Assessing Habitat Suitability for the Common Pochard, Aythya Ferina (Anseriformes, Anatidae) at different Spatial Scales in Orel’ River Valley, Ukraine

The habitat suitability for the Common Pochard, a duck species in decline, was studied in the middle reaches of the Orel’ River, Central Ukraine, in 2015–2017. The ducks were counted on their breeding grounds with the use of the ground survey technique. The positions of individual birds were estimated by GPS and plotted on the Google Earth map. The Ecological Niche Factor Analysis (ENFA) was applied to assess the habitat suitability. Sentinel-2 image was used to extract 13 ecogeographical variables and to get two measures of the ecological niche (marginality and specialization). The ENFA procedure was applied twice at landscape and sub-landscape levels to describe the habitat selection across sequential spatial scales. Both the axes of marginality and specialization of the ecological niche of the species proved to be significantly different from the random alternatives. At landscape level, the distribution may be predicted with the use of Aerosol/Coastal, Vegetation and Hydrothermal Composite indices (marginality) and Modified Normalized Difference Water (MNDW) Index along with several vegetation indices (specialization). At sub-landscape level, MNDW played a crucial role. The importance of MNDW is mediated by the preference for the wetlands with the stretches of open water which are used by the ducks to initiate flight safely and to optimize diving possibilities. The ENFA is a reliable tool for the assessment of the habitat suitability and for setting the conservation priorities for the Common Pochard.