Many migratory birds travel along the East Asian-Australasian Flyway seeking temporary refuge during the non-breeding season, between September to April. Some of these migratory birds are observed in Naujan Lake National Park (NLNP), a Wetland of International Importance (Ramsar Site), an initial component under the National Integrated Protected Areas System (NIPAS), and a Key Biodiversity Area (KBA) in Mindoro.
Waterbird censuses are conducted repeatedly for long-term monitoring of wetlands. The presence and number of observed waterbirds are important indicators to determine the health and quality of wetlands (Wetlands International, n.d.). On January 17-18, 2019, the NLNP Protected Area Office assisted by MBCFI, conducted the Asian Waterbird Census (AWC) for Naujan Lake with participants from various DENR offices and partner organizations. AWC aimed at monitoring the populations of migrant, resident and endemic waterbirds in NLNP; documenting new species records, if any; and institutionalizing and sustaining the conduct of waterbird census in NLNP.
The briefing and orientation were conducted in the afternoon of January 17, 2019. An overview of the physical and biodiversity profile of Naujan Lake National Park was provided followed by a briefing on the identification marks to distinguish waterbird species with similar appearance as well as methods for counting and estimating flocks of birds. Participants were assigned to teams, and target routes/sites were also discussed. The actual census started at 6:30 AM on January 18, 2019.
Among the waterbird species recorded, 16 are migratory species (47%), 15 are resident species (44%), and two are Philippine endemics (6%). Only one threatened species was recorded – the endemic Philippine Duck which is listed as Vulnerable (VU) by the International Union for Conservation of Nature (IUCN). A total of 3,653 individuals from 39 species were observed. The most numerous species is the migratory Whiskered Tern (Chlidonias hybrida) with 1,647 which comprised almost half of the total count. This is followed by 410 individuals of Wandering Whistling Ducks (Dendrocygna arcuata).
Noticeably absent are the huge flocks of thousands of migratory Tufted Ducks (Aythya fuligula) which ranged from 13,500 to 15,000 individuals annually between years 2011 to 2015. A total of 729 Tufted Ducks were recorded during a waterbird survey on the lake on December 3, 2018. Boatmen and local fishermen also report observing large flocks of ducks in few days prior to the census. Only 58 individuals were observed by Team 1 near the Western edge and an additional 59 by Team 3 from the Southeastern portion of the lake. There are several possible reasons for the very low counts of Tufted Ducks: (1) they could be in a secluded portion of the lake, (2) they may have transferred to another suitable wetland habitat other than Naujan Lake in response to yet unknown stimuli, or (3) they have started Northward migration, returning to their breeding grounds earlier than expected.