raptors

The Red-tailed Hawk, a varied and versatile predator

The Red-tailed hawk is probably the most common hawk in North America. Its winter range includes most of the United States and Northern Mexico, and its summer range extends into most of Canada.

Red tail portrait

Only the adults have the distinctive red tail. Tails of the juvenile birds are light brown that gradually turn red as they mature. Adults have a wingspan of about 49 inches and a body length of about 19 inches. Females are longer than males.

Red tail flying

The plumage of Red-tailed hawks is quite varied. So rather than try to describe it, I scanned page 122 from The Sibley Guide to Birds one of the best bird books available in my opinion.

Red Tail variations

 

Red-tailed hawks are versatile. They inhabit deserts, woodlands, plains, riparian areas, and open areas. Their main prey are rodents, rabbits, and squirrels. They also take other birds such as pheasants, quail, and blackbirds. They will eat snakes and carrion also. They can take and fly off with anything up to about five pounds. They often perch high and wait for prey to show up or soar on the breezes to scan their territory.

Red-tailed hawks often hunt alone, but they also hunt in pairs, especially when they are after squirrels in a tree. They will guard a hunting area and frequently chase off other hawks, eagles, and Great Horned Owls.

According to the Cornell Lab of Ornithology, “Courting Red-tailed Hawks put on a display in which they soar in wide circles at a great height. The male dives steeply, then shoots up again at an angle nearly as steep. After several of these swoops he approaches the female from above, extends his legs, and touches her briefly. Sometimes, the pair grab onto one other, clasp talons, and plummet in spirals toward the ground before pulling away.”

“Both members build the nest, or simply refurbish one of the nests they’ve used in previous years. Nests are tall piles of dry sticks up to 6.5 feet high and 3 feet across. The inner cup is lined with bark strips, fresh foliage, and dry vegetation. Construction takes 4-7 days.” They build the nests in the crowns of tall trees, on cliff ledges, and on structures such as billboards.

According to the Arizona-Sonora Desert Museum, Red-tailed hawk populations are stable and even increasing in some areas. How long do they live? Cornell claims “The oldest known Red-tailed Hawk was 28 years 10 months old.” I’m guessing that bird was in captivity, how else could they know its exact age? I suspect that average life-span in the wild is much shorter. Various sources put the life-span between 10-21 years. Among birds of prey, it is estimated that the mortality rate is as high as 80% during the first year of life due to predation, disease, and starvation. If they make it through the first year to reach adulthood, they can expect a longer life. Many of the birds I handle at the Arizona-Sonora Desert Museum are in their teens, senior citizens of the bird world.

For more photos, see the Arizona-Sonora Desert Museum digital library here. For additional photos, sound recordings, and videos, see the Cornell Lab of Ornithology page here.

Peregrine Falcons

The Arizona-Sonora Desert Museum has recently acquired a Peregrine falcon and a Great Horned owl for Docent handling and interpretation. I am excited because I will be able to handle these birds beginning in January if museum staff can get them trained. I currently handle and interpret Harris’ Hawks and Barn owls.

Peregrine falcon

The Peregrine falcon (Falco peregrinus) has a thousand-year history with humans as a hunting animal, i.e., falconry.

Adult peregrines have a body length of 14- to 19 inches and a wingspan of 39- to 43 inches and weight up to 3.5 pounds. The weight doesn’t sound like much, but try holding that weight on your hand and keeping your forearm horizontal for 45 minutes. That’s what Docent bird handlers have to do.

According to the Cornell Lab of Ornithology, “The Peregrine Falcon is one of the most widespread birds in the world. It is found on all continents except Antarctica, and on many oceanic islands.” It occurs year-round in the western U.S. Those that nest in the Arctic tundra migrate more than 15,000 miles to winter in South America.

Peregrine falcons often nest on ledges or cliff faces (and on buildings and towers). They don’t actually build a nest, just scrape a depression in the soil if they can. The male does most of the hunting while the female broods the chicks. When not breeding, a pair will hunt together.

Peregrines prey upon medium-sized birds, attacking them on the ground and snatching them out of mid-air. They initially strike prey with their feet, then return to capture the stunned bird in mid-air. Peregrines can fly at up to 69 mph in level flight and reach 200 mph in a spiral dive.

You might think that 200 mph air rushing into the nose holes (tubercles) might explode the lungs, but peregrines have a conical bony structure in the tubercles that baffles and slows the air.

Peregrines usually kill their prey by biting the neck. Most falcons (and some hawks and parrots) have a protrusion on the upper bill, called the “tomial tooth,” the purpose of which is to sever the spinal cord of the prey when the falcon bites the neck. You can see that protrusion in the photo below.

