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The diet of Yellow-vented Bulbul (Pycnonotus goiavier) in oil palm agroecosystems

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The Yellow-vented Bulbul (Pycnonotus goiavier) is one of the most sighted birds in oil palm plantation. A study on their dietary habits was conducted at the Durafarm Oil Palm Plantation from February 2011 to May 2013 to determine the reason behind their abundance. In this study, 45 individuals of P. goiavier were dissected for stomach content analysis. Ivlev's electivity index (E) was used to measure the degree of food selection by P. goiavier. The results showed that this bird species mainly selected the Order Coleoptera (mostly pollinating weevil) (E= +0.97) and Homoptera (E= +0.87) as their main food sources in the oil palm plantation. This bird also selected Order Diptera (E= -0.30), Hemiptera (E= -0.43) and Hymenoptera (E= -0.92) as a prey based on their abundance. However, this species mainly avoided feeding on insects from Order Odonata, Orthoptera, Dictyoptera and Lepidoptera (E=-1.0 each) in oil palm plantation. There is a weak negative correlation found for the distribution of P. goiavier with the abundance of insects in oil palm plantation. Further investigation is needed on this bird species towards predating the oil palm pollinating weevil, since it could possibly affect the population density of the pollinating weevil and subsequently the oil palm fruit set.
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Journal of Oil Palm Research Vol. 27 (4) December 2015 p. 417-424
ABSTRACT
The Yellow-vented Bulbul (Pycnonotus goiavier) is one of the most sighted birds in oil palm plantation.
A study on their dietary habits was conducted at the Durafarm Oil Palm Plantation from February 2011
to May 2013 to determine the reason behind their abundance. In this study, 45 individuals of P. goiavier
were dissected for stomach content analysis. Ivlev’s electivity index (E) was used to measure the degree of
food selection by P. goiavier. The results showed that this bird species mainly selected the Order Coleoptera
(mostly pollinating weevil) (E= +0.97) and Homoptera (E= +0.87) as their main food sources in the oil
palm plantation. This bird also selected Order Diptera (E= -0.30), Hemiptera (E= -0.43) and Hymenoptera
(E= -0.92) as a prey based on their abundance. However, this species mainly avoided feeding on insects
from Order Odonata, Orthoptera, Dictyoptera and Lepidoptera (E=-1.0 each) in oil palm plantation. There
is a weak negative correlation found for the distribution of P. goiavier with the abundance of insects in
oil palm plantation. Further investigation is needed on this bird species towards predating the oil palm
pollinating weevil, since it could possibly aect the population density of the pollinating weevil and
subsequently the oil palm fruit set.
Keywords: diet, Yellow-vented Bulbul, oil palm, Coleoptera.
Date received: 17 April 2015; Sent for revision: 21 April 2015; Received in nal form: 18 September 2015; Accepted: 25 September 2015.
THE DIET OF YELLOW-VENTED BULBUL
(Pycnonotus goiavier) IN OIL PALM AGRO-
ECOSYSTEMS
BETTYCOPA AMIT*; ANDREW ALEK TUEN**; KHALID HARON*; MOHD HANIFF HARUN*
and NORMAN KAMARUDIN*
* Malaysian Palm Oil Board,
6 Persiaran Institusi, Bandar Baru Bangi,
43000 Kajang, Selangor, Malaysia.
E-mail:bettycopa@mpob.gov.my
**
Institute of Biodiversity and Environmental Conservation,
Universiti Malaysia Sarawak,
94300 Kota Samarahan, Sarawak, Malaysia.
INTRODUCTION
The Yellow-vented Bulbul (Pycnonotus goiavier) is
the most common of all bulbuls and best-known
garden bird in Malaysia (Davison and Chew,
2008). This common resident bird can be found in
almost all habitats except the deep forest, starting
from mangrove to secondary forest and from rural
to urban areas (Wee, 2009). According to Tan and
Ria (2001) the success of P. goiavier in almost all
habitats is due to their diverse diet, consisting of
both plants and animals. In terms of food selection,
P. goiavier is considered a generalist where they feed
on owers, nectar, fruits, insects and even carrion
(Ward, 1969; Fishpool; Tobias, 2005; Wells, 2007),
foraging near ground level (Myers, 2009). P. goiavier
in oil palm plantations at Bah Jambi and Bukit
Maradja were reported to have parts of Lepidoptera,
Journal of oil Palm research 27 (4) (DecemBer 2015)
418
and Coleoptera (Curculionidae) and seeds in their
gut content (Chenon and Susanto, 2006). Now, they
have successful adapted themselves to become one
of the most abundant birds in cultivated areas such
as the oil palm plantation (Chenon and Susanto,
2006; Amit et al., 2011; Azman et al., 2011). This bird
species was also reported to contribute as a pest
control agent in the oil palm ecosystem (Chenon and
Susanto, 2006). The pollinating weevil (Elaeidobius
kamerunicus) was introduced into Malaysia to
overcome the inconsistencies of oil palm pollination
(Syed et al., 1982). The introduction of this species
increased pollination and fruit production from
20% to 30% (Syed, 1982; Basri et al., 1983). Now, this
seemingly exclusive diet of the bulbul towards the
pollinating weevil raises a new concern to the oil
palm planters; whether the abundance of this bird
species contributes to the low fruit set, as reported
by some oil palm plantations in peat areas.
The diet of birds has been studied through
examination of regurgitated samples (presumably
from the crop), stomach samples analysis and faecal
samples (Chapman and Roseberg, 1991; Major, 1990).
