Journal of Threatened Taxa |
www.threatenedtaxa.org | 26 March 2022 | 14(3): 20721–20732
ISSN 0974-7907
(Online) | ISSN 0974-7893 (Print)
https://doi.org/10.11609/jott.7748.14.3.20721-20732
#7748 | Received 09
November 2021 | Final received 25 January 2022 | Finally accepted 05 March 2022
Nest colonies of Baya Weaver Ploceus philippinus (Linnaeus, 1766) on overhead power
transmission cables in the agricultural landscape of Cuddalore
and Villupuram districts (Tamil Nadu) and Puducherry, India
M. Pandian
No. F1901, AIS Housing Complex, Natesan Nagar West, Virugambakkam,
Chennai, Tamil Nadu 600092, India.
pandian.m14@gmail.com
Editor: H. Byju, Coimbatore, Tamil
Nadu, India. Date of publication: 26
March 2022 (online & print)
Citation: Pandian, M. (2022). Nest colonies of Baya
Weaver Ploceus philippinus
(Linnaeus, 1766) on overhead power transmission cables in the agricultural
landscape of Cuddalore and Villupuram districts
(Tamil Nadu) and Puducherry, India. Journal of Threatened Taxa 14(3): 20721–20732. https://doi.org/10.11609/jott.7748.14.3.20721-20732
Copyright: © Pandian 2022. Creative Commons Attribution 4.0 International License. JoTT allows
unrestricted use, reproduction, and distribution of this article in any medium
by providing adequate credit to the author(s) and the source of publication.
Funding: None.
Competing interests: The author declares no competing interests.
Author
details: M.Pandian has completed MSc., PhD., in Botany and BLIS
from University of Madras and Bachelor of Education (BEd)
from Annamalai University, Chidambaram and now serves in Tamil Nadu Police Department.
His area of interest is ecology and nesting biology of birds and published a
few papers on House Sparrows, Baya Weavers, Munias,
Ring-necked Parakeets, and Indian Flying Fox.
Acknowledgements: I thank D. Balaji (Mailam), K. Sriram (Rettanai) for
assistance in the collection of data and photography, A. Giridharan
(Minnal), P. Logeswaran (Minnal), T. Selvapandian, and P.
Poornima (Odisha) for data analysis/ preparation of maps.
Abstract: Nesting habits of Baya Weaver Ploceus philippinus with specific reference to overhead power
transmission cables was studied between April and November 2021 in the agrarian
landscape of 10 villages covering Cuddalore and
Villupuram districts (Tamil Nadu), and Puducherry. A total of 408 nests of
various stages (wad stage-35, ring stage-21, helmet stage-227, egg-chamber
closed stage-49, complete nests-22, and abnormal nests-54) and 411 birds were
enumerated on 25 nest colonies. The number of nests in each colony ranged from
1 to 82. Baya Weavers had selected power cables as
nesting sites despite the availability of three nest-supporting trees (n=
2,255), such as Cocos nucifera, Borassus
flabellifer, and Phoenix sylvestris
within 500 m of nesting cables. Birds used leaves of sugarcane Saccharum officinarum,
Indian Date Palm Phoenix sylvestris, and
Narrow-leaf Cattail Typha angustifolia as a source of fibres for the
construction of nests. Twenty-three out of 25 nest colonies were found on power
cables running over sugarcane crops. Abnormal nests constituted 13.23% (n= 54)
of the total nests and 92.91% (n= 223) helmet stage nests had clay deposits on
the inner walls. A total of 285 fallen nests in various stages of development
were scattered on the ground. There were opportunistic sightings of avian
predators, such as House Crow Corvus splendens, Large-billed Crow Corvus
macrorhynchos, Rufous Treepie Dendrocitta
vagabunda, and Shikra Accipiter
badius found perched on power cables bearing
nests and caused damages to eight nests.
Keywords: Abnormal nests, clay deposit,
nest development, nest predation, threats.
