Kirke A. King

Effects of oil transferred from incubating gulls to their eggs

Abstract No. 2 fuel oil, or water, was applied to the breast feathers of incubating laughing gulls trapped at their nest site on an island colony in Texas. Gulls were released after treatment and allowed to incubate their eggs for 5 days. Oil was transferred from the feathers of incubating adults to their eggs and resulted in 41% embryo mortality compared with 2% in controls.

Effects of mercury, selenium, and organochlorine contaminants on reproduction of Forster's terns and black skimmers nesting in a contaminated Texas Bay

Mean mercury (0.40 μg/g), and geometric mean DDE (1.6 μg/g) and polychlorinated biphenyl (PCB) (2.3 μg/g) concentrations in Forsters tern (Sterna forsteri) eggs from Lavaca Bay were higher than those in tern eggs from a reference area in San Antonio Bay, but residues were not correlated with hatching success. Nest success was similar between bays. Selenium levels in Lavaca Bay tern eggs (0.71 μg/g) were also comparable to those in eggs from the reference area (0.68 μg/g).Clutch size (3.1 to 3.4) of Lavaca Bay black skimmers (Rynchops niger) was no different than that (3.4) at a reference colony near Laguna Vista. Nest success was similar among three Lavaca Bay colonies, but success was lower at one Lavaca Bay colony (40%) than at Laguna Vista (65%). Mean mercury (0.46 μg/g) and selenium (0.75 μg/g) concentrations in skimmer eggs from Lavaca Bay were higher than those (0.19, 0.33 μg/g) from Laguna Vista; however, concentrations of neither contaminant were related to hatching success. DDE concentrations in Lavaca Bay skimmer eggs (3.4 μg/g) were similar to those from Laguna Vista (3.2 μg/g) and DDE was negatively correlated with hatching success. PCBs were higher in eggs from Lavaca Bay (1.3 μg/g) than Laguna Vista (0.8 μg/g). Organochlorine and metal contaminants in most eggs were below embryotoxic levels. Eggshell thinning in Forsters terns (7%) and black skimmers (5%) was below that associated with lowered reproduction.DDE and PCBs were detected in 9 Caspian tern (S. caspia) eggs; maximum concentrations were 4.7 and 5.4 μg/g. Caspian tern and least tern (S. albifrons) eggs contained low (⩽0.9 μg/g) concentrations of mercury and selenium.

Ticks as a factor in nest desertion of California brown pelicans

first became intense during the 1920’ s as birds began to shift from aquatic habitat to cropland to feed. Wheat and other cereal grains are now an integral part of the diet of this species particularly during autumn. Agricultural tillage has also affected diet composition in wetland habitat. Krapu (197413) reported that wild millet (barnyard grass) formed 71% of the diet of breeding Pintail hens feeding in tilled basins. This annual grass is a dominant species in annually tilled wetland basins. Grains of wild millet are eaten from spring through fall during periods when tilled basins are flooded. We thank Mavis I. Meyer for assistance in preparing food habits data and Jerome R. Serie for critically reviewing the manuscript.

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).

Population trends, reproductive success, and organochlorine chemical contaminants in waterbirds nesting in Galveston Bay, Texas.

The effects of environmental contaminants on the reproductive success of olivaceous cormorants (Phalacrocorax olivaceus), laughing gulls (Larus atricilla), and black skimmers (Rhynchops niger) nesting in Galveston Bay, Texas were investigated from 1980 through 1982. Populations of cormorants and gulls have remained stable in recent years, but skimmer numbers may have declined. Cormorants produced 1.9 to 2.8 young per pair in nests that remained active throughout the season. Gull and skimmer reproduction was seriously limited by storms and predation. DDE and polychlorinated biphenyl (PCB) residues in carcasses and eggs generally were below levels associated with chronic poisoning and reproductive problems in most species of birds. Possible exceptions were four black skimmer carcasses with DDE concentrations that ranged from 20 to 92Μg/g and one olivaceous cormorant carcass with 20Μg/g DDE. The generally low levels of dieldrin, chlordane, HCB, toxaphene, and heptachlor epoxide were below those know to affect avian reproduction and survival. Mean DDE residues in cormorant and gull eggs were less than 1.8Μg/g. The mean DDE residue in skimmer eggs was less than 3.3Μg/g; 12% of the skimmer eggs contained at least 12Μg/g DDE, a level known to cause reproductive problems in some avian species. DDE in the eggs of all species declined from 1.5- to 7-fold over the past decade. Polychlorinated biphenyl was detected in all gull and skimmer eggs and in 90% of the cormorant eggs. Residues of PCB in cormorant and skimmer eggs in 1980–82 were lower than in 1970, but the frequency of occurrence in gull eggs increased. Polychlorinated styrenes were recovered in 45% of the cormorant carcasses at levels below 1Μg/g. Eggshell thicknesses in all three species were similar to those of eggshells collected before the widespread use of DDT.

Resuspension of oil: probable cause of brown pelican fatality

Coastal ecosystems are vital nesting and wintering areas for numerous bird populations. Increasing growth in costal areas, particularly development related to the recovery and transportation of oil, poses severe threats to coastal and marine bird species. The devastating effects of oil spills on waterbirds are now well documented; large numbers of marine birds die each year as a result of oil spills. Most mortality occurs within a few days after the spill; however, our recent observations in Texas indicate that mortality may occur at least 6 weeks after the original spill.