SHRIKES: LaniidaeWHITE HELMET-SHRIKE (Prionops plumatus): SPECIES ACCOUNTS
LOGGERHEAD SHRIKE (Lanius ludovicianus): SPECIES ACCOUNTS
Shrikes range in size from 5.7 to 19.6 inches (14.5 to 50 centimeters) and can weigh anywhere from 0.6 to 3.52 ounces (18 to 100 grams). They are predatory birds, living by feeding on other animals, and they usually have sharply hooked, raptor-like beaks and powerful legs. With so many species in the family, shrikes' coloring varies widely. Some are vividly colored in greens, reds, and yellows, such as the yellow-crowned gonolek and the gray-headed bush shrike, but many others are dramatically patterned with black masks and wing bars, showing pure white underneath and deep black, gray, or russet, a reddish brown, upperparts. The helmet shrikes are known for their bristly feathers on their forehead and, usually, colored wattles, fleshy folds of skin, around their eyes. Except for a few species, including the red-backed shrike, males and females of this family do not look very different. Young shrikes tend to be brown and have many wavy lines and patterns throughout their plumage, feathers.
Shrikes appear throughout the world in Europe, Asia, Africa, North America, Russia, and New Guinea. Virtually all of the bush-shrike species live in Africa, while the helmet-shrikes and the true shrikes live in sub-Saharan Africa. Of the true shrikes, the loggerhead is the only species to occupy North America. The other species are more widespread.
Just as shrikes inhabit many different areas of the world, they also live in many kinds of environments. For instance, many of the larger bush-shrikes occupy lowland and montane woodland up to 9,800 feet (3,000 meters), tending to keep to canopies, upper level of the forest, of trees or their undergrowth. Some shrikes, including the puffbacks, like to live in the tops of high trees in suburban gardens, whereas gonoleks and boubous prefer to look for prey near the ground in thick vegetation and scrub. Except for the marsh tchagra, tchagra shrikes search out dry, semi-open habitat with thick vegetation. Helmet shrikes are common in savannas and open woodlands, and are sometimes even seen in peoples' gardens. The true shrikes, meanwhile, require semi-open habitats with trees for perching so they can look down onto their hunting grounds.
Shrikes are generally insect eaters, but the larger bush-shrike species and the true shrikes add to their diet with small mammals and other birds' eggs, as well as berries and small fruits.
A FULL CUPBOARD IS A TURN ON
With their habit of impaling their prey on thorns and other sharp projections in their environment, loggerheads often create what biologists believe are "larders," or storehouses of food. These serve to both attract mates, who appreciate good providers, and tide the birds over when there is less prey available.
BEHAVIOR AND REPRODUCTION
Bush-shrikes, which make up the majority of the shrike family, make neat, cup-shaped nests of grass, fine roots, and small twigs, placing them in trees or bushes and sometimes using spider webs to hold them together or snake skins to decorate them. These birds are known to be territorial and monogamous (muh-NAH-guh-mus), having only one mate. After the breeding season, which is usually begins with the start of the rainy season, female bush-shrikes usually lay two or three eggs. Helmet-shrikes, of which very little is known about their breeding behavior, are cooperative breeders, where a dominant mating pair has a number of helpers that assist in feeding and caring for their nestlings, young birds that are unable to leave the nest. These are called "family parties." Helmet-shrikes make small, cup-shaped nests from bits of bark with spider web decorations. The females lay a clutch of two to five eggs. True shrikes also use cooperative breeding. Their nests are cup shaped as well, but sometimes messily constructed. Females lay clutches of three to eight eggs, and their nestlings remain in the nest for fourteen to twenty-one days. Some of the shrike species put on courtship displays, behaviors that lead to mating, such as males and females singing duets, showy flights, and puffing out their back feathers.
Because most shrike species live in heavily vegetated areas and are sedentary, stay in the same area throughout the year, biologists know relatively little about their behavior, because they are hard to find. Bush-shrikes sometimes give their presence away to birdwatchers by their distinctive, piercing whistles and bell-like sounds, especially those that live in dense bush or tropical forests. Helmet-shrikes, like the true shrikes, are more outgoing and visible, gathering and feeding in groups of up to thirty individuals. Twenty-three of the twenty-five true shrike species are extremely territorial and mark out individual areas for themselves that vary in size depending on the species. They generally practice ritual courtship feeding, where the male feeds the female.
