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Vol. 4 January 2013

CHED Accredited Research Journal, Category A

Print ISSN 2094-5019 • Electronic ISSN 2244-0461

doi: http://dx.doi.org/10.7828/ajob.v4i1.301

Asian Journal of Biodiversity

Art. #301 pp. 135-168

This Journal is in the Science Master Journal List of

Thomson Reuters (ISI) Zoological Record

Philippine-endemic and Mindanao-endemic

Bird Communities on Canticol

and Mt. Hilong-hilong, Philippines

SHERRYL L. PAZ

ORCID No. 0000-0002-8465-4997

sheter29@yahoo.com

Department of Biology, Caraga State University,

Ampayon, Butuan City, Philippines,

DUSIT NGOPRASERT

ORCID No. 0000-0002-2008-4809

ndusit@gmail.com

Conservation Ecology Program,

King Mongkut’s University of Technology Thonburi,

49 Thakham, Bangkhuntien, Bangkok, Thailand

OLGA M. NUNEZA

ORCID No. 0000-0002-7102-9674

olgamnuneza@yahoo.com

Department of Biological Sciences,

Mindanao State University-Iligan Institute of Technology,

Tibanga Highway, Iligan City, Philippines

NEIL ALDRIN D. MALLARI

ORCID No. 0000-0002-0357-9586

aldrin.mallari@gmail.com

Flora and Fauna International,

Silang, Cavite, Philippines

135

Asian Journal of Biodiversity Vol. 4 Jan. 2013

GEORGE A. GALE

ORCID No. 0000-0001-6988-1625

ggkk1990@gmail.com

Conservation Ecology Program,

King Mongkut’s University of Technology Thonburi,

49 Thakham, Bangkhuntien, Bangkok, Thailand

Abstract - The study assessed the Philippine-endemic and

Mindanao-endemic bird communities of two mountains in Agusan

del Norte – Canticol, Tubay and Mt. Hilong-hilong, Remedios

T. Romualdes (RTR) from September to November, 2008 using

eight-minute fixed-radius point counts. Habitat variables included

vegetation structure, elevation, slope and incidence of anthropogenic

disturbance. Non-linear regression analysis and AICc model selection

were used to determine the habitat variables that influence the richness

and abundance of endemics in the two sites. Canticol had lower mean

density of large and medium trees and higher degree of anthropogenic

disturbance than Mt. Hilong-hilong. There were 31 Philippine-

endemic birds (four threatened) and three Mindanao-endemics (one

threatened) on Canticol while there were 39 Philippine-endemics

(seven threatened) and six Mindanao-endemics (three threatened) on

Mt. Hilong-hilong. The diversity of endemics was significantly higher

on Mt. Hilong-hilong (H’=2.31). The study suggests that the two sites

need conservation attention to prevent forest loss and endangerment

of the threatened endemics. Vegetation structure and elevation had the

greatest influence on the endemic bird communities in the two sites.

Adequate regeneration of the disturbed sites in the region must also be

prioritized as part of a long-term management strategy.

Keywords - richness, abundance, habitat, threatened, avian

communities

INTRODUCTION

South-East Asia has the highest relative rate of deforestation which

has adversely affected its rich and unique biodiversity (Sodhi et al.,

136

Philippine-endemic and Mindanao-endemic Bird Communities

on Canticol and Mt. Hilong-hilong, Philippines

S. Paz, D. Ngoprasert, O. Nuneza,

N.A. Mallari, & G. A. Gale

2005). The Philippines exemplifies the dire situation for biodiversity

in Southeast Asia (Posa et al., 2006), where the country’s remarkably

high endemism (Peterson et al., 2000, Peterson 2006) and extensive

deforestation and severe loss of natural habitats has made the country

a global conservation priority (Myers, 2000). The Philippines as a

whole has lost 93% of its forests since 1900 (Onget et al., 2002) and the

country ranks second in terms of its annual forest loss in South-East

Asia and seventh in the world from 2000 to 2005 (Echanove, 2008).

Land use changes such as deforestation, forest fragmentation and

agricultural expansion resulting in habitat loss have been identified

as major threats to avian biodiversity (Brooks et al., 2002 and Sodhi,

2004). Within the Philippines, Eastern Mindanao has been declared

as one of the largest remaining blocks of tropical lowland rainforest

(Conservation International, 2008). However, much of the remaining

lowland dipterocarp forest is within logging concessions (75% of

the country’s timber comes from this area) while mining operations

proliferate throughout the Eastern Mindanao Biodiversity Corridor

(CEPF, 2001).

The Eastern Mindanao Biodiversity Corridor houses 196 bird

species of which 91 (46%) are Philippine-endemics which is more

than half (51%) of the country’s total number of endemic birds and

has 22 threatened species (PEF 2008). However, even basic quantitative

assessments of habitat and impacts of forest loss and other habitat

disturbances on the forest biota such as the Philippine and Mindanao-

endemic avifauna have been scarce (Posa et al., 2006). The scarcity of

the studies of these endemic bird communities makes it difficult to

determine the response of these endemics and other forest inhabitants

to various anthropogenic habitat alterations. Hence, in this study, the

Philippine-endemic and Mindanao-endemic bird communities were

investigated on the two mountains in Agusan del Norte particularly

Canticol, Tubay and Mt. Hilong-hilong, RTR which are expected to

contain several endemics.

