We used measurements of museum skins to assess morphological differences between the 22 currently recognized species of wheatear and to identify correlations between morphological features, behavioural traits and degrees of sympatry between species. Ground-dwelling species of steppe-like habitats have long tarsi, long claws and short tails; some are migratory and have long pointed wings and non-emarginated primaries ( O. isabellina and O. oenanthe ), while others are sedentary and have more rounded and slotted wings ( O. bottae , O. heuglini and O. pileata ). Vegetation-tolerant species ( O. pleschanka , O. hispanica , O. cypriaca and O. deserti ) have relatively long tails, short tarsi, long middle toes and long claws. The rock-dwelling species have short tarsi, long toes and short claws; they can be either relatively heavy ( O. leucura and O. monticola ) or light, like the wheatears inhabiting the most arid areas ( O. monacha , O. leucopyga and O. alboniger ). Although sedentary, the latter show intermediate characteristics between sedentary and migratory species, having relatively pointed wings with non-emarginated primaries. Together with their low wing-loadings, these traits may be related to the scarcity of resources in their habitats, which obliges them to make frequent and long flights. The clear morphological differentiation between wheatear species appears to be mainly related to their migratory and foraging habits, but seems to bear no relation to their degree of sympatry.

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