Modeling Marbled Murrelet nesting habitat: a quantitative approach using airborne laser scanning data in British Columbia, Canada

Abstract

The Marbled Murrelet (Brachyramphus marmoratus) is a tree-nesting seabird found along the Pacific coast of North America whose forest nesting habitat has dramatically declined over the last century. Mapping the remaining nesting habitat is a core step in the conservation of this species at risk. Fine-scale mapping efforts are expected to be enhanced by airborne laser scanning (ALS) data (an application of lidar technology), which provides quantitative measures of forest structure. We present an ALS-informed model for Marbled Murrelet nesting habitat in British Columbia (BC), Canada, using ecologically relevant predictors. Two rare species modeling approaches, i.e., ensembles of small models (ESMs) and maximum entropy modeling (MaxEnt), were evaluated to link 58 nest locations with ALS and non-ALS predictors at a 100-m resolution in Desolation Sound (DS). An independent model transfer was conducted in Clayoquot Sound (CS) with 21 nests. The top model that balanced parsimony with strong performance in both areas was built with MaxEnt using only two predictors, forest vertical complexity and internal forest gaps. This model achieved good performance in DS (AUC = 0.77, Boyce index = 0.99) and reasonable performance in CS (AUC = 0.63, Boyce index = 0.67). On average, the most suitable nesting habitat was found in small clusters (< 2 ha) within older forest and less suitable habitat within younger forest. Our results broadly align with existing maps of nesting habitat produced from low-level aerial surveys. However, we predicted additional suitable nesting areas not detected by aerial habitat mapping and found large variations in habitat quality within mapped areas of suitable forest. This study offers a quantitative method to predict the nesting habitat of an elusive species with a small sample of occurrence records. With successful field verification, our model could be a valuable tool for Marbled Murrelet management in BC.Modélisation de l'habitat de nidification du Guillemot marbré : une approche quantitative au moyen de données de balayage laser aérien en Colombie-Britannique, Canada RÉSUMÉ. Le Guillemot marbré (Brachyramphus marmoratus) est un oiseau marin arboricole qui se trouve le long de la côte pacifique de l'Amérique du Nord et dont l'habitat de nidification forestier a considérablement diminué au cours du siècle dernier. La cartographie de l'habitat de nidification restant est une étape essentielle en vue de la conservation de cette espèce en péril. La cartographie fine pourrait être améliorée grâce aux données de balayage laser aérien (BLA) (une application de la technologie lidar), qui fournissent des mesures quantitatives de la structure forestière. Nous présentons un modèle d'habitat de nidification du Guillemot marbré en Colombie-Britannique, au Canada, fondé sur les données de BLA et des prédicteurs écologiques pertinents. Deux approches de modélisation d'espèces rares, soit les ensembles de petits modèles et la modélisation par entropie maximale (MaxEnt), ont été évaluées pour relier 58 sites de nid...