OBJECTIVES OF THE STUDY

The study was conducted to (1) assess and compare the habitat

characteristics of the two sites (2) determine and compare the species

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Asian Journal of Biodiversity Vol. 4 Jan. 2013

richness, abundance, diversity, distribution and the status of the

Philippine-endemic and Mindanao-endemic birds of the two sites

(3) determine the influence of the various habitat variables on the

abundance and richness of the endemics and on the abundance of the

various feeding guilds in the two sites and (4) determine the implications

of the findings for conservation and land use management.

MATERIALS AND METHODS

Study Areas

Study sites were located in Canticol in between Tubay and Santiago

and on Mt. Hilong-hilong, RTR (Fig. 1). Both of the study areas

were situated in Agusandel Norte, Region 13, CARAGA, Mindanao,

Philippines. Canticol lies at the northwest of Agusan del Norte

(09°13’17.1’’N 125°38’47.2’’E) facing the municipality of Santiago on

its north and Dona Telesfora, Tubay on its south. Canticol is made up of

heterogeneous vegetation including grassland (two sampling points),

early secondary growth (nine points), advanced secondary growth

(12 points) as well as old growth forest (17 points). There has been no

documentation of the ecological, geographical and geological profile

of Canticol including its flora and fauna. Our habitat classification is

based on the dominance of large trees and the unique characteristics

of stand structure including tree size, age and spacing of trees and the

various stages of succession after logging (Gonzales-Salcedo, 2001).

The areas surveyed had an altitude range of 1,030-1,505 m in Canticol.

Mt. Hilong-hilong lies on the boundaries of Agusan del Norte,

Agusan del Sur and Surigao del Sur provinces, in the northern portion

of the Diwata range of northeast Mindanao (9°06’N 125°43’E) (Birdlife

International 2008). The mountain includes mostly montane forests

however lowland forests can also be found (Mallari et al., 2001). The

climate of Mt. Hilong-hilong is characterized by no pronounced dry

season (PEF 2008). Since Mt. Hilong-hilong is too wide to be sampled

rapidly, sampling was only done in the RTR section, Agusan del Norte

(09°05’20.3’ N 125°42’03.2’’ E). All of the 44 sample points on Mt.

Hilong-hilong were classified as old growth with an elevation range

of 1,115-1,810 m.

138

Philippine-endemic and Mindanao-endemic Bird Communities

on Canticol and Mt. Hilong-hilong, Philippines

S. Paz, D. Ngoprasert, O. Nuneza,

N.A. Mallari, & G. A. Gale

Bird Surveys

A preliminary survey was conducted in the two study areas during

June – August, 2008 to gain familiarity with the habitat characteristics,

existing bird species and to establish survey points. A total of four,

2-km lines were established in each study area. Each line was divided

into 10-11 sampling points placed every 200 m. There were 40 sampling

points on Canticol which covered various habitat types while there

were 44 sampling points on Mt. Hilong-hilong which covered only the

old growth.

Surveys were conducted in September to November 2008. Eight-

minute fixed-radius point counts were used in each study area between

500 to 800 hours when the bird activity was assumed to be highest.

Each survey was carried out under similar weather conditions i.e. no

strong winds and no heavy rain (Venegas, 2000). At every sampling

point, all birds encountered (either seen or heard) within 30-m radius

were recorded by the same two observers as above. Upon arrival at the

sampling point, an additional minute was allotted for resting before

commencing the count. Each point was surveyed twice whereby

counts were repeated the following day in reverse order, starting from

the farthest end of the line at dawn to minimize bias associated with

time of day. Bird species were recorded, and the abundance of birds at

each sampling point from the two surveys was summed.

Species richness and similarity of endemic bird communities in

the two sites was determined by calculating Sorensen’s similarity

(abundance-based) using SPADE software (Chao & Shen, 2009).

Diversity in each sampling point in the two sites was determined using

Species Diversity and Richness Software (Heanderson & Seaby, 2001).

Shannon-Wiener index was used to represent the bird species diversity

because it is the most commonly used diversity index (Cheng, 1999).

Mann-Whitney U tests were used to compare mean differences

between the two mountains in the richness, abundance and diversity

of the pooled Philippine-endemics and Mindanao-endemics only.

Moreover, the endemics were classified according to feeding guilds

following Round et al. (2006).

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Asian Journal of Biodiversity Vol. 4 Jan. 2013

Habitat Assessment

Nine variables were measured including the number of trees >40

cm diameter at breast height (dbh), 21-40 cm dbh, 10-20 cm dbh,

percentage of shrubs, percentage of herbs, percentage of bamboo,

elevation, slope, and presence/absence (+/-) of disturbance (defined

below). Habitat measurements were taken at every sampling point

using a modified habitat assessment procedure of Heaney (1986).

