Effects of habitat transitions on rainforest bird communities across an anthropogenic landscape mosaic

Abstract

We compared bird community responses to the habitat transitions of rainforest‐to‐pasture conversion, consequent habitat fragmentation, and post‐agricultural regeneration, across a landscape mosaic of about 600 km2 in the eastern Australian subtropics. Birds were surveyed in seven habitats: continuous mature rainforest; two size classes of mature rainforest fragment (4–21 ha and 1–3 ha); regrowth forest patches dominated by a non‐native tree (2–20 ha, 30–50 years old); two types of isolated mature trees in pasture; and treeless pasture, with six sites per habitat. We compared the avifauna among habitats and among sites, at the levels of species, functional guilds, and community‐wide. Community‐wide species richness and abundance of birds in pasture sites were about one‐fifth and one‐third, respectively, of their values in mature rainforest (irrespective of patch size). Many measured attributes changed progressively across a gradient of increased habitat simplification. Rainforest specialists became less common and less diverse with decreased habitat patch size and vegetation maturity. However, even rainforest fragments of 1–3 ha supported about half of these species. Forest generalist species were largely insensitive to patch size and successional stage. Few species reached their greatest abundance in either small rainforest fragments or regrowth. All pastures were dominated by bird species whose typical native habitats were grassland, wetland, and open eucalypt forest, while pasture trees modestly enhanced local bird communities. Overall, even small scattered patches of mature and regrowth forest contributed substantial bird diversity to local landscapes. Therefore, maximizing the aggregate rainforest area is a useful regional conservation strategy.

Species turnover in ant assemblages is greater horizontally than vertically in the world's tallest tropical forest

“…The number of species that we detected using precision fogging across vertical strata among 11 trees reached about 40% of the number of species sampled in a similar forest habitat elsewhere in Sabah from 99 trees (Floren et al, 2014). This finding of a relatively large proportion of regional biodiversity being sampled from small plots within rainforests is in line with patterns for herbivorous insects (Novotny et al, 2007), birds (Huang & Catterall, 2021), and butterflies (Daily & Ehrlich, 1995) and is likely driven by high structural complexity at small scales (Basset et al, 2012).…”

Species assemblage turnover is greater horizontally than vertically in a complex habitat

“…The number of species that we detected using precision fogging across vertical strata among 11 trees reached about 40% of the number of species sampled in a similar forest habitat elsewhere in Sabah from 99 trees (Floren et al 2014). This finding of a relatively large proportion of regional biodiversity being sampled from small plots within rain forest is in line with patterns for herbivorous insects (Novotny et al 2007), birds (Huang and Catterall 2021) and butterflies (Daily and Ehrlich 1995), and is likely driven by high structural complexity at small scales.…”

The Importance of Forest-Nonforest Transition Zones for Avian Conservation in a Vegetation Disturbance Gradient in the Northern Neotropics

“…At the landscape-level, human-induced habitat loss and fragmentation lead to the reduction of connectivity (Şekercioğlu et al., 2015) and composition (Ryberg & Fitzgerald, 2016). The resulting landscapes contain high contrast habitat matrices that disproportionately affect species with restricted distributions and strict habitat and resource requirements (Huang & Catterall, 2021; Şekercioğlu, 2012; Vázquez-Reyes et al., 2017). Whether bird species respond effectively to these pressures depends on their functional characteristics (e.g., dispersal ability and habitat breadth) and resource requirements (Boesing et al., 2021; Bueno et al., 2018).…”