Theoretically, prey content in regurgitated samples
should be easier to identify because the samples
represent recent feeding and has not undergone
much digestion. This would be followed by stomach
samples which represent slightly older feeding and
last faecal samples which represent undigested
food. There are several methods to extract prey
content in birds such as through stomach ushing
method (Martin and Hockey, 1993; Chou et al., 1998),
non-lethal potassium antimony tartrate method
(Zduniak, 2005; Asokan et al., 2009), faecal analysis
method (Rodway and Cooke, 2002; Parrish 1994),
and dissection method (Chenon and Susanto, 2006).
The method of inserting solution from oesophagus
to the stomach using syringe through exible plastic
tube and then removing the tube slowly leading
to the regurgitation of at least part of the stomach
content is similar between stomach ushing method
and potassium antimony tartrate method but
dierent in terms of the solution used. Stomach
ushing method (Martin and Hockey, 1993) used
water or saline solution while the other method used
potassium antimony tartrate (Zduniak, 2005). In this
study, the gut contents were determined through
dissecting method, to assess the diet of this bird,
which are available in oil palm ecosystem (Chenon
and Susanto, 2006).
Our knowledge of the diet of P. goiavier in oil
palm plantation on peat is still inadequate. Available
studies include the analysis of gut contents from
the Yellow-vented Bulbul in Indonesian oil palm
plantation (Chenon and Susanto, 2006) on mineral
soils and some observations on the behaviour of
P. goiavier (Wee, 2009). So far there is no detailed
information on the diet of P. goiavier in oil palm
plantations. The aim of this study is to determine the
diet of P. goiavier in oil palm plantations on peat via
dissection method.
MATERIALS AND METHODS
Location and Description of Study Site
Sampling was conducted 10 times between
2011 to 2013 at the Durafarm Oil Palm Plantation
(DFM) (Figure 1), located in Block 88 (N 01
o
23.827’
E 111
o
24.845’), Betong, Sarawak. This plantation
belongs to WTK Sdn Bhd with palms from 6 to 13
years old. It has an area of about 5022 ha and located
approximately 35 km from Betong town. Adjacent
Figure 1. Map of the sampling site at the Durafarm Oil Palm Plantation, Block 88, Betong, Sarawak, Malaysia.
419
THE DIET OF YELLOW-VENTED BULBUL (Pycnonotus goiavier) IN OIL PALM AGRO-ECOSYSTEMS
to this plantation is a peat swamp forest which was
logged about 20 years ago and has been earmarked
for oil palm development.
Field Method
Mist-net. In order to capture the bulbul, more than
10 mist-nets were set up at DFM. The nets were
deployed in three rows with ve nets per row. The
nets were operated from 6.00 am until 6.00 pm
for three days during each sampling periods and
checked at every 2 hr interval (Rahman and Tuen,
2006). The captured Yellow-vented Bulbul (Figure 2)
was placed in a cloth bag.
Laboratory Technique
Analysis of stomach content. The stomach contents
were classied into insect parts and others such
as plants, and arthropods. Identication of insect
species present in the stomach was done by
examining the samples under microscope and the
prey items found inside the stomach were identied
up to the Order level. The insect parts were identied
based on Borror et al. (1954) and Triplehorn and
Johnson (2005). The insect parts detected were head,
mouthparts, elytra, mandibles, body structure, legs
and wings. The insect parts were observed using
a compound microscope with a camera attached.
The images were taken by using Motic Image Plus
Version 2.0 software with resolution of 1600 x 1200
pixels and the magnication lens were adjusted
between the range of 2.0 7.5. The identied insect
parts were sorted and recorded up to their respective
Orders.
Statistical Analysis
Statistical analysis was carried out using
statistical package for social sciences (SPSS-Version
17). Pearson’s correlation coecient (r) measures the
closeness of the relationship between the abundance
of insect per month and the distribution of Yellow-
vented Bulbul per month in DFM. The value for a
Pearson’s can fall nearer to +1 or -1which shows the
perfect relationship between the two variables.
Ivlev’s Electivity Index
Ivlev’s electivity index (E) was used to measure
the degree of food selection by the Yellow-vented
Bulbul in DFM towards a particular prey species.
It is commonly used to compare the feeding habits
of predator with the availability of potential food
resources in the natural habitats (Strauss, 1979). The
relationship is dened as:
r
i
- p
t
E = ,
r
i
+ p
t
where,
E = measure of electivity;
r
i
= relative abundance of prey item i in the gut
(as a proportion or percentage of the total gut
contents); and
p
t
= relative abundance of the same prey item in the
environment.
The possible range of the index is - 1 to + 1. The
negative value indicates avoidance or inaccessibility
of the prey item, zero indicates random selection
Figure 2. Yellow-vented Bubul captured in the Durafarm Oil Palm
Plantation, Betong, Sarawak, Malaysia.
Out of 56 individuals recorded in this site, 45
individuals (80% of the total individual captured in
DFM) were dissected for stomach content analysis
and another 11 individuals were released back to
DFM. The stomach of each bird was dissected open
on site, washed and the contents rinsed into a vial
containing 70% ethanol for laboratory analysis
(Seefelt and Gillingham 2006; Durães and Marini,
2005). The samples were transported to a laboratory
in the Universiti Malaysia Sarawak (UNIMAS),
Sarawak, Malaysia for further analysis.
Distribution of food resources. A transect survey
for insects and fruits was carried out by walking
along the harvesting paths at Block 88, DFM. Three
line transects (50 m length for each transect) were
established at each row where the nets were set
up. This survey was carried out during the same
sampling day. All the insects and fruits available
along transect were recorded. Identication for
insects was done to the Order level only. Species of
fruit found along the trail which cannot be identied
on site were collected and brought to UNIMAS
laboratory for further identication.
