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Edible-nest Swiftlet

(Aerodramus fuciphagus, Thunberg 1812)

Image ModifiedAnticlockwise from top:  Edible-nest Swiftlet in flight

Footnote Macro

"Edible-nest Swiftlet in flight," by Lim Hong Yao, 2017. 

 , perched on nest

Footnote Macro

"Edible-nest

Swiftlet perched

Swiftlet on nest," by Lim Hong Yao, 2018. 

, harvested edible nest, prepared bird's nest soup.

1. Introduction Anchor111.1 General information Anchor1.11.1

Edible-nest swiftlets are small insectivorous birds from the swift family Apodidae. Weighing in at a mere 8·7–14·8 grams and measuring in at 11·5–12·5 cm in length, this species is known to be an excellent flyer and can spend the long periods foraging in the sky without rest (HBW). Edible-nest swiftlets may be observed over a wide variety of habitats (even far out at sea) and are widespread throughout South-east Asia today. This bird is well known (and studied) in the region due to its nest being widely collected or farmed as a delicacy known as bird’s nest soup or ‘燕窝’ in Chinese. Natural populations nest in caves, such as the Niah and Gomantong caves in Borneo. However, due to the practice of farming swiftlets in nest houses, many Edible-nest swiftlets have adopted nesting in man-made buildings as early as the 1880s. (Lim & Cranbrook 2002).

1.2 Identification Anchor1.21.2

A medium sized swiftlet with glossy dark brown upperparts. Rump tends to appear paler grey, but variable and can appear uniform. Brown-grey underparts except almost black undertail coverts, significantly forked tail. Naked or lightly feathered tarsi.

In Singapore, hardly indistinguishable in flight from slightly larger Black-nest Swiftlet (Aerodramus maximus) in flight, unless seen exceedingly well enough to determine the Edible-nest Swiftlet's slightly smaller (1-3 cm) size, slightly pointed tail ends with shallow a relatively deeper notch, and less bulky head and body. In hand, identification is possible as Black-nest Swiftlet has more extensive black feathering on tarsi. Appears to be indistinguishable in flight from potential migrant Himalayan Swiftlet (Aerodramus brevirostris).

1.3 Etymology Anchor1.31.3

The genus Aerodramus stems from two Greek words ἀερο (“aero”) and δρόμος (“dromos”), with aero meaning ‘air’ and dromos meaning ‘path’; the swiftlets are thus named because the air is their path.

The specific epithet fuciphagus originates from Greek as well, with φυκι (“fukos”) meaning ‘seaweed,’ and φαγος (“phagos”) meaning ‘to eat’. This is likely a result of the (false) historical belief that the swiftlets consume seaweed or substances from sea mist which allows it to produce a gelatinous substance with which it builds its nest with.

Column

Contents:

1. Introduction

    1.1 Description
    1.2 Identification
    1.3 Etymology

2. Range

3. Human interactions

    3.1 Bird's nest soup
    3.2 "Blood nests"
    3.3 House farming

4. Ecology and behaviour

    4.1 Feeding
    4.2 Reproduction
    4.3 Echolocation

5. Taxonomy and phylogenetics

  5.1 Species taxonomy
i 5.2 Phylogenetics of swiftlets
i 5.3 Subspecies taxonomy

2. Range and subspecies Anchor22

The Edible-nest Swiftlet has a large range starting from the South of Hainan island spanning southward along the coasts of Vietnam, Myanmar, Thailand and Cambodia, subsequently including Sumatra, Java, Lesser Sundas, Borneo, and West Philippines (Figure 1). Much of Peninsula Malaysia is often not indicated as part of its natural range as they were not historically observed to be breeding in the region naturally; birds currently inhabiting the area are likely to be from house farms.

Range map of Edible-nest SwiftletImage RemovedFigure 1: Range map of the Edible-nest Swiftlet, adapted from HBW (2018)

8 current subspecies are recognized. For more details, see subspecies taxonomy below.

3. Human interactions Anchor333.1 Bird's nest soup Anchor3.13.1

The Edible-nest Swiftlet’s nests are frequently prepared in a manner known colloquially as ‘birds’ nest soup’, which has long been a Chinese delicacy of immense value since the T’ang Dynasty (618–907 A.D.) Lau and Melville (1994). Like many other Chinese delicacies, birds’ nest soup is not especially tasty, and relies on other culinary additions to appeal to the palate (Thorburn 2015). Its value lies in its rumoured nutritional value and health benefits instead; the broth is said to help reduce inflammation, alleviate gastric problems, boost the immune system, metabolism, and mental performance, as well as improve skin complexion (Marcone, 2005). Several studies have shown that certain claims may hold some truth to them, as components such as sialic acid and other compounds that are purported to aid infant development and immunity were discovered to be present in the nests (Oda et al. 1998; Wang and Brand-Miller 2003; Ng et al. 1986; Kong et al. 1987; Roh et al. 2012). The Black-nest Swiftlet (Aerodramus maximus) also produces nests that are being collected and consumed, but their nests are worth less since they insert their feathers into the nests as additional material, which have to be removed to be eaten.

Given the high valuation of the nests (about USD$20 per nest (Marcone, 2005), nest harvesting naturally became a highly profitable exploit. Despite efforts to keep nesting colonies secret and manage the harvest rates, wild populations of the Edible-nest Swiftlets have plummeted from once immeasurable numbers, and many colonies have now been wiped out, or are critically endangered (Lau and Melville 1994; Sankaran 2001). Italy proposed to include the species under Appendix II of CITES to regulate trade in 1994, but opposition from the Southeast Asian nations prevented it (Thorburn 2015). 

3.2 "Blood nests" Anchor3.23.2

Some of the nests develop red stains in them, and were known collectively as “blood nests” under the false belief that the stains composed of swiftlet blood (Thorburn 2015). These nests are rarer and used to fetch up to five times the price of a regular nest (Marcone, 2005). Instead, the red was due to nitrifying bacteria reacting to ammonia vapours from decaying guano (swiftlet and/or bat excrement) (Thorburn 2015). Some swiftlet farmers discovered this and induced these “blood nests” by treating the white nests with ammonia. Both artificial and natural red nests are found to have abnormally high levels of nitrite, up to 4400mg/kg, which can increase one’s risk of cancer, and potentially cause food poisoning (Food Quality News 2011). As a result, China, once the largest importer of swiftlet nests, banned the import of all birds’ nest from Malaysia and Indonesia. This caused a huge shock to the industry as demand of both "blood nests" and regular nests dropped significantly; China currently only imports from several Malaysian firms that meet strict regulations that were subsequently set up after the ban (Lee 2014).

