INTRODUCTION
Thuong Tien Natural Reserve, spanning 7,308 hectares in Hoa Binh province's Thuong Tien and Quy Hoa communes, features a rich evergreen forest ecosystem characterized by a multi-layered structure Recognized as a gateway to the northwest ecoregions, this reserve is home to numerous rare plant and animal species endemic to Vietnam and the Indochina Peninsula Given its high faunal diversity, effective conservation and management strategies are essential, particularly for challenging wildlife species such as birds To ensure successful biodiversity monitoring and management, it is crucial for conservationists to gather accurate data on species diversity, population size, and density through quantitative survey methods.
Estimating the density and population size of animals presents unique challenges compared to plants Key difficulties include the low detection probability (less than 1) due to limited human resources and time for surveys, restricted visibility for smaller wildlife, the mobility of animals, and dense vegetation that obscures sight.
Before the widespread adoption of distance sampling methods, traditional survey techniques that did not account for detection probability were commonly employed These methods required the assumption that all individuals within the survey area were equally detectable, regardless of their proximity to the transects However, this assumption often fails, particularly in environments like tropical forests where limited visibility and the lack of distinct colors or calls make wildlife difficult to detect As a result, individuals located away from the transects may go unnoticed, leading to an underestimation of species density when using traditional survey methods.
To effectively detect all individuals in a survey, investigators can utilize narrow transects; however, this method is often inefficient A more effective approach for surveying large areas and achieving accurate density estimates is the distance sampling method This cost-effective technique estimates the absolute density of a population by analyzing the distance between the observer and the animals (Buckland et al 1993) By assessing how detection probability decreases with distance, distance sampling calculates the effective area sampled, allowing researchers to convert the observed counts into density estimates.
Distance sampling has emerged as a valuable method in wildlife studies globally, yet its application remains limited in Vietnam Accurately determining the density of bird species is crucial for effective management and conservation efforts, as well as for assessing the status of avian populations in the country This research utilizes distance sampling to estimate the density of several bird species, including the Black-crested Bulbul (Pycnonotus melanicterus), Puff-throated Bulbul (Alophoixus pallidus), and Yellow-bellied Warbler (Abroscopus superciliaris), which are relatively common in Thuong Tien Natural Reserve, Hoa Binh Province These species, belonging to the Passeriformes order, were detected through their distinctive calls and visual observations during the study.
OBJECTIVES
General objective
To provide the estimate of density of some birds species in Thuong Tien Natural reserve that can be used for management purpose.
Specific objective
1 To estimate detection probability of Black-crested bulbul (Pycnonotus melanicterus), Puff-throated bulbul (Alophoixus pallidus) and Yellow-bellied warbler (Abroscopus superciliaris) in Thuong Tien Natural reserve
2 To estimate the density of Black-crested bulbul, Puff-throated bulbul and Yellow-bellied warbler to serve for management work in Thuong Tien Natural reserve as well as make contribution to assess the status of bird species in Vietnam.
METHODS
Study area
Thuong Tien Natural reserve was established in 1995 by Decision No 676-QD /
The People's Committee of Hoa Binh province oversees an area of 7,308 hectares located in Thuong Tien commune of Kim Boi district and Quy Hoa commune of Lac Son district This region is positioned at geographical coordinates of 105° 20' to 105° 30' east longitude.
Thuong Tien Natural Reserve, located at 20°30' to 20°40' north latitude, features high mountainous terrain with elevations ranging from 300 to 1000 meters, including the prominent Cot Ca mountain range This reserve experiences a tropical monsoon climate with distinct wet and dry seasons, supporting a rich evergreen forest ecosystem characterized by a multi-layered structure The upper layer consists of large woody species such as Dipterocarpus retusus and Michelia balansae, while the lower layer is home to shade-tolerant trees like Syzygium cumini and Saraca dives, alongside a diverse shrub layer Spanning a total of 7,308 hectares, the reserve is divided into a strict nature reserve (1,496 ha) and an ecological restoration zone (5,812 ha) Recognized as a gateway to the northwest ecoregions, Thuong Tien is a habitat for numerous rare plant and animal species, boasting over 1,000 plant species and 300 animal species, making it a biodiversity hotspot in Hoa Binh province and the Indochina Peninsula.
