Sandgrouse is the common name forPteroclidae/tɛˈrɒklɪdiː/, afamily of sixteen species ofbird, members of the orderPterocliformes/ˌtɛrəklɪfɔːrmiːz/. They are traditionally placed in twogenera. The two central Asian species are classified asSyrrhaptes and the other fourteen species, from Africa and Asia, are placed in the genusPterocles. They are ground-dwelling birds restricted to treeless, open country, such as plains, savannahs, and semi-deserts. They are distributed across northern, southern, and eastern Africa, Madagascar, the Middle East, and India through central Asia. The ranges of theblack-bellied sandgrouse and the pin-tailed sandgrouse even extend into the Iberian Peninsula and France, andPallas's sandgrouse occasionallybreaks out in large numbers from its normal range in Asia.
Sandgrouse have small, pigeon-like heads and necks and sturdy compact bodies. They range in size from 24 to 40 centimetres (9.4 to 15.7 in) in length and from 150 to 500 grams (5.3 to 17.6 oz) in weight. The adults aresexually dimorphic with the males being slightly larger and more brightly colored than the females. They have eleven strong primary feathers and long pointed wings, giving them a fast and direct flight. The muscles of the wings are powerful and the birds are capable of rapidtake off and sustained flight. In some species, the central feathers in the tail are extended into long points.
The legs are short and members of the genusSyrrhaptes have feathers growing on both the legs and toes, and no hind toes, while members of the genusPterocles have legs feathered just at the front, no feathers on the toes, and rudimentary hind toes raised off the ground.[1]
Theplumage iscryptic, generally being in shades of sandy brown, grey and buff, and variously mottled and barred, enabling the birds to merge into the dusty landscape. There is a dense layer of underdown which helps insulate the bird from extremes of heat and cold. The feathers of the belly are specially adapted for absorbing water and retaining it, allowing adults, particularly males, to carry water to chicks that may be many miles away from watering holes.[2][3] The amount of water that can be carried in this way is 15 to 20 millilitres (0.5 to 0.7 fluid ounces).[4]
Members of the genusSyrrhaptes are found in thesteppes of central Asia. Their range extends from theCaspian Sea through southernSiberia,Tibet, andMongolia to northern and centralChina. They are normally resident, butPallas's sandgrouse can be locallymigratory and very occasionally is irruptive, appearing in areas well outside its normal range. This happened in 1863 and 1888, and a major irruption took place in 1908 when many birds were seen as far afield as Ireland and the United Kingdom where they bred inYorkshire andMoray.[3][4]
Members of the genusPterocles are mainly found in the drier parts of northern, eastern, and southernAfrica, though the range of some species extends into theMiddle East and westernAsia. The Madagascar sandgrouse is restricted toMadagascar. Theblack-bellied sandgrouse and thepin-tailed sandgrouse also occur inSpain,Portugal, and southernFrance. Most species aresedentary though some make local migrations, typically to lower altitudes in winter.[4]
Sandgrouse are principallyseed eaters. Other food items eaten include green shoots and leaves,bulbs, andberries. Insect food such asants andtermites may also be eaten, especially during the breeding season.[1] The diet of many sandgrouse is highly specialised, with the seeds of a small number of plant species being dominant. This may depend on local availability but in other cases it reflects actual selection of favoured seeds over others by the sandgrouse. Seeds ofleguminous plants are usually an important part of the diet. Inagricultural areasoats and other grain are readily taken. Seeds are either collected from the ground or directly from the plants.
Foraging techniques vary between species that coexist, which reduces competition; in Namibia,double-banded sandgrouse feed slowly and methodically whilstNamaqua sandgrouse feed rapidly, exploring loose soil with their beaks and flicking it away sideways.[5] Grit is also swallowed to help grind up food in thegizzard.[1]
Sandgrouse are gregarious, feeding in flocks of up to 100 birds. As a consequence of their dry diet, they need to visit water sources regularly. Drinking times vary among the species. Ten species drink at dawn, four at dusk, and two at indeterminate times.[1] When drinking, water is sucked into the beak, which is then raised to let the water flow down into the crop. By repeating this procedure rapidly, enough water to last twenty four hours can be swallowed in a few seconds.[1] As they travel to water holes, theycall to members of their own species and many hundreds or thousands synchronise their arrival at the drinking site despite converging from many different locations scattered over hundreds of square miles (kilometres) of territory.[6]
They are vulnerable to attack while watering but with a large number of birds milling about, predators find it difficult to select a target bird and are likely to have been spotted before they can get close to the flock.[3] The choice of a watering site is influenced by the topography of the nearby ground. The sandgrouse tend to avoid sites with cover for mammalian predators and their greatest risk is usually from predatory birds.[7]
Sandgrouse travel tens of miles to their traditional water holes and tend to disregard temporary water sources which may appear periodically. This clearly has a survival value, because a dried up water source in an arid region could result in dehydration and death.[3] The Burchell's sandgrouse in theKalahari Desert sometimes travels over 100 miles (160 km) daily to reach a water source.[4] Not all species need to drink every day, and theTibetan sandgrouse does not need to travel to drink, because of the abundance of water from melting snowfields in its habitat.[3]
Sandgrouse aremonogamous. The breeding season usually coincides with a crop of seeds after the local rainy season and at this time the feeding flocks tend to break up into pairs. The nesting site is a slight depression in the ground, sometimes lined with a few pieces of dry foliage. Most typically, three cryptic eggs are laid, though occasionally there may be two or four. The intricately patterned, precocial downy young, and egg colouration (though not shape) closely resemble those of manyCharadriiformes. Eggs are near elliptical.[8]Incubation duties are shared; in most species, the males incubate at night while the females sit on the eggs during the day. The eggs usually hatch after 20–25 days.