Peregrine face

Falcons have very good eyesight. Besides binocular vision, they also have a depression, or fovea, in the retina at the back of the eye which focuses light. This feature gives the bird something like telescopic vision that enables the falcon to follow objects up to a mile away. Each eye can track separate objects independently. When you see a falcon tilting its head, it is most likely using its “telescopic” vision from one eye.

See more information at the Cornell Lab of Ornithology.

See also:

American Kestrel

Barn Owls

Cactus Wren

Cardinals, Pyrrhuloxias and Phainopeplas

Cooper’s Hawks – swift predators

Creatures of the night – Nighthawks and Poorwills

Gambels Quail

Harris’ Hawks, Wolves of the Air

Observations on Mourning Doves

Parrots in the desert?

Ravens and Crows

The greater roadrunner, a wily predator

The Great Horned Owl

Vultures, the clean-up crew

Way of the Hummingbird

Western Screech Owl

 

 

 

The Great Horned Owl

The Great Horned Owls are back in the neighborhood. I hear them, but can rarely see them because they are masters of camouflage (see photo at the end of this post). They have a distinctive sound – a loud ho-ho-hoo hoo hoo, similar to, but deeper than a Mourning Dove. They are the only owls that actual go hoo-hoo. Listen to their sounds at the Cornell Lab of Ornithology here (Scroll down and click the “sound” tab). See 84 photos at the Arizona- Sonoran Desert Museum digital library here.

Great horned owl 1

The Great Horned Owl ranges from the boreal forests of Canada and Alaska to the southern tip of South America. They seem to prefer open, second-growth forest, agricultural areas, and suburban areas. The Great Horned Owl is the third largest owl (the Snowy Owl and Great Grey Owl are bigger), with a length of 15- to 25 inches and a wingspan of up to 5 feet. These owls can weigh over 5 pounds. Females are bigger than males.

Males and females have similar plumage, but that varies regionally. According to The Sibley Guide to Birds, “females average browner and more heavily marked than males. Eastern birds are richly colored. Birds in the western interior region are generally pale and grayish in tone….” The facial disk (which helps focus sound) is orange to gray and sets off yellow eyes.

The “horns” are actually tufts of feathers which can be erect or flat to the head depending on the mood of the owl. From my experience with owls, these tufts are most often erect when the owl is on the alert.

The Great Horned Owl will prey upon anything is can catch and that includes mammals, other birds, reptiles, and amphibians. In the Southwest, cottontail rabbits and jackrabbits are favored. The Great Horned Owls are the only owls known to prey upon skunks, perhaps because they have a poor sense of smell.

Great Horned Owls do not build their own nest but instead seek out the nests of other birds such as hawk nests, squirrel nests, tree holes, rock crevices and nooks in buildings. They begin nesting in January or February and will have up to 5 eggs at a time.

Typical life span in the wild is 13 years, but they have lived as long as 38 years in captivity.

Find the Great Horned Owl in the photo below:

Great horned owl 2

Raptor Free-Flight Returns to Desert Museum

With cooler weather, the raptor free-flight program has returned to the Arizona-Sonora Desert Museum. There are two shows each day at 10 am and 2 pm.

The morning flight features three to five birds which may include Chihuahuan Ravens, Barn Owls, Great Horned Owls, Ferruginous Hawks, Gray Hawks, Prairie Falcons, or Greater Roadrunners. The afternoon flight features a family of Harris’ Hawks.

The shows demonstrate the different behaviors of the birds and their hunting strategies. During the flights, some of the birds fly just inches over your head. After the flights, museum staff usually have the birds on their fist which provides another opportunity to get very close to the birds.

Raptors are birds that eat live prey and also have excellent vision, sharp talons or toenails, and hooked or curved beaks. The ravens and roadrunners are not considered raptors, but they do scavenge and hunt. The raven is an omnivore, and feeds on grains, cactus fruit as well as insects, other invertebrates, reptiles, and carrion. The roadrunner, a member of the cuckoo family, hunts snakes, large insects, lizards, rodents, and various small birds.

The free-flights will be presented each day, weather permitting, through April 11, 2011.

Western Screech Owl, a feisty little raptor

The Western Screech Owl (Otus kennicotti) breeds throughout the western U.S., from southern Canada to Baja California, and other parts of Mexico. This little owl is the fourth and smallest of the raptors I handle and interpret at the Arizona-Sonora Desert Museum. I’ve written previously about the Harris’ Hawk, the Barn Owl, and the American Kestrel. (I also handle snakes.)

