Characteristics of the breeding habitat of Endangered Kirtland's Warblers on a Canadian Military Installation

Abstract

Kirtland's Warblers (Setophaga kirtlandii) are an endangered species with specialized habitat requirements, and the only documented nesting location in Canada is an Army installation. From 2007 to 2010, I compared habitat characteristics of sites occupied and not occupied by Kirtland's Warblers at Garrison Petawawa located ∼200 km northwest of Ottawa, Ontario. Sites occupied by Kirtland's Warblers (N = 11) had greater percent cover of low sweet blueberry (Vaccinium angustifolium; 31.2%), coral lichen (Cladina stellaris; 0.4%), reindeer lichen (Cladonia rangiferina; 8.3%), and wavy-leaved moss (Dicranum polysetum; 4.3%) than unoccupied sites (N = 6). I found no difference in tree species composition between sites, with jack pine (Pinus banksiana), white pine (Pinus strobus), red pine (Pinus resinosa), poplar (Populus tremuloides), and red maple (Acer rubra) present in both used and unused sites. Forest stands occupied by Kirtland's Warblers were significantly younger (< 20 yr old) than unoccupied sites, and most occupied sites were within former fire zones and sites where jack pines had been planted. Thus, breeding habitat of Kirtland's Warblers in Canada consisted of young pine trees, with more red pine than in their breeding habitat in Michigan, and ground cover including blueberry, lichens, and mosses. These results suggest that Kirtland's Warblers may be less selective in their habitat requirements than previously thought, and should provide guidance for recovery groups and regulatory agencies in accurately delineating suitable habitat for these warblers in Canada. RESUMEN Caracteristicas del habitat de reproduccion de la especie amenazada, Setophaga kirtlandii, en una base militar Canadiense Setophaga kirtlandii es una especie amenazada con requerimientos de habitat especializados y la unica localidad de anidamiento registrada en Canada se encuentra en una base militar de la Armada. Entre 2007 y 2010, compare las caracteristicas del habitat de los sitios ocupados y no ocupados por Setophaga kirtlandii en Garrison Petawawa, ubicado 200 km al noroeste de Ottawa, Ontario. Sitios ocupados por Setophaga kirtlandii (N = 11) tienen un mayor porcentaje de cobertura de Vaccinium angustifolium (31.2%), Cladina stellaris (0.4%), Cladonia rangiferina (8.3%) y Dicranum polysetum (4.3%) que sitios no ocupados (N = 6). No encontre diferencia en la composicion de especies de arboles entre sitios, con Pinus banksiana, Pinus strobus, Pinus resinosa, Populus tremuloides y Acer rubra presentes en los sitios ocupados y no ocupados. Parches de bosque utilizados por Setophaga kirtlandii resultaron ser significativamente mas jovenes (< 20 anos) que los sitios no ocupados, y la mayoria de los sitios ocupados se encontraron dentro de zonas que fueron incendiadas y donde habia plantaciones de Pinus banksiana. En consecuencia, el habitat de reproduccion de Setophaga kirtlandii en Canada consistio de pinos jovenes con una mayor proporcion de Pinus resinosa que en los habitats de reproduccion en Michigan, y el recubrimiento del suelo incluyo arandano, liquenes y musgos. Estos resultados sugieren que Setophaga kirtlandii puede ser menos selectiva en los requerimientos de habitat de lo que se pensaba en el pasado, y provee una guia para las grupos de recuperacion y agencias regulatorias para delinear con precision habitats propicios para estas reinitas en Canada.