AVIFAUNAL ASSEMBLAGE IN THE EXPANSION SITES OF THE MT. HAMIGUITAN RANGE WILDLIFE SANCTUARY, MINDANAO, PHILIPPINES

The Protected Area of the Mt. Hamiguitan Range Wildlife Sanctuary (MHRWS) was proposed for expansion in 2016 to protect the remaining biodiversity of the buffer zones and to fortify the core zone. This study provides data on avifaunal assemblage and assessment on the added value of the ca. 2.99 km2 MHRWS expansion sites to the already protected zone. A combination of transect line survey and mist netting technique were used to sample bird species in four sampling sites in the MHRWS expansion sites. Our inventory of the MHRWS expansion sites revealed 41 species of birds distributed to 10 orders, 24 families and 34 genera. This adds 24 avifauna species to the previously reported birds in Mt. Hamiguitan Range making it a home to 83 species. The low species diversity in the MHRWS expansion sites could be attributed to the poor soil, low forest productivity and habitat loss. The presence of threatened and endemic species of birds in the Mt. Hamiguitan Range Wildlife Sanctuary expansion sites appeals for conservation initiatives by the stakeholders.


Introduction
The Philippines is one of the 18 mega biodiversity countries. It has been regarded by the World Conservation Union (IUCN) and other international conservation organisations as one of the highest priority countries in the world for conservation concern (Oliver & Heaney, 1996). The Philippines is home to 676 species of birds, of which 222 species (33%) are endemic to the Philippines, 325 (48%) are geographically restricted to Mindanao island and 90 (13%) globally threatened (Kennedy et al., 2000;Lepage et al., 2014).
The Mt. Hamiguitan Range Wildlife Sanctuary (MHRWS), Davao Oriental Province, Mindanao, is a protected area covering 68.34 km 2 . The highest peak in MHRWS reaches 1637 m a.s.l. It is characterised by a variety of vegetation types including a unique mossy pygmy forest (Amoroso et al., 2009;Amoroso & Aspiras, 2011). It is the only mountain peak in Mindanao with a pygmy forest inhabited by unique flora and fauna and is considered as the «hottest of the hotspots» (Ong et al., 2002). The mountain is a UNESCO World Heritage Site, ASEAN Heritage Park and also a Mindanao LTER Site. Recent surveys by Relox et al. (2011)  In 2016 municipal ordinances to expand the protected area of the MHRWS were issued to protect the remaining biodiversity of the buffer zones and to fortify the core zone. This study aimed to provide insights on the bird community and assessment of the added value of the ca. 2.99 km 2 expansion sites to the already protected core zone.

Study sites and emersion
Avifaunal inventories were carried out at the MHRWS expansion sites from late October to December 2016 and from February to April 2018. The study sites were distributed in the municipalities of San Isidro, Governor Generoso and Mati City in the province of Davao Oriental, Mindanao, Philippines (Fig. 1). The sites consisted of lowland mixed dipterocarp forest about 100 m to 5 km away from human habitation. The emergent trees were Shorea polysperma (Blanco) Merr., Ochrosia spp. and Gymnostoma rumphianum (Miq.) L.A.S. Johnson, reaching heights up to 32 m. Ficus spp., other fruit plants, and fallen logs were common (80%) on study site 1 but rare (20%) on study sites 2-4. Exposed rocks were common on all the study sites.

Permit statement
Prior informed consent from the communities was obtained by presenting the research to the stakeholders and members of the Protected Area Management Board (PAMB) of MHRWS for approval and issuance of the Gratuitous Permit (GP) from the Department of Environment and Natural Resources Reg. XI in the Philippines.

Sampling, processing and identification
Birds were caught during a total of 170 net days using12 × 2 m mist nets. A total of 42 net days were installed on sites 1-4. Mist nets were strategically placed in flyways, forest border, foraging areas and forest interior in a vertical forest stratum on the ground (1-5 m), middle canopy (5-10 m) and upper canopy (10-15 m). The nets were left open from 06:00 a.m. to 5:00 p.m. in order to capture diurnal birds and from 5:00 p.m. to 06:00 a.m. to collect nocturnal birds. The nets were monitored at least after every half an hour, and not more than one hour to prevent bird mortality.
Captured birds were immediately marked, photo documented and measured. Standard external measurements such as bill length, tarsus length, wing cord and total length were obtained from each bird. Age, sex and other distinguishing morphological characteristics of each species, if possible, were noted for taxonomic purposes. The captured birds were immediately released on the site of capture. The study employed captured, marked and released methods in which the captured birds' tarsus was tied with a thread to obtain an accurate count of the number of individuals per site.
To supplement the avifauna data, opportunistic sighting/point counting was done along the 2 km transect line. The birds were identified using «Birds of the Philippine Island» by Kennedy et al. (2000). The assessment of conservation and ecological status were based on the existing literature from the International Union for Conservation of Nature (IUCN) Red List and other published literature. The data were treated using BIOPRO software ver. 2.0.

