Trumpeter Swan - Mortality

Mortality

In captivity, this species has survived to 33 years old and, in the wild, has lived to at least 24 years. Young Trumpeter Swans may have as little as 40% chance of survival, due variously to disturbance and destruction by humans, predation, nest flooding and starvation. In some areas, though, the breeding success rate is considerably greater and, occasionally, all cygnets may reach maturity. Mortality in adults is quite low, usually being 80–100% annually, unless they are hunted by humans. Predators of Trumpeter Swan eggs include Common Raven (Corvus corax), Common Raccoon (Procyon lotor), Wolverine (Gulo gulo), American Black Bear (Ursus americanus), Brown Bear (Ursus arctos), Coyote (Canis latrans), Gray Wolf (Canis lupus) and Northern River Otter (Lontra canadensis). Nest location can provide partial protection from most mammalian nest predators, especially if placed on islands or floating vegetation in deep waters. Most of the same predators will prey on young cygnets, as will Common Snapping Turtle (Chelhydra serpentina), California Gull (Larus californicus), Great Horned Owl (Bubo virginianus) and American Mink (Mustela vison). Larger cygnets and, rarely, nesting adults may be ambushed by Golden Eagle (Aquila chrysaetos), Bobcat (Lynx rufus), Red Fox (Vulpes vulpes) and Coyote. When their eggs and young are threatened, the parents can be quite aggressive, initially displaying with head bobbing and hissing. If this is not sufficient, the adults will physically combat the predator, battering with their powerful wings and chomping down with their large bills, and have managed to kill predators equal to their own weight in confrontations. Predation of adults when they are not nesting is rare, although they may possibly be hunted by Golden and Bald Eagles. Photos of a Bald Eagle (Haliaeetus leucocephalus) exceptionally attacking an adult Trumpeter Swan in mid-flight were taken recently, although the swan managed to survive the predation attempt.