Figure 3.1: Location of study area
Data collection
Necessary equipments for investigation, data collection are binoculars, cameras, notebook, data sheet, map of survey area, GPS
Data collection took place from late July to August through a survey along three designated transects in Khu hamlet, Thuong Tien Commune These transects were mapped within a regeneration forest, spanning elevations of 300-800 meters and measuring 3-4 kilometers each Utilizing the distance sampling method, the width of the transects was not predetermined; however, during data analysis, researchers excluded certain recorded distances to enhance estimation accuracy To minimize boundary effects, the selected transects were strategically located at least 75 meters from the status boundary.
To ensure independence, transects were established at least 100 meters apart and were marked one month prior to the survey for ease of navigation Each transect was surveyed six times, resulting in a total length of 54 kilometers.
Figure 3.2: Simulating objects detected in line transects
The survey was conducted in optimal weather conditions during the early morning to noon when bird activity is highest Investigators moved at a pace of approximately 0.5 km every 40 minutes, using special calls and binoculars to observe and record points of interest.
During object detection, we estimated and recorded the number of each species along with the perpendicular distance from the line transect to the observed object To accurately identify bird species, we referred to the resource "Birds of Southeast Asia" by Craig Robson (2005).
“Chim Việt Nam” (Nguyen Cu et al 2000)
There are two ways to estimate the perpendicular distance from the line transect to the object ):
1 Direct estimation of perpendicular distance from the line transect to the object )
2 Sighting distances and angles were used to calculate perpendicular distances by using simple trigonometry (perpendicular distance = *sin ) These methods are illustrated in Figure 3.3
Figure 3.3: Distance sampling measurement from a line-transect within the study area (Buckland et al 1993)
X = position of object w = width of line transect ri = sighting distance (flushing distance) θ i (theta) = sighting angle yi = perpendicular distance (note: y = ri*sin θi )
Birds typically inhabit groups, making it challenging to accurately estimate the number of individuals within a single group Therefore, each group is treated as an independent entity, and the results are presented in terms of "groups" or "individuals," depending on the study's objectives.
Data sheet used to collect the required information for this study (Table 3.1)
Table 3.1: Field data sheets used to collect information Site: ……… Investigator: ………
Transect number: …… Time start/finish: ………
No Coordinates Time Species Quantity Distance(m) Heard/Seen
Estimating detection probability
To estimate the density of an object from raw data, investigators must first determine the detection probability, which is then used to adjust the density estimates This detection probability is calculated based on the frequency distribution at varying distances from the transect or observer The data analysis was conducted using DISTANCE 6.0 software (Thomas et al., 2010).
To calculate the detection probability, investigators must first establish the detection probability function In the distance sampling method, four primary functions are commonly utilized to model how detection probability varies with distance.
In which, g(y) is the detection probability of an object, given that it is at distances y (unit length) and w , , , b are the estimated parameters of the equation
Besides the four basic functions, simple polynomials series expansion also can be used to model better the variation of detection probability with distance (Buckland et al
In certain situations, particularly with small sample sizes, the application of complex functions can be challenging This is due to the increased number of parameters that need to be estimated when incorporating series expansion, which in turn raises the variance of the estimation The relationship can be expressed as g(y) = basic function(y) + series expansion(y).
The optimal detection probability function is chosen using the Akaike’s Information Criterion (AIC), which balances standard deviation and variance (Anderson, 2007) The function with the lowest AIC value is preferred, and its suitability is validated using the standard χ2 test Once the best function modeling detection probability variation by distance is identified, the detection probability (p a) is estimated to adjust density calculations This density is then estimated for each transect as well as for the entire study area.
