Reproductive success and environmental contaminants among bald eagles in Placentia and Bonavista Bays, Newfoundland

Dominguez, Laura (1999) Reproductive success and environmental contaminants among bald eagles in Placentia and Bonavista Bays, Newfoundland. Masters thesis, Memorial University of Newfoundland.

[English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (3MB)

Abstract

The bald eagle (Haliaeetas leacocephalus) population in Newfoundland is one of the largest in North America. The main breeding concentration is in Placentia Bay, the most industrialized bay in Newfoundland. This study investigated for the first time the reproductive and toxicological status of two major bald eagle breeding concentrations in Newfoundland. The main objectives of the study were: 1) to compare the reproductive performance and contaminant loads of bald eagles in a relatively industrialized area (i.e. Placentia Bay) and in a non-industrialized area (i.e. Bonavista Bay); 2) to compare the reproductive and toxicological status of bald eagles in Newfoundland with other bald eagle populations in North America. This study also provided baseline reproductive and toxicological data on the bald eagle population in Placentia Bay, before further large-scale industrial development (e.g. trans-shipment and storage oil facilities and proposed nickel smelter). -- Reproductive surveys and sampling of bald eagle nestlings for toxicological analyses were conducted in Placentia Bay in 1996 and 1997 and in Bonavista Bay in 1997. Both populations had high breeding densities (0.1 and 0.06 occupied nests/km of shoreline in Placentia and Bonavista Bays, respectively) and a stable reproductive performance (82 % nest occupancy, 71 % nest success and 1.1 chicks/occupied nest in Placentia Bay and 92 % nest occupancy, 83 % nest success and 0.9 chicks/occupied nest in Bonavista Bay). There were no significant differences in nest occupancy, nest success or chick production between bays. -- Organochlorine and metal concentrations in nestling blood and in addled eggs were relatively low in both Placentia and Bonavista Bays. Mean concentrations of PCBs and DDE in nestling plasma were significantly higher in Placentia Bay (PCB geometric mean (Gm) = 0.03 ppm (wet wt.) and DDE Gm = 0.009 ppm) than in Bonavista Bay (PCB Gm = 0.01 ppm and DDE Gm = 0.002 ppm, respectively). Mean concentrations of mercury in nestling blood were not significantly different between Placentia and Bonavista Bays (Gm = 0.08 ppm and Gm = 0.07 ppm, respectively). The US naval base in Argentia, located on the east side of Placentia Bay, has been identified as a potential local source of PCB contamination. Nests that were located nearer Argentia (NEAR nests) also had higher mean concentrations of PCBs and DDE than nests located more distantly (DISTANT nests), while metal concentrations were similar between both groups. Analyses of prey remains collected at nest sites showed no significant difference in the frequency of occurrence of bird and fish specimens between Placentia and Bonavista Bays, or between NEAR and DISTANT nests in Placentia Bay. Analyses of stable nitrogen isotopes in nestling blood samples showed no differences in trophic level either between bays or between NEAR and DISTANT nests in Placentia Bay. Results of these dietary analyses further support the relationship of higher PCB and DDE concentrations to a local source of pollution on the east side of Placentia Bay. The bald eagle breeding populations studied in Newfoundland had breeding densities and reproductive success higher than those reported for populations in more heavily industrialized regions such as the Great Lakes, Columbia River Estuary and Maine, and were comparable to those reported for stable and healthy populations in Alaska, inland Minnesota and Saskatchewan. Contaminant burdens in bald eagles from Newfoundland are lower than those reported for populations in the industrialized regions, and are lower than levels associated with impairment of reproduction.

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