Journal of oil Palm research 27 (4) (DecemBer 2015)
420
from the environment and positive values indicate
active selection (Strauss, 1979).
RESULTS AND DISCUSSION
Availability of Food Resources (insects and plants)
in Oil Palm Plantation
Agricultural ecosystem such as oil palm
plantation provides a source of food to many birds
in the form of grain, seeds, insects and rodents
(Asokan et al., 2009). Insects are one of the major
preys consumed by birds in oil palm plantation
(Chenon and Susanto, 2006; Koh and Wilcove,
2007). However, there is limited information on the
diversity of insects in oil palm plantation in relation
to bird diversity. Turner et al. (2008) and Turner
and Foster (2009) have reported on the impact of
conversion of forest to oil palm plantations on
inverterbrate biodiversity.
In this study, the distribution of food resources
(insects and fruits) in DFM was carried out by
walking along the line transect where the mist-
nets was set up. The results showed that a total
of 687 individuals from nine Orders of insects
were recorded for 10 times of sampling (Figure
3). The Order Hymenoptera (60.67%) especially
from the family Formicidae was most abundant,
followed by the Orders Diptera (13.50%), Odonata
(9.00%) and Hemiptera (6.17%). The abundance
of Hymenopterans from the family Formicidae
in oil palm plantation supported the ndings by
Turner and Foster (2009) and Bawa et al. (2011).
Family Formicidae is very important to the oil palm
ecosystem, aiding in decomposition, pollination and
preying on other pests besides acting as food sources
for predators such as birds (Turner and Foster, 2009).
The Order Homoptera was the least abundant insect
Order in DFM plantation.
In terms of fruit survey, Melastoma sp. was the
only fruit plant species recorded at the study site
besides oil palm fruitlet. In plantation management,
this noxious weed (Melastoma sp.) has to be
controlled due to competition with the oil palm for
nutrient, moisture and light (Barnes and Luz, 1990).
Plant diversity in oil palm plantation is restricted
to several adaptable natural ground cover or local
vegetation such as ground and epiphytic ferns (Koh,
2008).
Distribution of P. goiavier in DFM
A total of 56 individuals of P. goiavier were
captured in DFM through mist-netting methods.
The distribution of this bird in DFM throughout the
study period is shown in Figure 4. In this study, the
Yellow-vented Bulbul was abundant in February.
This is due to the breeding season for this bird,
being early in the year between January to March
(Myers, 2009), and they actively go out to search for
food to feed the nestlings. However, in November,
lesser number of this species was captured due to
the rainy season at the end of the year. The capture
rates of birds decreased during the rainy day
because the birds seldom forage for food during the
rain (Tuen et al., 2006; Gouk, 2009). The presence of
insect in oil palm plantation play an important role
to support the survival of birds that prey on insects
(Chenon and Susanto, 2006; Koh and Wilcove, 2008).
In this study, there is a weak negative relationship
between the distribution of Yellow-vented Bulbul
and abundance of insect in oil palm environment
(r= -0.218). This value indicates that as the number
of Yellow-vented Bulbul increases, the number of
insect in oil palm environment decreases.
Yellow-vented Bulbul and its Diet in Oil Palm
Plantation
In the study on the dietary of birds, there are some
factors that should be included in our explanation
such as foraging height, use of plant species,
habitat selection and competition (MacArthur, 1958;
Morse, 1968; Perrins and Birkhead, 1983). Hence,
the presence of prey items in the stomach and
availability of insect diversity in the environment
can be used to determine the diet selection of birds
at dierent habitats.
Figure 3. Percentage of individuals of each order of insect recorded in
the Durafarm Oil Palm Plantation (DFM) for 10X sampling through
line transect survey.
Figure 4. Total individuals of P. goiavier in the Durafarm Oil Palm
Plantation (DFM) at dierent months and years.
Percentage (%)
Hymenoptera
Diptera
Odonata
Hemiptera
Orthoptera
Lepidoptera
Coleopetra
Dictyoptera
Homoptera
Months
Feb-11 May-11 Jul-11 Nov-11 Jan-12 May-12 Jul-12 Nov-12 Feb-13 May-13
00 20.00 40.00 60.00 80.00
60.67
13.50
9.00
6.17
5.00
3.83
1.33
0.33
0.17
12
8
5
3 3
6
4
0
10
5
421
THE DIET OF YELLOW-VENTED BULBUL (Pycnonotus goiavier) IN OIL PALM AGRO-ECOSYSTEMS
A total of 45 individuals (80% of the total
individuals of P. goiavier recorded in DFM) of
P. goiavier were dissected to extract their stomach
samples. The insect parts found in the stomach were
grouped according to the Orders. Table 1 shows
the number of species and individuals of plant,
annelids and insects according to dierent Orders
and families found in the stomach of Yellow-vented
Bulbul at DFM. Some insect parts that had been
digested and could not be identied were recorded
as unidentied parts. Examination of stomach
content of P. goiavier showed that they feed on insects
as well as on annelids, small berries, leaets and oil
palm fruitlets (Figures 5, 6 and 7).
The Ivlev’s electivity index was used to measure
the degree of selection by the predator towards a
particular prey species. Table 2 showed the Ivlev’s
electivity index for dierent insect Orders by Yellow-
vented Bulbul.
The results showed that the Orders Coleoptera
(E= +0.97) and Homoptera (E= +0.87) were mainly
selected as prey items by P. goiavier and this result
reected that these Orders as the main food sources
for this adaptable species in oil palm plantation. This
bird seems to exclusively select as their food from the
Coleopteran family Curculionidae (the pollinating
weevil, Elaeidobius kamerunicus). This nding is
similar to that of Chenon and Susanto (2006) who
conducted their study at Bah Jambi and Bukit
Maradja, Indonesia. Elaeidobius kamerunicus is one of
the most important weevils in oil palm plantation.
