Blood lead concentrations in Alaskan tundra swans: linking breeding and wintering areas with satellite telemetry

Abstract

Tundra swans (Cygnus columbianus) like many waterfowl species are susceptible to lead (Pb) poisoning, and Pb-induced mortality has been reported from many areas of their wintering range. Little is known however about Pb levels throughout the annual cycle of tundra swans, especially during summer when birds are on remote northern breeding areas where they are less likely to be exposed to anthropogenic sources of Pb. Our objective was to document summer Pb levels in tundra swans throughout their breeding range in Alaska to determine if there were population-specific differences in blood Pb concentrations that might pose a threat to swans and to humans that may consume them. We measured blood Pb concentrations in tundra swans at five locations in Alaska, representing birds that winter in both the Pacific Flyway and Atlantic Flyway. We also marked swans at each location with satellite transmitters and coded neck bands, to identify staging and wintering sites and determine if winter site use correlated with summer Pb concentrations. Blood Pb levels were generally low (<0.2 μg/ml) in swans across all breeding areas. Pb levels were lower in cygnets than adults, suggesting that swans were likely exposed to Pb on wintering areas or on return migration to Alaska, rather than on the summer breeding grounds. Blood Pb levels varied significantly across the five breeding areas, with highest concentrations in birds on the North Slope of Alaska (wintering in the Atlantic Flyway), and lowest in birds from the lower Alaska Peninsula that rarely migrate south for winter.

Demographic outcomes of diverse migration strategies assessed in a metapopulation of tundra swans

“…Detection of birds actively shedding AI viruses was determined according to the standardized USDA National Animal Health Laboratory Network AI real time reverse transcriptase polymerase chain reaction (RT-PCR) protocol [ 38 – 40 ]. Previous work summarized levels of blood parasite infection [ 34 ] and lead contamination [ 41 ] in PTT-marked and unmarked birds from each population.…”

“…We considered a model in which survival varied linearly relative to mean annual migration distance for each breeding area. To account for additional sources of variation in survival such as those resulting from differences in migration routes, wintering locations, or factors specific to the breeding grounds (Table 1 , [ 41 ]), we examined a breeding area-specific model, and 2 simplified location models. Tundra swans in North America are managed as 2 distinct populations, the Western Population (WP) which winters on the Pacific coast of the United States and Canada and the Eastern Population (EP) which winters along the eastern seaboard of the United States.…”

“…Of the WP birds in our marked sample, LAP birds are unique in that many are mostly nonmigratory and winter near their breeding grounds on the Alaska Peninsula [ 45 ] (Table 1 ). YKD and KSL birds first migrate eastward and then south through western Canada, Montana, and Utah into California ([ 27 , 41 ]; Fig. 1 ).…”

Lead isotope ratio measurements as indicators for the source of lead poisoning in Mute swans (Cygnus olor) wintering in Puck Bay (northern Poland)

“…After the ingestion, with the help of the grinding mechanisms of the gizzard and in its acidic environment, Pb particles dissolve easily and get into the bloodstream causing poisoning (DeMichele 1984;Pain, 1990). This phenomenon has been a significant source of mortality for many years among various species of swans in different parts of the world (Blus et al, 1989;Ely and Franson, 2014;Nakade et al, 2005;Perrins et al, 2003). It was estimated globally that until the middle of 1990s, 10,000 swans from 14 different countries died as a result of Pb poisoning caused by ammunition pellets deposited in wetland habitats (Blus, 1994).…”

“…Tissues with faster Pb turnover should be more appropriate. The one which shows recent exposure (including a couple of previous weeks) is blood, already used in waterfowl biomonitoring studies, including cases of Pb poisoning (Binkowski and Meissner, 2013;Delves and Campbell, 1988;Ely and Franson, 2014;Gomez-Ramirez et al, 2011;Pain, 1989;Tsuji et al, 2008). Moreover, we included all the isotopes because previous studies by co-workers showed that, in many cases, their values overlapped among tissue, pellets and soil samples (Meharg et al, 2002;Scheuhammer and Templeton, 1998).…”