Effects of Human Recreational Activity on The Tameness of Common Loons (Gavia immer) in Northern Wisconsin

The Common Loon (Gavia immer) is an aquatic diving bird that lives in freshwater habitats in Canada and the northern U.S.. Human activity on a loon’s resident lake may affect its fitness and behavior, yet few studies identify or quantify these effects. We modified existing techniques that measure escape distances in other species to measure tameness as the distance at which individual loons dove in response to human approach by canoe. Tameness was similar between pair members, suggesting that common lake conditions or the behavior of a mate might influence the behavior. Sex, size within sex, and human activity did not influence tameness. However, our data for human activity characterized a lake for an entire breeding season rather than measure the amount of human activity present at the time tameness data was collected. Further studies using our technique for measuring tameness are needed to determine whether tameness is a result of the momentary influence of lake activity, a learned response, or if loons are unable to adjust their behavior in response to human activity. If loons do not have the ability to adjust their behavior to human activity, greater or more rigid set-back distances could be implemented to protect them from potential harm

Aging Male Loons Make a Terminal Investment in Territory Defense

Animals that senesce experience a decline in residual reproductive value (RRV), such that old individuals can expect reduced breeding success compared to young ones. According to life history theory, animals with low RRV, which thus have less to lose, should shift resources away from self-maintenance and towards reproduction, an expectation called terminal investment. In a population of common loons whose survival and territorial behavior were measured throughout life, males 14 years and older exhibited clear senescence, as they showed lower survival, reduced body mass, and far greater susceptibility to territorial eviction than younger males. While older males invested no more effort than young males in feeding or protecting their chicks, they increased territorial yodeling by 35%, showed more aggression towards territorial intruders, and, following eviction from original territories, resettled with great frequency on vacant, unproductive territories nearby. Our findings thus provide support for terminal investment in territorial behavior. Hyper-aggressive behavior by old, declining males might explain the unusual occurrence of lethal combat for territories in this species