Abstract
With the global rapid expansion of urban and developed areas, an understanding of how species adapt behaviourally and physiologically to changing environments is of ever-increasing importance. Anthropogenic land development is of particular significance to species that traverse long distances in groups, such as migratory birds. Despite the high energetic cost of powered flight, there has been little research into how bird species adapt their flight patterns in response to changes in topography. Notably, there remains a gap in our understanding of how terrain cover impacts the energetic cost of flight. We examined several parameters describing flight and flock behaviours in three cluster flocks of homing pigeons (Columba livia d.), including flap frequency as a proxy for energy expenditure. Each flock was flown repeatedly over a heterogeneous landscape of open, wooded, and urban habitats. We found that the birds adopted significantly slower flight and less dense flocking behaviour when traversing over woodland, while flying significantly faster with a lower flap frequency over urban areas. The causes of these trends are not immediately clear, and we discuss a range of potential explanations, including the influence habitat has on the wariness of individuals and the significance of landmarks and visual noise in aerial navigation.