VOLUME 15, ISSUE 1, ARTICLE 12 Harris, J. P., L. M. Smith, and S. T. McMurry. 2020. A multiscale analysis of Gray Vireo (Vireo vicinior) nest-site selection in central New Mexico. Avian Conservation and Ecology 15(1):12. https://doi.org/10.5751/ACE-01540-150112 Copyright © 2020 by the author(s). Published here under license by the Resilience Alliance. Research Paper A multiscale analysis of Gray Vireo (Vireo vicinior) nest-site selection in central New Mexico Jonathan P. Harris 1, Loren M. Smith 1 and Scott T. McMurry 1 1Department of Integrative Biology, Oklahoma State University ABSTRACT. There are many gaps in our understanding of Gray Vireo (Vireo vicinior) life history especially as it relates to nesting ecology. Our objective was to determine habitat features selected by Gray Vireos for nesting to improve management strategies for breeding populations. We searched for Gray Vireo nests on Kirtland Air Force Base in Albuquerque, New Mexico from 2016 to 2017. We estimated Gray Vireo nest-site selection at the tree level, the surrounding vegetation, and at two broader scales corresponding to selection within territories. Nest-site selection was estimated for 99 Gray Vireo nests. For tree-level selection, we compared characteristics of nesting trees with mean characteristics from groups of six randomly selected one-seed junipers (Juniperus monosperma) within a 25- m radius. We also compared overall vegetation characteristics at the 25-m scale for nesting plots and 66 randomly selected plots. Broad- scale cover proportions of nest sites and random points were estimated at 50- and 100-m radius spatial scales using a geographic information system. Gray Vireos selected nesting trees that were taller and wider than other adjacent junipers. Selection of vegetation characteristics surrounding nests showed a similar pattern, where Gray Vireos nested in areas where junipers were taller, wider, and had greater foliage density than was randomly available. Broad-scale analyses suggested that Gray Vireos selected nest sites in areas with higher proportions of junipers at low elevations (< 1954 m), and lower proportions of junipers in higher elevations (> 1954 m); however, juniper proportions at nest sites consistently ranged from 15 to 30% of available cover. Gray Vireos also tended to select areas with less pinyon pine than what was randomly available at the 100-m radius scale. Future management strategies should provide large patches of old-growth juniper to optimize Gray Vireo nesting habitat. Analyse multiéchelle de la sélection du site de nidification du Viréo gris (Vireo vicinior) dans le centre du Nouveau-Mexique RÉSUMÉ. Notre compréhension du cycle biologique du Viréo gris (Vireo vicinior) est incomplète, particulièrement en ce qui a trait à l'écologie de nidification. Notre objectif était de déterminer les caractéristiques d'habitat recherchées par les Viréos gris durant la nidification afin d'améliorer les stratégies d'aménagement destinées aux populations nicheuses. Nous avons cherché des nids de viréos sur la base des forces aériennes de Kirtland à Albuquerque, au Nouveau-Mexique, en 2016 et 2017. Nous avons évalué la sélection des sites de nidification des viréos à l'échelle de l'arbre, de la végétation environnante et à deux autres échelles plus grandes à l'intérieur des territoires des oiseaux. Nous avons analysé la sélection du site de 99 nids de Viréos gris. En matière de sélection à l'échelle de l'arbre, nous avons comparé les caractéristiques des arbres abritant un nid avec les caractéristiques moyennes de groupes de six genévriers monospermes (Juniperus monosperma) tirés aléatoirement dans un rayon de 25 m. Nous avons aussi comparé les caractéristiques de la végétation à l'échelle du 25 m des parcelles de nidification et de 66 parcelles tirées aléatoirement. La proportion de couvert à grande échelle aux sites de nidification et aux sites aléatoires a été calculée dans des rayons de 50 et 100 m, à l'aide d'un système d'information géographique. Les Viréos gris ont choisi des arbres de nidification qui étaient plus grands et plus gros que les genévriers adjacents. Les caractéristiques de la végétation voisinant le nid montraient une tendance similaire : les viréos ont niché dans des lieux où les genévriers étaient plus grands, plus gros et avaient une densité foliaire supérieure que ce qui était aléatoirement disponible. Les analyses à grandes échelles ont révélé que les viréos ont niché dans des endroits aux proportions plus élevées de genévriers à basse altitude (< 1954 m) et aux proportions plus faibles de genévriers à des altitudes plus élevées (> 1954 m); toutefois, la proportion de genévriers aux sites de nidification a toujours oscillé entre 15 et 30 % du couvert disponible. Les viréos avaient aussi tendance à choisir