Migration is over now, for the most part. Birds are where they are going to be for the winter. There may be some regional movements for species that are escaping extreme weather that limits food supply or access to it, but the long distances traveled by northern breeding birds to their southern homes has been accomplished.
Scott Weidensaul said it best when he wrote that migration is a leap of blind faith for most birds. When birds leave northern breeding areas that may be the far northern limits of the North American continent for species like these Snow Geese, they do so with the hope that the places where they have stopped to rest and refuel during previous journeys will still be there, that the habitat that support them will still be there, and that the food will be sufficient to replenish their energy reserves so they can survive the next leg of migration. There are no guarantees.
Snow Geese are lucky ones. They have adapted to habitat loss. They were once the goose of the marsh and they fed heavily on the tubers of Spartina along the Atlantic coast. Today, they are largely a goose of the fields, like their Canada Goose cousins, and feed on grain or the roots of cover crops like winter wheat. They have adapted to new habitats and sources of food over the past several decades and their populations have flourished. They have done so well that biologists are now concerned about breeding Snow Geese degrading the fragile Arctic tundra that supports so many North American birds, especially shorebirds.
I love the sound of Snow Geese. Their sound is captivating. To me, a flock of Snow Geese remind me of a rickety old train moving down a track; the sound of metal on metal with creeks, clangs, cracks, and honks of different pitches and notes. On the days when I used to sit in the marsh and hear the geese all day, the sound would stick with me through the night back home and I would swear that the geese were flying over the house. They were not, but their voices were in my head.
For this photo I arrived at the field late in the afternoon. Tundra Swans and a few Snow Geese were already there and many more were moving about. The sun was descending to the west and the moon, nearly full, was rising in the east. Shadows fell on the geese and swans in the field, but they continued to come and go occasionally crossing the big, bright moon made even larger by 600mm + 1.4x extender. It was a great way to end the day.