The Effects of Field Mowing on Adult Butterfly Assemblages in Central New York State

2 Corresponding author: [email protected] 3 Current address: Department of Biological Sciences, Binghamton University, Binghamton, NY 13902 ABSTRACT: We investigated the effects of mowing on butterfly counts in fields and woodland openings in upstate New York. We predicted that total counts of butterfly individuals would decrease immediately after mowing, but increase in the year following mowing at corresponding times in the growing season. To test these predictions, we used modified Pollard transects to obtain counts from three sampling sessions prior to and three sampling sessions after mowing. These counts were compared to those on similar dates in subsequent non-mowing years. The results show a significant decrease in counts of butterflies immediately following mowing, compared to the same periods in non-mowed years. The immediate decrease in counts following mowing may be due to the loss of nectaring sources, since nectaring and nectaring sources declined sharply following mowing, but recovered within a month following mowing. In the year following mowing, the rebound was significantly greater in fields (> 0.20 ha) than in woodland openings (< 0.19 ha). While species varied in their rebound, only two of 24 species (Pieris rapae and Danaus plexippus) declined significantly in the year following mowing.