Important Record of the White-faced Plover (Anarhynchus dealbatus) from the Western Coastal Ecosystem of Aceh Province

 Introduction

The western coastal landscape of Aceh represents one of the relatively intact coastal systems on the western side of Sumatra Island, characterised by a mosaic of habitats including sandy beaches, lagoons, estuaries, and dynamic coastal wetlands. This ecosystem is shaped by the interaction between oceanographic processes of the Indian Ocean and the discharge of major rivers from the mainland, creating productive intertidal zones that provide abundant food resources for waterbirds, particularly migratory shorebirds (Putra et al., 2017). In a regional ecological context, this area holds significant potential as an important stopover habitat along the East Asian–Australasian Flyway, although it remains relatively under-documented compared to other coastal regions in Southeast Asia.

Aceh’s coastal wetlands play a crucial role as stopover sites and refuelling grounds for various migratory shorebird species. Benthic organisms such as molluscs, small crustaceans, and other invertebrates, which are abundant in muddy and sandy substrates, constitute the primary food resources that determine the success of migration for these species (Khairunisak et al., 2022). According to Wetlands International, coastal wetland ecosystems in Southeast Asia form a vital component of the global ecological network that supports the life cycles of long-distance migratory birds. This is further reinforced by the East Asian–Australasian Flyway Partnership framework, which emphasizes the importance of coastal sites as ecological nodes in transcontinental migration.

In recent years, field observations along the western coast of Aceh have increasingly indicated a high frequency of stopovers by various migratory shorebirds, ranging from genera such as Tringa, Calidris, and Charadrius. One particularly noteworthy record is the presence of the White-faced Plover (Anarhynchus dealbatus), a shorebird species previously known to be primarily distributed along the coasts of East Asia. Its occurrence in Aceh not only enriches the regional avifaunal diversity but also raises important questions regarding distribution dynamics, migratory patterns, and the possibility of under-documented stopover sites in western Indonesia.

White-faced Plover (Anarhynchus dealbatus)

Scientifically, the record of the White-faced Plover along the western coast of Aceh holds considerable significance, both as a potential indication of range expansion and as a reflection of existing gaps in observational data for the region. Global databases such as eBird suggest that records of this species in Sumatra remain scarce, making each new documentation an important contribution to understanding its regional distribution. Therefore, this observation represents not merely a field encounter but also part of a broader effort to address biodiversity data gaps in the strategically important yet underexplored coastal ecosystems of Aceh.

Understanding the White-faced Plover

1. Taxonomy and Species Status

The White-faced Plover is a shorebird species belonging to the family Charadriidae that has undergone significant taxonomic revision in recent decades. It was previously considered part of the Kentish Plover (Anarhynchus alexandrinus), a group with a broad distribution ranging from Europe to Asia. However, studies on morphology, vocalisation, and genetic analyses have revealed consistent and significant differences, leading to the recognition of East Asian and parts of Southeast Asian populations as a distinct species, namely the White-faced Plover (Rheindt et al., 2011).

Kentish Plover (Anarhynchus alexandrinus)

This taxonomic revision is further supported by a comprehensive study by Kennerley (2008), which emphasises the importance of an integrative approach in defining species boundaries within shorebird groups that exhibit subtle morphological variation yet significant ecological differentiation. Currently, the White-faced Plover is recognised as a distinct species, with its primary distribution along the coasts of East Asia, including China, Taiwan, and Vietnam, and it is known to migrate to more southern regions during the non-breeding season (BirdLife International, 2023).

2. Field Identification Characteristics

Identifying the White-faced Plover in the field requires a high level of precision, particularly due to its similarity to other species within the same genus. In general, this species is small to medium in size and exhibits typical shorebird morphology, including a compact body, relatively long legs, and a short dark bill. The most distinctive feature, which underlies its common name, is its clean and contrasting white face, especially in adult individuals. Compared to the Kentish Plover, the White-faced Plover shows a lighter coloration on the face and neck, with a more clearly defined boundary between the white areas and the crown. In addition, the breast band in males tends to be narrower and more sharply defined, while the leg colour is usually darker than that of its closely related counterpart (Iqbal et al., 2010).

White-faced Plover and Kentish Plover

Record of the White-faced Plover on the Western Coast of Aceh

Based on field observations conducted in 2022 and 2023, the White-faced Plover (Anarhynchus dealbatus) was recorded in small numbers, with four individuals observed in 2022 and two individuals in 2023. The species was found in association with other shorebird communities that reflect a typical tropical coastal assemblage of Sumatra. This community was dominated by plovers and sandpipers , with recorded species including the Pacific Golden Plover, Kentish Plover, Eurasian Whimbrel, Common Sandpiper, Common Redshank, and Sanderling. Among these, the Pacific Golden Plover was the most abundant species in 2022, with a total of 26 individuals, while the other species were present in comparatively lower numbers.

Table of Shorebird Observations in Krueng Sabee, Aceh

No	Common Name	Scientific Name	Indv	Date
1	Pacific Golden-Plover	Pluvialis fulva	26	2022
2	Kentish Plover	Anarhynchus alexandrinus	2	2022
3	White-faced Plover	Anarhynchus dealbatus	4	2022
4	Eurasian Whimbrel	Numenius phaeopus	1	2022
5	Common Sandpiper	Actitis hypoleucos	1	2022
6	Common Redshank	Tringa totanus	1	2022
7	Sanderling	Calidris alba	7	2022
8	Pacific Golden-Plover	Pluvialis fulva	4	2023
9	Kentish Plover	Anarhynchus alexandrinus	3	2023
10	White-faced Plover	Anarhynchus dealbatus	2	2023
11	Common Sandpiper	Actitis hypoleucos	5	2023

Interestingly, during both observation periods, the White-faced Plover was observed flocking with the Kentish Plover, a species that is morphologically very similar. In 2022, two Kentish Plovers were recorded within the same group as four White-faced Plovers, while in 2023, three Kentish Plovers were associated with two White-faced Plovers. This pattern of association is particularly important in the context of field identification, as the presence of both species within the same flock increases the risk of misidentification, especially under suboptimal lighting conditions or at greater observation distances.

