Geology topics

Christine M. Custer

Publications and source records attributed to Christine M. Custer.

77 records · Page 5Linked to original sources

USGS1996

Food habits of diving ducks in the Great Lakes after the zebra mussel invasion

Zebra mussels (Dreissena polymorpha) invaded the Great Lakes in the mid-1980s and quickly reached high densities. The objective of this study was to determine current consumption of zebra mussels by waterfowl in the Great Lakes region. Feeding Lesser Scaups (Aythya affinis), Greater Scaups (A. marila), Canvasbacks (A. valisineria), Redheads (A. americana), Buffleheads (Bucephala albeola) and Common Goldeneyes (B. clangula) were collected in western Lake Erie and in Lake St. Clair between fall and spring, 1992-1993 to determine food habits. All 10 Redheads, 97% of Lesser Scaups, 83% of Goldeneyes, 60% of Buffleheads and 9% of Canvasbacks contained one or more zebra mussels in their upper gastrointestinal tracts. The aggregate percent of zebra mussels in the diet of Lesser Scaups was higher in Lake Erie (98.6%) than in Lake St. Clair (54.4%). Zebra mussels (aggregate percent) dominated the diet of Common Goldeneyes (79.2%) but not in Buffleheads (23.5%), Redheads (21%) or Canvasbacks (9%). Lesser Scaups from Lake Erie fed on larger zebra mussels ( = 10.7 i?? 0.66 mm SE) than did Lesser Scaups from Lake St. Clair ( = 4.4 i?? 0.22 mm). Lesser Scaups, Buffleheads and Common Goldeneyes from Lake Erie consumed zebra mussels of similar size.

Journal of Field Ornithology↗

USGS1996

Radio telemetry documents 24-hour feeding activity of wintering lesser scaup

We used radio telemetry to record 198 h of feeding behavior of five Lesser Scaup (Aythya affinis) on the Indiana Harbor Canal in northwestern Indiana during January and February 1994. Lesser Scaup fed for short periods of time intermittently during each 24-h period. Lesser Scaup fed a total of 96 min during the day and 226 min during the night. They fed more between sunset and midnight (31.9% of the period, P = 0.003) than between sunrise and noon (11.6%) or noon and sunset (19.5%); time spent feeding between midnight and sunrise (26.3%) did not differ from other times of day. Mean dive duration (22.9 ± 0.64 sec) did not vary by time of day ( P = 0.186-0.744). These results are the first 24-h feeding activity reported for individually marked Lesser Scaup.

The Wilson Bulletin↗

USGS1995

Transfer and accumulation of organochlorines from black-crowned night-heron eggs to chicks

Eggs and sibling 1-, 3-, and 5-d-old chicks from seven black-crowned night-heron ( Nycticorax nycticorax ) broods were collected from Green Bay, Wisconsin, and analyzed for organochlorines. The concentration (μg/g) of nine organochlorines either decreased ( n = 7) or remained the same ( n = 2) as the chicks grew older. In contrast, the total mass (μg) of these nine organochlorines increased ( n = 7) or remained the same ( n = 2) as the chicks grew older. Accumulation rates of mass (μg/d) between egg and 5-d-old chicks for each of the nine organochlorines were positive and varied from 0.2 μg/d ( p,p ′-DDT) to 42 μg/d (PCBs). These results suggest that the loss of contaminant mass from eggs to chicks reported in some earlier studies was because the entire carcass was not analyzed (i.e., not including skin, gastrointestinal tract, etc.). These results also support the use of contaminant accumulation rates as an indicator of local contamination.

Environmental Toxicology and Chemistry↗

USGS1994

Flow cytometry for monitoring contaminant exposure in black-crowned night-herons

The flow cytometry method (FCM) was employed to determine cellular DNA content of black-crowned night-heron ( Nycticorax nycticorax ) embryos and 10-day-old chicks collected at sites differing in types of chemical contamination. The coefficient of variation of DNA content (CV) in blood collected from embryos suggested cytogenetic damage at a site in Louisiana known to be contaminated with petroleum. Blood CV from chicks suggested genetic damage at a site in Texas also known to be contaminated with petroleum. Spleen CVs in chicks were significantly lower than respective means from the reference site. The CVs of chick blood and liver and spleen negatively correlated, suggesting recovery of spleen and liver cells after exposure to a clastogenic compound. Thus, the lower CVs may also have been indicative of genetic damage. Based on the findings of this study, FCM is a potential indicator of certain environmental contaminants in black-crowned night-herons.

Archives of Environmental Contamination and Toxico↗

USGS1993

Life history traits and habitat needs of the redhead

Redheads are one of five common diving duck species in North America. They are in the same taxonomic group as the pochards or bay ducks and are most similar in appearance and behavior to the canvasback. Smaller body size, late breeding, wintering in southern areas, and tolerance to salt in winter and in breeding areas differentiate the redhead from the canvasback and suggest an evolutionary origin in the arid areas of the West. Parasitism of other waterfowl nests is more pronounced in redheads than in other North American waterfowl. These and other aspects of the biology of the redhead are the subject of this leaflet. Readers who are interested in general references on redheads.

Fish and Wildlife Leaflet↗