Bush-shrikes tend to feed by rummaging through vegetation at different levels of the forest ecosystem. Helmet-shrikes are noisy, sociable hunters that search the woods from tree base to upper branches. The true shrikes depend upon their patience and sharp vision to catch prey, sitting for long periods on perches until something on the ground draws their deadly attention. However, they also jump into the air to catch insects.
SHRIKES AND PEOPLE
Shrikes have only recently overcome their reputation as "harmful" birds, although they are still hunted and either eaten or used as decoys to capture larger birds of prey. Founded in 1991, the International Shrike Working Group, along with numerous bird groups around the world, is working to protect this bird family and learn more about it.
Nine shrike species, including six bush-shrikes, two helmet-shrikes, and one true shrike, are currently on the World Conservation Union (IUCN) Red List, a list of globally threatened animals, those at risk of extinction. All of them are native to sub-Saharan Africa and all live in forest habitats, which are rapidly being cleared to make way for agriculture that use a lot of pesticides. Five other species are listed as Near Threatened, in danger of becoming threatened with extinction, for the same reason.
Physical characteristics: Also known as white-crested helmet-shrikes, white helmet-shrikes are distinguished by their helmet-like ruff of stiff white feathers around their bills and foreheads that blend into a long, erect crest. They range in size from 7.4 to 9.8 inches (19 to 25 centimeters) and typically weigh between 0.9 and 1.3 ounces (25 to 37 grams). Males and females look very similar, but the female is slightly larger. The birds' crown, sides of head, and cheeks are gray, with a dark bar on the sides of and around the neck. Otherwise, the upperparts are greenish black, with a narrow white stripe down the wing. Undersides are bright white, including the underside of the tail. The white-crested helmet has a greenish black bill, yellow eyes surrounded by a yellow wattle, and orange-yellow legs and feet. Young birds are similarly colored, but more subtly.
Geographic range: White helmet-shrikes are native and locally common in sub-Saharan Africa from the western side of the continent east to Eritrea and south along the eastern side of the continent to South Africa. They may also be found in southern Africa from northern Namibia east and south across northern Botswana and South Africa and south into Mozambique and Swaziland.
Habitat: The dominant breeding pairs live in deciduous broad-leaved woodlands, while subordinate, nonbreeding individuals often move farther out during the winter into savannah and cultivated gardens outside cities. This species will rarely breed in eucalyptus (yoo-kah-LIP-tus) plantations.
Diet: Like the majority of the Laniidae family, white helmet-shrikes forage, search for food, in the canopies of trees as well as on their branches and trunks, and on the ground. They also catch insects in the air on occasion. This species spends most of its foraging time in the winter on the ground, and stays in the trees during warmer seasons. White helmet-shrikes especially favor foraging in areas of recent fires. In general, they eat mainly caterpillars, moths, termites, and grasshoppers, but will also eat spiders and lizards.
Behavior and reproduction: White helmet-shrikes are often seen moving among trees in small flocks of three to twenty-four individuals. Their coloring and undulating, wave-like, flight pattern are unmistakable, as is its group chorus, which has been described as sounding like "krawow, krawow, kreee, kreee, kreepkrow, kreep-krow." They are extremely sociable birds, one calling bird will always cause the others in the group to respond. Growls, bill snaps, and squeaks are also used to alert others about prey, intruders, nesting needs, etc. Dominant and subordinate individuals have different calls. The birds are resident, but not sedentary, and leave their breeding territories to wander their local habitats after the young leave the nest.
White helmet-shrikes become sexually mature at two years of age, although the vast majority never get a chance to breed until they are five years old. This is due to the hierarchical (hi-uh-RAAR-kih-kul), rank, structure of their populations, in which there is only one mating pair allowed within a "family party." Other members of the family party are assistants to the dominant pair. The dominant pair chooses the nest site, but all members of the group help build the nest, incubate the clutch, and guard and feed the nestlings.
Dominance is asserted by nudging others away from food and getting prime spots at the roost, but obvious aggression is unusual. These shrikes are extremely social birds and tend to do everything together: preening, attacking intruders, and foraging. Their noisy communications echo through their forest homes as they coordinate activities among themselves. Groups of helmet-shrikes often join with other species of birds as they move around their territory. However, one group of white helmet-shrikes will firmly defend its territory against another group, with displays of bill snapping, calling, and stretching their heads upward. The face-off ends when members of one group fly at the other, hopefully causing the offending group to retreat.
