No abstract

We determined the importance of three landfills to a population of nesting Herring Gulls (Larus urgent&us, 3,250 pairs) on Lake Erie, Ohio, from May-July 1992. Fish was the dominant food ofadults and chicks throughout the study. Occurrence ofgarbage in the diet of adults and chicks remained low through chick-rearing then increased after fledging. Presence of telemetered adults at their nest sites decreased from incubation through post-fledging, in contrast to their increased presence at landfills during the same periods. Overall, females visited landfills more frequently and stayed longer than males; however, use of landfills by both sexes was minimal (~4% of total time) during all periods. Overall, gulls spent 43% and 4% of their time daily at the nest site and landfills, respectively. We estimate ?80% of the time remaining was spent on Lake Erie, presumably to forage. The estimated daily mean number of adult Herring Gulls at the landfills increased from incubation (143) to chick-rearing (723) to post-fledging (1,912). We estimate that 5-7%, 12-19%, and 35-55% of the adult nesting population was present at landfills at least once during incubation, chick-rearing, and post-fledging, respectively. The population turnover rate of adult Herring Gulls at one landfill decreased 50% from incubation and chick-rearing to postfledging. Significantly more gulls at the landfills were observed on areas other than exposed refuse and were not actively foraging, suggesting that landfills are important to Herring Gulls for other reasons such as loafing or social interaction. We conclude that landfills are unimportant to nesting Herring Gulls when alternate, higher quality food (e.g., fish) is available. The increased use of landfills by Herring Gulls during post-fledging, however, suggests that gull activity at landfills located near airports could dramatically affect aircraft safety during this time of year.

Marshes in the Gulf Coast Chenier Plain provide important winter habitats for many species of birds. Many of these marshes are managed intensively through a combination of fall/winter burning and construction of impoundments to improve wintering waterfowl habitat, reduce wedand loss, and create emergent wetlands. Little information is available on effects of this management on wintering birds, particularly passerines. We conducted experimental burns in impounded and unimpounded marshes on Rockefeller State Wildlife Refuge in southwest Louisiana and recorded species composition and abundance of birds during the 1996 and 1997 winters. We found that burning and impoundment influenced vegetation structure, which in turn influenced bird abundance and species composition. Blackbirds (lcteridae) preferred recently burned plots. Sparrows (Emberizidae) and wrens (Troglodytidae) avoided recently burned plots but recolonized these plots after one year of vegetation recovery. Sparrows and wrens present in burned plots during the first winter following burning generally were observed in scattered patches of unburned vegetation. Suitability of Chenier Plain marshes as winter habitat for several bird species was reduced during the winter in which burning was conducted, particularly if a high proportion of the plot was burned. We recommend that patchy burns be used, at both the landscape level and within specific burned areas, to achieve management objectives and still provide suitable winter habitat for non-target species. Although many groups of birds depend on Chenier Plain marshes for winter habitat, these groups differ in their specific habitat requirements. We recommend that a diverse wetland complex (e.g., impoundments managed for waterfowl foraging habitat interspersed with those managed for passerine winter cover) be maintained.

Many marshes in the Gulf Coast Chenier Plain, USA, are managed through a combination of fall or winter burning and structural marsh management (i.e., levees and water control structures; hereafter SMM). The goals of winter burning and SMM include improvement of waterfowl and furbearer habitat, maintenance of historic isohaline lines, and creation and maintenance of emergent wetlands. Although management practices are intended to influence the plant community, effects of these practices on primary productivity have not been investigated. Marsh processes, such as vertical accretion and nutrient cycles, which depend on primary productivity may be affected directly or indirectly by winter burning or SMM. We compared Chenier Plain plant community characteristics (species composition and above- and belowground biomass) in experimentally burned and unburned control plots within impounded and unimpounded marshes at 7 months (1996), 19 months (1997), and 31 months (1998) after burning. Burning and SMM did not affect number of plant species or species composition in our experiment. For all three years combined, burned plots had higher live above-ground biomass than did unburned plots. Total above-ground and dead above-ground biomasses were reduced in burned plots for two and three years, respectively, compared to those in unburned control plots. During all three years, belowground biomass was lower in impounded than in unimpounded marshes but did not differ between burn treatments. Our results clearly indicate that current marsh management practices influence marsh primary productivity and may impact other marsh processes, such as vertical accretion, that are dependent on organic matter accumulation and decay.