Ecological segregation in the wheatear genus Oenanthe is a complex and intriguing question in which the relationships between species are still uncertain. It also remains to be seen why several species often coexist in arid and apparently simple mono-layered environments and why there is a lack of evident differences between the etho-ecological characters of different species. We studied the patterns of coexistence of 11 species in their breeding grounds in the Zagros Mountains and in arid and semi-arid areas in the north-east of Iran. We focused on the relationship between habitat selection, behavioural characteristics and morphological traits in species with overlapping ranges. During point-censuses, we recorded 19 behavioural characteristics by monitoring each individual during a 20 minute period, using the sit-and-wait method, and measured 36 habitat variables within a 100-m radius around observed birds. We also measured 21 biometric variables in each species from a total of 179 museum skins. Our results showed that spatial overlapping between wheatear species in Iran is greater than has previously been reported. Habitat segregation seems to be more related to geomorphological features than to vegetation cover and/or vegetation type. Behaviour seems to be the most important element of niche segregation between syntopic species. We found no evidence of character displacement, although we did find marked differences between species (syntopic or otherwise) in behavioural characteristics that included feeding tactics, locomotion patterns and the use of perches. Morphological traits are more correlated to behavioural traits (especially foraging behaviour) than to habitat characteristics. Our results support the idea that morphology is an important cue for determining the ecological niche of a wheatear species.

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