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Breeding Ecology of the Edible-nest Swiftlet Aerodramus fuciphagus and the Glossy Swiftlet Collocalia esculenta in the Andaman Islands, India

Breeding Ecology of the Edible-nest Swiftlet Aerodramus
fuciphagus and the Glossy Swiftlet Collocalia esculenta in the
Andaman Islands, India
The intriguing biological feat of making a nest with its saliva is threatening the survival of the
edible-nest swiftlet. Ever since the16th century when bird’s nest became a delicacy in Chinese
cuisine and an important item in their pharmacy, edible nest swiftlets are found overexploited
all over. In the past two to three decades the production of the edible bird’s nests has reduced
drastically because of over-exploitation and uncontrolled harvesting that is directly affecting
the population of this cave-dwelling species. The high demand in the international markets has
put so much pressure that despite strict regulations on nest collection, the wild populations of
the edible-nest swiftlets is plummeting by as much as 80% to 90% and has reached local
extinction across some of their ranges.
India has four species of swiftlets: the Indian Edible-nest Swiftlet Aerodramus unicolor (Jerdon
1840), the Himalayan Swiftlet Aerodramus brevirostris (McLelland 1840), the Glossy Swiftlet
Collocalia esculenta (Beavan 1867) and the Edible-nest Swiftlet Aerodramus fuciphagus (Hume
1873). Edible-nest swiftlet, the producer of edible nests, is distributed only in the oriental region
of the world and the Andaman and Nicobar Islands of the Indian Territory. The collection of
these commercially valuable nests started in the Andaman and Nicobar Islands in the 18th
century. International demand led to widespread and uncontrolled nest collection in these
islands leading to a severe fall in population.
A programme to conserve the edible-nest swiftlet in the Andaman and Nicobar Islands
commenced in 1995, and is being implemented by the Department of Environment and Forests,
Andaman & Nicobar Islands (ANF) and Sálim Ali Centre for Ornithology and Natural History
(SACON) since 2001. The programme is implemented in 28 caves at Chalis-ek, Pattilevel,
North Andaman Island and one cave at Interview Islands Wildlife Sanctuary, Middle Andaman
Islands. These 29 caves hosting colonies of the edible-nest swiftlet are protected during the
breeding season between January and August. The species Aerodramus fuciphagus
inexpectatus (Hume 1873) was studied in its natural habitat as part of the programme. Though
data collection began in 2001, it was collected mainly between 2004 and 2007. As the glossy
swiftlet Collocalia esculenta affinis (Beavan 1867) of the island group has a significant role to
play in the ex-situ conservation of edible-nest swiftlet in urban areas, wild populations of this
species were initially studied along with the edible-nest swiftlet to know the ecology of these
species in their natural habitats.
The two sympatric species, i.e., the edible-nest swiftlet and the glossy swiftlet were studied for
their breeding ecology concerning their habitat requirements and the impact of protection on
the population of the edible-nest swiftlet in the Andaman and Nicobar Islands.
Nest-site characters, preference and the relationship with nesting success were studied to
understand the nest-site requirements of the edible-nest swiftlet. Results showed that the edible-
nest swiftlet and the glossy swiftlet are cave-dwelling trogloxenes and do not nest randomly
inside the caves. The ability to echolocate allows the edible-nest swiftlets to nest and roost in
the dark zones of the caves. The glossy swiftlet does not echolocate and therefore builds its
nests near cave openings in the dim-lit zones of the cave. The Edible-nest and glossy swiftlet
have shown their preference for rough and slightly rough-textured rocks, inwardly inclined
walls, with a presence or absence of supports and the different combinations of these
characteristics during nest-site selection. These preferred characteristics and their combinations
contribute substantially to nesting success among edible-nest swiftlet. Micrometeorological
parameters were studied inside the caves. The mean temperature showed a negative
relationship with nesting success, while relative humidity showed a positive relationship in the
case of edible-nest swiftlets. This information gives clear solutions to engineer better ex-situ
swiftlet houses for edible nest swiftlets.