3.3 House farming Anchor3.33.3

Two centuries ago, the Edible-nest Swiftlet nested solely on coastal habitats where caves were available, and there were no records of inland nesting colonies (Cranbrook et al. 2013). Swiftlets were first reported to nest in houses near cliffs in the village of Sedayu in East Java in 1880, and entrepreneurs eventually began developing methods to attract swiftlets to nest in houses (Lim and Cranbrook 2002). The industry grew as the use of broadcasting swiftlet calls to attract nesting birds became the norm, and a trade in swiftlet eggs began. House nesting swiftlets first appeared in the Malay Peninsula in the 1930s, reportedly first arriving in Singapore from Java, before spreading North across Malaysia (Chasen 1939; Gibson-Hill1948). The swiftlets have a high degree of nest fidelity, and house farmed swiftlets and their young would return to man-made houses (preferably the same one) to nest again (Kang et al. 1991), leaving the depleted natural populations and habitats unrestored (Cranbrook et al. 2013). Furthermore, house nesting swiftlets are suspected to be a hybrid population of A. f. fuciphagus and A. f. inexpectatus or A. f. germani in what could be an ongoing case of domestication; the population of house farmed swiftlets have since spread Northward up to Myanmar, where it may be competing with local subspecies. More extensive regional genetic studies are required to confirm these suspicions.

Image Removed

Edible-nest Swiftlet "blood nest". 
(Photo: Lim Hong Yao, 2018)

4. Ecology and behaviour Anchor444.1 Feeding Anchor4.14.1

Edible-nest Swiftlets are aerial insectivores that catch arthropods on the wing. Diet analyses have been conducted by examining regurgitated food boluses; hymenoptera, diptera and ephemeroptera made up majority of the food items, while arachnida, coleoptera and hemiptera made up most of the rest.

4.2 Reproduction Anchor4.24.2

Breeding has been observed to take place year-round but peak in October and February. (Nigel Langham 1979).

  • Nest building: Nests are made of salivary excrement that harden into a cement-like material. Each nesting pair will spend about 25 minutes a day to build the nest, which takes about 45 days to complete. (Kang et al 1991). Nests are re-used for subsequent clutches in the future if not harvested. (Nigel Langham 1979).
  • Chick development: Each pair of birds would usually lay two eggs and spend an average of 23 days incubating them. The chicks take about 43 days to develop and fledge, with an approximate 50% survival rate (Nigel Langham 1979).
4.3 Echolocation Anchor4.34.3

As Edible-nest Swiftlets nest in places which are completely dark, they have evolved the ability to echolocate using clicking sounds, along with many other species from the genus Aerodramus. This ability, however, is not diagnostic of the genus as the Pygmy Swiftlet (Collocalia troglodytes) has been proven to possess this ability too.

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nameT4254-Aerodramusfuciphagus-snd-1.mp3
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Sound recording of an Edible-nest Swiftlet's echolocating clicking calls. (Recorded by Lim Hong Yao, 2018)5. Taxonomy Anchor555.1 Original description Anchor5.15.1

The Edible-nest Swiftlet was originally described by Carl Peter Thunberg, a well renowned Swedish naturalist from the 19th century. Thunberg collected the specimen in Java and described it as Hirundo fuciphagus in his "Remarks about the Swallows that build jelly-like, edible Nests" (1812) (Figure 2), which, with help of Google Translate, roughly states that

  • he collected a specimen that appeared similar to Hirundo esculenta, but upon closer examination discovered it was an undescribed species. 
  • H. fuciphagus can be found in caves of the mountainous areas in Java and made jelly like nests that are a precious commodity.
  • The body of H. fuciphagus is black above and immaculate grey below, about four inches long
  • Tail is black and rounded and black above and below.
  • Wings black, twice the length of the tail and acute. Feet black and short.
  • Similar to H. esculenta but differentiated by the all black tail, chest and abdomen, no spots.
5.2 Phylogenetics of swiftlets Anchor5.25.2

Thunberg (1812) named the Edible-nest Swiftlets in Java Hirundo fuciphagus, mistakenly grouping them together with the swallows (Hirundo is a genus of swallows, which are passerines). By the 1900s swiftlets were recognized as a separate taxon and all its members were lumped in the genus Collocalia, then subsequently divided into 3 genera: Hydrochous (Giant Swiftlets) are sister to Aerodramus (medium sized brownish swiftlets)and Collocalia (small glossy plumaged swiftlets). Multiple recent phylogenetic analyses have been conducted to establish that Collocalia are the basal group that are more related to the swifts, followed by Hydrochous and Aerodramus being sister genera. (Cibois et. al 2018 and others)

Several studies have attempted to resolve the phylogenetic relationships of the Edible-nest Swiftlet, but success has been rather limited as it does not show up as a monophyletic clade on the tree; results often show that one or more individuals of A. fuciphagus are more closely related to the sister species A. salangana (Mossy-nest Swiftlet) than other A. fuciphagus (Cibois et. Al, 2018Price et. Al, 2005Rheindt et. al, 2014). The most recent tree constructed using mitochondrial and nuclear DNA analysis is shown on the right (Figure 2) (Cibois et. al, 2018).

*add info on methods of analysis in Cibois here*

The low genetic divergence between closely related taxa is likely due to occasional hybridisation events, which have been reported in Sabah (Lee, 1996), leading to genetic introgression in the form of mitochondrial DNA sweeps (Rheindt & Edwards, 2011) that cause some individuals to appear closer to sister species than its own. It is evident that mitochondrial DNA is not very effective as a taxonomic indicator in the case of the Aerodramus swiftlets, and genomic methods may be a better alternative to resolve these relationships.

