Avian community structure and habitat use of Polylepis forests along an elevation gradient

Abstract

Background. As one of the highest and most unique systems in the world, Polylepis forests are recognized both as center of endemism and diversity along the Andes and as a system under serious threat from human activities, fragmentation, and climate change. Effective conservation efforts are limited, in part, by our poor understanding of the habitat needs of the system’s flora and fauna. Methods. In 2014-2015, we studied bird communities and 19 associated local and landscape attributes within five forested glacial valleys within the Cordillera Blanca and Huascaran National Park, Peru. Birds were surveyed in dry (May-August) and wet (January-April) seasons at 130 points distributed along an elevational gradient (3,300-4,700 masl) and analyzed using Canonical Correspondence Analysis (CCA). Results. A total of 50 species of birds, including 13 species of high conservation concern, were associated with four basic habitat types: (1) Polylepis sericea forests at low elevations, (2) P. weberbaueri forests at high elevations, (3) Puna grassland and (4) shrublands. Four species of conservation priority (e.g., Poospiza alticola) were strongly associated with large forest patches (~10-ha) dominated by P. sericea at lower elevations (<3,800 masl), whereas another four (e.g., Anairetes alpinus) were associated with less disturbed forests of P. weberbaueri at upper elevations (>4,200 masl). Discussion. Results suggest that, in addition to conserving large (>10-ha) P. sericea forests at lower elevations as the cornerstone for maintaining bird diversity, any high elevation (>4,200 masl) relicts of P. weberbaueri, irrespective of size, should be prioritized for conservation.

Lower density of arthropod biomass in small high‐Andes Polylepis fragments affects habitat use in insectivorous birds

“…Besides showing direct responses to fragment size in their abundances (Lloyd 2008 b ), both species respond to habitat and tree quality, with positive impacts of larger trees as these contain relatively more arthropods as a food resource. Giant Conebill was previously known to be more abundant, and to have smaller home ranges, at sites with a high density of large, mature trees (Cahill and Matthysen 2007, Lloyd 2008 b , De Coster et al 2009, Sevillano‐Ríos and Rodewald 2017, Astudillo et al 2020), but we now show that the bird indeed preferentially forages on larger trees, and this more often so in large fragments, in response to higher arthropod density. Some other insectivorous birds have also been shown to select trees based on arthropod density for increased foraging efficiency.…”

“…Both insectivorous species forage primarily on bark‐dwelling arthropods from Polylepis trees; C. binghami selects mature trees and forages primarily on tree trunks by prying in the bark, whereas S. yanacensis forages on twigs and small branches (Lloyd 2008 a , Matthysen et al 2008). Previous studies have shown that their abundance is lower in smaller fragments and near fragment edges, like in other Polylepis bird specialists too (Cahill and Matthysen 2007, Lloyd 2008 b , Sevillano‐Ríos and Rodewald 2017). However, it is unclear if and to what extent this is related to habitat quality (i.e., lower abundance of food resources) or fragment size.…”

“…Considered among the world's highest elevation forest ecosystems, they are made up exclusively of Polylepis trees, whose bark consists of multi‐layered, exfoliating sheets that provide efficient protection against the harsh, high‐elevation (3000–5200 m asl) climatic conditions (i.e., extreme daily and seasonal variations in temperature and water availability: Rada et al 1996, García‐Núñez et al 2004). This protection applies not only to the individual trees but also to the wide array of endemic arthropod species living inside these loose layers of bark (Fjeldså 1993, Gareca et al 2010, Sevillano‐Ríos and Rodewald 2017). Specifically, Polylepis trees have been pointed out as important refuges for insects and arachnids (Fjeldså et al 1996), and this most probably so for thermoregulatory reasons in this high‐elevation ecosystem.…”

Differential seedling regeneration patterns across forest–grassland ecotones in two tropical treeline species (Polylepis spp.)

“…In addition, we modelled the environmental associations of adult presence/absence of each Polylepis species within our study areas using the information from our sample plots and an additional 130 points sampled for vegetation structure by Sevillano‐Ríos and Rodewald (). This dataset covered an elevational range of 3300–4700 m in five valleys on the western side of HNP, including the four sampled for seedlings.…”

Responses ofPolylepisbirds to patch and landscape attributes in the High Andes

“…We studied bird communities in five glacial valleys of Cordillera Blanca, within Huascaran National Park and Biosphere Reserve, Ancash, Peru (9°06′19″S, 77°36′21″ W) [see 68 and 69 for a more detailed description]. This area is recognized as a center of avian endemism and diversity of the High Andes [42,[70][71][72] and contains some of the largest remaining areas and patches of Polylepis forest in the world [47,73]. The five glacial valleys (Parón, Llanganuco, Ulta, Llaca and Rajucolta) are located on the western slope of Cordillera Blanca and discharge into the Santa River and the Pacific Ocean (Figure 2).…”