Foraging habitat requirements were studied near the breeding colonies of the species at Chalis-
ek. The aerial and foraging behaviors and their occurrence in different habitats and
microhabitats helped to estimate the foraging habitat requirements of both species. Both these
exclusively aerial foraging species showed a noticeable difference in their foraging habitat
requirements near their breeding sites. The edible-nest swiftlets depend on forest canopy to a
great extent, whereas the glossy swiftlets forage in both forest and open land habitats. Edible-
nest swiftlets preferred heights above the canopy level and also close to the top of the canopy.
Glossy swiftlets were seen foraging close to the canopy top in forested areas and below canopy
levels in the loose vegetations along streamsides in the deforested open patched. The current
rate of deforestation can severely affect the populations of the edible-nest swiftlets, whereas
the glossy swiftlets are much better adapted to forest alterations.
Nests of both the species were visited daily to study their breeding seasonality and chronology.
The study shows that the edible-nest swiftlets in the Andaman and Nicobar Islands have a well-
marked breeding season with two broods from December to August, whereas, the glossy
swiftlets in the wild breed throughout the year and fledge almost four broods per year. The
breeding seasonality in the edible-nest swiftlet is linked with rainfall. Glossy swiftlets do not
show any relation with meteorological parameters. Edible-nest swiftlets use the only saliva as
the nest material whereas the glossy swiftlets use moss, twigs, grass, vegetation matter, and
others, glued together with their saliva. The behavioral study of the edible-nest swiftlets
showed that they copulate mostly on the nests and have a slightly longer incubation and
fledgling period as compared to the glossy swiftlets. Both the species have a typical clutch size
of two eggs with comparatively successful first clutch than the second. Detailed information
on the breeding biology of the species provides support for planning the fostering programme
and also to predict the hatching and fledging success of the edible-nest swiftlet eggs in the
glossy swiftlet nests. This information can be utilized for proper scheduling of cave protection
and nest harvest timings and to develop a protection system for in-situ conservation.
The continuous improvement in the population growth has proved that the strategy of
protecting the populations of edible-nest swiftlet in their natural habitat with the involvement
of motivated nest collectors is a successful method of conserving edible-nest swiftlets in the
Andaman and Nicobar Islands. However, a population decline of over 73% in the unprotected
caves and local extinction from more than 60% of the unprotected caves surveyed within a
decade is alarming, which calls for the expansion of the edible-nest swiftlet conservation
programme all over the islands arc to prevent the extinction of the species.
Since the species was included in the Scheduled-I of the Wildlife Protection Act, 1972 in
September 2003, the post-breeding harvest of the bird’s nests is not possible. As a result, the
protectors deputed at the cave mouths are getting demoralized. It is to be noted that the
protectors were nest collectors who worked for the protection of the colonies with an incentive
to harvest the nests at the end of the breeding season. Their de-motivation could hinder the
expansion of the in-situ conservation programme. It is imperative to consider the removal of
the species from the schedules and to ensure the survival of the species through sustainable
practices, local participation, and scientific management.
... The cave-dwelling Edible-nest Swiftlet (Aerodramus fuciphagus inexpectatus) is subspecies endemic to the Andaman and Nicobar Islands (Cranbrook et al. 2013;Gill et al. 2020). The Edible-nest Swiftlet breeds between December and August and has a clutch size of two eggs with an incubation period of 22-25 days (Manchi 2009). Recent ecological studies (Manchi 2009;Manchi and Sankaran 2011;Mane and Manchi 2017) considered microclimate (temperature and humidity) and physical characteristics of cave surfaces as influential parameters of breeding and roosting habitat of the ENS. ...
... The Edible-nest Swiftlet breeds between December and August and has a clutch size of two eggs with an incubation period of 22-25 days (Manchi 2009). Recent ecological studies (Manchi 2009;Manchi and Sankaran 2011;Mane and Manchi 2017) considered microclimate (temperature and humidity) and physical characteristics of cave surfaces as influential parameters of breeding and roosting habitat of the ENS. Further studies on ENS habitat by Manchi and Sankaran (2011) revealed the importance of nest-site characteristics, nest-site selection, and preference towards nest success. ...
