So let's spend some time unpacking this new vocabulary, and hopefully you will also understand my enjoyment of cool words to describe bird behaviors. The first new word is crepuscular. This refers to the time of day that an organism is active. For other species, you can use the more commonly known terms: diurnal and nocturnal. But for organisms that are active at dawn and dusk, like Nighthawks and many species of bats, there is another, more specific term which is crepuscular.
The next term in my second description of Nighthawk behavior is insectivorous. This term is more commonly used and understood, but no less interesting. Insectivorous simply describes an organism that eats insects. What I find fascinating about this term, is how you can quickly delve into a whole new world of vocabulary regarding diet with a word like insectivorous. For example, after understanding you can discuss words like granivorous, nectivorous, frugivorous, and even piscivorous and then find species that eat seeds, nectar, fruits, and fish, respectively.
The final term that I used to describe Nighthawk behavior is hawking. This term is actually a main source of confusion when I talk to people about my study species. Hawking in this context refers to the manner in which Nighthawks catch insects; they visually seek out individual insects and then chase them down and catch them in their mouth. This behavior is what has led to the hawk in the Nighthawk name. Many other species use hawking behavior to catch their prey including many raptor species, and more specifically many species of hawks. This similarity in behavior does not imply relatedness among all hawking species, even though this is one of the most common assumptions when I tell someone that I study Nighthawks; Nighthawks are not hawks, they are not even raptors.
There are many more interesting terms than I discussed here when it comes to bird behaviors. If you get bored with behavior vocabulary, you can also take a look at the terms used to describe bird anatomy. Some of these terms are more intuitive than others, but hopefully all of them can lead to interesting discussions and greater understanding about how birds act.