Galliformes (Chicken-like Birds)
Family: Curassows, Guans, and Chachalacas
Family: Fowls and Pheasants
Family: New World Quails
Number of families 5
Number of genera, species 77 genera; 281 species
Evolution and systematics
Few birds have such a long relationship with people as the Galliformes, but their own history is even older. Fossils show that their predecessors date back to the Eocene period (50 to 60 million years ago), when northern latitudes were tropical. The earliest known cracid ancestor was found in the United States in Wyoming, although the megapodes are probably more primitive. All the Galliformes are of a similar, standard design, perfected for a terrestrial lifestyle that has been little modified by millions of years of evolution.
There are two tribes: the Craci (the megapodes, chachalacas, guans, and curassows) and the Phasiani (the turkeys, grouse, New World quails, pheasants, partridges, and guinea fowls). The two are distant in evolutionary terms, and no examples are known of a bird from one tribe hybridizing with one from the other. They are distinguished by the hallux, the hind toe, which in the Craci is in line with the other toes, but in the Phasiani is above the others.
The Phasianidae is numerically dominant, accounting for 155 species. Work on the mitochondrial DNA of birds in the late twentieth century has resulted in the New World quails (Odontophoridae) being split from the pheasants (Phasianidae). Discoveries continue to change our understanding. For example, the Udzungwa forest-partridge (Xenoperdix udzungwensis), discovered in southern Tanzania in 1991, is more closely related to the Asian hill-partridge (Arborophila torqueola).
Several characteristics are common to the Galliformes, all of which can be seen in the domestic chicken, derived from the red junglefowl (Gallus gallus) of Southeast Asia. Most gallinaceous species are medium to large in size, with a stocky body, small head, and short wings. The Old World quails are the smallest, the most diminutive being the Asian blue (Coturnix chinensis) at just 5–6 in (12–15 cm) and weighing less than 1 oz (20 g). By contrast, the wild turkey (Meleagris gallopavo) weighs 17–22 lb (8–10 kg); only the domesticated forms destined for the table can attain 44 lb (20 kg); while a large, male green peafowl (Pavo muticus) is up to 98 in (250 cm) long, although its immense tail accounts for more than half of this. Pheasants in particular show a significant size difference between males and females, with the tail often responsible for one-third of the total.
In many cases, males and females are mottled brown or black, adapted to camouflage in the forest or scrub. In a few species, however, males are colorful, with iridescent colors that have long made them attractive to humans. The male Indian peafowl (Pavo cristatus), the "peacock" of art and the movies, whose fanned tail has hundreds of "eyes" on the tips, is perhaps the most well known.
Feeding ecology and diet
Galliformes are terrestrial, spending their day foraging for food in grasslands or the understory of the forests. Birds have a short, often downcurved bill, used to peck plant material from the ground or from short vegetation, though several species in northern latitudes, such as the capercaillie (Tetrao urogallus), depend on the stiff needles of coniferous trees (Pinus) to see them through the long winter when snow covers the ground. They also have large, strong feet, a crucial attribute that allows them to expose seeds and roots that are inaccessible to most other animals (the name "megapode" is derived from the Greek words for "big foot"). These feet are capable of moving heavy branches or stones; the orange-footed scrubfowl (Megapodius
reinwardt) can move a stone up to eight times its own weight. Their heavy build indicates a diet based on bulky, vegetable matter, although the chicks of many species depend on insects and larvae during their first few weeks.
Gallinaceous birds have a roomy, flexible crop, which can be extended to cache food before beginning to digest it. They also have a very strong gizzard, used to grind down the hard exterior of seeds and nuts, and the tough fibers in green vegetation. To aid digestion, birds regularly swallow small stones. Even the most secretive forest Galliformes visit roads and tracks early in the morning in search of grit before their day's feeding. Some make only occasional visits to water, even during dry periods, but a few species visit salt licks, where they ingest claylike soil to supplement their diet with minerals.
Galliformes display a wide variety of breeding strategies. In general, species with the least sexual dimorphism in size and color are monogamous, and those in which the male has more resplendent plumage are polygynous. In many grouse species, males display at communal leks, seeking to be the dominant male to attract a harem of females.
