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Conservation and Management
Effects Of Human Activity
Shooting And Trapping
Prior to Migratory Bird Treaty protection (in 1919), shot for millinery trade, but impact on this species unknown. Forster’s Tern had habit of flying towards and hovering over those individuals that had been shot and thus was particularly vulnerable to millinery collectors (Brewster 1889, Finley 1917).
Pesticides And Other Contaminants/Toxins
No studies of Forster’s Terns in 1960s and 1970s, when effects of contaminants were greatest in other fish-eating birds. Organochlorine, heavy metal, and se-lenium (Se) concentrations measured in eggs from Wisconsin (Harris et al. 1985, 1993; Heinz et al. 1985; Kubiak et al. 1989; Smith et al. 1990), California (Ohlendorf et al. 1988), Texas (King et al. 1991), and New Jersey (Burger and Gochfeld 1997). Highest levels (geometric means, wet weight of egg contents) 2.9 parts per million (ppm) DDE at Green Bay, WI, in 1978 (Heinz et al. 1985); 22 ppm total polychlorinated biphenyls (PCBs) at Green Bay in 1983 (Kubiak et al. 1989); 47 parts per trillion 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) at Green Bay in 1983 (Smith et al. 1990); 0.9 ppm total mercury (Hg) at San Francisco Bay, CA, in 1982 (Ohlendorf et al. 1988); 2.0 ppm Hg (and as high as 3.8 ppm) on coastal New Jersey in 1992 (Burger and Gochfeld 1997); 0.75 ppm Se at Lavaca Bay, TX, in 1984 (King et al. 1991). Severe reproductive impairment (reduced hatching success [75% lower], lengthened incubation periods [4.6 d longer], reduced hatching masses [20% lower], abnormal embryos and hatchlings, biochemical changes in embryos, zero chick survival) at Green Bay in 1983 shown to be associated with contamination of eggs and adults, in study involving artificial incubation and exchanges of eggs with a less contaminated colony at Lake Poygan, WI (Hoffman et al. 1987, Kubiak et al. 1989). Effects attributed to “dioxin-like” PCB congeners, specifically PCB105 and PCB126 (Kubiak et al. 1989, Smith et al. 1990, Jones et al. 1993), although other contaminants also higher at Green Bay than at Lake Poygan. By 1988–1989, contaminant levels in eggs at Green Bay were reduced by 42–67% and breeding performance improved, although many chicks still showed growth retardation and low survival (Harris et al. 1993, Jones et al. 1993). Uptake of PCB congeners and other contaminants reported by Ankley et al. (1993). Eggshell thickness negatively correlated with DDE levels (range in individual eggs, 0.9–7.1 ppm) at San Francisco Bay, CA, in 1982 (Ohlendorf et al. 1988), and significantly reduced (by 7%) at Lavaca Bay, TX, in 1984 (King et al. 1991), but no effects on reproductive success measurable at those times. Hatching failure associated with high Se levels at Lavaca Bay in 1984 (King et al. 1991), but not significantly so.
Ingestion Of Plastics, Lead, Etc
Not reported.
Collisions With Stationary/Moving Structures Or Objects
Several terns foraging from bridge struck by vehicles (Reed 1985).
Fishing Nets
No mortality reported.
Degradation Of Habitat
Management activities reducing marsh and wetland habitats remove or reduce favored habitat for this species.
Disturbance At Breeding Colonies And Roost Sites
Most human disturbance at breeding colonies unintentional but vandalism has caused colony failure (Clapp et al. 1983). Reported to habituate to fishermen within 100 m of colony (Mossman 1989) and produce young at colony despite construction of causeway through colony (Hatch 1972).
Direct Human/Research Impacts
Response to observers in or near nests (see Behavior: predation, above) increases parental inattentiveness and may cause hypothermia-induced deaths of chicks that leave the nest and enter water (Hall 1989, Fraser 1994a).
Management
Conservation Status
In U.S., designated species of Special Concern in Michigan and Minnesota and Endangered in Illinois and Wisconsin (Mossman 1989, Cuthbert and Louis 1993, Fraser 1994a, Alvo and McNicholl 1996). In Canada, assigned indeterminate status by Committee on the Status of Endangered Wildlife in Canada.
Measures Proposed And Taken/Effectiveness Of Measures
Wetland preservation, especially of areas known to have been used for nesting, has been recommended for this species. Ability to colonize newly created marsh-like habitats (see Demography and populations: range, above) suggest that management and restoration of large wetland systems should benefit breeding populations (Mossman 1989). Management plans in Wisconsin have included placement of 60 × 64-cm wooden platforms to serve as artificial nesting sites (Techlow 1986, Mossman 1989).
Mcnicholl, Martin K., Peter E. Lowther and John A. Hall. 2001. Forster's Tern (Sterna forsteri), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/595