White helmet-shrikes and people: Although many shrikes are still hunted by humans, white helmet-shrikes have no other special significance to people.
Conservation status: White helmet-shrikes are not threatened. ∎
Physical characteristics: Also known as migrant shrikes and butcherbirds, loggerhead shrikes grow to about 8.2 inches (21 centimeters) long and 1.7 ounces (48 grams) in weight—about as large as a robin. This striking bird is relatively large within the Laniidae family, and has a large head as well, which may be the source of its unusual name. Males and females look similar, with gray, white, and black markings and a black mask that extends to just over the eyes. Their upperparts are gray with white bands at the shoulders, while the bottom half of the wing is black. Undersides are white and sometimes have a barred texture. The loggerhead's appearance varies subtly by region throughout its range.
Geographic range: The only shrike native to North America, the loggerhead also occupies large areas of Mexico, Alaska, and Canada, although its Canadian and Alaskan ranges shrink considerably during winter.
Habitat: Loggerhead shrikes live in many types of semi-open habitats that are dominated by short vegetation. Those native to Illinois, New York, and Maryland frequent pastures, while those endemic to western states prefer sagebrush, desert scrub, and pinyon-juniper woodlands with small shrubby trees. Residential areas with suitable perches often have a number of loggerhead shrikes occupying them, and the birds have been recorded in mountainous areas up to 6,600 feet (2,000 meters) as well.
Diet: Loggerheads eat mainly arthropods, invertebrates (animals without backbones) that have segmented bodies, but seem to prefer beetles and grasshoppers. They feed on small vertebrates, animals with backbones, such as mice, moles, lizards, small birds and snakes, bats, and fish, especially in winter.
Behavior and reproduction: Loggerhead shrikes kill their vertebrate prey by quickly breaking their necks and using their sharp, heavy bills, which have a special cutting tooth on the upper part, to sever the spinal cord. The birds carry prey up weighing as much as their own body weight to a fence or thorny bush where they can impale their meal. This technique also allows them to anchor their prey as they dismember and eat them, since their claws are not strong enough for this purpose.
The loggerhead's flight pattern is distinctive, characterized by wing fluttering followed by a glide. When hunting, the birds swoop down from their perch, hover briefly over an area of open ground, and then flap up to another perch.
This species mates in the spring, during which they are most vocal. They do not have a song, but rather a series of sounds more like shrieks or a metallic tapping. Loggerheads are sexually mature at one year, and are usually monogamous, although sometimes a female will mate with a second male and have a second brood during breeding season. Loggerheads sometimes even mate with other species of shrikes. They prefer to mate and raise their young in grassy pastures, shrubs or small trees, on utility wires, or high up in dead trees. Both sexes gather the nest materials, but the female alone makes the structure. The female lays a clutch of five to seven eggs and then begins to incubate them for about sixteen days. The male feeds her during this period. Both parents feed the nestlings, which remain under their care constantly for seventeen to twenty days. The young stay near the nest after fledging, growing the feathers needed for flight, returning at night to be warmed by the female parent, and they receive food from both parents for up to three weeks after leaving the nest. Soon after, the family group breaks up and the individuals begin migration.
Loggerhead shrikes and people: Humans are increasingly appreciative of the loggerhead's ability to control local populations of pest insects and mammals. These birds are also of major interest to conservationists, because their numbers are decreasing for no apparent reason. However, habitat fragmentation and destruction are thought to be major causes.
Conservation status: Loggerhead shrikes are considered endangered, facing a risk of extinction, in Quebec, Canada, but otherwise it is not yet officially on the threatened list. One of its subspecies, the San Clemente loggerhead, is highly endangered, although conservation efforts have improved its outlook. ∎
FOR MORE INFORMATION
Harris, T. Shrikes and Bush-shrikes. Princeton, NJ and Oxford, U.K.: Princeton University Press, 2000.
Van Nieuwenhuyse, D. "Global Shrike Conservation: Problems, Methods, and Opportunities." Aves 36 (1999): 193–204.
"Birds: Loggerhead Shrike." Hinterland Who's Who. http://www.hww.ca/hww2.asp?pid=1&id=52&cid=7 (accessed on July 2, 2004).
"Helmet-Shrikes Prionopinae." Bird Families of the World http://www.montereybay.com/creagrus/helmet-shrikes.html (accessed on July 2, 2004).