Breeding Success In Birds Within The Forest ???islands??? In Southern Forest-steppe Of Ukraine
S. O. Liulenko, L. M. Moroz, S. I. Sorokina
During 2005-2015 we conducted the research on the success of laying eggs in 82 species of birds nesting in the island oak and hornbeam forests of the region. 1095 cases of reproduction have been studied. The value of the masonry of each species has changed. 197 clutches (18%) out of 1095 are unfinished (we consider masonry to be unfinished if it consists of 50% or fewer eggs comparing with medium masonry). Very often unfinished masonry or even empty abandoned nests are observed in birds nesting on the ground. The anthropic factors are among the reasons preventing the end of the clutches. They are: grazing, sanitary felling, picking berries and mushrooms, visiting the forest lands for walks, etc. A significant part of the nests was left due to the death of one of the partners from predators or destroying the incipient clutches. The success of birds’ reproduction also reduces masonry or broods and the last ones die. This factor is also mentioned by A.S. Giliazov (1981). Due to the reproduction success, all 82 species of birds are divided into 7 groups with 10% interval between them. The highest success of nesting is observed in sedentary species (on average – 62.23%), and the lowest - in migratory species (on average – 54.03%). This indicates the better fitness of sedentary species to unfavourable weather conditions overcoming, stronger ecological plasticity in general, including all periods of their life cycle including reproduction.