If several territories occur on one lake, each is separated by points, narrows, etc. Pair bonds often established before arriving on breeding grounds. Monogamous pairs often nest solitarily. Incubation averages 29 days. Probably breed first at 2 yr.
Mortality is caused by hunters in populated areas, and locally by oil spills.
Nest failures sometimes caused by human disturbance, especially by motorboats. The common loon should be looked for in its former breeding range in northeastern California. Any individuals found in suitable nesting habitat in the breeding season should be protected from disturbance, and assisted to again breed in California. Life histories of North American diving birds. Cogswell, H. L. 1977.