Migrating monarch butterflies can be censused several ways, but studies that compare censusing methods are lacking. Furthermore, although it is known that monarch butterflies alter their flight strategies in varying wind conditions, it is not known if and how counts of monarchs made during migration are affected by wind conditions. We assessed the abundance of migrating monarchs in the fall of 2000 using three techniques, which each differ in the flight strategy they target. We tested for differences between the resulting counts and examined the influence of wind conditions on each method. We (1) censused monarchs on a five mile driving route, (2) counted monarchs from a hawkwatching platform, and (3) counted monarchs at a roost site. The hawkwatch and driving census produced similar overall indices of abundance. Furthermore, wind conditions affected each count. As we predicted, the driving census detected the most monarchs when wind speeds and directions were unfavorable for migration, and the most were counted with the hawkwatch census during light favorable wind directions. Unexpectedly, counts of roosting monarchs were highest during strong winds in both favorable and unfavorable directions. We recommend that long-term monarch monitoring stations employ a combination of techniques to obtain comparable counts of monarchs.
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