Hawk watchers are known to say that if a small falcon passes another raptor without taking a pass at harassing the other bird, it is probably not a Merlin Falco columbarius. This species is a fairly small raptor, but it is ruggedly built, fast and very agressive. At hawk watches Merlins are commonly seen making rapid swoops towards buteos, eagles and other larger raptors.
Merlins, like most falcons, hunt primarily by capturing other birds and insects in flight. Merlins capture insects, primarily dragon flies in late summer,small birds and bats.
Merlins have several color morphs, ranging from very dark to fairly light coloration.
Oftentimes Merlins hunt from a perch where they can survey large areas, and we often look for them on the very top of trees, like this individual.
In North America the only other small falcon commonly seen is the American Kestrel, which at rest or briefly seen in flight can look somewhat similar, but once moving with purpose, the difference is marked, with the American Kestrel looking relatively dainty and slow in comparison.
Falcons are always cool to see.
Good birding.