Male Galliformes have a range of adornments to attract females: bright colors, crests, unusually shaped tail feathers, or markings. Some have additional modifications, such as long, pendant wattles, dewlaps, combs, or "eyebrows." Most species display one of these "badges," or white patches on the wings or tail, although the curassows are the most highly evolved family, with colorful knobs, or ramphothecae, on their bill, which grow larger as the bird ages.
Unlike many nonpasseriform birds, calls play an important part in display and territorial ownership, and also simply to keep in touch with a mate. This is not surprising, since many species are solitary, living deep in scrub or forest, and crepuscular, being most active at dawn and dusk. In tropical areas, the wailing calls of tinamous and guans travel across the forest in the fading daylight, up to 4 mi (6.4 km) in some species. This is possible because a modification in the length of the trachea and a loop between the skin and the pectoral muscles enables some cracids to produce calls at a lower pitch and a higher volume than most other species, although swans (Cygnus) and cranes (Grus) have a similar modification.
The breeding strategy of the megapodes, which do not use body heat to incubate their eggs, is unique in the avian world, although it does not demonstrate a link to reptiles, as some have suggested. The male builds a huge mound of sand or plant material or constructs a burrow, invites a female to lay her eggs, then tends to the nest, regulating the temperature for many weeks until the young hatch. Indeed, some male megapodes are attached to their mound for 11 months of the year. In monogamous species, however, both birds help to rear the young, maintaining the pair bond through mutual preening or activities such as wing-drumming.
In most species, the young are precocious, able to feed semi-independently within a few hours of hatching. Generally, the first downy feathers are subdued in color to reduce the risk of a predator seeing them.
Distribution and habitat
Gallinaceous birds are found in a wide variety of habitats, in semideserts, steppes, savannas, forests, mountains, and farmland. The cracids are the most arboreal family, with most species spending at least part of the time in the forest canopy, but even some of the chachalacas feed in more open habitats. Members of other families are more specialized; for example, the British race of the red grouse (Lagopus lagopus scoticus) lives only on upland Calluna heather moorlands, devoid of any trees, whereas the other 18 races live around dwarf trees!
The Galliformes occur on every continent except Antarctica, with some families found on a single continent—megapodes in Australasia, cracids in Central and South America, turkeys in North America, New World quails in North and South America, and guinea fowl in sub-Saharan Africa. Only two families are spread across more than one continent—grouse in North America and Eurasia, and pheasants and partridges in Africa, Eurasia, and Australasia. There is relatively little geographic overlap between the families, perhaps not surprising given their sedentary nature; most birds moving only a few miles from where they hatched.
The social behavior of the Galliformes is complex, and the commoner species have been the subject of many studies by ornithological and hunting interests. Many species are solitary or spend the year in pairs; the males being strongly territorial, charging intruders with their neck raised and wings spread open. In some grouse species, this has developed into a mating display, in which males demonstrate their defensive prowess to females gathered nearby, a behavior known as "lekking." Outside the breeding season, some species, such as chachalacas, brush-turkeys, and pheasants, feed communally where there is a good supply. Some will also roost communally, flying to the tree canopy where they are safer from predatory ground mammals.
Many Galliformes have cryptic plumages. Birds sit tight in thick vegetation, hoping not to be noticed, and only when the threat is almost upon a bird will it move. A few species, such as the Nicobar scrubfowl (Megapodius nicobariensis), evade predation by running swiftly away, but most species explode into the air in a rush of wings. This is possible because Galliformes have strong breast muscles and strong legs, enabling a near vertical take-off. In flight, many are bulletlike, especially the partridges, their wings beating rapidly, although only over short distances. Birds fly close to the ground, although this brings its own problems. Many capercaillies and black grouse (Tetrao tetrix) are killed against high deer fences around European forestry plantations.
Most gallinaceous birds bathe, often visiting the same sites repeatedly, squatting in a shallow pit and beating their wings to shower sand or dust across their plumage to maintain the feathers and remove parasites. In tropical species, bathing and preening usually takes place during the middle of the day when birds are resting, whereas birds are more active, displaying and feeding, during the three hours around sunrise and sunset.
Most species are sedentary, but a few are altitudinal migrants, moving down the mountainsides outside the breeding season; four Old World quails (Coturnix) are true long-distance migrants, traveling from breeding grounds in Eurasia to sub-Saharan Africa.
