Breeding biology of the Little Cormorant Phalacrocorax niger (Pelecaniformes: Phlacrocoracidae)
in Bangladesh
Habibon Naher 1, Noor Jahan Sarker 2, Md. Khalilur Rahman 3 & Shawkat Imam Khan
4
1Lecturer
(Biology), Shahid Zia Girls’ College, Jatrabari, Dhaka 1204, Bangladesh
2,3Professor,
Department of Zoology, University of Dhaka, Dhaka 1000, Bangladesh
4Taxidermist,
Department of Natural History, Bangladesh National Museum, Shahbag,
Dhaka 1000, Bangladesh
Email: 4 sukhi_194@yahoo.com (corresponding author)
Date of online
publication 26 April 2009
ISSN 0974-7907
(online) | 0974-7893 (print)
Editor: Rajah Jayapal
Manuscript
details:
Ms # o1790
Received 27 May
2007
Final received
14 March 2009
Finally accepted
25 March 2009
Citation: Naher, H., N.J. Sarker, M.K. Rahman & S.I. Khan (2009). Breeding biology of the
Little Cormorant Phalacrocorax niger (Pelecaniformes:Phalacrocoracidae) in Bangladesh. Journal of
Threatened Taxa 1(4): 221-225.
Copyright: © Habibon Naher, Noor Jahan Sarker,
Md. Khalilur Rahman & Shawkat Imam Khan 2009. Creative Commons Attribution 3.0 Unported License. JoTT allows
unrestricted use of this article in any medium for non-profit purposes,
reproduction and distribution by providing adequate credit to the authors and
the source of publication.
Author Details: Habibon Naherhas been working as Lecturer of Biology for the last six years. Currently, she
has registered for a PhD on Kingfishers of Bangladesh. She has already published several scientific
papers on different aspects of wildlife of Bangladesh in different national and
international journals.
Noor Jahan Sarker is the Chairman of the Department of Zoology. She has published
nearly 70 research papers dealing with different aspects of Bangladesh’s
wildlife in national and international journals and more than 100 popular
scientific articles and four books.
Md. Khalilur Rahman is a Professor of Zoology and
has been doing several research works on wildlife and environmental issues in
Bangladesh. He specializes in Ornithology.
Shawkat Imam Khan is involved in wildlife research in Bangladesh for
the last seven years. Currently, he
works as a taxidermist.
Author
contribution:All of the authors have equal contribution to do the study and preparation of
the manuscript.
Acknowledgements: The authors are especially grateful to Mr. Tauhid Uddin Ahmed, Ex-Principal Scientific Officer, IECDR, Mohakhali, Dhaka, Bangladesh for
making helpful and constructive comments to enrich this paper.
Abstract:The breeding biology of the Little Cormorant Phalacrocorax niger was studied in a
nesting colony at Dhonagoda Village in Chandpur District, Bangladesh between 2003 and 2005. The breeding activities of the Little
Cormorant commenced in May and continued till October. The major nesting trees
of the colony included Albizzia procera, Mangifera indica, Ficus spp.,Streblus asperand Cocos nucifera.
Both partners took part in nest building (n=33). The nest building period was 8 to 15 days (mean±SD 10.85±1.98) and the clutch size (n=20) varied from
2 to 6 (3.75±0.8). The length and
diameter of the eggs (n=115) ranged between 4.05 and 4.98 cm (4.5±0.18) and 2.5
and 3.03 cm (3±0.07) respectively. The
eggs weighed between 14g and 25g (18.4±0.88). The incubation period was from 14 to 21 days (17.3±2.1) and the weight
of the hatchling varied from 4 g to 18.2g (10.45±3.6). The brooding period was
from 15 to 20 days (17.3±1.26). The young flew away from the nest at the age of
17 to 29 days (20.85±2.8) after hatching when the weight was 350g to 470g
(411.93±28.55). The breeding success was 78.76% in relation to eggs hatched and
68.26% in relation to eggs laid.
Keywords:Bangladesh, breeding season, clutch size, hatching success,
incubation, nesting material, mortality rate, Phalacrocorax niger.
For Figures & Tables –
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Introduction
Although the natural history
of Little Cormorant Phalacrocorax niger is well known through a large number of anecdotal
reports (Jerdon 1862; Whistler 1949; Wallace 1971;
Ali 1977, Barnes 1981; Welty & Baptista 1988; Perrins 1990), very few research works on the breeding
biology of the species exist (Sirriwannichkul1981). For scientific management of the
cormorant population and their conservation, it is imperative to study breeding
ecology, survival, and mortality and factors that influence their breeding
success. Though cormorants, as a group,
are well-studied, Little Cormorant has received scant attention from bird
biologists. In particular, there exists no published information on the
breeding biology of Little Cormorant in Bangladesh. In an attempt to fill this information gap,
this study was conducted to understand the breeding biology of the Little
Cormorant with emphasis on biometry of eggs and fledgling success in
Bangladesh.
