DOI: 10.5061/dryad.k98sf7mcm
title: Understory specialists in southern Chile

description: The simplification of forest structural complexity, caused by
 anthropogenic land-use practices, is one of the main threats to understory
 specialist birds. We examined the association of both single structural
 attributes and structural complexity, with the density of four understory
 bird species in the Global Biodiversity Hotspot “Chilean Winter
 Rainfall-Valdivian Forests” of South America. Between 2011 and 2013, we
 surveyed habitat attributes and conducted bird point counts in 505 plots
 in Andean temperate ecosystems in Chile. In each habitat plot, we measured
 understory density, volume of coarse woody debris (CWD), number of snags,
 diameter at breast height (DBH) of trees, and leaf litter depth. With
 these attributes, we developed an index of stand structural complexity
 (ISC). On average, old-growth forests had higher values ​​for understory
 density, CWD volume, DBH, and litter depth than secondary forests and open
 fields, and thus greater values of ISC. The density of understory birds
 was positively correlated with the ISC for the Rhinocryptidae Pteroptochos
 tarnii, Scelorchilus rubecula, and Scytalopus magellanicus. We also found
 a positive association between understory density and litter depth, with
 the density of the Furnariidae Sylviorthorhynchus desmursii. However, this
 latter species showed a negative association with the density of snags.
 Our results suggest the utility of using an index of structural
 complexity, rather than single or even additive habitat attributes, for
 determining the density of understory specialist birds. We recommend that
 management plans should promote the retention of habitat attributes that
 contribute to the structural complexity of temperate forests of South
 America and beyond.
description: We conducted
 bird sampling during 2
 reproductive seasons (2011-2012 and 2012-2013), between October and
 January. Point count stations were in the same plots used for habitat
 sampling, with the center of the plot at the center of the point count
 station. We sampled 81 sites (80.2%) in 2011-2012 and the
 remaining 20 (19.8%) in 2012-2013 (Ibarra and Martin 2015a). In each of the 101 sites, we established 5
 point counts that were systematically spaced 125 m apart and lasted 6
 minutes during which we recorded each individual seen and/or heard within
 a radius of 50 m (Bibby
 2000, Ibarra et al. 2017a).[A1] [A2] 
 To increase the detectability
 of understory specialist birds we performed playbacks. To avoid double
 counting at nearby stations. we reproduced playback at 3 out of the 5
 point count stations. After the period of passive counting (the first 6
 minutes), we reproduced the playbacks of the 4 understory specialist
 species. As each call by 30 seconds was followed by 30 seconds of
 listening in silence, the counting time for each station with playbacks
 totaled 15 minutes (Drever
 et al. 2009, Ibarra et al. 2017a). The distance to all the birds detected was
 estimated and grouped into one of two intervals for analysis (0-25 m and
 26-50 m; Bibby 2000,
 Ibarra and Martin 2015a).
 We also registered temperature (°C), humidity (%), and wind speed (m per
 s) at each point count station (Table 1) using a portable weather monitor
 (Kestrel 4200, Kestrel-meters, Birmingham, MI), to assess the influence of
 these covariates on the detectability of each
 species.