Typology of Great Cormorant (Phalacrocorax carbo) Nesting Colonies in the Azov-Black Sea Region of Ukraine

Abstract

This study presents an analysis of the nesting settlement typology of the Great Cormorant (Phalacrocorax carbo) in the Azov-Black Sea region of Ukraine. It was established that cormorants actively utilize a wide range of habitats for colony establishment, with a preference for natural islands of marine, riverine, and lagoon origin, where optimal conditions for successful nesting are formed. The choice of nesting sites is influenced by the availability of building materials, elevation above water level, distance from the mainland, and the presence of protection from predators. Cormorants build their nests on sandy-shell, clay, and rocky islands, as well as within vegetation cover, selecting trees, shrubs, and reeds.

A particularly interesting aspect is the cormorants' ability to adapt to nesting on man-made structures such as gas platforms, power line pylons, and sunken ships. This phenomenon is becoming increasingly widespread due to the limited availability of natural nesting sites, which is a consequence of anthropogenic impact, and reflects the species’ adaptation to environmental changes. An analysis of 72 colonies revealed that the number of birds significantly increases on artificial structures despite the annual removal of nests during maintenance operations. Cormorants demonstrate high resilience to such interventions, rebuilding their colonies even after destruction.

The study also examined the influence of various factors on nest site selection, including island area, availability of building materials, elevation above water level, and distance from the mainland and human settlements. A direct correlation was found between the number of nests and the size of the nesting territory. Additionally, it was noted that colonies located on islands closer to the mainland face higher risks due to increased accessibility for predators and humans.

This research provides new insights into the nesting ecology of the Great Cormorant in Ukraine and highlights the importance of further studies on the impact of artificial structures on the species’ nesting behavior.