Potential effects of passenger pigeon flocks on the structure and composition of presettlement forests of eastern North America

We considered the possible effects Passenger Pigeon (Ectopistes migratorius) flocks may have had on the disturbance regime and species composition of presettlement forests in eastern North America. We suggest that the activities of roosting and nesting Passenger Pigeons caused widespread, frequent disturbances in presettlement eastern forests through tree limb and stem breakage and nutrient deposition from pigeon excrement. We suspect that the deposition of fine fuels resulting from such disturbances may have influenced fire intensity and frequency in presettlement forests. Further, we propose that consumption of vast quantities of acorns by pigeons during the spring breeding season may partially explain the dominance of white oak (Quercus alba) throughout much of the presettlement north-central hardwoods region. Consequently, the pigeon's extinction may have facilitated the increase and expansion of northern red oak ( Quercus rubra) during the twentieth century. Although it is difficult to accurately quantify how physical and chemical disturbances and mast consumption by Passenger Pigeon flocks affected forest ecology, we suspect they shaped landscape structure and species composition in eastern forests prior to the twentieth century. We believe their impact should be accounted for in estimates of the range of natural variability of conditions in eastern hardwood forests.