Estimating density of species
To correctly estimate density in distance sampling, six fundamental assumptions need to be met (Buckland et al 1993; Buckland and Turnock 1992; Focardi et al 2002):
1 Objects are randomly distributed in space
2 Line transects are arranged randomly in the study area
3 Objects on the line transect are all detected (g(0) =1) It means that at zero meters of distance, all the objects on the line transect are detected with a probability of 1
4 Objects do not move before detection All measurements are made from the initial location of objects, before object was affected by the investigators
5 All angle, distance are measured accurately
6 The detections are independent events
Density of species is calculated by the formula:
The total number of objects detected in the survey is represented by n, while the detection probability is denoted by a value less than or equal to 1 The area of the survey is calculated using the formula a = 2.L.w, where L is the total length of the line transect and w is the width of the line transect.
The variance of density estimation is calculated by the formula:
The variance in density estimation reflects the fluctuations in the number of individuals observed across line transects, as well as the variability in group size and the estimation of detection probabilities.
RESULT
Describing field survey data
In the survey, a total of 66 Black-crested bulbul groups, 86 Puff-throated bulbul groups, and 91 Yellow-bellied warbler groups were identified Most of these groups were located within 30 meters of the transects, as indicated in Table 4.1 Notably, one Black-crested bulbul group was detected beyond 60 meters from the transect and was subsequently excluded from data analysis To accurately fit the detection probability function, the distance data was categorized into five intervals: 0-10m, 10-20m, 20-30m, 30-40m, and 40-50m, as shown in Table 4.1.
Table 4.1: Number of Black-crested bulbul group, Puff-throated bulbul group and
Yellow-bellied warbler group detected by distance in the survey
In a study of 66 Black-crested bulbul groups, 61% were identified through direct observation, while 39% were detected by their unique calls This indicates a higher detection rate for visual observations compared to auditory identification, which accounted for only 22% of the total detections.
Figure 4.1: Percentage of Black-crested bulbul detected by observation and hearing
Unlike the Black-crested bulbul, the Puff-throated bulbul and Yellow-bellied warbler were primarily identified through their acoustic signals Specifically, 58 groups of Puff-throated bulbuls were detected by their distinctive calls, representing over 67% of observations, while only 28 groups were identified through visual observation, making up just 33% of the total detections (Figure 4.2).
Figure 4.2: Percentage of Puff-throated bulbul detected by observation and hearing
Sixty five groups of Yellow-bellied warbler (71%) were detected by their special call while only 26 groups (29%) were detected by observation (Figure 4.3)
Figure 4.3: Percentage of Yellow-bellied warbler detected by observation and hearing
Modeling detection probability by distance
The detection probability decreases with increasing the distance from the line transects (Figure 4.4 to Figure 4.15)
The detection probability variation by distance for the Black-crested bulbul is best modeled by the Half-normal function, which has the lowest AIC value of 189.99 Following this, the Uniform, Hazard-rate, and Negative exponential functions also provide reasonable models Additionally, the χ² test results indicate that the Half-normal function aligns well with the characteristics of detection probability variation, showing a χ² value of 1.77 and a p-value of 0.62.
Table 4.2: Evaluating functions used to model the detection probability for Black- crested bulbul
Function form AIC value Detection probability CV (%) Density
The detection probability of the Black-crested bulbul is estimated at 0.55, indicating that only 55% of active Black-crested bulbul groups located within 50 meters of the transects were identified during the survey.
Figure 4.4: Uniform function for Black-crested bulbul Figure 4.5: Half-normal function for Black-crested bulbul
Figure 4.6: Hazard-rate function for Black-crested bulbul Figure 4.7: Negative exponential function for Black-crested bulbul
The analysis of the Puff-throated bulbul revealed that the Hazard-rate function best fits the variation of detection probability by distance, evidenced by the lowest AIC value of 216.32 Following this, the Negative exponential, Half-normal, and Uniform functions were also considered Additionally, the χ² test confirmed that the Hazard-rate function aligns well with the characteristics of detection probability variation by distance, yielding a χ² value of 0.33 and a p-value of 0.85.
