Population change and nest tree longevity of a small-island population of Redbreasted Sapsuckers (Sphyrapicus ruber) breeding in old-growth temperate rainforest

We recorded the population size and nest tree use of Red-breasted Sapsuckers (Sphyrapicus ruber) breeding in coastal, old-growth, temperate rainforest on East Limestone Island, Haida Gwaii, British Columbia, over 31 years (1990-2020). The populations density on the 48 ha island ranged from 10 to 46 occupied nests/km2, with numbers increasing and then decreasing from 1991 to 2005, followed by a gradual increase between 2006 and 2020. The population size was unaffected by a major windthrow event in 2010 that destroyed about a third of the preferred forest type. Nor did breeding birds avoid the remaining trees left within the blowdown area, suggesting that the retention of isolated dead trees within small forest openings may provide useful breeding sites for sapsuckers. Individual trees were used up to 10 times and continued to be selected for up to 21 years after first use, with use being more prolonged for Sitka spruce (Picea sitchensis) than for western hemlock (Tsuga heterophylla). Maximum span of use probably exceeds 23 years. There was a significant tendency for trees to be used in consecutive years. Modeling the availability of trees used at least once suggested that in all years there were ample suitable trees available, and hence that the population was not constrained by lack of suitable nest sites. Received 5 January 2022. Accepted 3 January 2023.