Catastrophic ongoing decline in Cambodia’s Bengal Florican Houbaropsis bengalensis population

Abstract

SummaryIn 2013 a prediction was made that the South-East Asian subspecies of Bengal Florican Houbaropsis bengalensis blandini would be extinct within 10 years. In 2018 we conducted a survey in the Tonle Sap floodplain, Cambodia, of the last population of Bengal Florican in South-East Asia. We found that the rate of decline in displaying males was 55% over five years, a decline comparable to that recorded between 2005–2007 and 2012. The estimated number of displaying males in 2018 was 104 (95% CI: 89–117), down from 216 (156–275) in 2012. We also conducted surveys by flushing birds in the non-breeding season, which indicated that the sex ratio of males to females is 3:1. We therefore estimate that the total population of adult Bengal Floricans in Cambodia in 2018 was 138 (119–156), making H. b. blandini the most threatened bustard taxon. The number of sites that support displaying male Bengal Floricans was reduced from 10 to four between 2012 and 2018. Between 2012 and 2018 we monitored numbers of displaying males in most years at the sites that support 80% of the total population. The only site where numbers of birds are stable is Stoung-Chikraeng Bengal Florican Conservation Area, where there were 44 (25–63) displaying males in 2018. This is the only site that has an ongoing NGO-government conservation programme. Our data indicate that Bengal Floricans are lost from sites when the area of grassland falls below 25 km2. We found evidence that displaying male Bengal Floricans abandon display territories when grassland is lost, this also creates hope that they may disperse and could colonise newly created habitat. All remaining sites that support Bengal Floricans in Cambodia are imperilled and we outline what must be done to reduce the possibility that H. b. blandini will be extinct by 2023.

A systematic expert‐based assessment of progress and priorities for conservation of the Bengal Florican Houbaropsis bengalensis

“…In South Asia, these management units are discrete protected areas that are each managed individually (7), a group of geographically proximate protected areas (1: Uttar Pradesh), or unprotected areas that support Bengal Floricans (2: Koklabari Rice Farm, which is legally part of Manas National Park [NP] but managed completely differently; and islands along the Brahmaputra River in Assam, hereafter chaporis ). In Cambodia, the management units were defined in 2005 and have been used by Wildlife Conservation Society (WCS) and others for research and conservation ever since (Gray et al, ; Mahood et al, ; Packman et al, ). Although all management units are centered on Bengal Florican breeding grounds, the threat assessment also attempted to include threats acting on birds in the known or assumed non‐breeding grounds that correspond to each management unit.…”

“…The population of H. b. bengalensis is 350–400 in India and <100 in Nepal (Collar et al, ). The population of H. b. blandini was estimated at about 200 in 2018, the smallest of any bustard taxon, and declining at over 10% per year (Mahood et al, ). Local population declines have also been documented at some protected areas in India and Nepal, although recent trends are uncertain (Jha et al, ).…”

“…The Bengal Florican Houbaropsis bengalensis is polytypic: the nominate subspecies is confined to protected areas in floodplain grasslands in north and north-east India and southern Nepal, and H. b. blandini is now restricted to the Tonle Sap floodplain of Cambodia (Collar, Garcia, & Sharpe, 2018;Mahood, Hong, Son, Sum, & Garnett, 2019). The population is highly fragmented.…”

Conserving a globally threatened species in a semi-natural, agrarian landscape

“…Unprotected sites were open-access resources recognized as state public land under national law. Traditional practices such as cattle grazing and cricket collecting were encouraged in the Northern Tonle Sap Conservation Landscape under co-management frameworks overseen by Community Management Committees (Mahood & Hong, 2013). Biodiversity monitoring, conservation outreach and enforcement activities were conducted in the Northern Tonle Sap Conservation Landscape by the government, with technical and financial assistance provided by the Wildlife Conservation Society (WCS).…”

“…Dry season rice expansion was initially driven by Economic Land Concessions (long-term land development leases) granted by the government to influential urban elites (Packman et al, 2013). However, recent research suggests local communities have capitalized on irrigation investments made by concessionaires and are also converting grasslands for dry season rice (Mahood & Hong, 2013), a trend that remains unquantified. Dry season rice is now thought to be the greatest threat to florican survival, with 44–66% population declines recorded for the Tonle Sap population since the emergence of dry season rice cultivation in 2004 (Packman et al, 2014), although studies suggest hunting may also threaten the species (Packman, 2011).…”