Material and
Methods
The study was conducted
in a nesting colony at Dhonagoda Village near Dhonagoda River under the Upazila Matlab (North) in the district of Chandpur,
Bangladesh. The colony was situated at
the northern side of Dhonagoda Bazar,
eastern side of Matlab-Dhonagoda embankment and
western side of Dhonagoda river, a place 47.5 km southeast
away from the capital city of Dhaka. The
geographical position of the area is 23028.334’N & 90041.610’E.
The study area has
typical tropical climate with May being the hottest (average 30.30C) and
January the coldest (average 17.20C) month. Temperature ranges from 12.20C to
34.40C (average 26.180C). The mean
annual rainfall was 173.75mm with a maximum of 754mm.
The total area of the
colony site was 20305.13m2. The colony
was located at the vicinity of two ponds. There was a passage in between the ponds, which was being used as access
path to the embankments. The Matlab-Dhonagoda road passes along the embankment. The area of the pond of the western side of
the passage was 14179.06m2 and another one was 8562.93m2. The pH level of the water of one pond was 8.9
and the other was 7.4. The water depth was 1.2m at the early breeding season
(March-April) and 3-3.6 m during monsoon.
We used pan-balance
(graduated between 0-2000g), spring balance (5-1000g), slide calipers, steel
scale (graduated up to 1mm), tape scale (1-150cm), meter tape (1cm - 50m),
manual counter, pH meter, and GPS (12XL, Garmin) during the study period. The area was visited twice a week during
breeding season and once a week during non-breeding season.
Windows spreadsheet
program Excel and statistical software SPSS (version 12) were used to do all
the computations and numerical analyses. All the mean values are provided with
standard deviations.
Results and Discussion
Breeding season
The breeding of the
Little Cormorant began in May and continued until October, similar to
observations by Whistler (1949), Smythies (1953), Ali
& Ripley (1968), Begum (1977), and Siriwannichkul(1981). The slight variations in the
above studies are to do with changes in the rainy seasons between southern
India, Sri Lanka and Thailand.
The peak month in
nesting was observed between July and August in the present observation but it
was February through July in Kerala, a southwestern state of India (Jayson
2001). Again, these differences of nesting months can be explained with the
advent of rainy season, which is different in different places.
Morphological
changes of the bird during breeding season
The colourof the feathers becomes dull at the early breeding season (May-June) with a
short occipital crest in both the sexes. Occurrence of Little Cormorant with
white and brown feathers was reported by Ripley (1962) & Jayson
(2001). Thomson (1965) mentioned the
ornamental patches in orbital skin and chin. In both sexes the whole margin of
the gular pouch was observed to become paler during
breeding period. Jerdon(1862) & Whistler (1949) observed that the gularpouch was livid. But Thomson (1965)
found colourful patches on the gularpouch of the bird. In the present study,
black bristle like plumes on either side of the beak and white eyelashes were
found on the body of the birds. Some
workers found livid eyelids during the breeding period of the birds (Jerdon 1862; Whistler 1949). Jerdon(1862) in his observation also found a white triangular spot on the head of the
bird.
Breeding Colony
During the study period
the Little Cormorant built their nests (n=294) with the Indian Pond Heron Ardeola grayii(n=37 constituting 11.11%,) and the Little Egret Egretta garzetta(n=2 forming 0.60%,). The Little
Cormorant breeds on trees in company with darter and egrets (Smythies 1953). Ali
& Futehally (1967) mentioned that the cormorants
frequently built their nests in mixed colonies with egrets and storks. Begum
(1997) reported that the Little Cormorant built their nests in mixed colonies
with Intermediate Egret and Flying Fox.
Selection of
nest site
From the study it was
found that, the cormorants built their nests on tress close to human
habitation, however, always near to water body. It is seen that cormorants build nests on trees close to water bodies
(Whistler 1949, Ali & Futehally 1967, Siriwannichkul 1981; Begum 1997); in rare occasions nesting
trees are also found away from water bodies (Ali 1977).
Nesting trees
The Little Cormorant has
been observed to nest on Albizzia procera (5.48%), Mangifera indica (61.07%), Ficus spp. (24.5%), Streblus asper (6.85%) and Cocos nucifera (2.1%). It bred only on trees (Jerdon 1862; Ali 1977). However, in India it occasionally bred in reed-beds (Whistler
1949). Smythies(1953) described that in Burma they bred in bamboo and palms as well as in
trees. The height and GBH (girth at
breast height) of the nesting trees ranged from 9.2m to 11.2m (10 ± 0.76m) and
66cm to 125cm (96 ± 20.97cm) respectively. The maximum height of nests ranged from 7.8m to 10.6m (9.4 ± 0.8) from
the ground and the minimum height was 6m to 10.2m (8.5 ± 1.25m). Begum (1997) reported that they built their
nests between 13.5m to 17.5m height above the ground.
