Assessing Mourning Dove Population Declines: Changes in Nesting Dynamics and the Role of Perch Sites

I replicated a nesting study carried out 40 years ago in southern Utah to assess reasons for long-term population declines of mourning doves (Zenaida macroura) in the western United States. I compared current nesting patterns to similar data collected in 1952. I saw little difference in nest success and nest predation, but reproductive output and nest density decreased dramatically. The number of young fledged per pair of adults was only 64% of that estimated in 1952. A 1-2 week delay in the nesting season contributed to this decrease, but cannot explain it entirely. Nest density was about 20% of that in 1952 and total reproductive output for the study area about 12-19%. Underlying causes for these changes are uncertain, but patterns of delayed nesting, high nest abandonments, and low reproductive output are similar to those seen in stressed bird populations (e.g., food/nutrient limitation or increased toxicant levels). Finally, highest nest density occurred in a habitat type (i.e., Chalk Creek) considered unimportant for doves in 1952. Nests in Chalk Creek suffered higher predation and abandonment rates than those in irrigation ditches. I also examined the effect of perch sites on nest density and distribution in two ways. First, I demonstrated a significant correlation between nest density and perch s:te density in riparian plots. Second, I erected artificial perch sites in the second year of the study and recorded changes in nest densities. For the year of the study only, nest density was higher in the experimental plots, but the difference was not statistically significant. From the levels recorded the previous year, however, nest densities increased in the experimental plots and decreased in the control plots. This difference was statistically significant, suggesting that mourning doves use the presence of perch sites as cues for habitat selection. Finally, in comparing the presence of other avian species, I found significantly more blackbirds (Aqelaius phoenicus and Euphaqus cyanocephalus) and western meadowlarks (Sturnella neglecta) in experimental plots than in control plots