Ball, J. P. 1984. Habitat selection and optimal foraging by mallards: a field experiment. Guelph, ON: University of Guelph. 44 p. Thesis. .STUDY LOCATION:
Soils were described as Rego Humic Gleysols.
PREFIRE PLANT AND ANIMAL COMMUNITY:
The principal vegetation was cattail (Typha spp.), mostly consisting of a hybrid (Typha × glauca), although narrow-leaved cattail (T. angustifolia) and common cattail (T. latifolia) were also present. The author states that this marsh contained a "continuum of phenotypes spanning the two parental types" (narrow-leaved cattail and common cattail) and assumes that all three entities respond similarly to treatment. Results of the study are reported for cattail species as a group.
Openings in cattail marsh can be used by mallards as foraging habitat. Aquatic macroinvertebrates, which feed on decaying plant litter, are an important food source for mallards. Invertebrate biomass varies from pond to pond and changes constantly throughout the summer.
Study sites were dominated by cattail marsh. Since water levels are maintained artificially throughout the summer on the study sites, historic fire regime information does not apply.PLANT PHENOLOGY:
Burning was conducted in February and March of 1982 and 1983. Fires burned over ice and did not burn cattail
rhizomes, indicating that fire severity was low.
Fire management objective: The objective of this study was to determine how mallards select foraging habitat by creating openings of different sizes (0.05 to 0.37 acres (0.02-0.15 ha)) and providing varying abundance of aquatic invertebrates.
Fire prescription and behavior: Circular plots surrounded by a 15-foot (6 m) wide fuel break were burned with a flamethrower. Burning began just after dawn. Fires were of "low intensity". Fires were initiated as headfires, and then backfires were ignited against the wind to keep the burns within control lines. Temperatures were near freezing, and wind speed was less than 12 miles per hour (20 km/hr). Rate of spread was 0.6 to 5 miles per hour (1-8 km/hr), varying with wind speed and cattail density. Flame heights averaged just over 6 feet (2 m) but sometimes exceeded 21 feet (7 m).FIRE EFFECTS ON PLANT AND ANIMAL COMMUNITY:
Mallard foraging effort was positively correlated with size of openings (0.05 to
0.37 acres (0.02-0.15 ha)). Mallard foraging was also positively correlated with invertebrate biomass (P<0.001).
The study reports that burning treatments had "much less litter" than mowing
treatments, so one could infer that burned patches contained less invertebrate
biomass than mowed patches and thus received less use by mallards.
However, this is not stated in the paper.
FIRE MANAGEMENT IMPLICATIONS:
Fire management objective: Mallards used the openings created by burning, although their abundance was not reported. Burning produced significantly (P<0.001) less cattail mortality than mowing in plots with water less than 24 to 28 inches (60-70 cm) deep; both methods produced nearly 100% cattail mortality in plots with water deeper than 31 inches (78 cm). Burning the same sites in successive years was not feasible because the regrowth did not provide enough fuel to carry fire.
Other fire management information: Fire was an effective tool for opening up dense cattail stands. Mowing was even more effective: A single mowing treatment reduced cattail density by 89%, and mowing the following winter produced 99% cattail mortality. If marshes are burned in winter, fires are less intense than in summer (in drained marshes) and thus easier to control. Following burning, cattail can be killed by submerging stubble to cut off oxygen to the rhizomes. In this study, backfires left the shortest stubble (7 inches (18 cm)), so water levels did not have to be raised much to kill the plants. If snow builds up on the ice before burning, the stubble may be taller and therefore require deeper flooding to kill the cattails. Burning in early winter or early spring might reduce this problem.
|Common name||Scientific name|
|hybrid cattail||Typha × glauca|
|broadleaf cattail||Typha latifolia|
|narrow-leaved cattail||Typha angustifolia|
1. Ball, J. P. 1984. Habitat selection and optimal foraging by mallards: a field experiment. Guelph, ON: University of Guelph. 44 p. Thesis.