Nested Distribution Patterns of Avian Assemblages in Wetlands

Nested subset patterns are used to describe nonrandom distributions of species in isolated habitats and require that species found in smaller, less diverse locations are also found in more species-rich assemblages. These distributions can be heavily influenced by a variety of biotic and abiotic factors, particularly the fragmentation that occurs as a result of urbanization and human disturbance. The size of the areas following human disturbance is a key factor in driving distribution patterns. Consequently, this model lends itself to the conservation and management of preserves including the determination of their size and distribution. The distribution of breeding wetland birds in northeastern Illinois was surveyed during the summer of 2015. These distribution and abundance data were analyzed using Monte Carlo simulations. Results of the simulations found the birds exhibited statistically significant non-random distribution patterns. Generally, the number of species became more diverse as habitat area increased and species found in small sites were also found in larger sites. These significant results strongly suggest that preservation of large preserves is necessary to protect area sensitive species. With limited land available, management strategies should predominantly target a few large preserves as opposed to numerous small preserves. When compared with past studies, simulation results show no significant change despite altered levels of human disturbance, suggesting that the distribution of wetland birds appears to be stable over time