Settlement patterns, territory size, and breeding density in the song sparrow (Melospiza melodia)

Abstract

In this study we investigated one possible proximate factor underlying year-to-year changes in mean territory size in song sparrows. We tested the hypothesis that birds defend smaller territories if they settle more or less at the same time, than if they settle on territories asynchronously. This idea is supported by some anecdotal field evidence in birds. To carry out the test, we did two types of removal experiments: (a) removing all the territory holders in an area at the same time and (b) removing territory holders one at a time, with 3- to 4-day intervals between each removal. Both types of removal were done in October 1972, coinciding with the fall peak of territorial activity, and in March 1973, coinciding with the spring peak. All the empty territories were rapidly refilled by juveniles that had previously been non-territorial; thus the breeding density of song sparrows is limited by territorial behavior. The replacement males were bird's that had been dominant in winter flocks of juveniles. For the two simultaneous-removal areas, territory size decreased significantly after resettlement, while for the successive-removal and control areas there was no such change. This shows that settlement patterns can influence mean territory size, and may be a proximate mechanism underlying annual fluctuations in size of territories.

Territory and group sizes in Eurasian beavers (Castor fiber): echoes of settlement and reproduction?

“…Once the territory pattern is established, change may only be possible through the vacation of adjacent territories, which would then allow replacements to repack territories within the newly created space (Knapton and Krebs 1974). Such a scenario is less likely in species with a low adult mortality since the likelihood that adjacent territories are simultaneously vacated will be lower (Knapton and Krebs 1974).…”

Reproductive Anatomy and Indices of Quality in Male Tree Swallows: The Potential Reproductive Role of Floaters

“…Some studies have shown that floaters were drawn from among the most dominant individuals in the non-territorial fraction of the population (Knapton and Krebs, 1974;Smith and Arcese, 1989). In several studies in which removed territory owners were held captive and later released, such birds mostly managed to displace their replacements to regain their territories and mates, either in the same year or the next (Watson and Jenkins, 1968;Harris, 1970;Smith, 1978;Szuba and Bendell, 1988;Village, 1990).…”

Delayed Plumage Maturation in Passerine Birds: Reliable Signaling by Subordinate Males?

“…Even if adult males were deceived by the "female-like" plumage of SY males, serious fights should ensue as soon as the young males begin to sing-escalated fights often occur when two males view themselves as residents (Krebs, 1982). Since there is considerable evidence that young male passerines are subordinate to older males (Knapton and Krebs, 1974;Rohwer, 1975), they almost certainly have a lower resource-holding potential. It is unlikely that an SY male would be able to win such a contest against a more experienced adult, and an SY male may risk serious injury in an escalated fight.…”