Vol.:(0123456789) Biodiversity and Conservation (2019) 28:3371–3386 https://doi.org/10.1007/s10531-019-01826-4 1 3 ORIGINAL PAPER Interspecifc networks of cavity‑nesting vertebrates reveal a critical role of broadleaf trees in endangered Araucaria mixed forests of South America Kristina L. Cockle 1,2  · José Tomás Ibarra 3,4  · Tomás A. Altamirano 2  · Kathy Martin 2,5 Received: 6 February 2019 / Revised: 10 July 2019 / Accepted: 24 July 2019 / Published online: 30 July 2019 © Springer Nature B.V. 2019 Abstract Cavity-nesting animals and their nest trees are linked in interspecifc facilitation networks known as nest webs, which play key roles in forest function but vary across biomes and with human perturbation. We examined the composition, structure and function of nest webs between two endangered old-growth forests representing the last remnants of the ancient coniferous family Araucariaceae in South America: pewen (Araucaria araucana; Endangered) in temperate Chile (2010–2018), and Parana pine (Araucaria angustifolia; Critically Endangered) in subtropical Argentina (2006–2018). Pewen and Parana pine accounted for 30 and 9% of forest basal area, but only 2 and 5% of nesting cavities, respec- tively. Instead, cavity-nesting birds and mammals nested disproportionately in coexisting broadleaf trees. Species richness, interaction richness, and mean number of links per spe- cies were much higher in Parana pine forest than in pewen forest, but the two nest webs had similar levels of evenness and nestedness. Most secondary cavity-nesting species depended on cavities formed by decay in Nothofagus spp. (98% of nest cavities in pewen forest) or Apuleia leiocarpa (26% of nest cavities in Parana pine forest). An exception was the glob- ally endangered Vinaceous Parrot, a Parana pine seed disperser, which made 50% of its nests in decay-formed cavities in Parana pine. To conserve the ecosystem functions of endangered Araucaria forests it is important to protect and recruit not only Araucaria trees but also a mix of broadleaf trees that can confer resilience to nest webs in the face of major disturbances. Keywords Cavity-nesting birds · Ecological network · Interspecifc interactions · Neotropics · Nest web · Old-growth forest Communicated by Karen E. Hodges. This article belongs to the Topical Collection: Forest and plantation biodiversity. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s1053 1-019-01826-4) contains supplementary material, which is available to authorized users. * Kristina L. Cockle kristinacockle@gmail.com Extended author information available on the last page of the article