Habitat loss caused by destructive human activities is pushing more and more species, including migratory shorebirds, to the brink of extinction.
These include wetland ecosystems in the Philippines, such as Manila Bay, currently the subject of land reclamation activities.
Shorebird abundance
Despite the threats, however, a recent study published in the International Wader Study Group revealed a significant shorebird abundance in northern Manila Bay.
The area includes the municipalities of Sasmuan and Masantol and Pampanga River Delta in Pampanga, and the municipalities of Barangay Sta. Cruz, Paombong and Barangay Pamarawan, both in Bulacan.
The study “Frequent, year-round monitoring reveals significant shorebird abundances in northern Manila Bay, Philippines” highlights the connectivity of habitats along a migratory bird flyway that is crucial for the survival of migratory shorebirds threatened by anthropogenic loss of coastline habitats.
The authors were Hui Zhen Tan, Movin Nyanessengeran, both of the Department of Biological Sciences, National University of Singapore, and Irene C. Dy, Wala. a bird watcher and bird tours facilitator. Dy also contributed to waterbird census.
According to the authors, a lack of regular monitoring in shorebird sites may prohibit accurate and comprehensive assessment of site importance and impede the identification of key sites for conservation.
Important shorebird areas
The authors presented a case where important shorebird areas in northern Manila Bay have been overlooked as previous bird counts were mostly made outside of the actual period of peak shorebird use.
The areas surveyed—Brgy. Tanza in Navotas City, Brgy. Pamarawan in Bulacan, and Pampanga province—host high numbers of shorebirds during migratory months, with Brgy. Tanza also having considerable numbers of over-summering shorebirds.
“Importantly, 14 species were recorded in abundance, exceeding 1 percent of their flyway populations. These areas in northern Manila Bay should be granted protection under the Ramsar Convention on Wetlands, and demonstrate the importance of frequent, year-round monitoring in assessing sites,” the authors noted.
Under grave threat
Unfortunately, northern Manila Bay is under grave threat as highly destructive developments and land reclamation are currently being carried out in the area, with additional coastal development projects being planned.
“We highlight the urgency of surveying other sites in the Philippines to prevent inadvertent loss of undervalued shorebird areas and to preserve crucial portions of the East Asian-Australasian Flyway,” the study said.
The authors pointed out that coastlines, with their proximity to trade and transport networks, are also sites for concentrated human habitation.
Coastlines are among the most exploited and degraded habitats today, threatened by encroachment for a range of economic activities, including tourism, aquaculture, agriculture and sand mining, they said.
East Asian-Australasian Flyway
The Philippines is in the path of the East Asian-Australasian Flyway (EAAF), which hosts the highest number of shorebirds.
Incidentally, almost half of the global human population also sits along the path.
“Southeast Asia, part of the EAAF, also holds some of the greatest expanses of mudflats and mangroves globally. These factors make the EAAF crucially important for safeguarding shorebird populations while being highly threatened,” the study said.
Conserving the EAAF requires a multi-pronged approach, exemplified by the formation of the EAAF Partnership, which coordinates concerted and collaborative efforts to protect and conserve the flyway.
Staging areas
Shorebirds use various sites along the EAAF for staging or fuelling when migrating between their breeding and wintering grounds.
Citing various studies, the authors said different shorebird species prefer different paths along the flyway.
“For instance, the Far Eastern curlew [Numenius madagascariensis] is more abundant along the eastern portion of the EAAF compared to the Eurasian curlew [Numenius arquata], which is more prevalent in the western regions,” the study said.
In conclusion, they said a network of sites along the length and breadth of the flyway is needed to safeguard its full suite of species.
Despite being relatively well-known, new information on the EAAF has demonstrated that much remains to be learned about it.
For instance, areas in southern Philippines that were not thought to be important for migrants were recently found to be used by overwintering critically endangered Chinese crested tern (Thalasseus Bernstein).
Dy said via email that the study surveyed the eastern edge of northern Manila Bay, particularly Brgy. Tanza mudflats, which is an extremely critical shorebird habitat.
Fascinating birds
“Shorebirds are a fascinating group of birds known for their annual feats of migration between their breeding grounds and their wintering areas. As they migrate, shorebirds use various habitats and, therefore; promote connectivity of ecosystems around the world,” Dy told the BusinessMirror on January 9.