5.3 Subspecies taxonomy Anchor5.35.3
Expand
titleClick here for subspecies ranges and descriptions
  • A. f. amechanus (Oberholser, 1912) – Anambas Is, off SE Peninsular Malaysia.
    • Paler underparts with greyer rump than germani
  • A. f. germani (Oustalet, 1876) – Coastline from W Hainan S around SE Asia to Malay Peninsula, including Mergui Archipelago (off S Myanmar); coastal N Borneo and W Philippines (Palawan E to Panay and Ticao).
    • Paler underparts and whitish rump
  • A. f. inexpectatus (A. O. Hume, 1873) – Andaman Is and Nicobar Is.
    • Slightly smaller than nominate race
  • A. f. vestitus (Lesson, 1843) – Sumatra, Belitung I and Borneo (except N coasts).
    • Darkest upperparts, lack contrasting rump
  • A. f. perplexus (Riley, 1927) – Maratua I, off E Borneo.
    • Some purple sheen on rectrices and remiges, slight contrasting rump
  • A. f. fuciphagus (Thunberg, 1812) – Java, Kangean Is and Bali to W Lesser Sundas (E to Sumbawa), and Tanahjampea.
    • Dark brown upperparts with slightly paler greyish rump. Underparts brownish-grey.
  • A. f. dammermani (Rensch, 1931) – Flores (EC Lesser Sundas).
    • Slightly paler rump
  • A. f. micans (Stresemann, 1914) – Sumba, Sawu and Timor (C Lesser Sundas).
    • Slightly greyer overall with contrasting rump

Several authors believe that this species should be split into two. In that treatment, ssp amechanus and germani are named Germain’s Swiftlet, while the rest of the subspecies retain the name of Edible-nest Swiftlet. However, taxonomical evidence for splitting the species has been unconvincing to many, and this species page will treat the group as a single species under the Biological Species Concept (see Taxonomy section).

Differences amongst subspecies are often subtle and difficult to distinguish in the field due to variations in lighting as well as difficulty in observing constantly fast-moving subjects.
According to the subspecies range, Edible-nest Swiftlets observed in Singapore should be A. f. germani which extends into the Malay Peninsula, but specimens collected appeared identical to the nominate race A. f. fuciphagus, likely because colonies in Malaysia and Singapore are of the house farmed variety (see House Farming below), which is suspected to be of Javan origin (ssp. fuciphagus). To complicate matters, their feeding ranges are not known and may overlap.

In 1931, Stresemann postulated that populations with a paler rump from A. f. germani and those of a darker rump from A. f. vestitus and fuciphagus formed a transition zone over Peninsula Malaysia where intergrades of rump colour can be observed.  Thus, it was proposed that the populations were interbreeding, and thus the taxa were regarded as subspecies of Aerodramus fuciphagus. Medway (1966) also arrived at a similar conclusion.

Subsequently, Cranbrook et. al (2013) re-examined the specimens for the subspecies and postulated that there was not a cline in morphology, but rather an overlap of feeding range in Peninsula Malaysia. As such, A. germani and A. inexpectatus were suggested as separate species and this treatment is currently adopted by several authors. Mitochondrial DNA analysis was conducted but only revealed significant differences between house farmed swiftlets and A. f. vestitus, while the parsimony tree constructed using neighbour joining techniques revealed poor support on the nodes and appeared inconclusive regarding the phylogenetic relationships between populations (Figure 3). Previous cytochrome-b mitochondrial DNA work by Lee et. al (1996) also failed to reveal any conclusive results (Figure 4). While morphological breaks separating the populations in different geographical ranges may exist, in applying the Biological Species Concept, there is insufficient evidence to establish reproductive isolation given that the colonies breed in allopatry. Additionally, Cranbrook et. al (2013) postulated that the house farmed swiftlets could be a hybrid population of A. f. fuciphagus and A. f. inexpectatus or A. f. germani, indicating that these taxa may not withstand the test of sympatry when brought together in nest houses. Therefore, A. fuciphagus is currently treated as a single species on this page and by several other authors. Future genomic research with Next Generation Sequencing can be conducted to help reveal the phylogenetic relationship of these taxa more conclusively.

*critique on methods of analysis in fig 3 and 4*

*How different species concepts would treat this*

Image Removed
Figure 2: Scans of the original swedish description of H. fuciphagus in Kungl. Svenska vetenskapsakademiens handlingar by Thunberg (1812), obtained from Biodiversity Heritage Library.
Image Removed
Figure 2: Phylogenetic tree of Aerodramus swiftlets obtained using nuclear and mitochondrial DNA analysis. Adapted from Cibois et. al (2018).
Image Removed
Figure 3: Phylogenetic tree of Edible-nest Swiftlets from different populations using mitochondrial DNA and neighbour-joining methods. Adapted from Cranbrook et. al (2013).

Image Removed
Figure 4: Phylogenetic tree of swiftlets using mitochondrial DNA. Adapted from Lee et. al (1996).

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Footnote Macro

"Edible birds nest bowl shape" by Ediblebirdsnest. Wikimedia Commons,19 March 2016. URL https://commons.wikimedia.org/wiki/File:Edible-birds-nest-bowl-shape.png (accessed on 19 Nov 2018)

, prepared bird's nest soup.

Footnote Macro

"Birds nest soup" by Crue. Blogger, 6 January 2010. URL http://ichikichikehem.blogspot.com/2010/01/thai-hatyai-bird-nest-soup-7ps.html(accessed on 19 Nov 2018)



1. Introduction
Anchor
1
1

1.1 General information
Anchor
1.1
1.1

Edible-nest swiftlets are small insectivorous birds from the swift family Apodidae. Weighing in at a mere 8·7–14·8 grams and measuring in at 11·5–12·5 cm in length, this species is known to be an excellent flyer and can spend the long periods foraging in the sky without rest.

Footnote Macro

Chantler, P. & Boesman, P. (2018). Edible-nest Swiftlet (Aerodramus fuciphagus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/55287 on 29 November 2018).

 Edible-nest swiftlets may be observed over a wide variety of habitats (even far out at sea) and are widespread throughout South-east Asia today. This bird is well known (and studied) in the region due to its nest being widely collected or farmed as a delicacy known as bird’s nest soup or ‘燕窝’ in Chinese. Natural populations nest in caves, such as the Niah and Gomantong caves in Borneo. However, due to the practice of farming swiftlets in nest houses, many Edible-nest swiftlets have adopted nesting in man-made buildings as early as the 1880s.

Footnote Macro

Lim, C. and Cranbrook, G. (2002). Swiftlets of Borneo. Natural History Publications (Borneo).


1.2 Identification
Anchor
1.2
1.2

A medium sized swiftlet with glossy dark brown upperparts.

Footnote Macro

Chantler, P. & Boesman, P. (2018). Edible-nest Swiftlet (Aerodramus fuciphagus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/55287 on 29 November 2018).

 Rump tends to appear paler grey, but variable and can appear uniform. Brown-grey underparts except almost black undertail coverts, significantly forked tail. Naked or lightly feathered tarsi.

Image AddedFigure 1: Photo composite of Edible-nest Swiftlets with diagnostic characters pointed out. (Composite and photos by Lim Hong Yao, 2018)

Footnote Macro

"Edible-nest Swiftlet identification characters composite," by Lim Hong Yao, 2018. 


