In Part I, we discuss certain factors affecting evidence of depredation found at duck nests destroyed by predators, or that cause variation in evidence left by individual predator species. Characteristics of Eggs Duck eggs are oblong and usually lie on their side in nests or outside nests when displaced by predators. Thus, the greatest damage to shells is likely to occur when eggs are depredated late in incubation. Size of duck eggs and shell thickness vary. Thickness of the shell affects ability of predators to open eggs, as well as the amount of fracturing of shell during consumption of contents.
Hens have more down to pluck during their initial nesting attempt than when renesting.
Thus, potential for obtaining information about predator displacement of nest material is greater for nests destroyed after most eggs are laid, and greater for first nests than renests. Number of eggs present when a duck nest is destroyed affects amount and quality of evidence likely to be found at the nest. As each egg is depredated, the pattern of depredation becomes more evident and chances of finding evidence to implicate the predator species increases. Location of a nest affects vulnerability of the nest to individual predator species. Location of a nest also affects amount and types of evidence likely to be found at the nest.