Ferruginous Hawk – The Largest of the Hawks

Ferruginous Hawk (Buteo regalis) photos by Mary Claypool

What in incredible way to bring in the new year! Our local Wintu Audubon Society chapter had a couple of excellent Christmas Bird Counts to end the 2007 season! The last count in our area was done on December 29th with a total of 126 species counted.

The following day was gorgeous and the birds were all out searching for food after several days of bad weather. One of the incredible birds I was able to see the last Sunday of the year was the beautiful Ferruginous Hawk.

The Ferruginous Hawk is the largest hawk in North America with a 52 – 56 inch wingspan. They are 22 – 27 inches long and can weigh over 4 pounds! The sexes are alike and, as with most raptors, the female is larger than the male. There are two color forms (morphs) of this large hawk:

• Light morph birds (most common) have a rust colored back and shoulders; head paler, grayish and streaked; white tail washed with pale rust. On the upperwing surface, large, white crescent-shaped patches make a bold flash in the extended primaries. The undersides are white with limited streaking; rusty leggings form a conspicuous “V” against the white in the adult bird, the leggings are white on juveniles. The legs are feathered to the toes.
• Dark morph birds (rare) are dark brown to cinnamon on both upperparts and underparts with light areas on the upper and lower wings.

The breeding habitat of the Ferruginous hawk is open country in mid-western North America, from eastern Washington and southern Alberta eastward to southwestern Manitoba and eastern South Dakota, southward to Arizona and the Texas panhandle. They winter from northern California and southern Nebraska southward to central Mexico. They may be found in semiarid grasslands with scattered trees, rocky mounds or outcrops, and shallow canyons that overlook open valleys. During migration they may be found along streams or in agricultural areas.

These large hawks begin nesting in March in some areas but in most areas of their breeding range they start nesting in May. They create a bulky stick nest, 3 feet across and 2 feet tall in trees (including cottonwoods, willows, and oaks), on rocky outcrops, hillsides or rock pinnacles. Sometimes the nest is lined with cattle dung. They may also build nests on transmission towers and sometimes nests are built right on the ground making them vulnerable to predation by coyotes and foxes.

Ferruginous hawks lay 3 to 5 white eggs, blotched with brown anytime from March through July. Both adults take turns incubating the eggs for 28 – 32 days. The young fledge when they are 38 to 50 days old and remain with the parents for several weeks after fledging. They raise a single brood per season and their survival rate is tied closely to their food supply.

Ferruginous hawks search for prey while flying over open country or from a perch. They often hover when hunting. They may also wait in ambush outside the prey’s burrow. Their main source of food are rodents found in their grassland habitat. Primarily ground squirrels, rabbits, gophers, kangaroo rats and prairie dogs. These small to medium sized mammals comprise the bulk of their diet but they will also eat snakes and large insects.

Birds have been known to live for 20 years in the wild but most Ferruginous hawks probably die within the first five years. Threats to the overall population include cultivation of native prairie grassland contributing to loss of habitat; habitat loss due to encroaching trees; reduction of food supply due to agricultural pest management; and, believe it or not, shooting and human interference. These birds are considered threatened in several states.

Ferruginous hawks are not common in northern California and I feel very fortunate to have seen two in the last two weeks. As I stated in my post back in October, “Fall is a Great Time for Bird Watching.” We get to see many birds that only stop by during the winter months.

I want to thank Mary Claypool for allowing me to use some of her incredible photos. You can see more of her work by clicking on her name above or her link in my blogroll.