Table 4.3: Evaluating functions used to model the detection probability for Puff- throated bulbul
Function form AIC value Detection probability CV (%) Density
The Puff-throated bulbul has an estimated detection probability of 42%, indicating that only 42% of the active groups within 50 meters of the transects were identified during the survey.
Figure 4.8: Uniform function for Puff-throated bulbul Figure 4.9: Half-normal function for Puff-throated bulbul
Figure 4.10: Hazard-rate function for Puff-throated bulbul Figure 4.11: Negative exponential function for Puff-throated bulbul
The Yellow-bellied warbler's detection probability by distance is best modeled by the Half-normal function, which has the lowest AIC value of 241.20 Following this, the Uniform, Hazard-rate, and Negative exponential functions also provide viable models Additionally, the χ² test indicates that the Hazard-rate function aligns well with the variation in detection probability, yielding a χ² value of 6.22 and a p-value of 0.10.
Table 4.4: Evaluating functions used to model the detection probability for Yellow- bellied warbler
Function form AIC value Detection probability CV (%) Density
The detection probability at a distance of 40-50m is notably higher than at 40m, likely due to investigators rounding distances to the nearest 50m This rounding error should be avoided during investigations, highlighting the importance of equipping investigators with proper surveying skills However, the difference in the number of groups detected at 40-50m compared to 40m is minimal, indicating that it does not significantly impact the estimated results.
The Yellow-bellied warbler has an estimated detection probability of 0.46, indicating that only 46% of the warbler groups active within 50 meters of the transects were successfully detected during the survey.
Figure 4.12: Uniform function for Yellow-bellied warbler Figure 4.13: Half-normal function for Yellow-bellied warbler
Figure 4.14: Hazard-rate function for Yellow-bellied warbler Figure 4.15: Negative exponential function for Yellow-bellied warbler
Estimating density of species in transects
The estimated density of Black-crested bulbuls across various transects ranges from 0.23 to 0.49 groups per hectare The overall estimated group density is 0.38 groups per hectare, with a confidence interval between 0.34 and 0.55 groups per hectare.
Table 4.5: Estimated density of Black-crested bulbul for transects
Transect Density (group/ha) LB UB
The Puff-throated bulbul exhibits a general estimated group density of 0.66 groups per hectare, with a range of 0.51 to 0.85 groups/ha Specifically, transect 1 has an estimated density of 0.64 groups/ha, transect 2 shows 0.69 groups/ha, and transect 3 also records 0.64 groups/ha, as detailed in Table 4.6.
Table 4.6: Estimated density of Puff-throated bulbul for transects
Transect Density (group/ha) LB UB
The Yellow-bellied warbler exhibits an estimated density ranging from 0.36 to 0.71 groups per hectare across various transects, with a general average density of 0.52 groups per hectare The density estimates have a lower boundary of 0.44 and an upper boundary of 0.63 groups per hectare, as detailed in Table 4.7.
Table 4.7: Estimated density of Yellow-bellied warbler for transects
Transect Density (group/ha) LB UB
From table 4.5 to table 4.7, we can see that density doesn't change much between transects And above results are suitable with ecological characteristics of each species.
DISCUSSION
Over the past decade, distance sampling has been employed in over 120 countries to accurately estimate the density and abundance of various wildlife species This method is favored by wildlife biologists due to its ability to incorporate detection probability, leading to more precise density estimates Without accounting for detection probability, the estimated densities can significantly underestimate actual wildlife populations For instance, in the case of the Black-crested bulbul, density estimates without detection probability were 0.21 groups/ha, compared to 0.38 groups/ha when detection probability was factored in Additionally, as the transect width decreases, the estimated density increases, approaching an asymptotic value of 0.34 When using a transect width of 10m, it is assumed that nearly all groups were detected, suggesting a detection probability close to 1.
Table 5.1: Comparing density estimation results using distance sampling method and traditional method for Black-crested bulbul
The Puff-throated bulbul has an estimated density of 0.28 groups per hectare when not accounting for detection probability, which increases to 0.66 groups per hectare when adjustments are made Additionally, as the width of the transect decreases, the estimated density rises and approaches an asymptotic value of 0.65 groups per hectare.
