Court Site Constancy, Dispersion, Male Survival and Court Ownership in the Male Tooth-billed Bowerbird, Scenopoeetes dentirostris (Ptilonorhynchidae)

Abstract

The Tooth-billed Bowerbird Scenopoeetes dentirostris was studied over 16 consecutive display seasons in 50 ha of upland rainforest on the Paluma Range, north Queensland. Eighty-two courts were plotted during the first 12 seasons. Of these an average of 55 were attended each season and 39 were attended for at least ten consecutive seasons at a mean nearest neighbour distance (NND) of 68 m. Court sites, particularly long-established ones, were more densely distributed on hill-tops and contiguous slopes or ridges. On hill-tops mean NND was 50 m. The dispersion of sites was similar each season. Data indicate the probability of males at courts forming exploded leks on higher topography, but court distributions in any one season showed a dispersion intermediate between an even spread over suitable habitat and true (i.e. exclusive) clumping (true lek). There was an average of one court per ha with an overall mean NND of 61 m. Ownership of 21 court sites involving 24 individually marked males were examined during 16 seasons. Of 24 males involved, 12 survived ten or more seasons, mean annual survival rate was 88% and mean expectancy of further life after banding was 8.1 years. Fidelity by individual males to a single court or court site was extremely high: 71% of marked birds attended only one site during the study. Males with paler mouth pigmentation (presumed to be younger individuals) established courts near, or between, long-established sites, and then sought to occupy the adjacent, long-established court sites of older, black-mouthed, males. The behaviour of younger males attempting to enter groups of immediately neighbouring older males and interactions between the age classes suggested females seek more experienced, older, males as indicated to them by court/male quality and court positionheaf decoration numbers. Several older males showed reluctance to relinquish a traditional court location by returning to one, having been kept from it by tree falls, after several years.