The Alaska Chilkat Bald Eagle Preserve was created by the State of Alaska in June of 1982. The Preserve encompasses river bottom land of the Chilkat, Kleheni, Tsirku, and Chilkoot rivers. The "flats" of the Chilkat River between miles 18 and 24 of the Haines Highway are the main viewing area for eagle watchers and considered critical habitat in the preserve. Thousands of Bald Eagles are attracted to the area by the availability of spawned-out salmon and open waters in late fall and winter. The Tsirku fan, a fan-shaped accumulation of gravel, rock, sand, and glacial debris, at the confluence of the Tsirku, Kleheni, and Chilkat rivers acts as a large water reservoir. During the warmer spring, summer and early fall seasons, water flows into the alluvial fan faster than it can flow out, creating a huge reservoir of water. When winter arrives, cold weather sets in and surrounding waters freeze. However, water in this large reservoir remains 10 to 20 degrees (F) above surrounding water temperatures. This warmer water "percolates" into the Chilkat River and keeps it from freezing. Salmon runs begin in the summer and continue on through late fall or early winter. The salmon die shortly after spawning and it is their carcasses which provide large quantities of food for Bald Eagles. This combination of open water and large amounts of food bring Bald Eagles into the Chilkat Valley from early October until the river freezes.
The Chilkat River is home for 200-400 Bald Eagles year round, and hosts the densest concentration of Bald Eagles anywhere in the world during the fall. The greatest number counted during any aerial survey was 3,988 Bald Eagles. A total count of 953 bald Eagles has been made from a single point on the ground. Bald Eagles tend to build up as long as the river remains unfrozen and then rapidly drop if there is a stretch of cold weather severe enough to freeze most of the river surface, which typically happens in late November. Low counts in the last half of the 1980's may be attributable to a freeze before the surveys. Specific Bald Eagle surveys in this area were discontinued in 2001.
The area also supports a significant and increasing number of breeding Trumpeter Swans. The peak count of 189 individuals, observed in 2003, included 149 adults and 41 cygnets.
Logging, mining, fishing, highway improvement, and housing construction are considered distant or limited threats, due to effective environmental controls. Commercial tourism is a bigger issue, as the wakes from jet boats may cause considerable erosion and disruption of salmon habitat. There appears to be a decreased management presence and oversight effort in the Preserve recently, as well as a decline in active research and management programs for eagles, salmon and other resources.
The Alaska Chilkat Bald Eagle Preserve is fully owned by the State of Alaska, and managed by the Division of Parks and Outdoor Recreation with the assistance of a 13-member Advisory Council.
The habitat is composed of riparian Cottonwood (Populus balsamifera) stands with scattered patches of Sitka Spruce (Picea sitchensis) and Western Hemlock (Tsuga heterophylla). Eagles roost in these trees throughout the night for thermal cover during the fall and early winter gathering, but spend a significant amount of time from first light until mid day on the alluvial bars and banks of the braided river of the Chilkat and Chilkoot Valleys.
The creation of the Preserve occurred after lengthy discussions regarding the maintenance of existing uses of the area. The continuation of subsistence and recreations uses while not compromising future economic opportunities were at the forefront of the discussion. The basic purposes of the preserve were to protect and perpetuate Bald Eagles and their essential habitat, protect and sustain the natural salmon spawning areas of the rivers, provide continued opportunities for research, and enjoyment of eagles and other wildlife, maintain water quality and quantity, provide for the continued traditional and natural resource based lifestyle of the people living in the area and provide for other public uses consistent with the primary purpose of the Preserve. Commercial tourism, particularly recreational use of jet boats has increased considerably since the early 1990s.