This species play an important role to increased
pollination and fruit production from 20% to 30%
(Syed, 1982; Basri et al., 1983). Other Coleopterans
TABLE 2. IVLEV’S ELECTIVITY INDEX OF DIFFERENT ORDERS
No. Order of insect Relative abundance of
prey item in the gut, ri
Relative abundance of the same
prey item in the environment, pi
Measure of
electivity, E
1 Coleoptera 85.37 1.33 +0.97
2 Homoptera 2.44 0.17 +0.87
3 Diptera 7.32 13.50 -0.30
4 Hemiptera 2.44 6.17 -0.43
5 Hymenoptera 2.44 60.70 -0.92
6 Odonata 0.00 9.00 -1
7 Orthoptera 0.00 5.00 -1
8 Dictyoptera 0.00 0.33 -1
9 Lepidoptera 0.00 3.83 -1
TABLE 1. NUMBER OF SPECIES AND INDIVIDUALS OF PLANT, ANNELIDS AND INSECTS FOUND IN THE GUT OF
YELLOW-VENTED BULBUL
Order Family Number of species Number of
individual
Plant species - - 8 11
Annelids Haplotaxida - 2 2
Insects Diptera Culidae 3 3
Hemiptera Unidentied 1 1
Hymenoptera Formicidae 1 1
Homoptera Cicadellidae 1 2
Coleoptera Staphylinidae 1 1
- Scolytidae 1 1
- Curculionidae 1 30
Unidentied - 1 1
Journal of oil Palm research 27 (4) (DecemBer 2015)
422
Figure 7. Other samples found in P. goiavier gut: (A) class annelids; earthworm, (B) order annelids, (C) small berries, (D) oil palm bres,
(E) oil palm bres and grass, and (F) grass part.
Figure 5. Elaeidobius kamerunicus parts found in P. goiavier: (A) rostrum and antenna, (B) body, (C) elytra and (D) legs.
Figure 6. Some of the insect parts found in P. goiavier gut: (A) Order Coleoptera; family Staphylinidae, (B) Order Coleoptera; family Scolytidae,
(C) Order Homoptera; body part, (D) Order Homoptera; mouth part, (E) Order Diptera; family Culicidae, (F) Order Diptera; family Culicidae,
(G) Order Hymenoptera; family Formicidae, and (H) Order Hemiptera; hind wings.
consumed by this bulbul are the bark beetles
(Scolytidae) and rove beetles (Staphylinidae) with
2.2% each from the total Order Coleoptera recorded
in their gut. Other Orders such as Hemiptera (E=
-0.43) and Diptera (E= -0.30) was selected by P.
goiavier as prey based on abundance. P. goiavier tries
to avoid preying on the Order Hymenoptera (E=
-0.92) in the oil palm environment. This bird also
avoids the Orders Odonata, Orthoptera, Dictyoptera
and Lepidoptera. These Orders were present in the
DFM but were absent in the birds gut.
This bird also feeds on oil palm fruitlets as
revealed by the presence of some palm fruit bres
in stomach content; and this was not reported
by Chenon and Susanto (2006). In terms of fruit
survey along the line transect in oil palm plantation,
Melastoma sp. was the only species of plant that was
recorded to produce fruit besides oil palm. A total
423
THE DIET OF YELLOW-VENTED BULBUL (Pycnonotus goiavier) IN OIL PALM AGRO-ECOSYSTEMS
of eight individuals of this bird fed on unidentied
plant species in oil palm plantation. This result
shows that Melastoma sp. is not the only fruiting
plant in the oil palm plantation because there were
other unidentied berries recorded in their stomach
content.
CONCLUSION
In an oil palm habitat, P. goiavier mainly select
the Order Coleoptera (specically from family
Curculionidae, Staphylinidae, and Scolytidae) as
their prey, followed by Homoptera (Cicadellidae),
Diptera (Culidae), Hemiptera and Hymenoptera
(Formicidae). This species avoids feeding on insects
from the Order Odonata, Orthoptera, Dictyoptera
and Lepidoptera. Even though the oil palm habitat
is providing food sources for this bird species to
continue their survival, further study is needed
on the eect of this bird population on oil palm
pollinating weevil and seasonal variation in their
diet.
ACKNOWLEDGEMENT
The authors would like to thank the Director-
General of MPOB for permission to publish this
article. They also wish to thank the sta from
TROPI, MPOB and the Institute of Biodiversity and
Environmental Conservation (IBEC), UNIMAS for
their great support and invaluable assistance.
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... Some bulbul species such as the grey-headed bulbul (Balakrishnan, 2014) and the common bulbul (Okosodo et al., 2016) consumed slightly more fruits in their diets. Although mixed-diets enable them to easily forage in a small home-range, the Yellow-vented Bulbul has one of the broadest foraging niches among the nonforest passerines (Ward, 1969;Fishpool and Tobias, 2005;Bettycopa et al., 2015). So far, there is no detailed information about the diet items consumed by the Yellow-vented Bulbul offsprings. ...
... Adult bulbul diets constituted 60-90% of plant species i.e., fruits, leaves, nectar (e.g. Bhatt and Kumar, 2001;Mandon-Dalger et al., 2004;Milla et al., 2005;Linnebjerg et al., 2010;Kerdkaew et al., 2014;Bettycopa et al., 2015;Oksodo et al., 2016) while invertebrates and vertebrates (if any) constitute about 10-35% of their diets (e.g. Bhatt and Kumar, 2001;Okosodo et al., 2016). ...