Of the 281 species, 104 are Threatened or Near Threatened, far above the average of 10% for all bird species. The pheasants and partridges are under the greatest threat, with 71 listed by the IUCN as Critically Endangered, Endangered, Vulnerable, or Near Threatened; one, possibly two, pheasant species have become extinct since 1600.
Gaps in our knowledge constrain the development of conservation measures for many of the species in the remotest habitats. There are many species, such as the Bruijn's brushturkey (Aepypodius bruijnii), for which further research is crucial to their conservation.
Hunting of adults or the collection of eggs for food remains a problem for several of these "game" birds. Historically, cracids were an important sustainable source of protein
for native Amerindians, but rapid human colonization since 1492 has led to over-exploitation of birds, as well as the destruction of their tropical rainforest habitat. Some species are now on the brink of extinction, with the Alagoas curassow (Mitu mitu) only known in captivity since the 1980s, the horned guan (Oreophasis derbianus) limited to a few isolated mountain ranges in Mexico and Guatemala, and the endemic Trinidad piping-guan (Pipile pipile) now restricted to a few square miles of montane forest on a single island. It is doubtful whether the harvesting of eggs from some species is sustainable, and over-exploitation has probably caused the extinction of several megapode species on Pacific Islands. Such gathering continues today, with, for example, an estimated five million eggs taken every year from a single site in New Britain where Melanesian scrubfowl (Megapodius eremita) gather to breed.
However, habitat destruction is the principal threat. Galliformes that depend on primary, tropical forests are under the greatest threat, with logging of timber or intensive burning to clear the land for agriculture being major problems, especially in Southeast Asia. As if the removal of the old forest was not enough, herbivorous livestock, such as cattle, sheep, and goats, compete with Galliformes for seeds and vegetation. The Galliformes' dependence on certain habitats makes them good indicators of environmental change. As consumers of a large biomass of seeds and roots, they also play a critical role in dispersing seeds, especially in tropical forests.
Our fascination with these amazing birds provides a potential, sustainable solution to the need of local people to earn an income. In parts of South America, for example, ecotourism can be more important to the local economy than logging or beef production, and is certainly better for the Galliformes that birdwatchers come to see.
Significance to humans
We can only guess when Homo sapiens first discovered that some Galliformes were relatively easy to catch and that their meat tasted good and was high in protein. Some time later, as people moved from being hunter-gatherers to farmers, they learned to domesticate several species, including turkeys, chickens, and guinea fowl, which remain part of human diet across the world. Galliform eggs are much sought after, with a high yolk content that provides a rich source of protein. The word "fowl," which is applied generically to game and domesticated birds, has its origins in the Old English fugol, the Old Norse fogl, and the modern German vogel.
During the last 200 years, many gallinaceous species have been moved between countries and continents for decoration or for shooting on vast, private estates. Introductions, whether deliberate or accidental, are the third most serious threat to global avifauna, after habitat destruction and degradation. Introductions are most problematic on islands, and although Galliformes are not known to be an special threat, they have been widely transferred. At least 45 of the 281 species have been introduced to two archipelagoes, Hawaii and New Zealand, though only two-thirds colonized successfully, the rest failing either because of poor stock or an inability to deal with predators that they were not used to facing.
The sedentary nature of most Galliformes makes them popular for shooting. Even in countries where strict legislation makes it illegal to shoot birds, many Galliformes are excluded. At the height of the British Empire, aristocrats and civil servants spent their leisure time in Africa and Asia shooting small game (Galliformes), and brought some of the most numerous back to Europe, most notably the ring-necked pheasant (Phasianus colchicus). Each year, tens of millions are reared and released for shooting. These and European game species, such as the gray partridge (Perdix perdix) and rock partridge (Alectoris graeca), were subsequently introduced into North America for sport.
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BirdLife International. Wellbrook Court, Girton Road, Cambridge, Cambridgeshire CB3 0NA United Kingdom. Phone: +44 1 223 277 318. Fax: +44-1-223-277-200. E-mail: [email protected] Web site: <http://www.birdlife.net>
World Pheasant Association. P. O. Box 5, Lower Basildon St, Reading, RG8 9PF United Kingdom. Phone: +44 1 189 845140. Fax: +44 118 984 3369. E-mail: [email protected] Web site: <http://www.pheasant.org.uk>
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