Butte Sink Wildlife Management Area has the highest concentration of waterfowl

Waterfowl

Waterfowl are certain wildfowl of the order Anseriformes, especially members of the family Anatidae, which includes ducks, geese, and swans....

 per acre in the world. Located in the Sacramento Valley

Sacramento Valley

The Sacramento Valley is the portion of the California Central Valley that lies to the north of the San Joaquin-Sacramento Delta in the U.S. state of California. It encompasses all or parts of ten counties.-Geography:...

 of California

California

California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

, it includes the Butte Sink National Wildlife Refuge

Butte Sink National Wildlife Refuge

Butte Sink National Wildlife Refuge is a National Wildlife Refuge in California. Located in Colusa, Butte, and Sutter Counties, it is wetlands managed as part of the Sacramento National Wildlife Refuge Complex.-References:*...

 and conservation easements acquired on adjacent private lands. The landscape is flat, bordered by the Sierra Nevada and Coast ranges, and surrounded by intensive agriculture (primarily rice

Rice

Rice is the seed of the monocot plants Oryza sativa or Oryza glaberrima . As a cereal grain, it is the most important staple food for a large part of the world's human population, especially in East Asia, Southeast Asia, South Asia, the Middle East, and the West Indies...

 and nut

Nut (fruit)

A nut is a hard-shelled fruit of some plants having an indehiscent seed. While a wide variety of dried seeds and fruits are called nuts in English, only a certain number of them are considered by biologists to be true nuts...

 orchard

Orchard

An orchard is an intentional planting of trees or shrubs that is maintained for food production. Orchards comprise fruit or nut-producing trees which are grown for commercial production. Orchards are also sometimes a feature of large gardens, where they serve an aesthetic as well as a productive...

s).

Within the 18000 acres (72.8 km²) Wildlife Management Area

Wildlife Management Area

Wildlife Management Areas are protected areas set aside in for the conservation of wildlife and for recreational activities involving wildlife.-United States:In the U.S., WMAs exist in the following states:* Alabama* Florida* Georgia* Louisiana...

, conservation easement

Easement

An easement is a certain right to use the real property of another without possessing it.Easements are helpful for providing pathways across two or more pieces of property or allowing an individual to fish in a privately owned pond...

s have been purchased on 10311 acres (41.7 km²), requiring landowners to maintain wetland

Wetland

A wetland is an area of land whose soil is saturated with water either permanently or seasonally. Wetlands are categorised by their characteristic vegetation, which is adapted to these unique soil conditions....

s on their property in perpetuity. These lands are privately owned and closed to public access. In addition, a 733 acres (3 km²) area (owned in fee title) was established in 1980 to protect wetlands for wintering waterfowl. This area is known as the "Butte Sink National Wildlife Refuge" and is also closed to public access.

Major refuge objectives are to provide feeding and resting habitat for wintering waterfowl; provide habitat and management for endangered

Endangered species

An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...

, threatened

Threatened species

Threatened species are any speciesg animals, plants, fungi, etc.) which are vulnerable to endangerment in the near future.The World Conservation Union is the foremost authority on threatened species, and treats threatened species not as a single category, but as a group of three categories,...

, or sensitive species of concern

Species of Concern

In wildlife conservation, Species of Concern is an informal term, not defined in the federal Endangered Species Act. The term commonly refers to species that are declining or appear to be in need of concentrated conservation actions. Many agencies and organizations maintain lists of these at-risk...

; protect and provide habitat for neotropical migratory land birds; preserve a natural diversity and abundance of flora and fauna; and alleviate crop depredation.

The Butte Sink

Butte Sink

Butte Sink is a depression that is the location of the Butte Sink Wildlife Management Area and Butte Sink National Wildlife Refuge....

 typically supports wintering populations of over 300,000 duck

Duck

Duck is the common name for a large number of species in the Anatidae family of birds, which also includes swans and geese. The ducks are divided among several subfamilies in the Anatidae family; they do not represent a monophyletic group but a form taxon, since swans and geese are not considered...

s and 100,000 geese

Goose

The word goose is the English name for a group of waterfowl, belonging to the family Anatidae. This family also includes swans, most of which are larger than true geese, and ducks, which are smaller....

. As 95 percent of wetlands of the Central Valley have been lost over the last 100 years, waterfowl have become increasingly dependent on the remaining wetlands within the Sacramento Valley.