Overall, these data indicate that the Krueng Sabee estuary functions not only as a stopover habitat but also as a site of interspecific interaction among migratory shorebirds, albeit in relatively small groups. The presence of the White-faced Plover within this diverse community further highlights the importance of the western coastal region of Aceh as part of a network of critical habitats for migratory birds in Southeast Asia.

In addition, observations conducted during two different periods revealed variation in daily activity patterns related to observation time and potentially tidal conditions. In 2022, morning observations showed that White-faced Plovers were active along open beach areas exposed to wave action, moving rapidly along the receding waterline while foraging. This behaviour reflects a typical shorebird foraging strategy, exploiting benthic organisms within the intertidal zone as a primary energy source.

In contrast, observations in 2023, conducted in the late afternoon, indicated that groups of White-faced Plovers were more frequently found in calm, shallow pools near the shoreline. This shift in microhabitat use is likely associated with daily tidal dynamics, where more stable water conditions in the afternoon may allow more efficient access to food resources while reducing disturbance from wave action.

These differences in habitat use between morning and afternoon suggest a degree of behavioural flexibility in the White-faced Plover in response to changing coastal environmental conditions. This finding underscores the importance of understanding temporal dynamics and tidal cycles when interpreting the ecology of shorebirds in intertidal habitats.

Discussion

The observations of the White-faced Plover in small yet consistent numbers across two different periods (2022 and 2023) suggest that this site likely functions as a stopover location rather than merely a site of incidental visitation. This is further supported by the presence of a diverse shorebird community, including Pacific Golden-Plover, Sanderling, and Common Sandpiper, all of which are long-distance migratory species that typically utilize intertidal habitats for energy replenishment. The composition of this community reflects the characteristic productivity of tropical coastal ecosystems, capable of meeting the energetic requirements of migratory birds.

A particularly significant aspect of these findings is the direct interaction between the White-faced Plover and the Kentish Plover within a mixed-species flock. This phenomenon has important implications for field identification, as both species exhibit high morphological similarity. Their co-occurrence increases the risk of misidentification, especially under limited observation conditions. Conversely, such associations also provide an opportunity for direct interspecific comparison, thereby enhancing the reliability of identification when conducted carefully and supported by adequate documentation.

Moreover, the observed variation in daily activity patterns between 2022 and 2023 offers additional insight into the behavioral flexibility of this species. Foraging activity on open beaches in the morning and subsequent shifts to calmer water pools in the afternoon indicate that the White-faced Plover can adjust microhabitat use in response to tidal dynamics. This pattern aligns with the energy management strategies typical of shorebirds, where foraging efficiency and disturbance minimization are key factors in habitat selection. Consequently, the Krueng Sabee estuary not only provides physical habitat but also supports behavioral dynamics critical for successful migration.

From a biogeographical perspective, these findings are also significant in the context of southern range extension. Previous records indicate that the primary distribution of the White-faced Plover is in East Asia, with a few notable records in Southeast Asia. The presence of this species in Aceh reinforces the hypothesis that the Sumatran region, particularly the western coast, may represent part of an under-documented migratory corridor. This aligns with earlier studies showing that new southern records often reflect limitations in observation efforts rather than actual changes in distribution.

Overall, these findings underscore the importance of a systematic and well-documented field observation approach, such as via the eBird platform, in filling gaps in species distribution data. In this context, the role of citizen science becomes increasingly crucial, as the involvement of birdwatchers from diverse backgrounds enables data collection across broad spatial and temporal scales, which would be difficult to achieve through conventional scientific surveys alone. The integration of quantitative data (e.g., number of individuals, species composition) and qualitative data (e.g., behavior, associations, habitat use) is key to understanding the ecological role of a site. Thus, combining scientific methodology with public participation through citizen science not only enhances the quality and availability of data but also strengthens evidence-based conservation efforts. In this regard, the Krueng Sabee estuary can be regarded as an important site with high conservation potential, particularly for migratory shorebirds that depend on the sustainability of coastal ecosystems.

Conclusion

Overall, the presence of the White-faced Plover along the western coast of Aceh, particularly at the Krueng Sabee estuary, provides important evidence that this area functions as a stopover site for migratory shorebirds along the East Asian–Australasian Flyway. This finding not only enriches regional biodiversity data but also highlights other significant aspects, such as its close association with the Kentish Plover within mixed-species flocks and the species’ daily behavioural flexibility in response to tidal dynamics. The consistent occurrence of this species over two consecutive years indicates that the western coastal region of Aceh warrants greater attention for long-term conservation and monitoring efforts.

From a scientific and conservation perspective, these observations underscore that substantial gaps remain in biodiversity data for western Indonesia, which need to be addressed through systematic field observations and active community participation (citizen science), for instance via platforms such as eBird. Each new record of a rarely documented species, such as the White-faced Plover, holds strategic value for understanding distribution dynamics, migratory patterns, and habitat protection priorities. Therefore, the Krueng Sabee estuary and the broader coastal ecosystems of Aceh should be managed sustainably, considering their crucial ecological role in supporting the survival of migratory shorebirds across Southeast Asia.

Reference

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Kennerley, P. R., Bakewell, D. N., & Round, P. D. (2008). Rediscovery of a long-lost Charadrius plover from South-East Asia. Forktail, 24, 63–79.

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