immigration
Bird migration is the regular seasonal movement, often north and south, along a flyway, between breeding and wintering grounds. Many species of bird migrate. Migration carries high costs in predation and mortality, including from hunting by humans, and is driven primarily by the availability of food.

I was lucky... This flock of birds, was flying around late in the afternoon, right outside my window in a really low flight ...
nature bluesky sky birds flickr immigration postcard travel flockofbirds beautiful fly reflections color life light bird god afternoon flock atmosphere