In the park next to where I live, with ponds and a large creek, waterfowl abounds. Depending on the time of year we have a diverse population including geese, ducks, coots, herons, egrets, seagulls, terns, pelicans and others. We're also under a well-used flight path to a couple of local airports. I don't remember if it was contrails or birds that inspired arc of flight, but I spend a good deal of time looking up in the sky when I'm out walking...