Sandgrouse is the common name for Pteroclidae , a family of sixteen species of bird, members of the order Pterocliformes . They are traditionally placed in two genera. The two central Asian species are classified as Syrrhaptes and the other fourteen species, from Africa and Asia, are placed in the genus Pterocles. 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 the black-bellied sandgrouse and the pin-tailed sandgrouse even extend into the Iberian Peninsula and France, and Pallas's sandgrouse occasionally breaks out in large numbers from its normal range in Asia.
Description
Sandgrouse have small, pigeon-like heads and necks and sturdy compact bodies. They range in size from in length and from in weight. The adults are sexually 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 rapid take 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 genus Syrrhaptes have feathers growing on both the legs and toes, and no hind toes, while members of the genus Pterocles have legs feathered just at the front, no feathers on the toes, and rudimentary hind toes raised off the ground.
The plumage is cryptic, 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 under down 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. The amount of water that can be carried in this way is 15 to 20 millilitres (0.5 to 0.7 fluid ounces).
Distribution
Members of the genus Syrrhaptes are found in the steppes of central Asia. Their range extends from the Caspian Sea through southern Siberia, Tibet, and Mongolia to northern and central China. They are normally resident, but Pallas's sandgrouse can be locally migratory 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 in Yorkshire and Moray.
Members of the genus Pterocles are mainly found in the drier parts of northern, eastern, and southern Africa, though the range of some species extends into the Middle East and western Asia. The Madagascar sandgrouse is restricted to Madagascar. The black-bellied sandgrouse and the pin-tailed sandgrouse also occur in Spain, Portugal, and southern France. Most species are sedentary though some make local migrations, typically to lower altitudes in winter.
Behaviour and ecology
Diet and feeding
Sandgrouse are principally seed eaters. Other food items eaten include green shoots and leaves, bulbs, and berries. Insect food such as ants and termites may also be eaten, especially during the breeding season. 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 of leguminous plants are usually an important part of the diet. In agricultural areas oats 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 whilst Namaqua sandgrouse feed rapidly, exploring loose soil with their beaks and flicking it away sideways. Grit is also swallowed to help grind up food in the gizzard.