Theprecocial chicks are covered with down and leave the nest as soon as the last hatchling has dried out. The parents do not provide them with food and they learn, with parental guidance, what is edible and what is not. The chicks obtain their water from the soaked downy feathers on the adults' breasts. Chicks are too small and young tothermoregulate at first, and their parents shade them during the hottest part of the day, and brood them to keep warm at night. The chicks remain with their parents, as a family group, for several months.[2]
The Pteroclidae was formerly included in theGalliformes due to the similarities the family shares with the true grouse. However, it was later discovered that these similarities are superficial and a result ofconvergent evolution.[9] Sandgrouse were later placed near theColumbiformes largely due to their reported ability to drink by the "sucking" or "pumping" action ofperistalsis of theesophagus, an unusual characteristic.[10] More recently, it has been reported that they cannot suck up water in this way,[11] and they are now treated separately in the order Pterocliformes. They have been considerednear passerine birds, and are thought by some to be closer to the shorebirds (Charadriiformes).[12]
In the DNA-study by Fain and Houde (2004)[13] they were included in theMetaves, together with the Columbiformes. In the larger study by Hackett et al. (2008)[8] they were once again positioned close to the Columbiformes, inColumbimorphae, but also with theMesites.
Length 31 to 39 centimetres (12 to 15 in) There are two subspecies:[16] P. a. alchata – Spain, Portugal, France, north west Africa P. a. caudacutus – Middle East, Turkey and eastward to Kazakhstan
Length 31 to 39 centimetres (12 to 15 in) There are three subspecies:[17] P. b. ansorgei – south west Angola P. b. bicinctus – Namibia, Botswana, north west Cape Province P. b. multicolor – Zambia, Malawi, Mozambique and Transvaal
There are five subspecies:[19] P. c. atratus – Saudi Arabia, Iran, Afghanistan P. c. coronatus – Sahara, Morocco to Red Sea P. c. ladas – Pakistan P. c. saturatus – Oman P. c. vastitas – Sinai, Israel, Jordan Status: Least concern
There are three subspecies:[20] P. d. decoratus – south east Kenya and east Tanzania P. d. ellenbecki – north east Uganda, north Kenya, Ethiopia, Somalia P. d. loveridgei – west Kenya, west Tanzania
There are six subspecies:[21] P. e. ellioti – Sudan, Eritrea, north Ethiopia, Somalia P. e. erlangeri – Saudi Arabia, Gulf States, Yemen P. e. exustus – Mauritania to Sudan P. e. floweri – Egypt (almost certainly extinct) P. e. hindustan – south east Iran, Pakistan, India P. e. olivascens – south Ethiopia, Kenya, north Tanzania Status: Least concern
There are two subspecies:[22] P. g. gutturalis – south Zambia, Zimbabwe, Botswana, South Africa P. g. saturatior – Ethiopia, Kenya, Tanzania, north Zambia
There are five subspecies:[24] P. l. targius – Sahara, Sahel, south Morocco to Chad P. l. lichtensteinii – Israel, Sinai, Egypt, Sudan, Ethiopia, Somalia P. l. sukensis – Sudan, Ethiopia, Kenya P. l. ingramsi – Yemen P. l. arabicus – Saudi Arabia, Iran, Afghanistan, Pakistan Status: Least concern
There are two subspecies:[26] P. o. arenarius – Kazakhstan, Pakistan and western China P. o. orientalis – Northwest Africa, Canary Islands, Iberian Peninsula, Cyprus, Middle East, Turkey and Iran
Sandgrouse have little interaction with people, primarily because most species live in arid unpopulated areas and at low densities. They are not generally sought after asgame birds as they are not especially palatable, although they have on occasion been taken in great numbers at water holes. An attempt tointroduce them intoNevada failed but they have been introduced toHawaii.[32] No species is considered to be threatened although there have been some localised range contractions, particularly in Europe.[33] A subspecies of the chestnut-bellied sandgrouse,P. e. floweri, was last seen in theNile Valley of Egypt in 1979. It is thought to be extinct, but the reasons for this are unknown.[34]
^Ward, P. (1972). "The functional significance of mass drinking flights by sandgrouse (Pteroclididae)".Ibis.114 (4):533–536.doi:10.1111/j.1474-919X.1972.tb00854.x.
^Ferns, P. N.; Hinsley, S. A. (1995). "Importance of Topography in the Selection of Drinking Sites by Sandgrouse".Functional Ecology.9 (3):371–375.doi:10.2307/2389999.JSTOR2389999.
^Maclean, G. L. (1967). "Die systematische Stellung der Flughühner(Pteroclididae)".Journal of Ornithology.108 (2):203–217.doi:10.1007/BF01671410.S2CID39713128.
^Lorenz, K. (1939). "Verhandl".Deutsch. Zool. Ges. (in German).41 (Zool. Anz. Suppl. 12):69–102.
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