Item talk:Q152515

Reproductive success of barn swallows nesting near a selenium-contaminated lake in east Texas, USA

Reproductive success and contaminant levels in 1986 and 1987 were compared between Barn Swallows nesting at selenium-contaminated Martin Lake, Texas, USA, and swallows nesting at a reference site. Nests were initiated about the same time or earlier at Martin Lake than at the reference site and clutch size was similar between the two locations. Nest success was significantly higher at Martin Lake than at the reference site and no embryo or chick deformities were documented. Selenium concentrations in 14 of 20 eggs from Martin Lake were above background (> 3 ppm, dry weight); two of 20 eggs contained > 5 ppm, a concentration associated with a 20% embryo mortality/deformity rate in some bird species. Selenium concentrations in the kidneys of adult swallows were higher at Martin Lake (mean = 14 ppm dry weight) than at the reference site (5·8 ppm). DDE, the only detected organochlorine compound, was in two of 10 eggs from Martin Lake; these concentrations were below those associated with chronic poisoning and reproductive problems. The maximum mercury concentration in livers of adult Barn Swallows (0·83 ppm, dry weight) was within the range for background levels (>5 ppm).