INTRODUCTION
Ploceidae is a family of small passerine
birds, called weavers or bishops. They are native to the Old World,
particularly Africa and tropical Asia. The genus Ploceus
contains 64 species, of which four—P. philippinus,
P. manyar, P. benghalensis,
and P. megarhynchus—occur in India (Craig
2010; Gill & Donsker 2010). Baya
Weaver Ploceus philippinus
(Linnaeus, 1766) (Aves: Passeriformes: Ploceidae) is
a social, polygamous, colonial nester and occurs in the Indian subcontinent
(Ali et al. 1956), Java, Malacca, Sumatra (Blyth 1845; Wood 1926), China,
Indonesia, Laos, Myanmar, Singapore, Thailand, and Vietnam (BirdLife
International 2016). The IUCN Red List of Threatened Species has classified Baya Weaver under organisms of ‘Least Concern’ (Birdlife
International 2016). In India, the breeding season of Baya
Weaver is from May to November (Ali & Ripley 1987; Rasmussen & Anderton
2005). Baya Weavers select a variety of trees
for nesting but prefer tall, unbranched trunks and long-swaying foliage of palm
trees to keep away predators and provide convenient leaf strips for building
nests (Davis 1974). Baya Weavers prefer Cocos
nucifera along the west coast of the Indian peninsula, Borassus
flabellifer along the east coast, and Acacia nilotica in the arid northwestern
region (Sharma 1989). Dense canopies of nest-bearing trees possibly provide
safety from predators and weather-related problems (Sharma 1991). The breeding
biology of this bird was studied by Ali (1931), Ali & Ambedkar (1956),
Ambedkar (1964), and Mathew (1977). Several workers have reported construction
of abnormal nests (Ali & Ambedkar 1956; Ambedkar 1964; Crook 1964; Sharma
1989; Pandian 2018). Nests of Baya Weavers were found
attached to telegraph lines along the Chittoor-Chandragiri routes (Kirkpatrick
1952), Kumaon Terai region
of Nainital District (Uttarakhand) (Ambedkar 1969), and between Bangalore and
Madras where sugarcane crops predominate (Subramanya 1982). Nests of Baya Weavers were recorded on electric cables in Assam and
Tamil Nadu (Davis 1974). A total of 135 nests were observed on four power
cables in Villupuram district, Tamil Nadu (Pandian 2018). Apart from these, no
other detailed studies are available on the nesting of this bird on power
cables in Tamil Nadu and Puducherry. Hence, the present study was carried out
to fill this gap.
In this paper, I sought answers to questions
relating to the choice of power cables for nest construction by Baya Weaver, with specific reference to Cuddalore
and Villupuram districts (Tamil Nadu) and Puducherry. The following objectives
were kept in mind in the study: (1) extent and pattern of selection of power
cables for nesting, (2) features of nest building including sources of nesting
materials, stages of nest developments, plastering of clay on inner walls, and
abnormalities, and (3) threats faced by the birds.
MATERIALS
AND METHODS
Study Area
The present study was carried out
in 10 villages covering Cuddalore and Villupuram northeastern districts of the state of Tamil Nadu and the
Union Territory of Puducherry from the first week of April to the second week
of November 2021. The study area spreads over 5,897 km2, with a
human population of c. 5,630,000 (2011 Census). Agriculture is the primary
occupation of the people. The major crops of the area are paddy Oryza sativa,
sugarcane Saccharum officinarum,
followed by jowar Sorghum bicolor, pearl millet
Pennisetum glaucum,
finger millet Eleusine coracana,
foxtail millet Setaria italica,
groundnut Arachis hypogaea,
and green gram Vigna radiata. Flower and vegetable cultivations also
occur. The maximum and minimum temperatures in the districts are 36 oC and 20 oC,
respectively. The average annual rainfall is 1,060 mm (Figure 1).
Methods
With help from field
assistants/informants (2), I identified villages having definite populations of
Baya Weaver and their nests on overhead power
transmission cables and nest-supporting palms, such as C. nucifera, B. flabellifer, and Phoenix sylvestris
in the agricultural lands in 10 villages in Cuddalore
and Villupuram districts (Tamil Nadu) and Puducherry. The nests attached to all
the power cables between two poles including solitary nests and nests observed
on tree crown were considered a single nest colony. These nesting colonies were
surveyed on daily basis between April and November 2021 without causing any
disturbance to the nests and inhabiting birds. The observations were carried
out from 0600 h to 1200 h and 1500 h to 1800 h when the birds were found
active. The heights of the cables from the ground were ascertained from the
details written on power transmission poles while heights between overhanging
nests and crops, and the distance between the overhanging nests from
bunds/pathways were measured using a dried bamboo stick. The sources of nesting
materials and the type of cultivating crops underneath the overhanging power
cables were recorded. Every 250 trips of males carrying fibres to power cables
and nest-supporting trees were observed using binoculars and analysed the type
nest materials carried by them. The locations of all the cables that bore
nests/nest colonies were determined using GPS (Gramin
Etrex 20x). The nests, their developmental stages
including abnormal nests on power cables and nesting trees were recorded.
Deposits of clay on the inner walls of helmet stage nests, damages to nests,
and sightings of avian predators near nest colonies were observed by
maintaining c. 30 m distance using Super Zenith 20 x 50 field binoculars,
without disturbing nests and their residents. Fallen nests under the
overhanging nest colonies were counted. Each nest colony was observed
uninterruptedly for 60 min and the maximum number of birds observed in that
colony was counted. To assess the proportions of three types of palms (C.
nucifera, B. flabellifer, and P. sylvestris) used by Baya
Weavers as nesting substrata within 500 m radii from nesting cables, all the
individuals of three palms bearing nests and without nests were enumerated and
preference assessed. The correlation between variables such as the total number
of birds and nests observed on power cables was calculated using Pearson’s
Correlation Coefficient test. Utmost care was taken not to disturb the nests or birds and a
minimum distance of c. 30 m was maintained during observations. No live nests,
eggs, chicks, or adult birds were disturbed, and only fallen nests were examined
during the study period. Nikon P 1000 digital camera was used for photography
and videography. Collected data were tabulated, analyzed
and shown as graphs.
