Woodpecker abundance and nest-habitat in a managed balsam fir ecosystem

Setterington, Michael A. (1997) Woodpecker abundance and nest-habitat in a managed balsam fir ecosystem. Masters thesis, Memorial University of Newfoundland.

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Abstract

Much of the balsam fir forest of western Newfoundland is limited to a 60-year timber harvest rotation, resulting in limitations on the amount of potential woodpecker habitat available in the later successional stages of these forests. The abundance of and nest-habitats of black-backed, downy, and hairy woodpeckers were quantified in 40-, 60-, and 80+ -year-old balsam fir forests in western Newfoundland. -- There were no significant differences in abundance among forest age-classes, but there has been a consistent trend for black-backed woodpeckers to be found in the oldest age class forests available throughout their range, and almost exclusively in the 80+ year-old balsam fir forests in western Newfoundland. Downy woodpeckers were more abundant and were equally distributed among the three age classes. Hairy woodpeckers were scarce and only found in the 40- and 60-year-old age classes. An extensive 60-year harvest rotation balsam fir timber management regime is reducing the habitat available for black-backed woodpeckers. Downy and hairy woodpeckers are associated more with the hardwood components of mixed stands, so they will most likely be unaffected by the loss of later successional stages of balsam fir stands. -- Woodpeckers have historically shown greater use of older forests because there was a greater density of cavity-trees in 80+ -year-old forests than in 40-, and 60-year-old forests. The mean diameter of cavity-trees was within the upper 25% of the diameter classes of trees found among the three age classes. The diameter of cavity-trees in the older forests was two diameter classes larger than in the younger forests. The diameter of active nest-trees were within the upper 5% of the diameter classes of trees found among the three age classes. -- All woodpeckers were found at nest-sites surrounded by a mean density of trees approximately 50% less than found in 40-year-old forests, and 25% less than found in 60- and 80+ -year-old balsam fir forests. Canopy cover was equally sparse~ and tree height surrounding nest-sites was shorter than that found in all forest age classes. There were no differences in mean tree diameter at breast height between trees surrounding nest-sites and those within 40-, 60- and 80+ -year old forests. Slowdowns and small defoliated areas, that occur primarily in later successional stages of balsam fir forests, accounted for the majority of nest sites found. Black-backed woodpeckers are particularly vulnerable to loss of nest-habitat as they were choosing nest-sites in conifer trees and are associated with conifer-dominated forests. Downy and hairy woodpeckers occupied a variety of nest-sites from remnant white birch snags in clearcuts, to rotting balsam fir snags in dense forest. They therefore may be able to persist under a short-rotation timber management regime as long as there is a residual hardwood component in the forests. -- Future research is needed only to improve the precision of the definition of habitat selection by woodpeckers. Managers should assume that eradication of older balsam fir forests adversely affects woodpecker populations and habitat, and should plan for inclusion of these stands at the landscape-level to avoid ecosystem deterioration and habitat loss. An incorporation of forest-growth projection models with spatial and temporal habitat variables will provide insight for woodpecker habitat management.

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