Long-term count data demonstrate the regional significance of Bako-Buntal Bay, Malaysian Borneo, for wintering shorebird conservation

Bako-Buntal Bay in Sarawak, Malaysia is among the most important coastal wetlands for migratory shorebirds in Borneo, and in insular Southeast Asia. However, since the multi-year waterbird surveys of the Sarawak coast during 2010–2012, there has been little published work on migratory shorebirds here. Our study assessed the status and populations of migratory waterbirds utilizing two sites within Bako-Buntal Bay: (1) the extensive mud and sand flats of Buntal Bay used as a neap tide roost site, and (2) the man-made (ash) ponds at Sejingkat regularly used as spring tide roost sites. We counted waterbirds twice a month from October 2018 to March 2019, and compiled monitoring data from the Asian Waterbird Census and other surveys starting in either 2006 or 2007. We found a total of 32 waterbird species in Buntal and 31 species in Sejingkat, including globally significant numbers of four threatened species: Far Eastern Curlew Numenius madagascariensis (EN), Great Knot Calidris tenuirostris (EN), Nordmann’s Greenshank Tringa guttifer (EN), and Chinese Egret Egretta eulophotes (VU). Our study showed that the total counts of waterbirds at Buntal, and especially Sejingkat, have increased consistently from 2006–2007 to 2019, particularly with an increasing trend for Far Eastern Curlew and a sudden increase in Great Knot numbers in 2019. Using flag resightings, we established connections between our study sites and sites along the East Asian-Australasian Flyway, e.g. Chongming Island in Shanghai, China and Kamchatka in Russia. We are unsure of the factors driving the increase of shorebird numbers, but hypothesize a possible decline in habitat extent and quality elsewhere on Borneo or in the wider Southeast Asian region. Our work demonstrates the continued importance of Bako-Buntal Bay for shorebirds, especially the Far Eastern Curlew, in Southeast Asia, and the need for sustained conservation measures.