Note that plumage can have subspecies variations.

In Singapore, difficult to distinguish in flight from slightly larger Black-nest Swiftlet (Aerodramus maximus), unless seen exceedingly well enough to determine the Edible-nest Swiftlet's slightly smaller (1-3 cm) size, relatively pointed tail ends with a deeper notch, and less bulky head and body. In hand, identification is possible as Black-nest Swiftlet has more extensive black feathering on tarsi.

1.3 Etymology
Anchor
1.3
1.3

The genus Aerodramus stems from two Greek words: ἀερο, "aero" which means 'air', and δρόμος,"dromos" which means racecourse or path.

Footnote Macro

Jobling, J. (2011). The Helm dictionary of scientific bird names. London: Christopher Helm.


The specific epithet fuciphagus originates from Greek as well, with φυκι, "fukos" meaning ‘seaweed,’ and φαγος, "phagos" meaning ‘to eat’. This is likely a result of the (false) historical belief that the swiftlets consume seaweed or substances from sea mist which allows it to produce a gelatinous substance with which it builds its nest with.

2. Range
Anchor
2
2

The Edible-nest Swiftlet has a large range starting from the South of Hainan island spanning southward along the coasts of Vietnam, Myanmar, Thailand and Cambodia, subsequently including Sumatra, Java, Lesser Sundas, Borneo, and West Philippines (Figure 2).

Footnote Macro

Chantler, P. & Boesman, P. (2018). Edible-nest Swiftlet (Aerodramus fuciphagus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/55287 on 29 November 2018).

 Inland Peninsula Malaysia is part of its natural range but Edible-nest Swiftlets from house farms are currently inhabiting the area. 8 current subspecies are recognized. For more details, see subspecies taxonomy below.

Range map of Edible-nest SwiftletImage AddedFigure 2: Range map of the Edible-nest Swiftlet, adapted from HBW (2018)

Footnote Macro

Chantler, P. & Boesman, P. (2018). Edible-nest Swiftlet (Aerodramus fuciphagus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/55287 on 29 November 2018).

3. Nest building and human interactions
Anchor
3
3

3.1 Nest construction
Anchor
3.1
3.1

The Edible-nest Swiftlets nest in natural caves, and man-made houses. Breeding has been observed to take place year-round but peak in October and February.

Footnote Macro

Langham, N. (2008). Breeding biology of the edible-nest swiftlet Aerodramus fuciphagus. Ibis, 122(4), pp.447-461.


  • Nest building: Nests are made of salivary excrement that hardens into a cement-like material. Each nesting pair will spend about 25 minutes a day to build the nest, which takes about 45 days to complete.

    Footnote Macro

    Kang, N., Hails, C. and Sigurdsson, J. (2008). Nest construction and egg-laying in Edible-nest Swiftlets Aerodramus spp. and the implications for harvesting. Ibis, 133(2), pp.170-177.

     Nests are re-used for subsequent nesting by the same pair in the future if not harvested.

    Footnote Macro

    Langham, N. (2008). Breeding biology of the edible-nest swiftlet Aerodramus fuciphagus. Ibis, 122(4), pp.447-461.

     Here is a video of the nest building process:

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urlhttps://www.youtube.com/watch?v=ngPs3kINUXE
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Footnote Macro

"Salivating for a new nest | Wild Borneo" by National Geographic. Nat Geo WILD YouTube Channel, 3 January 2017. URL: https://www.youtube.com/watch?v=ngPs3kINUXE  (accessed on 30 Nov 2018).

3.2 Bird's nest soup
Anchor
3.2
3.2

The Edible-nest Swiftlet’s nests are frequently prepared in a manner known colloquially as ‘birds’ nest soup’, which has long been a Chinese delicacy of immense value since the T’ang Dynasty (618–907 A.D.).

Footnote Macro

Lau, A. and Melville, D. (1994). International trade in swiftlet nests with special reference to Hong Kong. Cambridge, U.K.: Traffic International.

 Like many other Chinese delicacies, birds’ nest soup is not especially tasty, and relies on other culinary additions to appeal to the palate.

Footnote Macro

Thorburn, C. (2015). The Edible Nest Swiftlet Industry in Southeast Asia: Capitalism Meets Commensalism. Human Ecology, 43(1), pp.179-184.

 Its value lies in its rumoured nutritional value and health benefits instead; the broth is said to help reduce inflammation, alleviate gastric problems, boost the immune system, metabolism, and mental performance, as well as improve skin complexion.

Footnote Macro

Marcone, M. (2005). Characterization of the edible bird’s nest the “Caviar of the East”. Food Research International, 38(10), pp.1125-1134.

 As with any claims of these sort, it is crucial to adopt an evidence-based approach in judging if the edible-nests are actually a health product. Thus far, several studies have shown that certain claims may hold some truth to them. The paper Wong (2013) summarises several potential biological effects published in studies, some of which include pro-mitogenic effects, epidermal growth factor-like activity, pro-proliferative effects for lymphocytes and corneal keratocytes, increased anti-body production, anti-oxidative effects, ability to bind to influenza virus to inhibit damage, and potential bone strengthening and skin thickening/enhancing effects.

Footnote Macro

Oda, M., Ohta, S., Suga, T. and Aoki, T. (1998). Study on Food Components: The Structure of N-Linked Asialo Carbohydrate from the Edible Bird's Nest Built by Collocalia fuciphaga. Journal of Agricultural and Food Chemistry, 46(8), pp.3047-3053.

Footnote Macro

Roh, K., Lee, J., Kim, Y., Park, J., Kim, J., Lee, J. and Park, D. (2012). Mechanisms of Edible Bird's Nest Extract-Induced Proliferation of Human Adipose-Derived Stem Cells. Evidence-Based Complementary and Alternative Medicine, 2012, pp.1-11.

Footnote Macro

Wong, R. (2013). Edible bird’s nest: Food or medicine?. Chinese Journal of Integrative Medicine, 19(9), pp.643-649.

 However, it is important to note that all the above-mentioned studies either used ex vitro methods or experimented on mice or rabbits. As such there is no currently no definitive evidence of edible-nests being medicinal in nature after being consumed by humans. Many of the metrics pointing to potential effects may not actually result in desirable effects or appreciable effect sizes; increased femur calcium content and thicker skin does not translate to improved health and beauty. The current state of knowledge regarding the biological effects of edible-nests has not yet been able to prove the numerous claims associated with it, despite the studies pointing to its potential benefits. 

Given the high value of the nests (about USD$20 per nest, nest harvesting naturally became highly popular.

