Spatial and Temporal Dynamics of Owls Feeding and the Ornithogenic Deposits Formation

Deposits accumulated by raptors over long periods of time can record changes in small mammal populations. However, between the natural community and the paleocommunity of small mammals in the ornithogenic localities, a number of stages of the taphonomic process pass. The initial stage is associated with the selectivity and plasticity of the predator’s diet. We have studied an accumulation of great gray owl (Strix nebulosa) pellets in order to better understand this process. For seven years, during the nesting period, 712 pellets were collected at four study sites containing 6328 identified remains (NISP) of 2350 individuals (MNI). Several years of pellet accumulation is not enough to form a complete list of all available prey. Prey ratios can be established in ornithogenic deposits during several phases of the small mammals’ population cycle, but they depend significantly on the habitat conditions of the nesting area. A significant change in the diet structure during the nesting period from the stage of egg laying and incubation to the stage of nestling feeding was noted. Given that most of the remains accumulate in the second stage, the features of the diet that are characteristic of it are enhanced. The uneven remains accumulation of prey more and less preferred by the owl at different phases of the small mammals’ population cycle was described. This should be taken into account in morphological studies, since many morphological characteristics of small mammals differ in different phases of the cycle.