Some types of birds in the course of their life create forms of the earth’s surface, which sometimes can be present on quite large territories. Most often these landforms have the rank of pico-, nano- and, more rarely, microrelief.
Depending on the character of influence on the earth’s surface and existing relief, birds can perform the roles of “constructors”, “destructors”, “compilers” and “conveyors”. “Constructors” create accumulative biogenic relief forms, “destructors” take an active part in the formation of denudation relief forms, “compilers” participate in the accumulation of sediment, while “conveyors” take part in the relocation of sediment. As a result of their activities, two types of relief are formed, namely accumulative (formed by “constructors” and “compilers”) and denudation (created be “destructors”).
Among the accumulative biogenic relief forms created by birds within the territory of Ukraine, there can be named mounds at the foot of steep slopes and hills within the nesting cells, created by sand martins and bee-eaters; nest cones of flamingos; nests of Eurasian coots, etc. As regards the denudation relief forms, burrowing nests of many birds can be specified. It should be mentioned, that the biogenic denudation relief forms created by birds (burrowing nests) are found in different parts of our country much more frequently than accumulative ones. In many cases, they form a porous surface of mural slopes, composed of friable material.
The results of field research of biogenic relief forms within the territory of Ukraine give grounds to assert that the most extensive relief-forming activity among the birds within our state is done by European sand martins and European bee-eaters.
Sand martins, which nest in large colonies up to 1.5 (sometimes even more) thousand pairs, in the course of their life, have a very significant influence on the earth’s surface and existing relief. They build their nests-burrows oh high steep shores of large bodies of water made of soft loose soil. More rarely, birds use quarry slopes, hills on the roadside or construction sites. The horizontally located hole is excavated at the top part of the precipice at a height of at least 1-1.5 m from its bottom. Its length ranges from 20 cm to 1 m, although sometimes it can reach 1.5 and even 2 m. The height of the entrance in the hole is 50-100 mm, and the width is 60-120 mm. The hole ends with a small extension (a nesting cell) the size of 80-120 mm × 100-120 mm. There is a litter composed of grass, straws, feathers and so on in the nesting cell. Its thickness in the central part can reach 2.5 cm. With height, the density of holes increases and their number can reach more than two dozen per 1 m². During the field research, the areas of slopes with holes of sand martins up to 1 km long were identified.
The construction and functioning of nests provoke the emergence of the scree-forming process, which leads to the formation of screen cones. The height of individual cones can reach 1m.
Bee-eaters also equip burrowing nests and form a porous surface of slopes. These birds nest in colonies ranging in numbers from several birds to several dozen or even hundreds of pairs. They mostly equip nests at a height of 3-5 m from the bottom of the precipice. For digging holes, bee-eaters prefer loam, although the soil does not play a large role. In a dense soil, the birds dig a hole with a short passage from 0.5 to 1 m, whereas in a loose soil it is built with a long passage, up to 1.5 (sometimes 2-3) m. The holes of bee-eaters are almost always horizontal and end with an extended nesting cell, which does not have a picohill in the middle.
Biogenic relief forms within the territory of Ukraine are also created by common kingfishers, blue-cheeked bee-eaters, European rollers, rosy starlings, woodpeckers, Eurasian coots and flamingos, but the scale of their relief-forming activity influence on earth’s surface is considerably smaller in comparison with sand martins and bee-eaters.
Water Erosion in the Moulouya Watershed and its Impact on Dams' Siltation (Eastern Morocco)
