Emperor Goose (Anser canagicus) Nest Survival Encounter History from the Yukon-Kuskokwim Delta, Alaska, 1994-2017

We monitored nests of Emperor Geese at the Manokinak River on the Yukon-Kuskokwim Delta in western Alaska from 1994–2017. We searched 14 contiguous plots (approximately 23 km2) annually for all Emperor Goose nests by systematically searching all areas within a plot that were able to hold a nest (i.e., not over water or mud). Timing of initial nest searches was variable but typically took place during early or mid-incubation. Once we located a nest, we aged eggs using floating (Westerkov 1950) or candling (Weller 1956) and recorded coordinates of nests using handheld GPS receivers. After initial nest checks, we revisited nests at irregular intervals until a fate could be determined (hatched, preyed upon, abandoned, etc.). We considered a nest successful if pipped eggs, goslings, or eggshell fragments with intact detached membranes were found in the nest. We considered a nest to be preyed upon if eggs in the nest were broken without sign of detached membranes or if all eggs were missing, and we considered a nest abandoned if all eggs in the nest were cold and a female was not present. As part of a concurrent mark-resight study, we trapped females on the nest using bow-net traps (Salyer 1962) or mist-nets (Bacon and Evrard 1990) during late incubation or hatch and marked them with a U.S. Geological Survey metal leg band and a plastic tarsal band with a 3-character alphanumeric code.