Nesting
materials
Major plant species
used for collecting nesting material by Little Cormorants include Capsicum frutescens, Eucalyptus citriodora,Coriandrum sativum, Cynodon dactylon, Enhydra fluctuans, Corchorus olitorius, Ziziphus jujuba, Mangifera indica and Polygonum sp (Table 1). Twigs used in nest building were observed by
Ali & Futehally (1967). Sticks used in the nest construction were
observed by several authors (Lewis 1929; Kortlandt1938, 1940; Whistler 1949; Smythies 1953; Ali 1977;
Barnes 1981). Thomson (1965) mentioned
sea-weeds, vegetation of sticks as nesting material depending on the site. Caesalpinia pulcherrima were used in captivity as nesting material (Sarker& Naher 2007).
Measurement of the nests
The nest was a cup
shaped structure with a depression in the middle. The maximum height of the
nests varied from 7.8m to 10.6m (9.4 ± 0.8) from the ground.
The outer diameter of
the nests (n=20) varied from 19 to 45cm (27.15 ± 5.8) while the inner diameter
of the cup ranged from 9 to 20cm (14.3 ± 2.8). The depth of the cup was from 4 to 8cm (5.4 ± 1.4).
Nest building
Both of the partners
took part of the collection of the nest material and the arranging of the material, that used their breast, legs and bill to give the
nest a proper shape. The observed
participation of both the sexes of Little Cormorant in nest-building was also
mentioned in Ali & Ripley (1968).
The Little Cormorant
took 8 to 15 days (10.85 ± 1.98 days) (n=20) for nest building. Begum (1997) reported that they took 4 to 6
days (average 4.9 days).
Egg laying
It was observed that
most of the eggs were laid at one-day interval. Begum (1997) also had similar observation in a study in Tangail district of Bangladesh. But a few eggs (10%) were also laid at an
interval of two days in our study. Interestingly, two eggs were laid on the same day in one instance, one
in the morning and the other in the evening.
Clutch size
The clutch size of the
Little Cormorant varied from 2 to 6 (3.75 ± 0.8) (n=20) as observed during the
present study. The clutch size has been
observed to range from 2 to 5 sometimes 7 (Jerdon1862; Whistler 1949; Thomson 1965; Ali & Ripley 1968; Ali 1977; Siriwannichkul 1981; Barnes 1981; Begum 1997).
Shape of the eggs
The shape of the eggs
was oval, more or less pointed at one end and the other end was round in
concurrence with the observation of Barnes (1981).
Colourof the eggs
The newly laid egg was
white to bluish-white. Jerdon (1862) mentioned that the eggs were pale green in colour. Barnes
(1981) & Begum (1997) mentioned that the eggs were white or bluish-white incolour when freshly laid. Ali (1977) described that the colour was pale bluish-green with a chalky surface.
In the present study,
it was observed that the eggs were becoming brownish or yellowish as incubation
proceeded (Image 1). Such soiling of
egg-shells with time has been reported in Little Cormorants before as well
(Whistler 1949; Barnes 1981). Wallace (1971), however, described that the egg colour may change strikingly with age beyond the mere tarnishing
that goes with continued incubation.
Measurement of
the eggs
The length of the eggs
ranged from 4.05 cm to 4.98cm (n=115) (mean 4.5 ± 0.18cm). The average diameter
of egg was 3 ± 0.07cm (n=115) with a variation of 2.5 to 3.05cm. The weight of
the eggs varied from 14 g to 25g (n=115) (mean 18.4 ± 088g).
The mean dimension was
4.5 x 3cm (1.77 x 1.14in) and Whistler (1949) reported it was 1.75 x
1.15in. The average size was 4.48 x
2.9cm (Ali & Ripley 1968). Begum
(1997) described that the average size of 38 eggs to be 4.4 x 2.8cm.
From the statistical
analyses it was revealed that the length was positively correlated with weight
and girth and the tests were statistically significant (Table 1).
Incubation
The female started
incubating immediately after laying the first egg. This was also reported by Ali & Ripley
(1968) and Begum (1997). Both the sexes
are said to take equal part in incubation (Ali & Ripley 1968).
The incubation
period
The incubation period
varied from 14 to 21 days (mean 17.3 ± 2.1) and it increased significantly with
the clutch size (r = 0.671, n=20, p < 0.05). The length of the incubation period was marginally lower in the present
study in comparison with the published observations elsewhere, which was 22-26
days (Siriwannichkul 1981; Perrins1990; Begum 1997).
