Saw a flock of around a dozen this morning which I believe are the first arrivals here from their home grounds in Central America. These acrobatic fliers are the most common of American swallows. If you have an open barn, you will get their poo all over your tractors and stuff. We would always put a tarp over the tractor.
You can read about these cool birds at All About Birds: Barn Swallow
I also saw my first Tree Swallow of the season this morning.