A network approach to prioritize conservation efforts for migratory birds.

Yanjie Xu,Diann J Prosser,Peng Gong,Qiang Liu,Willem F De Boer,John Takekawa,Yali Si,Shenglai Yin,Herbert H T Prins

doi:10.1111/cobi.13383

Abstract

Habitat loss can trigger migration network collapse by isolating migratory bird breeding grounds from nonbreeding grounds. Theoretically, habitat loss can have vastly different impacts depending on the site's importance within the migratory corridor. However, migration‐network connectivity and the impacts of site loss are not completely understood. We used GPS tracking data on 4 bird species in the Asian flyways to construct migration networks and proposed a framework for assessing network connectivity for migratory species. We used a node‐removal process to identify stopover sites with the highest impact on connectivity. In general, migration networks with fewer stopover sites were more vulnerable to habitat loss. Node removal in order from the highest to lowest degree of habitat loss yielded an increase of network resistance similar to random removal. In contrast, resistance increased more rapidly when removing nodes in order from the highest to lowest betweenness value (quantified by the number of shortest paths passing through the specific node). We quantified the risk of migration network collapse and identified crucial sites by first selecting sites with large contributions to network connectivity and then identifying which of those sites were likely to be removed from the network (i.e., sites with habitat loss). Among these crucial sites, 42% were not designated as protected areas. Setting priorities for site protection should account for a site's position in the migration network, rather than only site‐specific characteristics. Our framework for assessing migration‐network connectivity enables site prioritization for conservation of migratory species.

Highlights

In recent years, the populations of many migratory species have declined rapidly because of loss and degradation of habitats, caused by rapid economic development, intensive human disturbance, and inefficient conservation policies (Syroechkovskiy 2006; de Boer et al 2011; Studds et al 2017)
The migration network structure of waterfowl in the East Asian–Australasian Flyway partly explains the population size fluctuations of these migratory birds because population sizes decrease with losses of migration network functional connectivity (Xu et al 2019a)
We quantitatively evaluated the robustness of migratory birds’ migration network and identified crucial stopover sites in terms of contribution to network connectivity and degree of habitat loss

Summary

Introduction

The populations of many migratory species have declined rapidly because of loss and degradation of habitats, caused by rapid economic development, intensive human disturbance, and inefficient conservation policies (Syroechkovskiy 2006; de Boer et al 2011; Studds et al 2017). The greater white-fronted goose (Anser albifrons), bar-headed goose (Anser indicus), and whooper swan (Cygnus cygnus) are widespread and abundant in the wild and are categorized as least concern species, but their populations have rapidly declined in many areas, indicating inadequate conservation efforts for these migratory birds (Syroechkovskiy 2006; Si et al 2018). Degradation and loss of stepping-stone nodes from a habitat network may limit a species’ ability to shift ranges, which is an important strategy used by migratory birds to cope with environmental changes (Saura et al 2014). To better understand how environmental changes affect existing migration networks and to guide targeted conservation measures, it is important to evaluate a migration network’s connectivity and resilience and to identify crucial sites that might trigger network collapse

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