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The parental care strategy and diet requirements of the yellow-vented bulbul Pycnonotus goiavier chicks were studied. The assessment was conducted based on the (1) number of feeding bouts (bouts/hour), (2) average time intervals between each feeding (minutes/bouts) (3) feeding strategies (perch-go-in or direct-go-in) and (4) types of food items carried to the nest to feed the chicks. A total of 6000 minutes of direct observation from a close distance was performed for 10 days from 28th May 2016 until 6th June 2016 between 0700-1900 hours. Out of 816 independent feeding bouts, the parents preferred the perch-go-in (80.03%) as compared to the direct-go-in (19.97%) feeding strategy to feed the chicks in their nest. The average time spent for feeding was 7.50 ± 3.84 minutes / bout (7.50 ± 1.23 bouts/h), with the least number of bouts during the morning feeding time at 5.68 ± 3.09 bouts/h. The most frequent food items comprised of invertebrates such as dragonflies (16.15%) and grasshoppers (11.35%) and fruits including Murraya koenigii (14.02%). The success of raising both the chicks depended on the nest placement, feeding strategy, food availability, predation risk and commitment of both parents.
... The variation in EK population among the hybrids may be as a result of natural enemies, which included, but were not limited to, rodents, birds, and spiders as the most compelling evidence. Earlier studies showed that the larvae of this important and efficient oil palm pollinator weevil had been used as feed by predators such Pycnonotus goiavier bird species, ants, and rats [41,49]. An increase in the Rattus tiomanicus population caused extreme damage to oil palm inflorescences [50]. ...
... HA and Dzulhelmi [50] reported that the decline in fruit-set was likely due to an increase in natural enemies or insecticide applications against the E. kamerunicus or other predators. The yellow-vented predator bird, Pycnonotus qoiavier, was affirmed in Malaysian palm plantations to consume this noteworthy oil palm pollinator weevil as over 80% of its diet [49]. The variation in E. kamerunicus population among the hybrids may also be associated with the weevils being less active at pollination, especially during unfavorable conditions. ...
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This study was conducted to assess the Elaeidobius kamerunicus (EK) population density among the biparental dura × pisifera hybrids’ palms on deep peat-soil. Twenty-four hybrids derived from 10 genetic sources were used. Variance analysis showed that the EK population density varies between different oil palm hybrids, with a more noticeable variation of a low population mean in the male weevil across the hybrids. The highest weevil population mean/spikelet was attained on the third day of anthesis. The maximum monthly population of EK/spikelet (12.81 ± 0.23) and population density of EK (1846.49 ± 60.69) were recorded in January. Accordingly, 41.67% of the hybrids recorded an EK population density greater than the trial means of 973.68 weevils. Hybrid ECPHP550 had the highest mean of EK/spikelet (10.25 ± 0.11) and the highest population density of EK/palm (1241.39 ± 73.74). The parental mean population was 963.24 weevils and parent Deli-Banting × AVROS recorded the highest EK population density (1173.01). The overall results showed a notable disparity in the EK population among the biparental hybrids. Parental Deli-Banting × AVROS and hybrid ECPHP550 could be more useful to optimize the weevil population for pollination improvements in palm plantations. However, we suggest that volatile production should be included as a desirable trait in oil palm selective breeding.
... Orthotomus sp., was observed only feeding on the pollinating weevil Elaeidobius kamerunicus. Even Pycnonotus aurigaster also reported to feed on the weevil [25]. In this case, bird species like these may deplete the weevil population, resulting in a lower fruit set. ...
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Indonesia has declared the green economy paradigm; as one of the strategic sectors in implementing the green economy, oil palm plantations are expected to start reducing the use of chemical fertilizers, fungicides, pesticides and etc. Additionally, oil palm plantations are expected to be able to optimize the roles of biodiversity in oil palm plantations. So, it will enhance sustainable and environmentally friendly plantation management. Therefore, there is a need for further studies on the species potential and role of birds in oil palm plantations. The study was conducted on four types of land cover at PT Gunung Tua Abadi (PT GTA) with a line transect method in the morning and afternoon with three repetitions. The number of bird species in the Young Oil Palm (YP) is as many as 20. Meanwhile, the lowest number of species was found in Medium Oil Palm (MP) and Old Oil Palm (OP), as many as 10 species. In addition, if grouped by a guild, the birds in PT GTA belong to 8 guilds. Each type of guild is thought to have its role to assist in oil palm operations, including the role of controlling insect pests ( Centropus sinensis, Centropus bengalensis, Collocalia linchi ); seed dispersal ( Trerons vernans ), and also as pest control ( Tyto alba, Elanus caeruleus ). Further research is needed to determine more deeply the effectiveness of the role of each bird species in oil palm plantation.
... The results of this study are consistent with Hawa et al. (2016), who reported these birds' species in oil palm plantations. Amit et al. (2015) also mentioned that the most dominant species in oil palm plantation was Yellow-vented Bulbul and stated that this species feed on oil palm pollinators weevil such as Elaeidobius kamerunicus. The abundance of these birds relies on the thickness of the vegetation cover, which provides refuge from predators which possibly related to their anti-predator strategies and provides food resources (such as arthropods and seeds) (Azhar et al. 2011;Tamaris et al. 2017;Ashton-Butt et al. 2018). ...
