Katherin Munro’s Owl Study Proposal

In 1999, the Western Newfoundland Model Forest started the Biodiversity
Assessment Project (BAP) to develop a set of tools to predict the influence of various forest management scenarios on biodiversity (Dolter, 2005). Three species were selected for habitat modelling to act as indicators of how different management plans might influence the broader community. The three species are the Woodland Caribou, Pine Marten, and Boreal Owl, and were selected because of their specific life history requirements or conservation status, The Boreal Owl (Aegolius funereus) was chosen because it is an obligatory secondary cavity nester and likely to be sensitive to forest harvesting practices. A habitat suitability index (HSI) model was developed as part of BAP for the Boreal Owl in Forest Management District 15 (Côté, et al., 2004).

The Boreal Owl is a difficult species to study due to its large home range and nocturnal habits (Hinam, 2001). They are solitary animals, only interacting with conspecifics during the breeding season. In late winter/early spring the males will sing from a perch near a nesting cavity, in attempt to attract a female. During the breeding season, male Boreal Owls tend to remain on the same territory, even when food availability is low, while females will move between successive breeding attempts (Korpimäki, 1988). However, data on home range is limited.

Once a pair is formed, the male will forage for the female while she incubates the eggs. In North America egg laying dates range from the middle of March to the end of May (Hayward, 1994). Once the eggs have hatched, the female will feed the young with food provided by the male (Heinrich et al., 1999). Both parents care for the young until independence is reached at approximately 5-6 weeks of age (Korpimäki, 1989).

This small raptor is widely dispersed throughout the northern hemisphere. It has a circumboreal distribution from Scandinavia to Siberia and across North America from Alaska to Newfoundland and Labrador. In North America, the Boreal Owl mainly nests in cavities excavated by Pileated Woodpeckers (Dryocopus pileatus) and Northern Flickers (Colapates auratus) or natural cavities. Habitats are mainly characterized by spruce (Picea spp.), aspen (Populus tremuloides), poplar (Populus balsamea), birch (Betula papyrifera), and balsam fir (Abies balsamea; Hayward and Hayward, 1993). Boreal Owls are typically associated with old growth forest stands that contain large trees with decreased growth rates. These tend to provide natural or woodpecker cavities (Heinrich et al., 1999).

The Habitat Suitability Index model predicts the suitability of a habitat for a species based on an assessment of habitat attributes such as habitat structure, habitat type, and spatial information (Heinrich, 1999). These data are generally compiled using literature reviews and expert opinion. In Newfoundland, very little data are available about the Boreal Owl’s habitat requirements and therefore the model’s assumptions are based on data from elsewhere in North America and Europe. The final product is a map that categorizes different habitats found on forest inventory maps and then ranks those habitats from least to most suitable. A forest stand with an HSI value of 1 is considered to represent the best possible habitat, while an HSI of 0 is given to unsuitable habitat, often occurring in young forest stands with no suitable nesting cavities. The HSI model can then be used to support rapid decision-making about forest harvesting practices in situations where little data is available.

Before these models can be utilized they must be tested for both accuracy and reliability. Testing the model with field data can be used to validate the accuracy of the model in a certain area. The original model can then be modified based on the new information. Sensitivity analyses are also used to test the accuracy and reliability of the model. They indicate which model parameters are the most sensitive and can therefore be used to focus field efforts (Rickers et al., 1995). Using both field data and sensitivity analyses is an effective way to validate the HSI model. Preliminary sensitivity analyses on the Boreal Owl HSI model determined that home range size, foraging radius, and density of living and dead stems in nesting areas are the three most sensitive parameters of the model (X. Zhu, unpublished data).

The current study is part of a larger project conducted by the Newfoundland Model Forest and will incorporate field data from the previous year. Much of the fieldwork will be replicating the previous year’s work; except for nest site characteristics and nest productivity since no nests were located in the 2005/2006 field season.

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