Species richness and composition
The avifaunal inventory in the Mt. Hamiguitan Range Wildlife Sanctuary (MHRWS) expansion sites revealed 41 species of birds distributed to 10 orders, 24 families and 34 genera. Of the total number of species, six (15%) bird species were assessed as threatened:  (Relox et al., 2011, Mohagan et al., 2015 making it a home to 83 species. To date the MHRWS expansion sites is home to 49% of the bird species occurring in the entire range.  Relox et al. (2011) nor by Mohagan et al. (2015) in Mt. Hamiguitan Range. EN -Endangered, VU -Vulnerable, NT -Near Threatened, LC -Least Concern, PE -Philippine Endemic, ME -Mindanao Endemic.

Diversity and similarity index
The sites 1 (H' = 1.27) and 3 (H' = 1.26) had the most diverse bird fauna, which was low on the sites 2 (H' = 1.08) and 4 (H' = 1.11). This could be attributed to the presence of more intact forest community with emergent trees (e.g. Shorea polysperma, Lithocarpus spp.), that are 26-30 m high on site 1 and 3 compared to site 2 and 4. The sites 1 and 3 may be providing suitable habitats for avifauna species.
Most of the bird species were discordant as shown in Fig. 4. The species compositions of the sites were unique with a low similarity of (< 50%). Sites 1 and 3 have the greatest similarity value of 43%. Moreover sites 2 and 1 were related with 40% similarity value, as these sites were adjacent.

Discussion
The result is comparable to the 20 species of birds recorded in the lower montane forest, 0.01 km 2 plot of Mt. Hamiguitan and upper montane forest in Mt. Kitanglad (27 species), Mt. Malindang (32 species) and Mt. Apo (38 species) (Mohagan et al., 2015). Lowland and upper dipterocarp forest has the highest species richness and relative abundance compared to the mountain forest and mossy forest (Silvosa et al., 2007;Caro & Nuñeza, 2008).
On the contrary the work of Peterson et al. (2008) in Mt. Kitanglad showed that species richness is low at the lowest elevations. The sites sampled in this work ranged from 169-622 meters above sea level.
Sites 1 and 3, which harbours 24 and 21 species of birds respectively, were the most species rich. Sites 2 and 4 had a low species composition with only 13 species of birds on each site. This could be attributed to the presence of more intact forest community with emergent trees (e.g. Shorea polysperma, Lithocarpus spp.), reaching heights from 26 to 30 m high on sites 1 and 3.  The vegetation type can influence the avian species diversity and any reduction to the forest will also cause decrease in the species population (Joshi et al., 2012). Moreover, big trees are important determinant of avian species preferred habitat (Mallari et al., 2011). The presence of anthropogenic activities like mining and illegal logging has caused habitat degradation, which leads to biodiversity loss (Suarez & Sajise, 2010). An increase in anthropogenic activities causes the decline of local populations by limiting habitat sustainability, breeding and foraging opportunities and increasing the rate wildlife local extinctions (Sheta et al., 2010). The low species diversity in the MHRWS expansion sites could be attributed to the poor soil (UNESCO, 2014), leading to low forest productivity (Kumar & Maiti, 2013) and habitat loss due to illegal logging, mining and shifting cultivation observed in the sampling sites. The past avifauna surveys in the Philippines revealed that birds were vulnerable or even extinct in the wild due to habitat loss and conversion of forestland (Oliver & Heaney, 1996 (Mohagan et al., 2015). The vegetation type can influence the avian species diversity and any reduction to the forest will also cause a decrease in the species population (Joshi et al., 2012). Moreover, big trees are an important determinant of avian species preferred habitat (Mallari et al. 2011). The presence of anthropogenic activities like mining and illegal logging has caused habitat degradation, which leads to biodiversity loss (Suarez & Sajise, 2010). An increase in anthropogenic activities causes the decline of local populations by limiting habitat sustainability, breeding and foraging opportunities and increasing the rate wildlife local extinctions (Sheta et al., 2010). The low species diversity (H' = 1.25) (Fig. 2) in avifauna is attributed to Mt. Hamiguitan's ultramafic soil (UNESCO, 2014) leading to poor plant productivity and sparse vegetation (Mohagan et al., 2015) and habitat loss (Oliver & Heaney, 1996;Mohagan et al., 2015).
The low similarity (43%) on sites 1 and 3 can be attributed to less anthropogenic disturbances on both sites. Moreover, anthropogenic activities can result to the decline of bird populations by limiting foraging and breeding success that further leads to local extinction (Sheta et al., 2010).

Conclusions and Recommendations
Our inventory of the MHRWS expansion sites revealed 41 species of birds distributed to 10 orders, 24 families and 34 genera. This adds 24 avifauna species to the previously reported birds in Mt. Hamiguitan Range making it a home to 83 species. The low species diversity (H' = 1.25) in the MHRWS expansion sites could be attributed to the poor soil, low forest productivity and habitat loss. The species compositions in the four sampling sites (5-15 km apart) were unique with a low similarity (< 50%). Six (15%) avifauna species were threatened and 17 (ca. 42%) species are endemic to the Philippines. As the MHRWS expansion sites is home to 49% of the bird species occurring in the entire mountain range and habitats, the current study supports the need for conservation initiatives by the stakeholders.