Niche separation of larks (Alaudidae) and agricultural change on the drylands of the former Soviet Union

Variation in the distributions of different species of lark was assessed along the two main agricultural gradients in the steppe and semi-desert zones of Kazakhstan: the intensity of grazing and the time since abandonment of cereal fields. Vegetation structure and composition varied significantly with time since abandonment, and with changing grazing pressure. The studied lark species responded in non-linear ways to both these gradients and showed a high degree of niche separation, with black lark, calandra lark and skylark preferring denser and taller vegetation compared to white-winged lark and short-toed lark. Lark populations generally are likely to have benefited from agricultural abandonment and a decline in livestock numbers over large parts of the steppes and semi-deserts of the former Soviet Union. The results suggest that an assessment of future changes in steppe bird communities based upon projections of changes in the area of gross habitat types can be improved by a better understanding of the responses of different species to more subtle environmental gradients.