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It is well established that oil palm is one of the most efficient and productive oil crops. However, oil palm agriculture is also one of the threats to tropical biodiversity. This study aims to investigate how set-aside areas in an oil palm plantation affect bird biodiversity. The research area includes two set-asides areas: peat swamp forest and riparian reserves and two oil palm sites adjacent to reserved forest sites. A total of 3,074 birds comprising 100 species from 34 families were observed in an oil palm plantation landscape on peatland located in the northern part of Borneo, Sarawak, Malaysia. Results showed that efforts by set-asides forest areas in large scale of oil palm dominated landscapes supported distinct bird species richness. High percentage of the canopies and shrub covers had a positive effect on bird species richness at area between oil palm and peat swamp forest. Herbaceous cover with height less than 1 m influenced the abundance of birds in the plantation closed to the peat swamp forest. The set-aside areas in oil palm plantations are essential in supporting bird’s refuges and should be part of oil palm landscape management to improve biodiversity conservation. Thus, provided the forest set-aside areas are large enough and risks to biodiversity and habitat are successfully managed, oil palm can play an important role in biodiversity conservation.
... For example, the positive effect of nearby forest on fruit set might be explained by intraguild predators (i.e., consumers of both mesopredators and their shared pollinator prey), such as birds and bats that spill over from the forest (Karp and Daily, 2014;Martin et al., 2013). Though such larger predators can potentially disrupt pollination services by consuming E. kamerunicus (Amit et al., 2015;Ponnamma et al., 2006;Yue et al., 2015), they could also decrease overall predation pressure on E. kamerunicus and other pollinators if they simultaneously reduce mesopredators that more effectively suppress pollinator activity (Polis and Holt, 1992). In a bird and bat exclusion experiment in oil palm in Jambi, Denmead et al. (2017) found that increased bird activity was associated with lower arthropod predator abundance and higher E. kamerunicus abundance, consistent with a release effect. ...
Article
Natural habitat plays a role in many agroecosystems as a source of pollination services and other ecological spillover, but these effects are largely unquantified in oil palm (Elaeis guineensis), a globally important crop linked to deforestation. In a field experiment in Sumatra, Indonesia, we manipulated floral visitor access to female oil palm inflorescences over a 100 m distance gradient from forest into oil palm and sampled insects with sticky traps placed above male and female inflorescences. Full exclusion of floral visitors decreased mean oil palm fruit set to 12%, demonstrating that insect pollination was necessary to maintain favorable fruit set and yield. Treatment group means of fruit set under open pollination (62%) and when excluding large (>1.4 mm diameter) organisms (72%), did not differ significantly from open pollination augmented with hand pollination (61%), suggesting no difference in pollen limitation. In contrast, when we examined change in fruit set with distance from forest, we found a significant trend of higher fruit set in oil palms closer to the forest when large organisms were excluded, which increased estimated fruit set at the forest edge to 87%, compared to open-pollinated palms (70%). This trend with distance from forest was absent when we fully excluded floral visitors, showing that the effect of forest was not likely due to an abiotic gradient (e.g., changing soil nutrients). Of the arthropod taxa collected from sticky traps, Drosophilidae (Diptera) and Gelechiidae (Lepidoptera) decreased and increased with distance from forest, respectively. The taxa Elaeidobius kamerunicus (Coleoptera: Curculionidae), Gelechiidae, and the families Thripidae and Phlaeothripidae (Thysanoptera) were abundant on both male and female inflores-cence sticky traps. Elaeidobius kamerunicus, an introduced oil palm pollinator, had the only significant relationship with fruit set. Our results confirm pollination by insects as a key ecosystem service for oil palm production. Although further work is needed to clarify the relationship between fruit set, biodiversity, and distance from forest, we speculate that excluding large organisms could have increased fruit set closer to forest by mediating interactions between pollinators, forest predators, and farm mesopredators. Understanding the relationships between nearby forest and pollination services could better connect oil palm production to its landscape context and associated biodiversity. This would be important for landscape-scale conservation planning that considers both the ecosystem service needs and ecological impacts of oil palm agriculture.
... It has been reported that poor fruit formation indicates insufficient pollination due to the low population of the oil palm pollinating weevil (Prasetyo et al. 2014). The population of the weevil is affected by various factors such as excessive insecticide application (Asib & Musli 2020;Ismail et al. 2020;Ming & Bong 2017;Prasetyo et al. 2018;Prasetyo & Susanto 2019;Yusdayati & Hamid 2015), predator activities (Amit et al. 2015;Muhammad Luqman et al. 2017) and spikelet number/characteristics (Latip et al. 2018;Mohamad et al. 2020). In addition to pollination efficiency, the soil types also influenced the production of the crop. ...
Article
Full-text available
The oil palm pollinating weevil, Elaeidobius kamerunicus, plays a vital role in the oil palm fruit formation process. An insufficient pollinator population may cause poor fruit set formation, resulting in a high number of parthenocarpic fruitlets and malformed fruit bunches. This study examines the population level of E. kamerunicus at two sites in Peninsular Malaysia and its relation to the fruit set formation. Each site represented different soil types, viz, mineral and peat soil. Preliminary results of the study showed that both sites had high adult weevil population density, averaging at 68662.87/hectare and 89270.93/hectare for peat soil and mineral soil, respectively. The average sex ratio of inflorescences in peat soil area (58.09%) was significantly higher than those at mineral soil area (45.01%, F = 6.75, P = 0.016). The average fruit set percentage in both study areas was satisfactory (more than 60%). The average fruit set in mineral soil area (83.08%) was significantly better than those recorded at the peat soil area (69.47%, F = 4.42, P < 0.05). Even though there are differences in terms of the population level of the pollinator, the fruit set formation in both areas is still satisfactory. © 2021, Penerbit Universiti Kebangsaan Malaysia. All rights reserved.