Egg mortality
We observed clutch loss to the
tune of 13.74% in the Little Cormorants in the current study. Earlier, Begum (1997) reported 36.82% egg
mortality. Stealing (by the local boys for consumption) was the main cause of
the egg loss in the present study (Fig. 1). Other causes that have been attributed to loss include predation
(10.52%), human interference (7.89%), infertility (5.26%), handling (5.26%) and
sudden fall (2.63%) (Begum 1997).
Weight variation of eggs
The weight of the egg
varied significantly during incubation period. During first 10 days of incubation, the weight increased, by 3.11% of
the original measure. However, egg
weight decreased afterwards drastically by 38.86% of the original weight. The weight loss of the eggs varied from 8 to
10g in the present study (Fig. 2) in sharp contrast to earlier studies, which
recorded the loss in the range of 1 to 4g (Begum 1997).
Hatching success
The eggs hatched during
daytime, with a crack of the eggshell at the middle of the egg in an interval
of 1 to 3 days (n=20). The egg was
broken at transverse section with the help of the egg tooth. The hatching success was 86.26% in the
present study, while in a previous study it was 63.15% (Begum 1997). Elsewhere it was reported to be 80% (Kopciewicz et al. 1999).
Brooding
After the first of the
eggs hatched, the female started to brood. Both the mates took turns to brood. Brooding continued until the
development of primaries and secondaries. When the
feathers developed densely (7th to 10th day), the brooding was
discontinued. From the first day of
hatching to the seventh day, the skin of the hatchling was naked and this was
the time when continuous brooding was observed. At night the female brooded continuously and the male sat on the branch
beside the nest. The brooding period varied from 15 to 20 days (17.3 ± 1.26).
Opening of the
eyes
During hatching, the
eyes of the hatchlings were closed, opening gradually as time progressed and as
they grew. They opened their eyes
completely when the chicks were 8 to 12 days old (9.8 ± 0.95 days). From the data it was found that the eyes of
the comparatively healthier nestlings opened first than the low weight
nestlings and this difference was found to be statistically significant
(t=26.762, df=19, p<0.01). Palmer (1962) described that eyes opened
between 4 to 5 days of age in case of Large Cormorant. At the time of the opening of the eyes the
weight of the nestlings varied from 132g to 240g (197.6 ± 31.81) in the present
study. Begum (1997) reported that it was
40 to 89g.
Disappearing of the egg tooth
The egg tooth disappeared
when the chicks were 12 to 17 days old (mean 14.4 ± 1.4 day). Begum (1997) mentioned that the nestlings
took 15 to 25 (mean 18.68) days to shed their egg teeth. At that time the weight varied from 220g to
365g in the present study whereas Begum (1997) reported that the average weight
was 224.6g.
Development of feathers
Little Cormorant are nidicolous species and as such, the body was transparent
and naked at the first day of hatching. Within 7 to 10 days the primaries of
the wing and the rectrices of the tail feathers
started to develop. The fine down feathers were also observed emerging on the lower
belly. Begum (1997) reported that the
blackish pre-pennae of fine down feathers became
visible on the wings and the pectoral region from the first day up to seven
days of age. By days 12 and 13 the whole
body was covered by down feathers except the head.
Fledging period
The juvenile birds left
the nest between 17 to 29 days (20.85 ± 2.8) (n=20) after hatching. The fledging time was not positively
correlated with the weight of the fledgling (r = 0.219, df=18, t=76.231,
p>0.05). According to Siriwannichkul (1981) the young fledged in 35 to 42
days. Begum (1997) reported it to be 39
to 45 days (mean 41.04 days).
During the fledging
time the weight varied from 350g to 470g (n=20), whereas the weight ranged
between 400g to 445g in a similar study (Begum 1997).
Nestling mortality
In the study period,
23.3% nestlings failed to fledge. The
main cause of loss was that 18.45% were stolen by the local boys (Fig. 3). In another study, Begum (1997) reported
predation by other birds (12.5%) and loss due to natural causes (12.5%). Jayson (2001) reported that House Crow was the
main predator of the eggs and nestlings of many species including the Little
Cormorant. He also stated that the
common Rat Snake (Ptyas mucosus)
was a potential threat to eggs and nestlings. Fortunately, the House Crow was not seen in
the area during the study period. During
heavy rain, many nestlings fell down and were easy prey to the ground predators
(Subramanya & Moni1996; Jayson 2001). Kopciewicz et al. (1999) observed that very strong winds may cause considerable
increase in egg and chick mortality.
Conclusion
The result of the study
has some quite interesting information on breeding, as well as major threats to
nest, egg, and survival of chick of the Little Cormorant. Human disturbance and habitat destruction was
the main causes for decreasing the population. So, public awareness should take the major role for the conservation of
the Little Cormorant.
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