Table 5.2: Comparing density estimation results using distance sampling method and traditional method for Puff-throated bulbul
The estimated density of Yellow-bellied warblers is 0.24 groups per hectare without considering detection probability, while adjusting for detection probability yields an estimated density of 0.52 groups per hectare based on data collected within 50 meters Additionally, as the width of the transect decreases, the estimated density increases, approaching an asymptotic value of 0.51 groups per hectare.
Table 5.3: Comparing density estimation results using distance sampling method and traditional method for Yellow-bellied warbler
The findings indicate that using detection probability to adjust wildlife density estimates is crucial for accuracy Within a distance of 0-20 meters, groups are effectively detected through their distinct calls and visual observation However, groups located further from the transect that do not emit acoustic signals may go unrecorded due to limited visibility, especially in regeneration forest habitats characterized by high tree density and a sparse canopy This limitation results in significantly lower estimated densities that do not account for detection probability, emphasizing the need for its estimation in wildlife surveys The detection probabilities for three bird species in these habitats are notably low, with the Black-crested bulbul at 0.55, the Yellow-bellied warbler at 0.46, and the Puff-throated bulbul at just 0.42 The Black-crested bulbul has the highest detection probability due to its distinctive appearance and frequent vocalizations, while the Puff-throated bulbul, despite its larger size, has the lowest probability due to its ability to evade detection in dense foliage and its infrequent calls This highlights the varying detectability of species based on their characteristics and habitat conditions.
CONCLUSION
The survey identified a total of 66 Black-crested bulbul groups, 86 Puff-throated bulbul groups, and 91 Yellow-bellied warbler groups Among the Black-crested bulbul, 61% (40 groups) were detected through observations, while 39% (26 groups) were identified by their distinctive calls In the case of the Puff-throated bulbul, 67% (58 groups) were found using their calls, with 33% (28 groups) detected through observation Similarly, for the Yellow-bellied warbler, 71% (65 groups) were recognized by their calls, whereas 29% (26 groups) were observed.
The detection probability by distance for the Black-crested bulbul and Yellow-bellied warbler is best modeled using the Half-normal function, while the Puff-throated bulbul's detection probability is most accurately represented by the Hazard-rate function.
The detection probabilities for various bird species reveal that the Black-crested bulbul has a detection rate of 0.55, the Puff-throated bulbul stands at 0.42, and the Yellow-bellied warbler is at 0.46 In terms of group density, the Black-crested bulbul has a density of 0.38 groups per hectare, while the Puff-throated bulbul exhibits a higher density of 0.66 groups per hectare, and the Yellow-bellied warbler has a density of 0.52 groups per hectare.
Neglecting detection probability when estimating wildlife density can lead to significant underestimations, with estimates being 2 to 2.5 times smaller than actual densities Consequently, accurately estimating detection probability is essential for effective wildlife surveys and monitoring efforts.
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Black-crested bulbul (Pycnonotus melanicterus)
The Black-crested bulbul (Pycnonotus melanicterus), a member of the Pycnonotidae family, is a passerine bird found across the Indian subcontinent and Southeast Asia Measuring approximately 19 cm in length, this bird features a distinctive black head and a body adorned with various shades of yellow Both male and female bulbuls share similar plumage, while juvenile birds exhibit a duller coloration compared to their adult counterparts.
The Black-crested bulbul feeds on fruit and insects And this is a bird of forest and dense scrub
Figure 1: Black-crested bulbul (Pycnonotus melanicterus)
Puff-throated bulbul ( Alophoixus pallidus )
The puff-throated bulbul ( Alophoixus pallidus ) is a species of songbird in the
The Pycnonotidae family, commonly known as bulbuls, is found across several Southeast Asian countries, including Cambodia, China, Laos, Burma, Thailand, and Vietnam This notable bulbul species measures approximately 23 cm in length and is characterized by its olive upper-parts and yellow under-parts, complemented by fluffy white throat feathers A distinctive feature is its elongated crown feathers, which form a moderately pointed crest While it resembles the white-throated bulbul, it has less vibrant under-parts Both males and females share similar physical traits, with black feet and brown irises and bills, making them visually indistinguishable.