... The population size of ENS inside each study cave was estimated using the nest count method (Sankaran 2001;Manchi and Sankaran 2014). As ENS are known to be monogamous (Koon and Cranbrook 2002), each nest was considered equal to a breeding pair or two adults (Manchi 2009). The ENS starts nest-building during December and continues till mid-February when the egg-laying starts. ...
Decision rules allow individuals of a species to decide whether or not to return to the same site in the following year or season, based on their immediate breeding success. We checked the decision rule phenomenon and simultaneously tested the prior-experience hypothesis for the cave-dwelling Edible-nest Swiftlet (Aerodramus fuciphagus inexpectatus; ENS) in the Baratang Cave Complex, Andaman and Nicobar Islands, India. We used the capture-mark-recapture method to understand the decision rule in ENS. Assuming that breeding success affects the decision, we monitored 234 individuals for two consecutive breeding seasons (2017 and 2018). We also documented habitat variables (cave morphometry and microclimate) to understand the correlates of breeding success. We captured 88% (207 birds) of adult birds from the study caves in 2017 and recaptured 66% (137 birds) of adults from the same caves in 2018, which confirmed fidelity towards the cave by the species. There was no significant correlation between the rates of breeding success in 2017 and 2018. Multiple regression models revealed an insignificant relationship between cave structure and breeding success of the species. Additionally, microclimate variables (temperature and humidity) did not influence the breeding success of the birds. Our results indicate that ENS individuals seem to chose decision rule by rejecting the prior-experience hypothesis. The existing conservation strategies associated with enhancing the ENS population in the Andaman and Nicobar Islands can benefit from our findings. We further recommend long-term studies and population monitoring to understand the breeding cave fidelity in ENS.
... The ecology and biology of these birds are now studied mostly in the artificial conditions of houses specially built for them. However, wild populations in caves have also been studied to gain information on their breeding biology (Medway 1962a, Langham 1980, Nguyen 1994, Lim and Cranbrook 2002 and ecology (Medway 1962b, Harrisson 1976, Phach and Voisin 1998, Nguyen et al. 2002, Manchi 2009). The Oilbird (Steatornis caripensis) of South America and swiftlets (Aerodramus and Collocalia spp.) of South Asia, the Pacific Islands, and northeastern Australia are the only birds known to possess the ability to echolocate (Price et al. 2004). ...
... Further, a conservation program for the species, initiated in 2000 (Sankaran 2001), is still ongoing Manchi 2008, Manchi andMane 2012). Most of the ecological studies regarding breeding biology, nesting, and foraging ecology were conducted simultaneously (Sankaran and Manchi 2008, Manchi 2009, Manchi and Sankaran 2010, Manchi and Mane 2012. The roosting ecology of the species has been studied for more than a decade; however, a more detailed explora-tion was initiated in 2011 (Manchi and Mane 2012). ...
... We performed 1-sample t-tests to find temporal (hourly) variations in the movements (entry and exit) of birds. Considering the wide foraging range and synchronous breeding pattern of the species (Manchi 2009, Manchi andSankaran 2010), we thought that the daily movement of the Andaman Edible-nest Swiftlet would be uniform across different study sites. Presuming every bird would leave and enter the cave at least once in a day, we considered the expected proportion of birds roosting in an hour as 100% divided by 24 h (i.e., 4.16% per hour). ...
