Variation of Dates of Bird’s Spring Arrival in Eastern Europe as a New Ecogeographical Rule

Abstract

After three classical zoogeographical rules (Bergman’s, Allen’s and Gloger’s) many other ones became known. Along our studies of bird migrations in Ukraine and nearby countries in Eastern Europe, we paid attention to terms of bird arrival during many years in different locations. Early in the spring, birds can arrive in wide span of terms depending on weather conditions but late migrants arrive at terms that are more definite.