Diet mainly berries, although some insects taken It will also take nectar Its natural habitat is subtropical or tropical moist lowland forests
Figure 1: Puff-throated bulbul ( Alophoixus pallidus )
Yellow-bellied warbler (Abroscopus superciliaris)
The Yellow-bellied Warbler (Abroscopus superciliaris) is a small bush warbler belonging to the Sylviidae family, measuring approximately 9 cm in length and weighing between 6 to 7 grams This species is distributed across various countries in Asia, including Bangladesh, Bhutan, Brunei, Cambodia, China, India, Indonesia, Laos, Malaysia, Myanmar, Nepal, Thailand, and Vietnam It thrives in natural habitats such as temperate forests and subtropical or tropical moist lowland forests Characterized by its almost featureless yellow-and-olive plumage, the Yellow-bellied Warbler also has a relatively large bill, short undertail-coverts, and a narrow tail.
The Yellow-bellied warbler feeds on almost entirely tiny invertebrates, tiny spiders (Araneae), small dipteran flies including mosquitoes, etc
Figure 2: Yellow-bellied warbler (Abroscopus superciliaris)
Appendix 2: Definition of some terms often used
DETECTION PROBABILITY FUNCTION: the key function of distance sampling
The probability P of detecting an object at a perpendicular distance y from a fixed observation point is represented by the function y=g(x) Typically, this probability decreases as the distance increases.
ESTIMATED DENSITY: it is the number of animals for each sample area, represented by D
Appendix 3: List of bird species in Thuong Tien Natural reserve
(Source: Thuong Tien Natural reserve)
TT Vietnamese name Scientific name English name Status
1 Cò trắng Egretta garzetta Little Egret 1,2
2 Cò ruồi Bubulcus ibis Cattle Egret 2
3 Cò bợ Ardeola bacchus Chinese Pond Heron 1,2
4 Cò xanh Butorides striatus Little Heron 1
5 Diều hoa miến điện Spilornis cheela Crested Serpent Eagle 1,2, NĐ 32-
6 Ưng ấn độ Accipiter trivirgatus Crested Goshawk 1,2, C-IIB
7 Diều nhật bản Buteo burmanicus Himalayan Buzzard 1, C-IIB
8 Cắt lưng hung Falco tinnunculus Common Kestrel 2, C-IIB
9 Gà so ngực gụ A choloropus Scaly-breasted
10 Gà rừng Gallus gallus Red Junglefowl 1,2
11 Gà lôi trắng Lophura nycthemera Silver Pheasant 1,2, Vu
12 Rẽ giun á châu Gallinago stenura Pintail Snipe 2
13 Cu gáy Streptopelia chinensis Spotted Dove 1,2
14 Gầm ghì vằn Macropygia unchall Barred Cuckoo Dove 2
15 Cu luồng Chalcophaps indica Emerald Dove 1,2
16 Gầm ghì lưng xanh Ducula aenea Green Imperial Pigeon 1,2
TT Vietnamese name Scientific name English name Status
17 Gầm ghì lưng nâu Ducula badia Mountain Imperial
18 Vẹt ngực đỏ Psittacula alexandri Red-breasted Parakeet 1
VII Bộ Cu cu Cuculiformes
19 Tìm vịt Cacomantis merulinus Plaintive Cuckoo 1
20 Cu cu đen Surniculus lugubris Drongo Cuckoo 1
