The small clutch size of seabirds means that when a population has been reduced, it will grow slowly toward its former abundance. The growth rates of seabird populations on the New England coast since their release from human predation reflects this. Species such as black guillemots with only two eggs per clutch and herring gulls with three eggs per clutch have increased more slowly than have the populations of common eiders or double-crested cormorants both with three to six eggs per clutch (Drury 1973).
If the species that nest in colonies show a high degree of site tenacity, they are not likely to reestablish a colony after it has been eliminated. An exception to this is the food subsidy provided by man, which seems to have been important in creating a nonbreeding population of herring gulls large enough to form a "critical mass" for the formation of a new gullery.
Because the main element of population size--the number of breeding adults--is limited by the number of breeding colonies and the food available to those colonies, one assumes that the total numbers of seabirds is much less than could be supported by the larger areas of productive oceans. Hence one suspects that there is lessened competition for food outside the breeding season and that lack of competition for food is a major reason for seabirds being long-lived, often to extremes little suspected until recently. Mortalities of 10-12% per year are common, and some as low as 4% (wandering albatross, _Diomedea exulans_; Tickell 1968) have been recorded.
In contrast, songbirds with large clutches, such as the titmice studied by Kluyver (1951), produce a large number of young with whom they and other adults must compete for food during the winter period of food shortage. Because the titmice are permanent residents, they occupy all of the available habitat throughout the year. Hence titmice suffer intense intraspecific competition, which shortens the survival of adults. Kluyver's experiments (1966) with nest boxes used by a closed population of great tits on Vlieland, The Netherlands, showed that by artificially reducing clutch size the survival of adults was increased.
Similar competition for the few territories available on marshes and consequent shortened life expectancy, can be expected in waterfowl with large broods. The effect should be less marked for geese with smaller clutches that nest in less confined habitats.