# Identification of Keystone Plant Species for Avian Foraging and Nesting in Beijing’s Forest Ecosystems: Implications for Urban Forest Bird Conservation

## TL;DR

This study identifies key tree species in Beijing's forests that are crucial for birds' food and nesting, offering insights for urban bird conservation.

## Contribution

The paper introduces a network analysis approach to identify keystone plant species for urban bird conservation.

## Key findings

- Morus and Prunus are key food sources for birds in Xishan Forest Park.
- Robinia pseudoacacia is a critical nesting substrate for birds.
- Scrublands provide essential resources for small-bodied birds.

## Abstract

With accelerating urbanization, the urban ecosystem and wildlife conservation benefit expanding populations. Identifying keystone species for bird foraging and nesting enables targeted bird conservation in urban forests. By analyzing the associations of birds with their diets and nest plants in Beijing’s Xishan Forest Park during the breeding season, our study revealed the keystone dietary tree genera (Morus and Prunus) sustaining food webs and critical nest substrate species (Robinia pseudoacacia). The key food resources varied, along with phenological shifts such as fruit phases. Scrublands served as a unique habitat for small-bodied birds, providing nesting sites and food. These findings suggest management measures to sustain or enhance these keystone resource species and the maintenance of vertical vegetation stratification.

Urban wildlife conservation is emerging as a critical component of sustainable city ecosystems. Rather than simply increasing tree abundance or species richness, conservation management should focus on key species. In this research, Xishan Forest Park in Beijing was chosen as a case study. Our aim was to identify keystone taxa critical for avian foraging and nesting during the breeding season. We performed a network analysis linking bird species, their diets, and nest plants. Dietary components were detected using DNA metabarcoding conducted with avian fecal samples. Nest plants were identified via transect surveys. Two indices of the network, degree and weighted mean degree, were calculated to evaluate the importance of the dietary and nest plant species. We identified 13 bird host species from 107 fecal samples and 14 bird species from 107 nest observations. Based on the degree indices, fruit trees Morus and Prunus were detected as key food sources, exhibiting both the highest degree (degree = 9, 9) and weighted mean degree (lnwMD = 5.21, 4.63). Robinia pseudoacacia provided predominant nesting sites, with a predominant degree of 7. A few taxa, such as Styphnolobium japonicum and Rhamnus parvifolia, served dual ecological significance as both essential food sources and nesting substrates. Scrublands, as a unique habitat type, provided nesting sites and food for small-bodied birds. Therefore, targeted management interventions are recommended to sustain or enhance these keystone resource species and to maintain the multi-layered vertical vegetation structure to preserve the diverse habitats of birds.