21 Phướn Phaenicophaeus tristis Green-billed Malkoha 1
22 Bìm bịp lớn Centropus sinensis Greater Coucal 1
23 Cú mèo latusơ Otus spilocephalus Mountain Scops Owl 2, C-IIB
24 Cú mèo khoang cổ O bakkamoena Collared Scops Owl 2, C-IIB
25 Cú vọ mặt trắng Glaucidium brodiei Collared Owlet 1,2, C-IIB
26 Cú vọ G cuculoides Asian Barred Owlet 1,2, C-IIB
27 Yến cọ Cypsiurus balasiensis Asian Palm Swift 2
28 Yến cằm trắng Apus affinis House Swift 2
29 Nuốc bụng đỏ Harpactes erythrocephalus Red-headed Trogon 1,2
30 Bồng chanh Alcedo atthis Common Kingfisher 1,2
TT Vietnamese name Scientific name English name Status
31 Trảu lớn Nyctyornis athertoni Blue-bearded Bee- eater 1
XII Bộ Gõ kiến Piciformes
32 Thầy chùa lớn Megalaima virens Great Barbet 1,2
33 Thầy chùa đít đỏ M lagrandieri Red-vented Barbet 1,2
34 Thầy chùa đầu xám M faiostricta Green-eared Barbet 2
35 Gõ kiến lùn mày trắng Sasia ochracea White-browed Piculet 1,2
36 Gõ kiến nhỏ đầu xám Dendrocopos canicapillus
37 Gõ kiến xanh gáy vàng Picus flavinucha Greater Yellownape 1,2
38 Gõ kiến nâu cổ đỏ Blythipicus pyrrhotis Bay Woodpecker 1,2
39 Gõ kiến nâu đỏ Gecinulus grantia Pale-headed
40 Mỏ rộng hung Serilophus lunatus Silver-breasted
41 Mỏ rộng xanh Psarisomus dalhousiae Long-tailed Broadbill 1,2
42 Đuôi cụt đầu xám Pitta soror Blue-rumped Pitta 2
43 Đuôi cụt bụng vằn P elliotii Bar-bellied Pitta 2
44 Nhạn bụng trắng Hirundo rustica Barn Swallow 1,2
45 Chìa vôi núi Motacilla cinerea Grey Wagtail 1
46 Chìa vôi trắng M alba White Wagtail 1,2
47 Chim manh vân nam Anthus hodgsoni Olive-backed Pipit 1,2
TT Vietnamese name Scientific name English name Status
48 Phường chèo đỏ lớn Pericrocotus flammeus Scarlet Minivet 1
49 Phường chèo đen Hemipus picatus Bar-winged
50 Chào mào vàng mào đen
Pycnonotus melanicterus Black-crested Bulbul 1,2
51 Chào mào P jocosus Red-whiskered Bulbul 1,2
52 Bông lau tai trắng P aurigaster Sooty-headed Bulbul 1,2
53 Bông lau họng vạch P finlaysoni Stripe-throated Bulbul 1
54 Cành cạch lớn Alophoixus pallidus Puff-throated Bulbul 1,2
55 Cành cạch nhỏ Iole propinqua Grey-eyed Bulbul 1,2
56 Cành cạch xám Hemixos flavala Ashy Bulbul 2
57 Cành cạch hung Hemixos castanonotus Chestnut Bulbul 1,2
58 Cành cạch đen Hypsipetes leucocephalus Black Bulbul 1,2
59 Chim nghệ ngực vàng Aegithina tiphia Common Iora 1
60 Chim xanh hông vàng Chloropsis hardwickii Orange-bellied
61 Chim xanh nam bộ C cochinchinensis Blue-winged Leafbird 1,2
62 Bách thanh mày trắng Lanius cristatus Brown Shrike 2
63 Bách thanh đầu đen L schach Long-tailed Shrike 1,2
64 Hoét đuôi cụt mày trắng
65 Chích chòe Copsychus saularis Oriental Magpie
TT Vietnamese name Scientific name English name Status
66 Đuôi đỏ đầu xám Rhyacornis fuliginosa Plumbeous Water
67 Chích chòe nước đầu trắng Enicurus leschenaulti White-crowned
68 Sẻ bụi đầu đen Saxicola maurus Eastern Stonechat 1,2
