Those of us who have been wildlife watchers for many years usually know what to anticipate when we head outdoors at any given time of year. But it is the occasional unexpected discovery that stokes our ongoing enthusiasm. One such event occured last evening.
At 7PM, I went outside to put away a few tools and, just as I exited the back door, a common nighthawk swooped through the yard. Used to watching them hunt well above the treetops (see my Blog of 9-1-07), I was surprised by its low level foray. But this mild shock soon became full-bodied awe as I watched a large scale aerial attack take place 20-30 feet above the ground. Nighthawks were swooping in from all directions, strafing the roofline and veering among the trees. Like a squadron of fighters, they darted above our property, made a quick change of course and sailed back in from a different heading. At least 20 of these agile hunters seemed to be involved in the attack, which continued for half an hour.
The reason for their frenzied behavior was soon apparent as a swarm of dragonflies moved overhead, zigzagging in response to the nighthawk maneuvers. Dragonfly swarming, most often seen in September, is a documented but poorly understood event; whether it represents a true migration, a dispersal of regional populations or a response to high prey concentrations remains an open question. In this case, the swarm obviously attracted the attention of a migrating flock of nighthawks, offering an easy target and plenty of nourish-ment for their journey to the south.
