Bigjohnt, the Butte Sink is an area of natural riparian marsh habitat that encompasses over 12,000 contiguous acres. It is in northern California, between the towns of Colusa on the west and from Yuba City to Gridley on the east. It's about 40 miles north of Sacramento, as the duck flies. It is almost entirely private duck clubs, other than the Butte Sink National Wildlife Refuge, which is only 400 acres. Once, the area was surrounded on all sides by rice fields, but over the last 25 years or so, some of those fields have been converted back to natural habitat and put into conservation easements with USFWS, so the natural habitat area is expanding, mostly to the north. Some of those areas that have been converted back are many hundreds of acres, owned by only one or two individuals and they function as sanctuary land, as much as duck clubs. The Butte Sink will always be natural, as the clubs within the sink proper have all committed to the long term preservation of the area.
The Butte Sink NWR was originally a farmed bean field and when the owner died, he left it to the US Fish and Wildlife Service, with the caveat that it had to be maintained as a natural habitat for the protection and propagation of waterfowl. The area doesn't hold anywhere near the number of ducks that it used to, but I can remember back in the late 1970s when official counts had over 1,000,000 ducks and geese packed onto just that 400 acres. It was sometimes wall to wall waterfowl covering 400 acres!
The Butte Sink is tule marsh, with lots of live oaks, willows, cottonwoods and other deciduous tress and brush. The wildlife includes not only ducks and geese, but also blacktail deer, pheasants, wild turkeys, otters, beaver, and way too many predators - mainly racoons, but also growing numbers of coyotes. In the winter when the ducks migrate in, the raptor population soars, with many redtail hawks, coopers hawks, red shouldered hawks, and occasional bald eagle or osprey, and a lot of owls. We have a few Great Horned Owls that roost in the exact same trees each winter, and they always seem to arrive within a few calendar days each year. When you think about it, that's kinda cool that they use the very same trees year after year, it gives a pretty good indication that they're likely the same bird each winter. We also have good fish populations, mostly channel cats and largemouth bass, but also a lot of chinook salmon and some steelhead that migrate through the sink to spawn in the upper reaches of Butte Creek. It is one of the most productive pieces of inland king salmon spawning habitat in California, but very few people realize it.
In a big valley that has converted to cities and agriculture and lost about 95% of it's natural habitat, the Butte Sink is a treasure that more and more people are slowly learning about.