We collected data from 10 caves (3 sites) in the North and Middle Andaman Islands to determine the spatiotemporal changes in the roosting pattern of the Andaman populations of Edible-nest Swiftlet Aerodramus fuciphagus inexpectatus. The echo-locating diurnal aerial forager showed temporal (hourly) variation in their round the clock entry and exit patterns. With spatiotemporal variations (site wise, cave wise, hourly, and monthly), more than 98% of birds returned daily to the roosting caves between 1700 h and 2000 h. However, their daily departure time (between 0400 h and 0700 h) did not vary spatially (site wise and cave wise). The movements of birds at the cave openings were higher during nestling period in April and May. The daily roosting period inside the caves (525.20 ± 82.98 SD min) also depicted spatiotemporal variations. The length of the day affected the movement of the birds before and after sunset and sunrise. We conclude that roosting movement of the Andaman Edible-nest Swiftlet varied spatiotemporally in the Andaman Islands. This first detailed description of such variations in the roosting movements of the species will stimulate further exploration of the various biological and environmental factors affecting movements of this cave-dwelling endemic.
... Germain's swiftlet feeds on flying insects whose distribution is influenced by climatic conditions (Srygley and Dudley 2008) and by land cover/land use (Petkliang et al. 2017). Overall, bird breeding activities and other energetically costly activities such as molting appear to be affected by the food supply (Sodhi 2002) and rainfall appears to be strongly linked to swiftlet breeding seasonality (Manchi 2009). Wind has also been shown to play an important role in the ecology of insectivorous birds in general (Dunn et al. 2011;Møller 2013;Ö berg et al. 2015). ...
... Although most Aerodramus spp. breed twice per year, such as the breeding swiftlets in Vietnam (Phong et al. 2015) and Andaman and Nicobar Islands (Manchi 2009), and some swiftlets can raise a third brood in wet months, when there are more food resources than in dry months (Petkliang et al. 2017), the timing and duration of this reproduction appears to vary regionally. Thus, some birds demonstrate reproductive flexibility by reducing reproductive activity during dry months or very wet periods and increase it as the food supply rebounds (Visser et al. 2006). ...
... When rainfall was lower than 100 mm month À1 or over 300 mm month À1 , the percentage of breeding birds and total insect biomass decreased. Such an association between swiftlet breeding and rainfall has also been found in central Thailand (Viruhpintu 2002), Penang, Malaysia (Langham 1980;Anun et al. 2014), Nicobar Islands in India (Manchi 2009) and Sarawak, Malaysia (Lim and Cranbrook 2002;Lim 2011) (Table 1). ...
The Germain's swiftlet (Aerodramus inexpectatus germani) feeds on flying insects whose distribution and abundance are influenced by climatic conditions, especially rainfall. In turn, insect availability influences the onset of breeding by swiftlets, hence regions with different climatic conditions such as the west and the east coasts of peninsular Thailand should differ in swiftlet breeding chronology. Here we aimed to determine the variation in breeding chronology between the west and east coast colonies and relate this to insect availability. For each side of the peninsula, at least 40 breeding pairs were continuously observed (July 2014 to October 2015), using 'internet protocol' infrared cameras installed inside four commercial swiftlet houses. Flying insects were trapped every two weeks using sticky traps at three permanent stations within major foraging habitats. The onset of breeding in the western colonies was earlier than in the eastern colonies. These significant differences were explained by rainfall and food availability that showed synchrony between the nestling feeding period and peaks in insect biomass. Rainfall of 100-300 mm month⁻¹ overlapped with peak breeding and peak insect biomass. These findings have significant implications for the sustainability of swiftlet nest harvesting and demonstrate that, to minimise negative reproductive outcomes for swiftlets where nests are harvested, the timing of harvesting should consider regional climatic conditions.
... As the echolocation ability of the Edible-Nest Swiftlet is not as developed as that of bats (Chiroptera), Edible-Nest Swiftlets apparently echolocate only for navigation in the darkness (Medway 1967;Langham 1980 and Murphy 1994), within or outside their roosting caves (Medway 1967;Waugh and Hails 1983;Chantler 2000;Manchi and Sankaran 2010). However, their roosting behaviour is thought to vary in relation to breeding stages (Nguyen et al. 2002;Manchi 2009). ...
... We also recorded environmental temperature, humidity and sunset time on each observation day. Following Manchi (2009), breeding chronology/seasonality data were collected from the accessible nests in 10 different caves (six caves selected for roost counts along with four other caves). Though the Edible-Nest Swiftlet breeds between December and August in Baratang, our observations were restricted to the period January to May, as the data gathering was hampered by nest harvesting after the first brood. ...
