Sand and snow: Wings in the desert

Our third story in the series Specimen Tales

Anand Krishnan writes ~

Birds have colonized some of the most inhospitable environments on earth, and deserts are no exception. The sandgrouse are one of those Afro-Asiatic bird families that symbolize just how birds may adapt to these extreme environments. Famed for their specially adapted breast feathers, which enable adult birds to soak up water and transport it for many kilometers to their young, few other birds are as symbolic of the arid, windswept deserts. Several species of the family Pteroclidae are adapted to breed in the hottest deserts on earth, a fact suggested by the word “sandgrouse”. Although 19th century ornithologists considered them somewhat intermediate between pigeons and gamebirds, they have also been allied with the shorebirds. A comprehensive study by Hackett et al. (2008)[1] placed them close to the pigeons and doves yet again.

In spite of the Sahara-esque connotations that the term “sandgrouse” implies, not all species live in hot deserts. The 14 species of the genus Pterocles span a range of open-country habitats, from stony ground to scrub jungle to cultivated steppe. The remaining two species form a separate genus, Syrrhaptes, characterized by fully feathered toes, and are perhaps the most interesting of all in that they occur in cold deserts in temperate Asia. Regarding the Pallas’ Sandgrouse Syrrhaptes paradoxus (first described from the Kazakh steppe in 1773), John Gould wrote in his seminal Birds of Asia: “This singular bird forms so important a feature of the avifauna of Asia that a figure of it must necessarily be included in a work on the birds of that region.” By then the bird was also known to breed in the Gobi of Mongolia, but the likely reason for Gould’s statement was the intermittent irruptions of large numbers of these birds across Europe. Indeed, several such events in the late 1800s resulted in numbers of birds reaching as far as the British Isles, where they even bred! Birds have also been known to irrupt southwards, with a single female specimen having been collected in Rajasthan, India, in 1924. Nowadays, even a single bird turning up in the UK may create much excitement within the birding community; a bird in Shetland in 1990 drew birders from far and wide.

PallasSandgrouse
– Specimen of a male Pallas’s sandgrouse at the Smithsonian National Museum of Natural History, Washington D.C., in dorsal and ventral view

Gould himself described the second species of Syrrhaptes in 1850, the Tibetan Sandgrouse S.tibetanus. Once again, writing about this much larger species in the birds of Asia his excitement is evident: “…cannot fail to be of interest to the naturalist…from the structure of its feet, being very different from other members of its family, we may infer that some diversity also occurs in their habits.” The type specimen was collected at Tso Moriri in Ladakh, India. The bird is nowadays known to inhabit open country and rocky areas at high altitudes in Central Asia, going as high as 17,000 feet above sea level, feeding on grass shoots and seeds. Could temperature regulation suggest a function for the densely feathered toes of these birds? Given the remarkable interest in the habits, distribution and seasonal movement patterns of members of this genus, many aspects of their behavior and physiology are still poorly understood. Imagine what insight could be obtained by studying such a remarkable bird family, one that has managed to colonize both extremes of temperature known to mankind! Stay tuned for more on this fascinating subject.

TibetanSandgrouse
-Specimen of a male Tibetan sandgrouse at the Smithsonian National Museum of Natural History, Washington D.C., in dorsal and ventral view.

References:
1. Hackett, S. J. et al. 2008 A Phylogenomic Study of Birds Reveals Their Evolutionary History. Science (80-. ). 320, 1763–1768. (doi:10.1126/science.1157704)

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