Species-Specific Management (SSM)

Mergansers or The Hooded Merganser

Rarely considered one of the forest animals, the hooded merganser, is one on the long list of animals in the southern Appalachian forest having water as a major life requirement. There are three species of mergansers potentially found in the southern Appalachian forest region: common mergansers (Mergus merganser), red-breasted mergansers (Mergus serrator), and hooded mergansers (Lophodytes cucullatus). In the southern Appalachian region, the hooded merganser is the only potential breeder, and is often found here year-round. The red-breasted merganser and common merganser can only be found here in the winter, although red-breasted mergansers are usually rare and only seen when migrating.

The hooded merganser also called fish duck, sawbill, summer duck, and sheldrake, is a wary, medium-sized duck with fast flight and a rapid wing beat. It is prized both for hunting and esthetics. Widespread destruction of its nesting habitat has caused declines in its populations.

Mergansers are diving fish ducks that reside in rivers, lakes, ponds, and streams. They prefer the open waters of large rivers and lakes with shorelines composed of heavily wooded areas mixed with rocky areas. Dead forest trees, both standing and half-submerged, are critical for optimal habitat. Stumps, both at the shoreline and in the water, are also important.

The diet of mergansers consists of small fish, crayfish, eels, frogs, and insects, with a small portion of vegetable matter.

Hooded mergansers nest in tree cavities or rocky crevices found in woodlands adjacent to the water. Upon leaving the nest, the young birds rely on vegetative cover along shorelines for concealment from predators.

The average landowner will have difficulty managing his or her land for mergansers, but owners with land adjacent to a river, lake, pond, or large stream can encourage merganser activity by implementing the following management practices:

1. Ponds can be developed by damming streams that flow year-round. Similarly, build a small, brushy pond to flood standing timber and provide aquatic habitat. Damming a stream provides optimum habitat because flowing water resists freezing. Hooded mergansers predominantly migrate ahead of the water "freeze line." Log jams or rock jams can be constructed to achieve this. Prior to damming, make sure any flooding will not cause problems with other land uses or adjacent landowners. Water regulation, plus or minus, is a key action.
2. Build a stair-case pattern in the stream to increase the number of aquatic invertebrates (e.g., crayfish). These invertebrates serve as a major food source for adult mergansers.
3. Provide standing pools of shallow water for broods to utilize. Chicks can dive up to 25 inches while feeding. Also, small fishes often congregate in shallow water, providing food for adult mergansers.
4. Prevent water turbidity since it decreases the feeding efficiency of adults.
5. Shallow water allows sunlight infiltration to the bottom. Providing shallow water allows aquatic vegetation to flourish. Aquatic vegetation also attracts insects, the staple diet for hooded merganser chicks. Do not cut trees or vegetation near water since cutting near nesting sites may increase water turbidity and remove concealment from predators.
6. Optimum nesting habitat is very important for hooded mergansers. Optimum habitat includes tree cavities in bottomlands, beaver ponds, or swamps.
7. Heavily forested shorelines, the riparian volumes, can be maintained by avoiding timber harvest and allowing stands to mature.
8. Planned burns can be conducted in forests along the shore to eliminate ground cover and reduce competition for resources. This will allow forests to mature more rapidly.
9. Snags for nesting can be created by injecting select large diameter trees (greater than 12 inches dbh) with heart rot. Trees should be killed at a density of 1 per acre, within 5 - 15 yards of the shoreline. Snags for foraging cover (and woodpecker-created nesting cavities) can be produced by girdling trees directly on the shoreline at a density of at least 2 per acre. Girdling will weaken the trunks and allow snags to fall into the water, creating needed stumps as well.
10. Cavities must have a sufficient opening (6 inches diameter), be well-insulated (thick tree "walls"), and be protected from the wind and rain.
11. Nesting boxes can be provided to encourage nesting. Box dimensions can \follow those used for wood duck boxes (hooded mergansers are similar to wood ducks in size and nesting habits). Hooded mergansers readily nest in wood duck boxes provided the box is located in the forest adjacent to water.
12. Prevent predation on the nest box by placing cones around the supporting pole.
13. Raccoons frequently prey on hooded merganser nests. Consider trapping or hunting raccoons around suitable merganser habitat. (Raccoon pelts can be sold and the meat is tasty if fixed properly).
14. Stocking lakes and ponds with fish, eels, and other food sources can increase food availability, often the limiting factor in merganser populations. Reducing water pollution wil increase food more than attempting stocking. Only feed them in extreme emergency situations.
15. Grit piles (coarse sand) can be supplied along shorelines (sloping end of islands) to meet digestive requirements.
16. Block off areas from excessive human disturbance which often leads to nest abandonment or even site abandonment.
17. Provide overflow areas of shallow water (3 - 5 feet maximum) where young birds can practice foraging before reaching open waters.
18. Add structure to the water for fish cover; encouraging already existing fish populations to increase can also be attractive to mergansers. Structure can include downed trees and columns of tires fixed together.
19. Encourage nesting areas and refuges in southern Canada (e.g., snags, rocky areas) because these birds are migrants it is equally important to try to encourage beneficial habitat conditions and protection in their alternative environments.
20. Construct a concealed viewing blind to make bird observations with minimal disturbance and keep records. Record time and costs spent so that returns on "investments" can be made and efficiencies improved. Keep records of birds present and their responses to practices. Adapt practices after several years to increase the population or benefits (e.g., viewer recreation hours) from it. Compare your results with neighbors.
21. Join nature groups or local bird watching clubs that stress conserving and maintaining hooded merganser populations.
22. If choosing to harvest, strictly follow federal harvest regulations and bag limits. Be aware that intense hunting pressure may cause hooded mergansers to leave the area. The merganser's intense homing behavior and lightened hunting pressure will allow the ducks to return.
23. Join Ducks Unlimited on the federal level as well as your local chapter.
24. Charge a modest fee for property use to help reduce habitat maintenance costs.
25. If choosing to harvest, strictly follow federal harvest regulations and bag limits. Be aware that intense hunting pressure may cause hooded mergansers to leave the area. The merganser's intense homing behavior and lightened hunting pressure will allow the ducks to return.
26. Keep records of birds present and their responses to practices. Adapt practices after several years to increase the population or benefits from it.

A contribution of Michael J. Chamberlain and Joseph C. Ferdinandsen (1993), Courtney A. Couch (1991), and Daniel Miller (1992), Department of Fisheries and Wildlife Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0321

References

Bellrose, Frank C. 1976. Ducks, Geese, and Swans of North America. Stackpole Books, Harrisburg, Pa. 177-194.

Kitchen, D.W. and G.S. Hunt. 1969.Brood habi tat of the hooded merganser. Journal of Wildlife Management. 33(3): 605-608.

Kortright, Francis H. 1967. Ducks, Geese, and Swans of North America. Stackpole Books, Harrisburg, Pa. p. 45.

McGilvrey, F.B. 1966. Nesting of hooded mergansers on the Patuxent Wildlife Res. Center, Laurel, Maryland. Auk.83(3): 477-479.

Morse, T.E.. J.L. Jakabosky, and V.P. McCrow. 1968. Some aspects of the breeding biology of the hooded merganser. Journal of Wildlife Management. 33: 596-604.

This Web site is maintained by R. H. Giles, Jr.
Last revision January 17, 2000.