... Jenis semut yang disebutkan pertama bersifat karnivora, sedangkan jenis-jenis lainnya lebih generalis dalam hal mencari makanan. (Amit et al. 2015) yang teramati dalam penelitian ini ataupun bagi jenis Pycnonotidae lain pada umumnya (Linnebjerg et al. 2010). Serangga pada umumnya juga menjadi bagian kecil dalam makanan burungburung dari keluarga Nectariniidae, Ploceidae, dan Estrildidae (Zweers et al. 1994;Cheke et al. 2001). ...
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Stingless bees have been considered as the excellent option in the apiary sector as they produce valuable products such as honey, bee pollen and wax. Apiary business with stingless bee at its core has shown progressive increment especially in West Sumatra. Therefore, to maximize the production of the stingless bee apiary, knowing detrimental predator or pest organisms as well as the way of managing them are essential. This article described potential predators and pests of stingless bee identified through rapid observation conducted on 14 April 2019 at a community apiary in Padang Pariaman Regency, West Sumatra. There were 17 predators and pests identified, consist of six bird species, five odonate species and six ant species. The predation, competition and disadvantage possibly emerge from the existence of these organisms around stingless bee apiary are discussed, along with the feasible mitigation effort.
... Jenis semut yang disebutkan pertama bersifat karnivora, sedangkan jenis-jenis lainnya lebih generalis dalam hal mencari makanan. (Amit et al. 2015) yang teramati dalam penelitian ini ataupun bagi jenis Pycnonotidae lain pada umumnya (Linnebjerg et al. 2010). Serangga pada umumnya juga menjadi bagian kecil dalam makanan burungburung dari keluarga Nectariniidae, Ploceidae, dan Estrildidae (Zweers et al. 1994;Cheke et al. 2001). ...
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Stingless bees have been considered as the excellent option in the apiary sector as they produce valuable products such as honey, bee pollen and wax. Apiary business with stingless bee at its core has shown progressive increment especially in West Sumatra. Therefore, to maximize the production of the stingless bee apiary, knowing detrimental predator or pest organisms as well as the way of managing them are essential. This article described potential predators and pests of stingless bee identified through rapid observation conducted on 14 April 2019 at a community apiary in Padang Pariaman Regency, West Sumatra. There were 17 predators and pests identified, consist of six bird species, five odonate species and six ant species. The predation, competition and disadvantage possibly emerge from the existence of these organisms around stingless bee apiary are discussed, along with the feasible mitigation effort.
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Sarawak is Malaysia’s largest state, covering most of northern Borneo. It has a remarkable history of scientific bird study, starting in the 1840s and growing ever since. To set the stage for the gazetteer, which is the core of this paper, we start with a review of this history and discuss various forces that have influenced the direction of bird research in the state. Following this introduction comes the gazetteer, which is an annotated list of c. 865 sites in Sarawak where birds have been collected, studied, or regularly observed. The gazetteer provides the latitude, longitude, and elevation of each site, and it lists publications, reports, and museum collections associated with each site. The purpose of the gazetteer is to help interested parties locate sites and investigate their research history. It is also intended to help museum curators geolocate specimens for various kinds of studies, including the assessment of bird distributions in relation to habitat change over time. A notable byproduct of the historical review and gazetteer is a bibliography of c. 750 references related to Sarawak ornithology. Another is the identification of areas in Sarawak where birds are better known and areas where they are not.
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Urbanisation is the transformation of a natural ecosystem into more artificial habitat to give way for development and is occurring at an unprecedented rate globally. The urban expansion involves alterations of urban landscapes, resulting in habitat loss and threatening biodiversity. Landscape attributes of urban areas are known to influence urban bird composition, but to what extent is still poorly understood. Thus, several urban areas in west Peninsular Malaysia with varying intensity of urbanisation were chosen to determine the effect of landscape attributes on bird communities. A total of 4936 individual birds from 20 species representing 14 families, were recorded throughout the observations, dominated by Corvidae (crows). Based on the functional groups, only garden birds and omnivory feeding guild showed a significant difference in their abundance among different urban sites. Omnivory was the most abundant feeding guild (80%), dominated by House crow (Corvus splendens). This study shows that species composition is not influenced by level of urban intensity, but by the landscape attributes of each urban area. Multiple Regression analysis indicated that water bodies and roads significantly predicted species richness of birds, whereas high vegetation cover, road, and open area significantly predicted bird abundance. The canonical correspondence analysis (CCA) ordination indicated that urban birds are not selective of landscape attributes, unlike other bird groups. This study revealed that heterogeneity of landscape attributes is essential to enhance bird composition and ultimately biodiversity in urban areas, thus key factors in designing ecocentric cities.
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Insect species of sole oil palm, sole cocoa and oil palm cocoa intercrop was studied at the CSIR-Oil Palm Research Institute; on plot K4 while cocoa monocrop at a farm on the boundary of the Institute’s plantation at Kusi, in the Eastern Region of Ghana. The objective was to identify the occurrence and relative abundance of these insect species in oil palm-cocoa intercrop to compare these insects with existed ones in oil palm and cocoa monocrops over a period of six months (September 2008 to February 2009). Chemical knockdown application method by fumigation was employed to collect insect. An area 0.5 ha plot each was demarcated for the treatments; i.e oil palm monocrop, cocoa monocrop and oil palm-cocoa intercrop. The oil palm and cocoa plantations were 29 years and 21 years respectively. Vinyl sheets measuring 2.8 X 8 m each were placed beneath the selected trees for the insect collection, and the trees were hot-fogged early in the morning between 5:00–7:30am with Plan D EC25 insecticide (Deltamethrin 25g active ingredient/L) at a rate of 20ml insecticide/ 4.5 l of diesel using a Puls FOG machine (K-10SP). Results showed that relatively more insects occurred in the oil palm-cocoa intercrop compared to the oil palm and cocoa monocrops. Insect species belonging to six orders were collected as follows; Hymenoptera (12), Coleoptera (30), Diptera (10), Hemiptera (6), Thysanoptera (1) and Orthoptera (1). Oecophylla longinoda Latr. was the dominant insect species in studied plots. There were more beneficial insect species (predators and parasitoids) in the intercrop when compare to the monocrops. There were significant differences (p < 0.001) in the number of insect species between cocoa monocrop and oil palm monocrop, similarly oil palm monocrop and oil palm-cocoa intercrop. However there was no significant difference (p > 0.001) species between cocoa monocrop and oil palm-cocoa intercrop. The study revealed that the two crops do not have common insect pests and in association will not compound insect pests problem of either crop.
