Reproductive demographics, use of marine habitats, and exposure to contaminants of red-throated loons breeding in Alaska. Numbers of Red-throated Loons (Gavia stellata) breeding in Alaska declined by 53% from 1977 to 1993. Managers are concerned about this decline, but they lack the information needed to decide how to manage this species. Despite a long history of aerial population surveys in Alaska which yield the most rigorous trend data anywhere for Red-throated Loons, only fragmentary knowledge exists about this species' ecology. Four information needs listed by the USFWS include data on demographic parameters, distribution among wintering areas and their links to breeding areas, subsistence by-catch in fishing nets, and exposure to contaminants. One hypothesis is that exposure to heavy metals is causing declining loon populations. On their breeding areas, another marine diving bird, the threatened Spectacled Eider, raises its young on the same ponds as Red-throated Loons. Eiders experience high rates of lead poisoning (from spent shot used by subsistence hunters) and consequently incur increased mortality. Selenium may also be of concern as sympatrically breeding Emperor Geese had unexpectedly high levels of this element in their blood. Elevated selenium concentrations are known to impair reproductive success of aquatic birds. Exposure of loons to other contaminants is possible on wintering areas. Although the location of Alaska loon populations during winter is unknown, Red-throated Loons are known to winter in several coastal marine locations where organochlorine levels are elevated. Despite a widespread winter distribution on both Pacific and Atlantic coasts, evaluation of such hazards for Red-throated Loons breeding in Alaska is not possible until links are established between specific breeding and wintering populations. Exposure of loons to other contaminants is possible on wintering areas. Although the location of Alaska loon populations during winter is unknown, Red-throated Loons are known to winter in several coastal marine locations where organochl... levels are elevated. Despite a widespread winter distribution on both Pacific and Atlantic coasts, evaluation of such hazards for Red-throated Loons breeding in Alaska is not possible until links are established between specific breeding and wintering populations. An ecological clue to the trends documented by Groves et al. is that sympatric populations of Pacific and Common Loons in Alaska appear stable, in contrast to Red-throated Loons. A closer examination of distribution and foraging behavior suggests two possible reasons for these species differences. Red-throated Loons are more tightly associated with the coast than the other two loon species. This distribution is likely a consequence of diet differences; whereas all three loons rear their young on fresh or brackish ponds, only Red-throated Loons feed their chicks and themselves marine fish almost exclusively, whereas the other species forage on their natal ponds. Ecosystem shifts in forage fish communities in coast... waters of western Alaska have been documented, and these shifts are believed to be a principal reason for widespread reproductive failure in other piscivorous marine birds occurring in Alaska. This ecosystem shift began in the mid 1970s, and correspondingly, the decline of Red-throated Loons began soon thereafter. Thus, a hypothesis is that marine forage fish availability or nutritional quality has declined and impacted some aspect of survival or reproduction, with reproductive consequences more likely. Another hypothesis for declines is suggested by this coastal distribution. On the Yukon-Kuskokwim Delta, the majority of waterfowl and subsistence hunting occurs in this coastal zone. Thus, the distribution of lead shot likely parallels the distribution of Red-throated Loons more closely than for the other two loon species. Additionally, gill nets for salmon and whitefish are distributed by subsistence users throughout these coastal areas on tidal rivers and sloughs. These fishing activities are of great economic and sociologic importance to the people of western Alaska. However, an unknown magnitude of by-catch occurs as a consequence of such fishing. Although Red-throated Loons rear their chicks on ponds and lakes, they go to these rivers and sloughs to feed, resulting in periodic entanglement. Our objectives are to (1) describe migration routes and provide links between loons from two breeding areas and their wintering areas using satellite telemetry, (2) measure heavy metal and organochlorine levels in the blood of loons from two breeding areas and in any addled eggs we discover, (3) estimate clutch size, hatching success, and chick-rearing success of loons and compare these values to that observed in other populations, and (4) begin discussions with USFWS personnel to develop means of surveying local people about their knowledge of by-catch in fishing nets.

Principal Investigator: Joel Schmutz, Research Wildlife Biologist

Linking Breeding and Migration/Wintering Areas of Red-throated Loons with Satellite Telemetry