Northern Prairie Wildlife Research Center
In most cases birds are affected more by the abrupt habitat change than the fire itself.
Researchers believe fire suppression has greatly reduced the extent of waterfowl nesting habitat because some grassland habitat has reverted to woodlands.
Vogl (1967) stated that areas in Wisconsin that used to produce thousands of ducks are now forested and produce few ducks. Kirsch and Kruse (1973) speculated that the highest populations of prairie nesting ducks in the Dakotas occurred around 1880, after the decimation of big game herds had reduced grazing and before settlement introduced fire suppression to prairie vegetation.
Most information on the response of waterfowl to burning concerns spring burns. The obvious immediate effect of Spring fires on upland nesting waterfowl is destruction of nests and their contents by fire (Leedy 1950; Moyle 1964; Erwin and Stasiak 1979).
Adult birds often return to a nest after a fire and try to resume incubation. Bent (1923) observed a northern pintail (Anas acuta) incubating a clutch of scorched eggs immediately after a burn. Leedy (1950) found a mallard (A. platyrhynchos) nest with scorched eggs plus four that had been laid after a fire. He also found an American black duck (A. rubripes) still incubating a nest with twelve scorched eggs. Moyle (1964) mentioned similar cases of hens continuing to incubate eggs damaged by a prairie fire. Fritzell (1975) saw a green-winged teal (A. carolinensis) remove one burned egg from a nest and later lay four more.
Kruse and Piehl (1986) found that in North Dakota prairie burns there are sometimes "skips," or areas that remain unburned where active nests are not affected. These "skips," usually dense patches of shrubs with little or no understory vegetation, are also utilized by birds that start nesting after the fire.
Kruse and Piehl (1986) also found 20 clutches of eggs in the unburned vegetation on the burns; 15 hatched. They concluded that burning an area during the nesting season does not necessarily eliminate all ground nesting in the area for that year.
Kirsch and Kruse (1973) compared nesting on similar plots of unburned and burned prairie for several years following burning. They found that 52% of the duck nests on burned grassland habitat were successful, compared to 33% on unburned areas. During the second season after the fire, duck production was greater on the burned plot than on the unburned.
They also noted that the greatest measured change in vegetation after burning was a marked increase in plant variety. Burning also changes the growth form and pattern of nesting cover, which may make it more attractive to nesting waterfowl.
Prescribed burning to improve nesting cover has been practiced mainly in spring. A major concern is the presence of active nests, which can be avoided by fall burns.
Higgins (1986b) compared nesting success of waterfowl on mixed prairie areas burned in spring with those fall burned in North Dakota. Duck nesting success was greater in the fall burn plots than in spring burn plots, when all species were combined and when success was compared during the first few post-burn years.
He found that in the first spring after a fall burn there is little cover available for nesting and the area is sparsely utilized. However, the second year after a fall burn, the available nesting cover is much taller and denser than on spring burn areas, and ducks had greater nesting success on fall burn plots.
Upland waterfowl nesting response was nearly equal between the spring and fall burns after the third post-fire growing season. Higgins (1986b) concluded that duck production can be greater on fall burns than on spring burns, if averaged over 3 or 4 post-burn years.
Areas recently burned are sometimes utilized by nesting waterfowl. In Iowa, Glover (1956) observed blue-winged teal (A. discors) initiating nests in May after an April burn, and Messinger (1974) found more duck nests on burned versus control plots but with 1973 nesting success reduced on plots burned April 5, 1973. Keith (1961) found 17 northern pintail nests on bare ground after an April burn, with some very near unburned areas with good cover. No other duck species used this burned area.
Fritzell (1975) found higher rates of nesting success on burned as compared to unburned areas but fewer nests per unit area in Manitoba. He stated that spring burning is more detrimental to early nesters such as mallard and pintail than to later nesting species. He also mentioned that mallards may be particularly susceptible to spring burns due to their preference for heavier cover which often burns.
Fritzell (1975) also concluded that controlled burning is an efficient tool in wildlife management, but indiscriminant annual burning reduced the quality and quantity of waterfowl nesting cover.
Fire can benefit waterfowl in ways other than improved nesting cover. Prescribed burning is used as a marsh management tool to burn out thick growths of cattails and phragmites. This increases the edge cover which improves brood habitat. Marsh burning can also initiate the growth of preferential duck food (Vogl 1967).
Ward (1968) reported that both spring and summer fires are used for marsh management at Delta, Manitoba. The spring fires are set prior to April 20 when mallards and pintails begin nesting. The primary purpose of the spring fires is to create more edge for nesting and brood cover. Summer fires have a greater effect on regrowth and are directed toward lasting changes in the plant community. At Delta, summer burns were used to remove phragmites, because it was seldom utilized by waterfowl, and to enhance the growth of whitetop (Ward 1968).