Footnote Macro

Marcone, M. (2005). Characterization of the edible bird’s nest the “Caviar of the East”. Food Research International, 38(10), pp.1125-1134.

 Despite efforts to keep nesting colonies secret and manage the harvest rates, wild populations of the Edible-nest Swiftlets have plummeted from once immeasurable numbers, and many colonies have now been wiped out, or are critically endangered.

Footnote Macro

Lau, A. and Melville, D. (1994). International trade in swiftlet nests with special reference to Hong Kong. Cambridge, U.K.: Traffic International.

Footnote Macro

Sankaran, R. (2001). The status and conservation of the Edible-nest Swiftlet (Collocalia fuciphaga) in the Andaman and Nicobar Islands. Biological Conservation, 97(3), pp.283-294.

 Italy proposed to include the species under Appendix II of CITES to regulate trade in 1994, but opposition from the Southeast Asian nations prevented it, leaving it unlisted and thus unregulated.

Footnote Macro

Thorburn, C. (2015). The Edible Nest Swiftlet Industry in Southeast Asia: Capitalism Meets Commensalism. Human Ecology, 43(1), pp.179-184.


The Black-nest Swiftlet (Aerodramus maximus) also produces nests that are being collected and consumed, but their nests contain inedible feathers that need to be removed. 

3.3 "Blood nests"
Anchor
3.3
3.3

Some of the nests develop red stains in them, and were known collectively as “blood nests” under the false belief that the stains composed of swiftlet blood.

Footnote Macro

Thorburn, C. (2015). The Edible Nest Swiftlet Industry in Southeast Asia: Capitalism Meets Commensalism. Human Ecology, 43(1), pp.179-184.

 These nests are rarer and used to fetch up to five times the price of a regular nest.

Footnote Macro

Marcone, M. (2005). Characterization of the edible bird’s nest the “Caviar of the East”. Food Research International, 38(10), pp.1125-1134.

 Instead, the red was due to nitrifying bacteria reacting to ammonia vapour from decaying guano (swiftlet and/or bat excrement).

Footnote Macro

Thorburn, C. (2015). The Edible Nest Swiftlet Industry in Southeast Asia: Capitalism Meets Commensalism. Human Ecology, 43(1), pp.179-184.

 Some swiftlet farmers discovered this and induced these “blood nests” by treating the white nests with ammonia. Both artificial and natural red nests are found to have abnormally high levels of nitrite, up to 4400mg/kg, which can increase one’s risk of cancer, and potentially cause food poisoning.

Footnote Macro

Chibber, A. (2011). China finds nitrite in edible bird's nests from Malaysia. [online] Food navigator-Asia. Available at: https://www.foodnavigator-asia.com/Article/2011/08/25/China-finds-nitrite-in-edible-bird-s-nests-from-Malaysia [Accessed 30 Nov. 2018].

 As a result, China, once the largest importer of swiftlet nests, banned the import of all birds’ nest from Malaysia and Indonesia. This caused a huge shock to the industry as demand of both "blood nests" and regular nests dropped significantly; China currently only imports from several Malaysian firms that meet strict regulations that were subsequently set up after the ban.

Footnote Macro

News Asiaone. (2013). China lifts ban on bird's nest imports to Malaysia. [online] Available at: http://news.asiaone.com/News/Latest%2BNews/SoShiok/Story/A1Story20130621-431216.html [Accessed 30 Nov. 2018].


Anchor
3.4
3.4

3.4 House farming

Two centuries ago, the Edible-nest Swiftlet nested solely on coastal habitats where caves were available, and there were no records of inland nesting colonies.

Footnote Macro

Cranbrook, E., Goh, W. L., Lim, C. K., and Rahman, M. A. (2013). The species of white-nest swiftlets (Apodidae, Collocaliini) of Malaysia and the origins of house-farm birds: morphometric and genetic evidence. Forktail, 29, pp. 107–119

 Swiftlets were first reported to nest in houses near cliffs in the village of Sedayu in East Java in 1880, and entrepreneurs eventually began developing methods to attract swiftlets to nest in houses.

Footnote Macro

Lim, C. and Cranbrook, G. (2002). Swiftlets of Borneo. Natural History Publications (Borneo).

 The industry grew as the use of broadcasting swiftlet calls to attract nesting birds became the norm, and a trade in swiftlet eggs began. House nesting swiftlets first appeared in the Malay Peninsula in the 1930s, reportedly first arriving in Singapore from Java, before spreading North across Malaysia.

Footnote Macro

Cranbrook, E., Goh, W. L., Lim, C. K., and Rahman, M. A. (2013). The species of white-nest swiftlets (Apodidae, Collocaliini) of Malaysia and the origins of house-farm birds: morphometric and genetic evidence. Forktail, 29, pp. 107–119

 The swiftlets have a high degree of nest fidelity, and house farmed swiftlets and their young would return to man-made houses (preferably the same one) to nest again

Footnote Macro

Kang, N., Hails, C. and Sigurdsson, J. (2008). Nest construction and egg-laying in Edible-nest Swiftlets Aerodramus spp. and the implications for harvesting. Ibis, 133(2), pp.170-177.

, leaving the depleted natural populations and habitats unrestored.

Footnote Macro

Cranbrook, E., Goh, W. L., Lim, C. K., and Rahman, M. A. (2013). The species of white-nest swiftlets (Apodidae, Collocaliini) of Malaysia and the origins of house-farm birds: morphometric and genetic evidence. Forktail, 29, pp. 107–119

 Furthermore, house nesting swiftlets are suspected to be a hybrid population of A. f. fuciphagus and A. f. inexpectatus or A. f. germani in what could be an ongoing case of domestication; the population of house farmed swiftlets have since spread Northward up to Myanmar, where it may be competing with local subspecies. More extensive regional genetic studies are required to confirm these suspicions.



Image Added

Bird's nest soup prepared with red dates and rock sugar.
(Photo: Steamy Kitchen, 2017)

Footnote Macro

"Chinese birds nest soup" by Jaden Hair. Steamy Kitchen, 19 June 2017. URLhttps://steamykitchen.com/44260-chinese-birds-nest-soup-recipe.html. (accessed on 19 Nov 2018)




Image Added

Edible-nest Swiftlet "blood nest". 
(Photo: Lim Hong Yao, 2018)

Footnote Macro

"Swiftlet blood nest," by Lim Hong Yao, 2018. 