... Similar to the observations of Manchi (2009) from Chalis-ek, in the Andaman Islands, breeding chronology affected the roosting pattern of the Edible-Nest Swiftlet at Baratang. The food/energy requirements in different breeding stages (Manchi 2009) may influence the changes in the roosting patterns. The percentage of birds roosting within PRH during incubation and nestbuilding periods is significantly higher than nestling and fledging periods. ...
Full-text available
Environmental conditions and biological rhythms can affect the behavioural routines of animals. However, the effect of lunar phase on individual roosting behaviour remains uninvestigated in most species. Here, we monitored the effect of lunar phase, sunset time, temperature, humidity and the breeding chronology on the roosting patterns of the Edible-Nest Swiftlet (Aerodramus fuciphagus) of the Andaman Islands, across breeding stages. Counts revealed that more than 98% of the population returned to the roosting caves during peak roosting hours, i.e. 1700–2000h. The proportion of birds roosting in caves was highest during the ‘new moon’ phase and when birds were at the nest-building and fledging stage of their breeding cycle. We confirmed that the variation in the roosting behaviour of the Edible-Nest Swiftlet is linked both to the stages in the breeding cycle and to the lunar phase. We hypothesise that the cause for the lunarphilic roosting pattern is an anti-predator strategy. Feeding habits and food requirements during different breeding stages are presumed to influence the roosting pattern of the species. An improved understanding of the association of the behaviour, physiology and the environmental conditions which influence these traits can only help us improve conservation outcomes for this economically important species.
... Chalis-ek contains a group of inland limestone caves in a hill at Pattilevel near Ramnagar in the south-east of North Andaman Island (Sankaran, 1998(Sankaran, , 2001Manchi & Sankaran, 2009b). Of the 30 known caves in the hill, 28 are occupied by the white-nest swiftlet and have been under continuous protection since 2001, particularly during the breeding season of January-July (Sankaran & Manchi, 2008;Manchi, 2009). These caves are protected by 14 former nest collectors who operate from eight temporary camps at the base of the hill. ...
... The 133 km 2 Interview Island is the largest Wildlife Sanctuary on the Andaman and Nicobar Islands (Pande et al., 1991) and is the westernmost uninhabited island of North and Middle Andaman. This island has at least 34 caves, of which 18 are known to host breeding colonies of the white-nest swiftlet (Sankaran, 1998;Sankaran & Manchi, 2008;Manchi, 2009). One of the caves (Manchi & Sankaran, 2009b) has been under protection since 2000 (during January-September; Sankaran & Manchi, 2008). ...
... The population at Chalis-ek declined during the breeding season following the commencement of protection. This was attributed to the absence of yearlings in the breeding season subsequent to their birth; they would usually return to their parental cave at the end of the season and breed in the following season (Sankaran & Manchi, 2008;Manchi, 2009). The population increased from 2002 onwards until the earthquake of December 2004, which altered the structure and microclimate of the caves and appeared to lead to a decline in the population (Manchi & Sankaran, 2009b). ...
Full-text available
International trade of swiftlet nests has affected wild populations of edible-nest swiftlets throughout their range. The white-nest swiftlet Aerodramus fuciphagus of the Andaman and Nicobar Islands lost 80% of its population in the 1990s. Conservation efforts for the species were initiated in 2000, with the active involvement of former nest collectors. To measure the efficacy of protection measures we collected data on the swiftlet, using the nest count method. We monitored annual breeding populations in 28 protected caves on Chalis-ek and one on Interview Island during 2000-2008, and in 168 unprotected caves on Baratang and Interview Islands during February-April 2008. The swiftlet population in protected caves increased by 39%, whereas it declined by 74% in unprotected caves. Nearly 61% of the 152 caves on Baratang Island were abandoned by the swiftlet during 1997-2008. This study highlights the importance of extending protection to the unprotected caves on the Andaman and Nicobar Islands.
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