des endroits avec moins de pins pignons que ce qui était disponible aléatoirement à l'échelle du rayon de 100 m. Pour optimiser l'habitat de nidification du Viréo gris, nous recommandons que les futures stratégies d'aménagement visent à fournir de grands îlots de vieux genévriers. Key Words: Gray Vireo; nest-site selection; pinyon-juniper; Vireo vicinior Address of Correspondent: Jonathan P. Harris, 501 Life Sciences West, Stillwater, OK , USA 74078, [email protected] Avian Conservation and Ecology 15(1): 12 http://www.ace-eco.org/vol15/iss1/art12/ INTRODUCTION Utah, where populations were completely extirpated following An understanding of the habitat preferences for species of juniper thinning (Crow and van Riper 2010). However, small conservation concern is one of the most fundamental goals of populations in California can be found in arid chapparal without ecological research (Southwood 1977). For migratory birds, nest- junipers (Hargrove and Unitt 2017). Nests in this part of their site selection patterns are arguably the most important life-history range were located in chamise (Adenostoma fasciculatum), desert consideration for habitat management, as nest sites can influence ceanothus (Ceanothus greggii), and mountain mahogany reproductive success and population growth for migratory (Cercocarpus betuloides) (Hargrove and Unitt 2017). Nest success breeding birds (Schmidt 2004, Kus and Whitfield 2005). Nest-site in this region was low, with an average probability of nest survival selection studies can be used to create and enhance management of 0.08 (Hargrove and Unitt 2017). Additional work on the prescriptions for breeding birds (Manly et al. 2002). nesting ecology of Gray Vireos has been limited to federal and state reports. In New Mexico, Gray Vireos have been studied Nest-site selection is continuously influenced by evolutionary extensively on military lands over the last 10 years. These reports forces, such as predation (Martin 1993), brood parasitism suggest that Gray Vireos in central New Mexico nest almost (Forsman and Martin 2009), and microclimate (DuRant et al. exclusively in junipers and nested in taller trees than what was 2013). These selection pressures can interact, resulting in randomly availably (Johnson et al. 2012, Wickersham and perceived trade-offs to maximize reproductive output and Wickersham 2016). Additionally, selection for nest sites at fine offspring survival (Rauter et al. 2002, Tieleman et al. 2008). These scales (0.04 ha) was predominately driven by the presence of more trade-offs in nest placement have been demonstrated in Water trees than what was randomly available (Johnson et al. 2012). Pipits (Anthus spinoletta; Rauter et al. 2002) and Hoopoe Larks (Alaemon alaudipes; Tieleman et al. 2008), where predation risk Gray Vireos are considered a species of conservation concern by is higher in locations with optimal microclimate, resulting in nest the U.S. Fish and Wildlife Service, New Mexico Partners in Flight, locations that minimize the negative effects of both conditions. and a threatened species by the New Mexico Department of Game These interactions can be difficult to quantify in nest-site selection and Fish (NMDGF). The conservation concerns largely stem studies but they are important to consider when managing nesting from a limited breeding range (Barlow et al. 1999), low population habitat for species of conservation concern. densities (Schlossberg 2006), and susceptibility to habitat loss (Pierce 2007). Pinyon-juniper woodlands are anticipated to The nesting ecology of many species within the Vireonidae family decline because of climate change-induced drought in the future is not well understood. Specifically, several species with breeding (Clifford et al. 2011). Consequently, various populations have ranges in the Southwestern United States are of conservation been considered vulnerable under future climate change concern, yet we lack detailed data on their nesting requirements projections (Gardali et al. 2012). (Bent 1965). Information about vireo nest-site selection is generally vague site characteristics and varies greatly by species Given the conservation concerns and our minimal understanding and region. For example, the federally endangered Black-capped of their life-history, our goal was to identify Gray Vireo habitat Vireo (Vireo atricapilla), favors higher proportions of woody requirements for breeding populations in central New Mexico. cover at multiple spatial scales and greater proportions of edge Specifically, our objective was to analyze Gray Vireo nest-site habitat (Bailey and Thompson 2007). Similarly, Bell’s Vireo (Vireo selection at multiple spatial scales to describe second and third- belli) in Nevada, Arizona, and
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