Image Added

Swiftlet house farm in Thailand
(Photo: Alexander Heitkamp, 2007)

Footnote Macro

"Chinese birds nest soup" by Alexander S. Heitkamp. Wikimedia Commons, 2007. URL https://commons.wikimedia.org/wiki/File:Nestinghouse_003.jpg. (accessed on 30 Nov 2018)

4. Ecology and behaviour
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4
4

4.1 Feeding
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4.1
4.1

Edible-nest Swiftlets are aerial insectivores that catch arthropods on the wing. Diet analyses have been conducted by examining regurgitated food boluses; hymenoptera (bees, wasps and ants), diptera (flies) and ephemeroptera (mayflies) made up majority of the food items, while arachnida (spiders and other arachnids), coleoptera (beetles) and hemiptera (true bugs) made up most of the rest.

Footnote Macro

Lourie, S. and Tompkins, D. (2008). The diets of Malaysian swiftlets. Ibis, 142(4), pp.596-602.


4.2 Reproduction
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4.2
4.2

  • Chick development: Each pair of birds would usually lay two eggs and spend an average of 23 days incubating them. The chicks take about 43 days to develop and fledge, with an approximate 50% survival rate in nest houses when under observation (Nigel Langham 1979). Mortality is mostly attributed to eggs or chicks falling off the nests; it is not known why so many of them fall off the nest.


4.3 Echolocation
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4.3
4.3

As Edible-nest Swiftlets nest in places which are completely dark, they have evolved the ability to echolocate using clicking sounds, along with many other species from the genus Aerodramus.

Footnote Macro

Jordan Price, J., P. Johnson, K. and H. Clayton, D. (2004). The evolution of echolocation in swiftlets. Journal of Avian Biology, 35(2), pp.135-143.

 This ability, however, is not diagnostic of the genus as the Pygmy Swiftlet (Collocalia troglodytes) has been proven to possess this ability too.

View file
nameT4254-Aerodramusfuciphagus-snd-1.mp3
height150

Sound recording of an Edible-nest Swiftlet's echolocating clicking calls. (Recorded by Lim Hong Yao, 2018)


5. Taxonomy
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5
5

5.1 Original description
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5.1
5.1

The Edible-nest Swiftlet was originally described by Carl Peter Thunberg, a well renowned Swedish naturalist from the 19th century. Thunberg collected the specimen in Java and described it as Hirundo fuciphagus in his Remarks about the Swallows that build jelly-like, edible Nests published in Kungl. Svenska vetenskapsakademiens handlingar (1812)

Footnote Macro

Thunberg. (1812). Remarks about the Swallows that build jelly-like, edible Nests. Kungl. Svenska vetenskapsakademiens handlingar, Vol. 1, pp.151-156. Accessed from https://www.biodiversitylibrary.org/page/47088095#page/165/mode/1up

(Figure 3), which, with help of Google Translate, roughly states that

  • he collected a specimen that appeared similar to Hirundo esculenta, but upon closer examination discovered it was an undescribed species. 
  • H. fuciphagus can be found in caves of the mountainous areas in Java and made jelly like nests that are a precious commodity.
  • The body of H. fuciphagus is black above and immaculate grey below, about four inches long
  • Tail is rounded and black above and below.
  • Wings black, twice the length of the tail and acute. Feet black and short.
  • Similar to H. esculenta but differentiated by the all black tail, chest and abdomen, no spots.

Type information could not be located online as far as my efforts went.

Image AddedFigure 3: Scans of the original swedish description of H. fuciphagus in Kungl. Svenska vetenskapsakademiens handlingar by Thunberg (1812), obtained from Biodiversity Heritage Library.

Footnote Macro

Thunberg. (1812). Remarks about the Swallows that build jelly-like, edible Nests. Kungl. Svenska vetenskapsakademiens handlingar, Vol. 1, pp.151-156. Accessed from https://www.biodiversitylibrary.org/page/47088095#page/165/mode/1up

5.2 Phylogenetics of swiftlets
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5.2
5.2

Current accepted classification of the species: Animalia - Chordata - Aves - Apodiformes - Apodidae - Aerodramus - A. fuciphagus 

Footnote Macro

Cibois, A., Thibault, J., McCormack, G. and Pasquet, E. (2018). Phylogenetic relationships of the Eastern Polynesian swiftlets (Aerodramus, Apodidae) and considerations on other Western Pacific swiftlets. Emu - Austral Ornithology, 118(3), pp.247-257.

Thunberg (1812) named the Edible-nest Swiftlets in Java Hirundo fuciphagus, mistakenly grouping them together with the swallows (Hirundo is a genus of swallows, which are passerines).

Footnote Macro

Thunberg. (1812). Remarks about the Swallows that build jelly-like, edible Nests. Kungl. Svenska vetenskapsakademiens handlingar, Vol. 1, pp.51-156. Accessed from https://www.biodiversitylibrary.org/page/47088095#page/165/mode/1up

 By the 1900s swiftlets were recognized as a separate taxon Collocalini 

Footnote Macro

Stresemann, E. (1931). Notes on the systematics and distribution of some swiftlets (Collocalia) of Malaysia and adjacent subregions. Bulletin of the Raffles Museum, 6, pp.83–101.

and all its members were initially lumped in the genus Collocalia, then subsequently divided into 3 genera: Hydrochous (Giant Swiftlets) are sister to Aerodramus (medium sized brownish swiftlets)and Collocalia (small glossy plumaged swiftlets). Multiple recent phylogenetic analyses have been conducted to establish that Collocalia are the basal group that are more related to the swifts, followed by Hydrochous and Aerodramus being sister genera (Figure 4).

Footnote Macro

Cibois, A., Thibault, J., McCormack, G. and Pasquet, E. (2018). Phylogenetic relationships of the Eastern Polynesian swiftlets (Aerodramus, Apodidae) and considerations on other Western Pacific swiftlets. Emu - Austral Ornithology, 118(3), pp.247-257.

Footnote Macro

Päckert, M., Martens, J., Wink, M., Feigl, A. and Tietze, D. (2012). Molecular phylogeny of Old World swifts (Aves: Apodiformes, Apodidae, Apus and Tachymarptis) based on mitochondrial and nuclear markers. Molecular Phylogenetics and Evolution, 63(3), pp.606-616.

Footnote Macro

Price, J., Johnson, K., Bush, S. and Clayton, D. (2005). Phylogenetic relationships of the Papuan Swiftlet Aerodramus papuensis and implications for the evolution of avian echolocation. Ibis, 147(4), pp.790-796.

