger
17 Day Old Peregrines on Interstate Bridge By Bob Sallinger