She said that in the Philippines, the arrival of large numbers of these shorebirds from higher latitudes in the Northern Hemisphere marks the migratory season from August to March each year.
According to Birdlife International, more than 50 million migratory waterbirds, including 8 million shorebirds across hundreds of species, use the EAAF annually.
Decreasing population
According to Dy, while they do not have data in the study for definite interpretation of long-term trends, observations made during their surveys over three migratory cycles have suggested a decrease in shorebird populations, which was also the observation of previous studies.
“Considering that large-scale and ongoing reclamation and quarrying that started in the third quarter of 2022 in Bulacan will destroy and degrade much of the surrounding shoreline habitats, we expect that future studies will find that such activities would have greatly affected shorebird populations due to a reduction in feeding and roosting grounds,” she said.
Dy explained that local reduction in shorebird populations can also indicate changing qualities of the shoreline habitats, which could have implications for residents and industries relying on the intact ecosystem of the bay.
Reclamation, quarrying woes
Dy said the first major threat to migratory shorebirds in the study sites is the loss of habitats due to reclamation of critical mudflats.
“This has already happened at [Brgy.] Taliptip in Bulacan, which used to hold good numbers of Far Eastern curlew [an endangered species under IUCN] and Eurasian curlew, and could have spillover effects on [Bgy.] Tanza, Navotas, an important site for the Far Eastern curlew that has seen the highest count in the Philippines currently known to date,” she said. IUCN stands for International Union for Conservation of Nature, an international organization on nature conservation and sustainable use of natural resources.
Dy added that planting mangroves on mudflats is further reducing the available mudflat area where shorebirds feed and roost.
“The second threat to our migratory shorebirds as well as fishermen in the area is the deepening of the bay due to large-scale quarrying of sand and mud for reclamation projects, such as the [building of] new international airport [in Bulacan],” she pointed out.
“Changing hydrology has also been observed in [the municipality of] Obando and [Brgy.] Taliptip [in Bulacan], where water levels have risen due to altered drainage around the reclaimed area for the airport. Interactions between these threats and other factors are possible, and the severity of the outcomes is often difficult to predict. Possible losses of migratory bird populations due to land reclamation, such as in southern Manila Bay, should be a cautionary tale,” she explained.
Healthy sites, healthy birds
According to Dy, it is important to maintain healthy migratory shorebird habitats, which means a healthy migratory shorebird population.
“The importance of having a healthy migratory shorebird population in the Philippines means that these birds can gain sufficient energy reserves to fly back to their northern breeding grounds. Since a network of healthy sites is necessary to support shorebird migration, just like how airports facilitate our [human] travels, the loss of shorebird habitats in the Philippines will affect the entire East-Asian Australian Flyway all the way to Siberia,” she further explained.
As such, Dy said there is an urgent need for stringent measures to safeguard or protect these migratory shorebirds and their habitats from threats.
“These migratory shorebirds and their habitats could be protected with a critical evaluation of the environmental impacts of ongoing and future development projects in Manila Bay, and more surveys to identify important shorebird habitats in the Philippines that may have been overlooked,” she said.
More legal protection
Dy pointed out that urgent and drastic action to afford these habitats with more legal protection, such as under the Ramsar Convention on Wetland, are needed.
“Past conservation successes in Manila Bay, such as the Las Piñas-Parañaque Critical Habitat and Ecotourism Area Ramsar site, demonstrate that cooperation between public and private sectors can effect meaningful change for the ecosystem, birds, and coastal residents,” she said.
Protecting these habitats also means safeguarding the mudflats, wetlands, fishponds and rice fields that contributes to the integrity of the communities.
She said Bulacan province, Brgy. Tanza in Navotas, Iloilo province, Mandaue in Cebu, Zamboanga Sibugay, Lingayen Gulf and Palawan province, are just a few of the critical areas for wintering and transiting shorebirds in the Philippines and in this region of the EAAF.
“As a party to the Convention on the Conservation of Migratory Species of Wild Animals, the Philippines has been committed to environmental protection. We need to do our part [so] that birds that come to our shores are able to fly back to their breeding grounds,” Dy pointed out.
Image credits: Irene Dy