69 Sẻ bụi xám Saxicola ferreus Grey Bushchat 2
70 Hoét đen Turdus mandarinus Chineses Blackbird 2
71 Hoét bụng trắng T cardis Japanese Thrush 2
72 Chuối tiêu đất Pellorneum tickelli Buff-breasted Babbler 1,2
73 Chuối tiêu ngực đốm Pellorneum ruficeps Puff-throated Babbler 1,2
74 Họa mi đất mỏ dài Pomatorhinus hypoleucos
75 Họa mi đất mỏ đỏ P ochraciceps Red-billed Scimitar
76 Họa mi đất ngực luốc
77 Họa mi đất ngực hung
78 Khướu đá đuôi ngắn Napothera brevicaudata
79 Khướu bụi vàng Stachyridopsis chrysaea Golden Babbler 1,2
80 Khướu bụi đầu đen Stachyris nigriceps Grey-throated Babbler 1,2
81 Khướu bụi đốm cổ S striolata Spot-necked Babbler 1,2
82 Khướu bụi bụng trắng Erpornis zantholeuca White-bellied Yuhina 1,2
83 Chích chạch má vàng Macronous gularis Striped Tit Babbler 1,2
84 Khướu đuôi dài Gampsorhynchus torquatus Collared Babbler 2
TT Vietnamese name Scientific name English name Status
85 Khướu đầu trắng Garrulax leucolophus White-crested
86 Khướu bạc má G chinensis Black-throated
87 Khướu má hung G.castanotis Rufous-cheeked
88 Kim oanh tai bạc Leiothrix argentauris Silver-eared Mesia 1,2
89 Khướu lùn cánh xanh Minla cyanouroptera Blue-winged Minla 2
90 Chích bụi rậm Cettia canturians Manchurian Bush
91 Chiền chiện đầu nâu Prinia rufescens Rufescent Prinia 1
92 Chiền chiện bụng hung P inornata Plain Prinia 1,2
93 Chích đuôi dài Orthotomus sutorius Common Tailorbird 1,2
94 Chích bông cánh vàng O atrogularis Dark-necked
95 Chích mày lớn Phylloscopus inornatus Yellow-browed
96 Chích bụng hung P subaffinis Buff-throated Warbler 2
97 Chích hông vàng P proregulus Pallas's Leaf Warbler 1,2
98 Chích ngực vàng P ricketti Sulphur-breasted
99 Chích đớp ruồi đầu xám Seicercus valentini Bianchi’s Warbler 2
100 Chích đớp ruồi mày xám S tephrocephalus Grey-crowned
101 Chích đớp ruồi bụng vàng
102 Đớp ruồi xanh xám Eumyias thalassina Verditer Flycatcher 2
TT Vietnamese name Scientific name English name Status
103 Đớp ruồi mugi Ficedula mugimaki Mugimaki Flycatcher 2
104 Đớp ruồi cằm đen Niltava davidi Fujian Niltava 1
105 Đớp ruồi đầu xám Culicicapa ceylonensis Grey-headed Canary
106 Đớp ruồi trắng Cyornis concretus White-tailed
107 Đớp ruồi hải nam C hainanus Hainan Blue
108 Rẻ quạt họng trắng Rhipidura albicollis White-throated Fantail 1,2
109 Bạc má Parus minor Japanese Tit 1
110 Chim mào vàng Melanochlora sultanea Sultan Tit 1
111 Chim sâu vàng lục Dicaeum minullum Plain Flowerpecker 1
112 Hút mật họng tím Cinnyris jugularis Olive-backed Sunbird 2
113 Hút mật đỏ Aethopiga siparaja Crimson Sunbird 1,2
114 Hút mật ngực đỏ Aethopiga saturata Black-throated
115 Vành khuyên nhật bản Zosterops japonicus Japanese White-eye 1,2
116 Di cam Lonchura striata White-rumped Munia 1
117 Sẻ Passer montanus Eurasian Tree
118 Tử anh Oriolus traillii Maroon Oriole 1