Footnote Macro

Rheindt, Frank E., Janette A. Norman & Les Christidis. (2014). Extensive diversification across islands in the echolocating Aerodramus swiftlets. Raffles Bulletin of Zoology, 62, pp.89-99.



Image Added

Figure 4: Phylogenetic tree of swiftlets obtained using nuclear and mitochondrial DNA analysis, estimated with Bayesian and Maximum Likelihood methods. Node support is denoted as posterior probabilities/bootstrap values. Adapted from Cibois et. al (2018).

Footnote Macro

Cibois, A., Thibault, J., McCormack, G. and Pasquet, E. (2018). Phylogenetic relationships of the Eastern Polynesian swiftlets (Aerodramus, Apodidae) and considerations on other Western Pacific swiftlets. Emu - Austral Ornithology, 118(3), pp.247-257.


5.3 Species taxonomy
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5.3
5.3

Many studies have attempted to resolve the phylogenetic relationships of the Edible-nest Swiftlet, but A. fuciphagus has often shown up as a paraphyletic clade with one or more individuals of A. fuciphagus are more closely related to A. salangana than other A. fuciphagus.

Footnote Macro

Cibois, A., Thibault, J., McCormack, G. and Pasquet, E. (2018). Phylogenetic relationships of the Eastern Polynesian swiftlets (Aerodramus, Apodidae) and considerations on other Western Pacific swiftlets. Emu - Austral Ornithology, 118(3), pp.247-257.

Footnote Macro

Price, J., Johnson, K., Bush, S. and Clayton, D. (2005). Phylogenetic relationships of the Papuan Swiftlet Aerodramus papuensis and implications for the evolution of avian echolocation. Ibis, 147(4), pp.790-796.

Footnote Macro

Rheindt, Frank E., Janette A. Norman & Les Christidis. (2014). Extensive diversification across islands in the echolocating Aerodramus swiftlets. Raffles Bulletin of Zoology, 62, pp.89-99.


 Even the most recent tree constructed using mitochondrial and nuclear DNA analysis depicts this (Figure 4). The low genetic divergence between closely related taxa is likely due to occasional hybridisation events, which have been reported in Sabah

Footnote Macro

Lee, P., Clayton, D., Griffiths, R. and Page, R. (1996). Does behavior reflect phylogeny in swiftlets (Aves: Apodidae)? A test using cytochrome b mitochondrial DNA sequences. Proceedings of the National Academy of Sciences, 93(14), pp.7091-7096.

, leading to genetic introgression in the form of mitochondrial DNA (mtDNA) sweeps that cause some individuals to appear closer to sister species than its own.

Footnote Macro

Rheindt, F. and Edwards, S. (2011). Genetic Introgression: An Integral but neglected component of speciation in birds. The Auk, 128(4), pp.620-632.

Furthermore, some authors disagree with classifying all 8 subspecies under a single species A. fuciphagus. The eight recognised subspecies for A. fuciphagus are as follows (descriptions are relative to nominate race unless stated)

Footnote Macro

Chantler, P. & Boesman, P. (2018). Edible-nest Swiftlet (Aerodramus fuciphagus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/55287 on 29 November 2018).

:

  • A. f. amechanus (Oberholser, 1912) – Anambas Is, off SE Peninsular Malaysia.
    • Darker upperparts with green sheen and paler underparts, with greyer rump than germani
  • A. f. germani (Oustalet, 1876) – Coastline from W Hainan S around SE Asia to Malay Peninsula, including Mergui Archipelago (off S Myanmar); coastal N Borneo and W Philippines (Palawan E to Panay and Ticao).
    • Paler underparts and whitish rump
  • A. f. inexpectatus (A. O. Hume, 1873) – Andaman Is and Nicobar Is.
    • Slightly smaller than nominate race
  • A. f. vestitus (Lesson, 1843) – Sumatra, Belitung I and Borneo (except N coasts).
    • Darkest upperparts, lack contrasting rump
  • A. f. perplexus (Riley, 1927) – Maratua I, off E Borneo.
    • Some purple sheen on rectrices and remiges, slight contrasting rump
  • A. f. fuciphagus (Thunberg, 1812) – Java, Kangean Is and Bali to W Lesser Sundas, and Tanahjampea.
    • Dark brown upperparts with slightly paler greyish rump. Underparts brownish-grey.
  • A. f. dammermani (Rensch, 1931) – Flores (EC Lesser Sundas).
    • Slightly paler rump
  • A. f. micans (Stresemann, 1914) – Sumba, Sawu and Timor (C Lesser Sundas).
    • Slightly greyer overall with contrasting rump

Differences amongst subspecies are often subtle and difficult to distinguish in the field due to variations in lighting as well as difficulty in observing constantly fast-moving subjects.

According to the subspecies range, Edible-nest Swiftlets observed in Singapore should be A. f. germani which extends into the Malay Peninsula, but specimens collected appeared identical to the nominate race A. f. fuciphagus, likely because colonies in Malaysia and Singapore are of the house farmed variety (see House Farming below), which is suspected to be of Javan origin (ssp. fuciphagus). To complicate matters, their feeding ranges are likely overlapping.

Several authors believe that this species should be split into two or three. Table 1 on the below presents a summary of the 3 different treatments.

Table 1: Summary of the authors' different species treatments of the Edible-nest Swiftlet complex.

AuthorSpecies

Subspecies

HBW

Footnote Macro

Chantler, P. & Boesman, P. (2018). Edible-nest Swiftlet (Aerodramus fuciphagus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/55287 on 29 November 2018).

& Stresemann (1931)

Footnote Macro

Stresemann, E. (1931). Notes on the systematics and distribution of some swiftlets (Collocalia) of Malaysia and adjacent subregions. Bulletin of the Raffles Museum, 6, pp.83–101.

A. fuciphagusall 8 listed above

Clement's checklist

Footnote Macro

Clements, J. F., T. S. Schulenberg, M. J. Iliff, D. Roberson, T. A. Fredericks, B. L. Sullivan, and C. L. Wood. 2018. The eBird/Clements checklist of birds of the world: v2018. Downloaded from http://www.birds.cornell.edu/clementschecklist/download/ 

A. germani

germani, amechanus

A. fuciphagus

fuciphagus, vestitus, inexpectatus, perplexus, dammermani, micans

Cranbrook et al. (2013)

Footnote Macro

Cranbrook, E., Goh, W. L., Lim, C. K., and Rahman, M. A. (2013). The species of white-nest swiftlets (Apodidae, Collocaliini) of Malaysia and the origins of house-farm birds: morphometric and genetic evidence. Forktail, 29, pp. 107–119

A. fuciphagus

fuciphagus, vestitus, dammermani, micans

A. inexpectatus

inexpectatus, germani, perplexus

A. amechanusamechanus



The Clement's checklist treatment appears to be based on morphology and original descriptions of the subspecies, but does not appear to explicitly explain the treatment in any publication or platform. Despite this, many authors have adopted this treatment.

