Boreal owls in western Newfoundland: using local field data to assess home range characteristics and test a habitat suitability index model

A habitat suitability index (HSI) model based on scientific literature and expert opinion was developed for the Boreal Owl (Aegolius funereus) in western Newfoundland, Canada. Preliminary analyses conducted on the model suggested outputs were most sensitive to variation in home range size, foraging radius, and density of living and dead stems in nesting areas. Over a 2-yr period data were collected on 307 winter point count locations and nine Boreal Owl home ranges using radio telemetry to examine habitat use and test the HSI model. Owls were detected at 24% of point count locations during two breeding seasons. Home range sizes during breeding varied with a median range of 429 ha. Log-ratio compositional analyses of roost locations and home ranges indicated that Boreal Owls do not occupy these sites at random. For roost locations, owls selected old and young softwood stands and avoided bogs, disturbed stands and scrub. Owl home ranges favored old softwood and disturbed stands and avoided old mixedwood and hardwood stands. HSI values produced by the original model did not differ significantly from those updated with local data on home range size. While owls were not occupying sites at random based on HSI values, the model was not able to predict boreal owl presence at levels better than chance alone. The HSI model failed to produce values greater than 0.60 (out of 1.00) suggesting that input values from the literature for other parts of the Boreal Owl range may not be reflective of habitat suitability for Boreal Owls in Newfoundland. Further research is needed to address knowledge gaps about parameters identified as sensitive (nesting habitat and nest tree availability). The island of Newfoundland may also contain far less suitable habitat than other comparable areas of North America, or Boreal Owls in Newfoundland may be less habitat-specific than previously thought