UBC Theses and Dissertations
A general study of the primary and secondary productivity of the northern Pitt meadows with special reference to their use by waterfowl Barnard, Anthony Erwin
The lowlands of the study area consist of nearly 4,600 acres of developed and undeveloped farmlands and approximately 3,100 acres of freshwater marsh and associated wildlands and bogs. At present the latter areas attract, a wide range of recreation oriented activities. In addition, the marshes were believed to play an integral part in waterfowl utilization of the Lower Fraser Valley. The basic objectives of the study were to delineate, various indices of biological production, particularly as they pertained to waterfowl, between habitats within the study area and between the study area as a whole and wetlands elsewhere. To this end, the importance of cover in influencing faunal distribution was recognized and schematically presented in a cover-map. Basic characteristics of soils subjected to varying hydric conditions were described. The quality of waters in the different habitats appeared to reflect current land. use. In this respect, waters of the marshes, wildlands, bogs and large tracts of undeveloped farmlands were oligotrophic in nature. Conversely, waters in and adjacent to actively farmed areas were relatively eutrophic. The water regime of the lands subjected to pumping is fairly stable whereas in the unpumped habitats wide fluctuations in water level occur bi-annually. Yields of major plant communities were monitored throughout the growing season, thus indicating primary production capabilities of the area. In the unpumped habitats a large proportion of the nitrogen per unit area of vegetation is "tied up" in accumulations of old growth and duff. In both pumped and unpumped habitats, hardhack communities were shown to account for much of the nutrient "short-stopping" in the study area. Secondary succession is in effect in both pumped and unpumped habitats and vegetation development suggests long-term development towards peat bog in many areas. In terms of both total invertebrate yield and yield of twelve families considered potentially important to young waterfowl, the Ag. II habitat is more productive than Ag. I or the Sturgeon Slough marsh. Based on brood and invertebrate production in Ag. I, feed for ducklings is not a factor in low brood production in Ag. II but may contribute to that currently experienced in the Sturgeon Slough marsh. The major nesting species of waterfowl were mallard, cinnamon teal and wood duck. Twenty-four broods were actually censused in 1972 and twenty in 1973. Calculation of brood production based on breeding pairs and estimates on areas too large to census indicated seventy-eight broods were raised in the habitats investigated in 1973. For the entire study area, production was calculated to be 8.3 broods/sq. mile in 1973. Rapid increases in water level during May and June conflict with the nesting period of both mallard and teal in the unpumped habitats, and probably are a major factor in current levels of brood production in these areas. Marshes of the unpumped habitats were extensively used by moulting mallards and wood duck and may serve the moulting needs of most summer resident waterfowl in the Lower Fraser Valley. Harvest of most local mallards occurs predominantly in or adjacent to their natal area. Adult wood ducks are apparently non-migratory and undergo little pressure after the first two weeks of hunting. Approximately one-third of the immature wood duck harvest occurs in their natal area, generally by late October. The remaining harvest is distributed between the Willamette Valley of Oregon and the Central Valley of California and generally occurs during late November and December. Less than 10% of the study area is available for public hunting resulting in a disproportionate hunting effort and success rate. Fall and winter waterfowl use has apparently declined considerably in the last twenty years. Control and regulation of the water, regime in the unpumped habitats must be realized before proper management of these lands for waterfowl can be realized. Immediate management opportunities do exist, however, for increasing the breeding population of wood duck in the study area. It is strongly recommended that only controlled hunting be permitted in the unpumped habitats if maximum year round production of waterfowl is the management objective in these areas.
Item Citations and Data