• Sources and effects of strontium in waterfowl eggs

      Latty, Christopher J.; Hollmén, Tuula E.; Matz, Angela C.; Powell, Abby N.; Hobson, Keith A.; Adkison, Milo D. (2021-05)
      Strontium (Sr) may be a contaminant of concern for wild birds. Because of chemical similarities to calcium (Ca), Sr is readily incorporated into calcified tissues, such as eggshells. My objectives were to determine the potential drivers of both total and radio-Sr in the eggshells of waterfowl, and to assess the relationship between eggshell Sr and thickness. I collected eggs from sympatrically nesting waterfowl species in interior Alaska from 2011-2013. I measured total and radio-Sr in eggshells, environmental chemistry, and eggshell thickness. Local water chemistry explained much of the variation in eggshell Sr for canvasback (Aythya valisineria) and northern shoveler (Spatula clypeata), but not lesser scaup (Aythya affinis). Most of the remaining variation was associated with heterogeneity among eggs in the same nest (intra-clutch variance). General trends in eggshell Sr/Ca among species aligned with what would be expected had diet and/or endogenous reserve use affected eggshell chemistry. Results were similar for radio-Sr, with local water chemistry accounting for far less ⁹⁰Sr in the eggshells of lesser scaup, compared to the other species studied. At the site where water chemistry was stable, canvasback and northern shoveler eggshell thickness was not related to eggshell Sr, but lesser scaup eggshells with more Sr were thicker. At the site where water chemistry was variable, canvasback and northern shoveler eggshells with more Sr were thicker at low to intermediate concentrations, but this effect was moderated when the source of eggshell Sr appeared to be explained by the local environment. In contrast, lesser scaup eggshells with more Sr were consistently thicker, but only at higher concentrations. The different relationships between eggshell Sr and thickness across species, and interactions with apparent Sr sources, suggest the relationship between eggshell thickness and Sr is not a simple dose-dependence. My results show that for some species like lesser scaup, factors associated with the laying hen (e.g., diet or physiology) may have a larger impact on both eggshell total and radio-Sr, as well as how Sr interacts with eggshell quality, than the local environment.