 Stresemann (1931) postulated that populations with a paler rump from A. f. germani and those of a darker rump from A. f. vestitus and germani formed a transition zone over Peninsula Malaysia where intergrades of rump colour can be observed.

Footnote Macro

Stresemann, E. (1931). Notes on the systematics and distribution of some swiftlets (Collocalia) of Malaysia and adjacent subregions. Bulletin of the Raffles Museum, 6, pp.83–101.

 Thus, it was proposed that the populations were interbreeding, and thus the taxa were regarded as subspecies of A. fuciphagus. Medway (1966) also arrived at a similar conclusion.

Footnote Macro

Medway, L. (1966). Field characters as a guide to the specific relations of swiftlets. Proceedings of the Linnean Society of London, 177, pp.151–172.


Cranbrook et. al (2013) on the other hand, re-examined the specimens used in Stresemann (1931) and postulated that there was not a cline in morphology, but rather an overlap of feeding range in Peninsula Malaysia.

Footnote Macro

Cranbrook, E., Goh, W. L., Lim, C. K., and Rahman, M. A. (2013). The species of white-nest swiftlets (Apodidae, Collocaliini) of Malaysia and the origins of house-farm birds: morphometric and genetic evidence. Forktail, 29, pp. 107–119

 It was observed that the specimens could be grouped into two main groups: grey-rumped and brown rumped (Figure 5). Given that the rump colour was maintained as a character amongst these two groups with no gradation, it was concluded that these two should be grouped into two species, while amechanus was considered an endemic given its unusual glossy colouration and variable rump band. Grey-rumped swiftlets were grouped under A. inexpectatus while brown-rumped swiftlets remained as A. fuciphagus. Mitochondrial DNA analysis was also conducted in the study with both Maximum Parsimony and Neighbour Joining methods using cyt-b haplotypes but the nodes were all poorly supported and the tree appeared inconclusive regarding the phylogenetic relationships between populations (Figure 6).

However, upon examining the plates, it is apparent that rump colouration can vary significantly within a subspecies; A. inexpectatus germani of plate 3A (Figure 5) clearly shows an individual with a brown rump instead of a whitish rump as described for germani and shown in plate 1A. This raises concerns about using rump colour as a diagnostic trait to treat the species complex (HBW also mentions that the white on the rump is often overstated.

Footnote Macro

Chantler, P. & Boesman, P. (2018). Edible-nest Swiftlet (Aerodramus fuciphagus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/55287 on 29 November 2018).

 Even if the morphological breaks separating the populations in different geographical ranges are real, in applying the Biological Species Concept

Footnote Macro

Wheeler, Quentin D., and Rudolf Meier, editors. Species Concepts and Phylogenetic Theory: A Debate. Columbia University Press, 2000. JSTOR, www.jstor.org/stable/10.7312/whee10142.

, there is insufficient evidence to establish reproductive isolation given that the colonies breed in allopatry. Additionally, Cranbrook et. al (2013) suggested that the house farmed swiftlets could be a hybrid population of fuciphagus and inexpectatus, or fuciphagus and germani, indicating that these taxa may not withstand the test of sympatry when brought together in nest houses. Therefore, A. fuciphagus is currently treated as a single species (encompassing all 8 subspecies) on this page and by several other authors.

In considering the Phylogenetic species concept sensu Wheeler & Platnick (2000)

Footnote Macro

Wheeler, Quentin D., and Rudolf Meier, editors. Species Concepts and Phylogenetic Theory: A Debate. Columbia University Press, 2000. JSTOR, www.jstor.org/stable/10.7312/whee10142.

, most of these subspecies are likely to be elevated to the rank of species given that the different populations appear to have a unique set of character states in terms of size and plumage differences. However, more work needs to be done as well to adequately sample the different populations to establish the existence of these different character states.

Future taxonomic work is required to concretely establish the relationships between these taxa, both in terms of confirming morphological differences as well as investigating molecular evidence. Goh et. al (2018) recently investigated more house farmed Edible-nest Swiftlets from Peninsula Malaysia and found that they appeared to be closest to A. f. vestitus rather than A. f. fuciphagus (which was first to be recorded in the Malay Peninsula), but the node was not very well supported (bootstrap = 78) and no conclusive statements about their origin could be made.

Footnote Macro

Goh, W.L., Siew, W.S., Davies, S.E.W., Ball, S. Ball., Khoo, G., Lim, C.K., Rahman, M. A., and Cranbrook, E. (2018). Genetic diversity among white-nest swiftlets of the genus Aerodramus (Aves: Apodidae: Collocaliini) of house-farms in Malaysia. Raffles Bulletin of Zoology, 66, pp.350–360

 Given the many unsuccessful attempts with mtDNA thus far, it is likely that mtDNA is unsuitable as a marker for intraspecific studies as it is only maternally inherited. Coupled with the issues of mtDNA sweeps, it is evident that mtDNA is not an effective  taxonomic indicator for the Edible-nest Swiftlets, and adopting genomic methods using Next Generation Sequencing is likely the way forward to unravel the true relationships between these populations.

Image Added


Image Added

Figure 5: Photo plates by Cranbrook et. al (2013) depicting the grey-rumped and brown rumped Edible-nest Swiftlet specimens examined

Footnote Macro

Cranbrook, E., Goh, W. L., Lim, C. K., and Rahman, M. A. (2013). The species of white-nest swiftlets (Apodidae, Collocaliini) of Malaysia and the origins of house-farm birds: morphometric and genetic evidence. Forktail, 29, pp. 107–119

.


Image AddedFigure 6: Maximum Parsimony tree created using cyt-b haplotypes from Edible-nest Swiftlet samples by Cranbrook et. al (2013)

Footnote Macro

Cranbrook, E., Goh, W. L., Lim, C. K., and Rahman, M. A. (2013). The species of white-nest swiftlets (Apodidae, Collocaliini) of Malaysia and the origins of house-farm birds: morphometric and genetic evidence. Forktail, 29, pp. 107–119

. Numbers at nodes are the Neighbour Joining/Maximum Parsimony bootstrap values (tree topology was identical for both methods). 

References: 

Display Footnotes Macro

This page was authored by Lim Hong Yao

Last curated on 3 December 2018