Western screech owl

The Western Screech Owl has a body length of 8- to 10 inches, and a wingspan of 20- to 24 inches. (The infamous Cactus Ferruginous Pygmy Owl is slightly smaller.) The yellow eyes are very penetrating. When alert or excited, it raises some feathers on its head – “ear” tufts. The owl is usually gray and streaked with black and white (there is a red race). The only other owl in this region it may be confused with is the Elf Owl, which is much smaller (5 inches in length) and lacks the ear tufts. The screech owl’s toes are zygodactylous (two pointed forward, two pointing backwards). There’s a word for Scrabble fans.

Screech owls generally do not migrate. They are cavity nesters, so you might see one peeking out of a hole in a saguaro cactus. (They will also nest in boxes.) The female lays 4- to 6 eggs, each about 2- to 3 days apart. The chicks hatch after about 26 days and open their eyes after about a week. The female broods the chicks for two weeks while the male brings food. The chicks stay in the nest for about five weeks, all the time being fed by their parents. Life expectancy in the wild is 4- to 6 years, but captive birds are known to have reached an age of 18 years.

The Screech owl is a fierce predator and will attack prey much larger, relative to its size, in comparison with other owls. The screech owl will attack large Norway rats, mice, lizards, insects, smaller birds, scorpions, spiders, ground squirrels, and fish. Its normal habitat in the desert is the wooded areas near mountains, or along tree-lined rivers. In wooded areas, the owl’s dull color makes good camouflage.

Despite its name, the owl doesn’t screech. Instead, it has a series of trilling calls. Screech owls have keen hearing which help in capturing prey, but their hearing is not as specialized as that of the Barn Owl.

Barn Owls, Tyto Alba?

Tyto alba is a denizen of the night who stalks his prey by sound and stealth. He may have passed you close by but you didn’t notice, or maybe you felt a brief ghostly presence. On silent wings, the Barn Owl (Tyto alba) can hunt in almost complete darkness, relying only on the faint sounds made by his intended meal. Fringe-like feathers on the leading edge of the wings help make the flight silent.

The barn owl is a very adaptable bird of prey that is found in specific habitats on all continents except Antarctica. It is the most widely distributed land bird. Barn owls eat rodents, and perhaps because we humans attract such beasties, barn owls favor nesting near human habitation in barns, under bridges, in mine shafts, and in palm trees. In the southwest, barn owls also nest in undercuts in arroyos, and may be found in desert grasslands, and in trees around agricultural fields.

Barn owls often swallow their prey whole, but they can’t digest fur and bone, so they regurgitate pellets. (Dissection of pellets allows researchers to study what the owls eat.)

Barnowl-female

 

 

 

 

 

 

 

 

 

 

Barn-owl-male

Barn owls are sexually dimorphic, that is, the males and females have differing plumage as you can see in the photos. The females tend to be bigger, darker, and more speckled than the males. The birds average about 12 inches in body length and have wingspans of about 33 inches. Weights in adults vary from 10 to 20 ounces.

The feathers form a facial disk designed to focus sound to the owl’s ears. The ears themselves are not symmetrical on the skull as in other animals. Rather the left ear points downward, and the right ear points upward. Therefore, sound reaches each ear at slightly different times and allows the owl to exactly pinpoint the source. Some researchers claim that each ear hears with slightly different frequency sensitivity. That also aides in sound location. Barn owls are smart and learn all the squeaks and twitters of their prey so that they can identify not only where it is, but also what it is. Perhaps the only rodent with equally good hearing is the Kangaroo Rat.

Birds have four toes or talons. They are configured either three in front – one in back, or two and two. The barn owl can move its outer toes to form both configurations. That enables the owl to form a good web-like trap when snatching prey. The barn owl has serrations on the claw of the middle toe to aid grooming.

Barn owls have many vocalizations, some researchers count as many as 15 distinct calls as well as tongue clicking and wing clapping. Some of the sounds are for proclamation of territory, others are for alarm, and some are for courtship and mating rituals. Many of the sounds are screaming or screeching; others include hissing or wheezing, and whistling. None of the sounds are what we would call an owl hoot.

Nesting occurs in the spring in most areas, but can occur any time of year if there is abundant prey available. The female may lay up to six eggs each one to two days apart. Incubation takes 33 days and the young hatch one to two days apart. If the parents don’t provide enough food, the older chicks starve out and may even consume the younger chicks. The chicks will fledge seven to eight weeks after hatching. Barn owls typically breed at an age of one year, and there is a high mortality rate in the wild. Typical wild life expectancy is 2 years, but captive birds have lived into their high teens.

Barn owls are difficult to observe in the wild because of their nocturnal habits. I have seen them sleeping in mine shafts. If you want to seem them close up, go out to the Arizona-Sonora Desert Museum where Docents frequently have them on display.

Barn-owl-chicks