Editing Greater scaup (section)

==Threats==
[[File:Zwemmende toppereenden-4961904.webm|thumb|Video of greater scaup.]]
Common predators of the greater scaup are [[owls]], [[fox]]es, [[skunk]]s, [[raccoon]]s, [[coyote]]s, and humans.<ref name=USFauna/> Greater scaup often become entangled in fishing nets, and large numbers of them drown in this way each year. Greater scaup can catch [[avian influenza]], so future outbreaks have the potential to threaten their populations.<ref name=Birdlife/>

Although the greater scaup faces numerous threats, the most significant challenge to their survival is habitat degradation caused by a mix of human development and runoff.<ref name=NBII/> Greater scaup, when moulting and during the winter, are threatened by escalated levels of organochloride contaminants. Oil and sewage pollution also threaten this duck. Since 80% of the greater scaup population winters in the urbanised part of the [[Atlantic Flyway]], these ducks are subject to high levels of organic contaminants, along with increased levels of heavy metals in foods and habitat.<ref name=BirdsNorthAmerica/>

A joint group of American and Canadian scientists researching scaup migration across the Great Lakes found that 100% of female greater scaup and 77% of female lesser scaup had escalated levels of [[selenium]] in their bodies. Selenium is a [[semimetal]]lic [[trace element]] that occurs naturally in some soils; minute amounts of it are necessary for animal life. However, excessive selenium can cause reproductive harm and is highly toxic. On their migration across the Great Lakes, greater scaups are at risk of ingesting selenium by eating the invasive [[zebra mussels]], which can render the female scaup [[infertile]].<ref name=Bluebills/> This sterilization is causing the population to decrease.

In a study of 107 scaup, they all had traces of [[iron]], [[zinc]], [[manganese]], [[copper]], [[lead]], [[cadmium]], [[cobalt]] and [[nickel]] in their tissue samples with varying concentrations of metals in different types of tissues. The kidneys had the highest levels of cadmium, the liver had the highest levels of copper and manganese, the liver and the stomach had the highest levels of zinc, and the lungs and liver had the highest levels of iron.<ref name="Trace metals in the soft tissues of scaup"/> There was no difference in concentrations when comparing sexes.