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The diversity and the feeding guilds of birds in three different habitats (secondary forest, oil palm plantation and paddy field) were investigated in riparian areas of the Kerian River Basin (KRB), Perak, Malaysia. Point-count observation and mist-netting methods were used to determine bird diversity and abundance. A total of 132 species of birds from 46 families were recorded in the 3 habitats. Species diversity, measured by Shannon's diversity index, was 3.561, 3.183 and 1.042 in the secondary forest, the paddy field and the oil palm plantation, respectively. The vegetation diversity and the habitat structure were important determinants of the number of bird species occurring in an area. The relative abundance of the insectivore, insectivore-frugivore and frugivore guilds was greater in the forest than in the monoculture plantation. In contrast, the relative abundance of the carnivore, granivore and omnivore guilds was higher in the plantation. The results of the study show that the conversion of forest to either oil palm plantation or paddy fields produced a decline in bird diversity and changes in the distribution of bird feeding guilds.
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Ivlev's electivity index and the forage ratio, two commonly used measures of food selection, are significantly biased when the sizes of the prey samples from the gut of the predator and the habitat are unequal. Approximate confidence-interval expressions are derived for these indices. A stochastic (Monte Carlo) model was used to validate these expressions and to explore the statistical properties of the indices. The statistical reliability of each index is shown to be a function of the absolute and relative sample sizes and the relative abundances of the prey species in the environment. A linear index of food selection is proposed which avoids most of the statistical and mathematical inadequacies of these indices. Regardless of the index used, however, inadequate habitat sampling, differential availability of prey to the predator, and differential digestion of prey may be significant sources of error in the interpretation of food selection data.
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Ivlev's electivity index and the forage ratio, two commonly used measures of food selection, are significantly biased when the sizes of the prey samples from the gut of the predator and the habitat are unequal. Approximate confidence-interval expressions are derived for these indices. A stochastic (Monte Carlo) model was used to validate these expressions and to explore the statistical properties of the indices. The statistical reliability of each index is shown to be a function of the absolute and relative sample sizes and the relative abundances of the prey species in the environment. A linear index of food selection is proposed which avoids most of the statistical and mathematical inadequacies of these indices. Regardless of the index used, however, inadequate habitat sampling, differential availability of prey to the predator, and differential digestion of prey may be significant sources of error in the interpretation of food selection data.
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Contents of 78 stomachs from four widespread and sympatric species of Amazonian woodcreepers (Dendrocolaptidae) were examined to assess the role of diet in resource partitioning. Orthopterans (25-35%) and beetles (10-32%) dominated the diets of all four species, despite large differences in foraging behavior. A higher proportion of spiders in the diet of Dendrocincla merula was associated with specialized ground-foraging at army ant swarms; however, specialization on dead leaves by Xiphorhynchus guttatus resulted in no significant dietary differences from the substrate generalist X. spixii. Overlap in diet was much greater than overlap in behavior for all species pairs, and the degree of diet specialization was unrelated to behavioral specialization. Taxonomic representation of prey in stomach contents differed significantly from field sampling of available prey in the three species tested, with orthopterans apparently selected by all species and beetles selected by D. fuliginosa. We suggest that behavioral differences may have evolved to reduce overt aggression (interference competition) but may not serve to reduce diffuse competition for food among syntopic species. Segregation in substrate use, however, may allow high diet overlap, suggesting a case of niche complementarity among these species.
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The effectiveness of stomach flushing as a method for determining diet was tested experimentally on captive white-fronted chats, Ephthianura albifrons. The relative retrieval rates of six taxa of prey depended on their size and the durability of identifiable parts. For Scatella sp. (Diptera), flushing was best performed 15 min after ingestion. Stomach flushing produced a better recovery rate (up to 70% of fly wings) than faecal analysis (2%). Birds were each flushed 14 times without mortality and recapture rates of 319 wild birds which had been flushed did not differ from 364 unflushed birds.
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Bird ecology and behaviour are considered from an evolutionary point of view in the sense that the authors discuss various aspects of avian biology in terms of their functions or adaptive significance. Following an introduction which considers the idea of natural selection, Chapter 2 looks at territoriality and coloniality. Chapter 3 examines different kinds of breeding systems - mating systems themselves, brood parasitism, and cooperative breeding. Reproduction itself is discussed in the next 2 chapters firstly by exploring the significance of breeding seasonality, and then by considering why clutch sizes might vary within as well as between species. In Chapter 6, a review is made of life cycle and population studies, not only in terms of demography and the natural control of population density, but also regarding practical applications, eg. species protection, control of pest bird species, and management of game birds. Bird communities are the focus of Chapter 7, with ideas on ecological niche, competition, and island biogeography mooted. Foraging behaviour is then examined, with information on decisions made on what and where to eat, on central place foraging, and on solitary versus group (flock) feeding; the notion of optimization is used in attempts to explain bird decisions. In Chapter 9, migration and other forms of movement are discussed.-P.J.Jarvis Edward Grey Inst of Field Ornithology, Univ of Oxford, UK.