Contents lists available at ScienceDirect Forest Ecology and Management journal homepage: www.elsevier.com/locate/foreco Conserving nest trees used by cavity-nesting birds from endangered primary Atlantic forest to open farmland: Increased relevance of excavated cavities in large dead trees on farms Eugenia Bianca Bonaparte a,b, ⁎ , José Tomás Ibarra c,d , Kristina L. Cockle a,b,e a Instituto de Biología Subtropical, CONICET- Universidad Nacional de Misiones, Bertoni 85 Puerto Iguazú, Misiones 3370, Argentina b Proyecto Selva de Pino Paraná, Vélez Sarsfield & San Jurjo S/N, San Pedro, Misiones 3352, Argentina c ECOS (Ecology-Complexity-Society) Laboratory, Centre for Local Development (CEDEL), Pontificia Universidad Católica de Chile, Villarica, Chile d Millennium Nucleus Centre for the Socioeconomic Impact of Environmental Policies (CESIEP) & Centre of Applied Ecology and Sustainability (CAPES), Pontificia Universidad Católica de Chile, Santiago, Chile e Department of Forest and Conservation Sciences, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1Z4, Canada ARTICLE INFO Keywords: Argentina Atlantic Forest Cavity-nesting community Habitat gradient Nest-cavity occurrence ABSTRACT Understanding nest-site selection is critical to conserving tree-cavity-nesting wildlife, but nest-sites may vary across landscapes. We examine variation in the characteristics of trees and cavities used by cavity-nesting birds from globally-threatened primary Atlantic Forest to open farmland with isolated trees. We predicted that nests would occur in the largest trees available, but that secondary cavity nesters (non-excavators) would increase their use of bird-excavated cavities and dead and exotic trees in open farmlands. We used a stratifed case-control design and 20 random plots to assess variation in characteristics of trees and cavities (used and available) across gradients of canopy cover and distance to forest edge in subtropical Argentina. For secondary cavity nesters, nest cavities were more likely to occur in larger-diameter trees across all stand conditions, but more likely to occur in dead trees as canopy cover declined (i.e., in open farmland; n = 123 nest trees). For primary excavators, nest cavities were more likely to occur in dead (vs. live) trees, with larger diameter, regardless of stand conditions (n = 54 nest trees). Available cavities declined from 4/ha in primary forest to 0.4/ha in open farmland. Cavities were increasingly of excavated origin in open farmland, including both available cavities and those used by secondary cavity nesters, which indicates that avian excavation may partly compensate for the loss of decay-formed cavities when large trees are cleared. As forest landscapes shift toward a predominance of agroecosystems, dead trees and primary cavity nesters may take on important roles in conserving cavity-nesting communities and their ecosystem functions. However, nest cavities declined in height and depth, and increased in entrance size toward open farmland, raising the possibility that birds increasingly use suboptimal cavities as forest cover declines. 1. Introduction Nest-site selection theory has a long-standing history in forest ecology and management, and it is helpful for assessing the condition of ecological communities under global and regional changes (e.g. Bergmanis et al., 2019; Newell and Rodewald, 2011). Among the many forest birds that nest in tree cavities globally, about 26% of species can excavate their own cavities (primary excavators), and must select a suitable substrate for excavation; the rest (secondary cavity nesters or non-excavators) select a nest site among existing cavities formed by primary excavators or by tree decay (van der Hoek et al., 2017). Sui- table cavities and substrates can limit breeding density (Newton, 1994; Saunders et al., 2020), and may become increasingly scarce as primary forest landscapes are replaced by logged forest and agroecosystems (Aitken and Martin, 2012; Ibarra and Martin, 2015; Manning and Lindenmayer, 2009; Politi et al., 2010), leading to declines in popula- tions of cavity-nesting birds, many of which have key roles in seed dispersal, local culture, and ecotourism (e.g., toucans, parrots, horn- bills, quetzal; Anderson 2017; Bennett et al. 1997; Renton et al. 2015). However, the nest-site requirements of cavity-nesting species, and the processes involved in cavity formation, may vary across habitats, al- lowing cavity nesters to reproduce even in highly-modifed environ- ments (Bonaparte and Cockle, 2017; Manning et al., 2006b; Monterrubio-Rico et al., 2009). As native forest cover declines in many https://doi.org/10.1016/j.foreco.2020.118440 Received 20 May 2020; Received in revised form 13 July 2020; Accepted 14 July 2020 ⁎ Corresponding author at: Instituto de Biología Subtropical, CONICET- Universidad Nacional de Misiones, Bertoni 85 Puerto Iguazú, Misiones 3370, Argentina. E-mail addresses: ebbonaparte@gmail.com (E.B. Bonaparte), jtibarra@uc.cl (J.T. Ibarra), kristinacockle@gmail.com (K.L. Cockle). Forest Ecology and Management 475 (2020) 118440 0378-1127/ © 2020 Elsevier B.V. All rights reserved. T