Monitoring contaminants in gull and tern eggs is a useful tool for gaining insights into local environmental conditions because gulls and terns are integrators of processes occurring at lower levels in the food web and their eggs are generally formed using local food sources. Therefore, the chemical composition of the egg will reflect the chemical characteristics of the region in the vicinity of the breeding colony, including level of contaminants, such as mercury. Eggs are collected any time after laying, ideally well before hatching, but after the full clutch size (3 eggs) has been reached, generally around the middle of June. The collection site is a colony on Lake Mamawi, in the Peace Athabasca Delta; in addition to collection sites outside the park. One egg is collected from 10 different nests for both species (Ring-billed Gull and Common Tern). Park staff measure the length and width of all eggs in each nest. and the number of nests are counted. Eggs are shipped to the lab for analyses.