Can Marbled Murrelet Use of Nesting Habitat be Predicted from Mapped Forest Characteristics?

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Book Chapter

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We tested whether the use of nesting habitat by Marbled Murrelets (Brachyramphus marmoratus) could be predicted from mapped information. Our goal was to evaluate the feasibility of modelling habitat suitability on a large scale in preparation for building a sophisticated model, and to determine whether such a habitat suitability model could make basic predictions on murrelet nesting activity. In this study we did not build an elaborate habitat suitability model, but rather tested the predictions from a simple, preliminary model, based on a single mapped forest characteristic. Of the forest and terrain characteristics available on resource maps, tree height was the most useful variable to predict suitability of murrelet habitat in an analysis of data from 118 vegetation plots collected previously in the study area. We compared audio-visual detections of murrelets at 11 pairs of stands, selected using Vegetation Resource Inventory maps, with each pair having one stand with trees ON AVERAGE >35 m tall (TALL) and one with trees(SHORT). Our prediction was that the TALL stands would show more activity associated with breeding by murrelets than the SHORT stands. Each pair of stands had a similar elevation, distance to ocean, slope position and aspect. We performed standardized audiovisual surveys at paired stands on the same morning to avoid biases caused by weather and season. We observed significantly higher numbers of occupied detections and subcanopy detections (both thought to be related to nearby breeding) in the TALL stands than in SHORT stands. Thus, we were able to show that Marbled Murrelet breeding activity can be predicted based on a mapped forest characteristic, a result that set the stage for the more sophisticated habitat model.