Walking past a small pond today, I happened to notice some very fast movement over the water. At first blush, these creatures look like bats at dusk, except it's in the middle of the morning. I was introduced to these fast little buggers last year at the Concord Wildlife Refuge. Tree Swallows are migratory and go to Central America for the winter. Having arrived in the northeast in the past few days, I had the pleasure to watch their acrobatic musings. They fly horizontally, then all the sudden dive towards the water to scoop up a bug that had no chance. Their zig-zag flying patterns are hard to follow and can cause a bit of dizziness.
Swallows are quite hard to photograph, simply because they are so fast. There is a line in Monty Python where the bridgekeeper asks King Arthur 'What's the airspeed velocity of an unladen swallow?', followed by the question 'What do you mean? An African or European swallow?' Of course, this prompted me to Google this exact question. And lo and behold, someone has actually gone to the trouble to create a web page that explains the physics of swallow flight: http://style.org/unladenswallow/
Based on this science, it explains why photographing a Tree Swallow is exceptionally difficult, and even more difficult while holding a heavy lens. But on occasion, I am able to catch these cute little birds on their quest for food, and, on many occasions, just happy to watch them dip and dive.