Vegetation measurements were recorded within 10 m and 20 m radius

circular plots. The number of trees within a specific size (dbh) group

was quantified in each sampling point using a dbh tape measure. The

tree size range that was assessed within 20 m radius circular plots at

each sampling point was >40 cm dbh and the tree size ranges that

were assessed within the 10 m radius circular plots: 21-40 cm dbh

and, 10-20 cm dbh. The percent cover of shrubs, herbs and bamboo

were assessed by estimating their percentage cover within a 10-m

radius of each sampling point. The elevation of each sampling point

was determined using an altimeter. The geographic coordinates of

each sampling point were recorded using an etrex Vista HCx Garmin

GPS. The degree of slope at the sampling points was determined

using a clinometer. The specific type of site disturbance was identified

through visual observation and interviews with local people. Presence

or absence of disturbance was recorded as 0 = undisturbed and 1 =

disturbed. The specific type of forest disturbance (e.g. mining, logging,

burning of trees, etc.) was also noted.

Mann-Whitney U-tests were used to test for significant differences

between the two sites for all of the above habitat variables. The

percentage data (shrubs, herbs and bamboo) was arcsine transformed

prior to analysis. We used a Z-test to compare the degree of disturbance

(the proportion of sites disturbed) between the two sites (Sheskin,

2000).

Habitat models

Non-linear regression (Poisson family) was used to determine the

habitat variables that most influenced the species richness and negative

binomial family of non-linear regression to assess the habitat effects

on abundance of the Philippine-endemics and Mindanao-endemics.

140

Philippine-endemic and Mindanao-endemic Bird Communities

on Canticol and Mt. Hilong-hilong, Philippines

S. Paz, D. Ngoprasert, O. Nuneza,

N.A. Mallari, & G. A. Gale

The habitat and the endemic bird data from Canticol and Mt. Hilong-

hilong were pooled for the non-linear regression analysis. Candidate

models were defined for the species richness and abundance of the

endemics by using Akaike’s Information Criterion corrected for

small samples (AICc) (Burnham and Anderson, 1998). Explanatory

variables were entered into models in the following combinations:

(1) each of the individual variables run separately to determine the

influence of each individual variable, (2) vegetation variables only, (3)

vegetation and topographic variables, and (4) vegetation, topographic

and disturbance variables. The top models were evaluated based on

the lowest AICc scores and the strength of evidence indicated by the

model weights, wi(Johnson et al., 2004). We evaluated models by using

differences in AICc values, with Δ AICc<2 indicating nearly equivalent

support between models (Burnham and Anderson, 1998). Relative

importance weights were determined by summing AIC weights of all

models containing each respective variable and comparing these sums

proportionally (Burnham and Anderson, 1998).

Fig. 1. Map showing the two sampling sites,

Canticol and Mt. Hilong-hilong

RESULTS AND DISCUSSION

Habitat characteristics

Four of the six vegetation variables tested were significantly different

between Canticol and Mt. Hilong-hilong (Table 1). Mt. Hilong-Hilong

141

Asian Journal of Biodiversity Vol. 4 Jan. 2013

had significantly higher mean densities of large trees (>40 cm dbh)

and medium-sized trees (21-40 cm dbh). There were no trees >160 cm

dbh recorded in Canticol. Mt. Hilong-hilong had significantly greater

values for percent herb cover (P 0.003) and bamboo (P 0.025). In terms

of the topographic attributes, Mt. Hilong-hilong was at significantly

higher elevation than Canticol. The two sites showed no significant

difference in mean density for small diameter trees (10-20 cm dbh),

percentage shrub cover and slope. The significantly lower mean value

for large trees (>40 cm dbh) and medium trees (20-40 cm dbh), the

absence of >160 cm dbh trees in Canticol and the disturbance index

implied recent tree extraction and that more sites were in early stages

of regeneration and generally more disturbed relative to Mt. Hilong-

hilong. The variability of the vegetation characteristics between

Canticol and Mt. Hilong-hilong can be attributed to the varying

topographic characteristics and types and extent of anthropogenic

disturbances in the two sites.

Moreover, Canticol is significantly lower in elevation compared to

that of Mt. Hilong-hilong making it more accessible to local people

which is especially important as this is a mineral-rich area. Hence,

the results revealed that there was a significantly lower incidence of

disturbed points on Mt. Hilong-hilong than on Canticol (Table 1). The

anthropogenic disturbances (70% of the points) identified in Canticol

included small-scale gold mining operations such as tunneling and

gold panning, cutting of trees for mining tunnels, firewood and for

houses of the miners and bird hunting.

The increasing human population on Canticol if not given due

attention, would most likely increase the level of tree extraction in the

remaining forest especially the advanced secondary growth and the

old growth. Additionally, the people in the area were also observed

resorting to bird hunting for food (D. Abrinica pers. comm. 2008). This

might eventually harm the bird community as well as the habitat for

other forms of wildlife.

On the other hand, Mt. Hilong-hilong is explicitly more well-known

than Canticol. Aside from being the largest block of the country’s

remaining dipterocarp forests and one of the important bird areas

in the country, it is also part of the Eastern Mindanao Biodiversity

Corridor and it is one of the priority biodiversity conservation areas

142

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