Landscape-scale effects of forest degradation on insectivorous birds and invertebrates in austral temperate forests

Vergara, Pablo M.; Fierro, Andrés; Alaniz, Alberto J.; Carvajal, Mario A.; Lizama, Marlene E; Llanos, José Luis

doi:10.1007/s10980-020-01133-2

Cited by 20 publications

(4 citation statements)

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“…Finally, the richness of primary and secondary cavity users shared their responses to some environmental variables (biomass and tree species richness), suggesting those variables exerted control on multiple levels. This interpretation is consistent with a previous study testing how the effects of environmental variables on invertebrates transmit to insectivorous birds in temperate Chilean forests (Vergara et al., 2020) and provide evidence of the importance of bottom‐up forces in cavity‐nesting networks.…”

Section: Discussionsupporting

confidence: 92%

Unravelling the cavity‐nesting network at large spatial scales: The biogeographic role of woodpeckers as ecosystem engineers

Alaniz,

Carvajal,

Quiroz

et al. 2023

Journal of Biogeography

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AimPrimary cavity nesters (e.g. woodpeckers) act as ecosystem engineers by providing tree cavities to several vertebrates that use them as nests or refuges. Although diverse assemblages of primary excavators are assumed to increase the number of tree cavities, environmental factors can limit populations of primary excavators, thus weakening their ecological function. We aim to test the biogeographical‐scale relationships between primary excavators and cavity users by distinguishing the contribution of environmental variables.LocationSouthern South America.Materials and MethodsWe used species distribution models, which combine bioclimatic and remote sensing derived variables, to map the richness of vertebrates composing the cavity‐network of temperate and Mediterranean forests of South America. Based on a resampling procedure for ensuring spatial independence, we fitted structural equation models to estimate relationships between forest characteristics and cavity user vertebrates.ResultsRichness of secondary cavity users (mammals, obligated, habitat generalists and forest specialists) were positively and strongly influenced by the richness of primary excavators. Environmental variables affected differently the richness of primary and secondary cavity users. The richness of primary cavity users responded to tree richness and height while that of habitat specialist secondary users was positively affected by primary productivity and negatively by sclerophyll forests.Main ConclusionsOur results confirm the role of primary excavators as ecosystem engineers but highlight the importance of considering large spatial scales when analysing cavity‐nesting networks. Biogeographical patterns of tree diversity and forest structure can be important drivers of cavity nesting networks that remain hidden when studies are conducted over fine spatial scales.

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Section: Discussionsupporting

confidence: 92%

Unravelling the cavity‐nesting network at large spatial scales: The biogeographic role of woodpeckers as ecosystem engineers

Alaniz,

Carvajal,

Quiroz

et al. 2023

Journal of Biogeography

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“…One basis for Wagner's skepticism is that neither bat nor bird declines is as great as predicted by insect declines. Similarly, Vergara et al (2020) argue that birds and insects are impacted differently and independently by degradation of temperate, austral forests. Thus, bottom-up causes of insectivorous tropical bird declines are plausible, albeit far from certain.…”

Section: Insect Declinesmentioning

confidence: 99%

Sensitivity of Tropical Insectivorous Birds to the Anthropocene: A Review of Multiple Mechanisms and Conservation Implications

Sherry

2021

Front. Ecol. Evol.

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Epigraph: “The house is burning. We do not need a thermometer. We need a fire hose.” (P. 102, Janzen and Hallwachs, 2019). Insectivorous birds are declining widely, and for diverse reasons. Tropical insectivorous birds, more than 60% of all tropical birds, are particularly sensitive to human disturbances including habitat loss and fragmentation, intensive agriculture and pesticide use, and climate change; and the mechanisms are incompletely understood. This review addresses multiple, complementary and sometimes synergistic explanations for tropical insectivore declines, by categorizing explanations into ultimate vs. proximate, and direct versus indirect. Ultimate explanations are diverse human Anthropocene activities and the evolutionary history of these birds. This evolutionary history, synthesized by the Biotic Challenge Hypothesis (BCH), explains tropical insectivorous birds' vulnerabilities to many proximate threats as a function of both these birds' evolutionary feeding specialization and poor dispersal capacity. These traits were favored evolutionarily by both the diversity of insectivorous clades competing intensely for prey and co-evolution with arthropods over long evolutionary time periods. More proximate, ecological threats include bottom-up forces like declining insect populations, top-down forces like meso-predator increases, plus the Anthropocene activities underlying these factors, especially habitat loss and fragmentation, agricultural intensification, and climate change. All these conditions peak in the lowland, mainland Neotropics, where insectivorous bird declines have been repeatedly documented, but also occur in other tropical locales and continents. This multiplicity of interacting evolutionary and ecological factors informs conservation implications and recommendations for tropical insectivorous birds: (1) Why they are so sensitive to global change phenomena is no longer enigmatic, (2) distinguishing ultimate versus proximate stressors matters, (3) evolutionary life-histories predispose these birds to be particularly sensitive to the Anthropocene, (4) tropical regions and continents vary with respect to these birds' ecological sensitivity, (5) biodiversity concepts need stronger incorporation of species' evolutionary histories, (6) protecting these birds will require more, larger reserves for multiple reasons, and (7) these birds have greater value than generally recognized.

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“…Forest structural attributes such as litter, snags, coarse woody debris, and understory are not only crucial for breeding purposes, but also for the presence of invertebrates, which are the main food item of these 4 specialist bird species (Sieving et al 1996, De Santo et al 2002, Reid et al 2004, Díaz et al 2005, Altamirano et al 2012a, Ibarra et al 2017b, Navedo and Biscarra 2018, Medrano et al 2020, Vergara et al 2021). For example, S. rubecula and P. tarnii dig for food in the litter (Altamirano et al 2017).…”

Section: Discussionmentioning

confidence: 99%

“…This guild is generally considered, in the literature, as vulnerable to land use change that reduces the supply of certain structural attributes of forests (Reid et al 2004, Díaz et al 2005). These species feed mainly on the invertebrates found in the understory, dead trees, and litter (Figure 2; Sieving et al 1996, De Santo et al 2002, Reid et al 2004, Díaz et al 2005, Altamirano et al 2012b, Ibarra et al 2017a, 2018, Medrano et al 2020, Vergara et al 2021). They frequently nest under the dense understory, especially bamboo (Díaz et al 2005, Ibarra et al 2017a).…”

Section: Methodsmentioning

confidence: 99%

Structural complexity is a better predictor than single habitat attributes of understory bird densities in Andean temperate forests

Concha,

Caviedes,

Novoa

et al. 2023

Ornithological Applications

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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 4 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.

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Landscape-scale effects of forest degradation on insectivorous birds and invertebrates in austral temperate forests

Cited by 20 publications

References 75 publications

Unravelling the cavity‐nesting network at large spatial scales: The biogeographic role of woodpeckers as ecosystem engineers

Unravelling the cavity‐nesting network at large spatial scales: The biogeographic role of woodpeckers as ecosystem engineers

Sensitivity of Tropical Insectivorous Birds to the Anthropocene: A Review of Multiple Mechanisms and Conservation Implications

Structural complexity is a better predictor than single habitat attributes of understory bird densities in Andean temperate forests

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