Tracking movements of an endangered bird using mark-recapture based on DNA-tagging

Knowing the location and movements of individuals at various temporal and spatial scales is an important facet of behaviour and ecology. In threatened populations, movements that would ensure adequate genetic flow and long term population viability are often challenged by habitat fragmentation. It is also in those endangered populations where capturing and handling individuals to equip them with transmitters or to obtain tissue samples may present additional logistical challenges. DNA-tagging, i.e. individual identification of samples obtained via non-invasive approaches, can reveal certain movement patterns. We used faecal material genetically assigned to individuals to indirectly track movements of a large-bodied, endangered forest bird, Cantabrian capercaillie (Tetrao urogallus cantabricus), for three consecutive mating seasons. We identified 127 individuals, and registered movements of 70 of them (22 females, 48 males). Most movements were relatively short for capercaillie, mostly concentrated around display areas. We did not find differences in movement distances between females and males within mating seasons, or between them. Several longer, inter-valley movements up to 9.9 km of planimetric distance linked distant display areas, showing that both females and males of Cantabrian capercaillie were able to move through the landscape, complementing previous studies on gene flow. Those longer movements may be taking birds outside of the study area, and into historical capercaillie territories, which still include substantial forest cover. Tracking animals via DNA tagging, particularly those on endangered populations, showed clear advantages like non-intrusiveness and potential for sample sizes much larger than via direct handling. However, it also misses out on direct observation and natural history, which would provide key information like social status and timing of movements.