RESULTS
AND DISCUSSION
Males started to visit power
cables carrying plant fibres during the third week of May 2021, and commenced
nest construction. In total 408 nests of various developmental stages and 411
adult birds were enumerated on power cables/nest colonies at 25 sites. The
number of nests in each colony ranged from 1 to 82, and three nest colonies
with solitary nests were also recorded (Table 1). An average of 16.3 nests and
16.4 birds were counted on each nest colony. At 22 sites, the nesting power
cables were found passing over sugarcane crops, while one passed over foxtail
millet Setaria italica
crop, guava Psidium guajava orchard, and
Narrow leaf Cattail T. angustifolia reed (Image 1). The study also
revealed that grain crops such as paddy, jowar, sorghum, finger millets, and
foxtail millets were being cultivated within a 1-km radius of nest colonies. It
indicates that the birds had chosen nesting sites on power cables running
adjacent to grain crops, probably for forage for adult birds. Pearson’s
correlation coefficient test was conducted between the number of nests and the
number of birds enumerated on the power cables bearing nests. The test
indicated a strong positive correlation (0.939) between the number of nests and
the number of birds observed on power cables (Figure 2).
Power cables as nesting
substratum
Baya Weaver used power cables as
nesting sites and constructed nests attached to these power cables. Electricity
poles rose c. 5.6 m above the ground, while the cables were 5.2 m above the
ground, with a distance of 60 m between two poles. A total of 408 nests in 25
nest colonies were observed. Within 500 m radii from the power cables bearing
nest colonies, there were 2,296 nest-supporting trees, such as C. nucifera
(n= 1,856), B. flabellifer (n=
409), and P. sylvestris (n= 31) in 10
villages. The birds had utilized only 1.78% (n= 41) of those nest-supporting
trees and the remaining 98.22% nest-supporting trees (n= 2,255) of those three
palm species (Arecaceae) were found not utilized by
the birds for the construction of nests. A total of 727 nests of various
developmental stages were enumerated on those 41 nest-supporting trees. Out of
2,296 available nest supporting trees, the birds had proportionately utilized
1.78 % of C. nucifera trees (n= 33), 1.47% of B. flabellifer trees (n= 6), and 6.45% of P. sylvestris trees (n= 2). It reveals that the
birds had proportionately preferred P. sylvestris,
followed by C. nucifera, and B. flabellifer
trees (Table 2). The utilization of only 41 trees out of 2,296 trees indicate
that Baya Weavers selected power cables as nesting
sites in the study area despite the availability of abundant nest-supporting
trees (n= 2,255) around the power cables bore nests.
Colonization of Baya Weavers on telegraph and power lines has been reported
earlier in Kumaon Terai
region of Nainital District, Uttarakhand (Ambedkar 1969), Chittoor and
Chandragiri regions (Kirkpatrick 1952), Tamil Nadu, and Assam (Davis 1974).
Subramanya (1982) observed the presence of nests of Baya
Weavers on telegraph wires between Bangalore and Madras (Chennai) regions. The
occurrence of nest colonies on the power cables in the present study area
corroborates the findings of Ambedkar (1969), Kirkpatrick (1952), Davis (1974),
and Subramanya (1982). Baya Weavers showed a
preference for telegraph wires in the Bangalore–Madras regions where sugarcane
and paddy crops predominate (Subramanya 1982). Similarly in the present study
area, Baya Weavers used power cables as substrata for
the construction of nests that passed over sugarcane crops (22 out of 25
sites). Birds have been found to have made nests at odd places like electric
transmission cables when other suitable nesting sites were scarce (Toland 1990;
Chace & Walsh 2006). However, in the present study area, it was found that
despite availability of a sufficient number of nest-supporting palm trees (n=
2,255) within a 500 m radius, the birds chose power cables, indicating that in
this instance it was not the absence of traditional nesting sites that led
birds to choose power cables, as found by Toland (1990) and Chace & Walsh
(2006).
Subramanya (1982) put forward
several reasons for birds preferring power cables overhanging sugarcane crops:
(i) safety from terrestrial predators like snakes and
lizards, (ii) availability of sugarcane crops throughout the breeding season,
(iii) availability of paddy crops, and (iv) sugarcane crops serve as roosting
sites during the non-breeding season. From the present we can add: (i) abundant nesting materials, i.e., sugarcane leaves were
available beneath 22 power cables and nearby (330–700 m) to another three power
cables throughout the breeding season; (ii) availability of foraging grain
crops such as paddy, pearl millet, finger millet, and foxtail millet, found
within 500–1,000 m of nest colonies, and (iii) fewer anthropogenic disturbances
like frequent climbing of palm trees by humans for fruits, leaves, and toddy,
pruning of leaves bearing nests, and nest predation by humans. Hence, the
present observations partially match the suggestions of Subramanya (1982).
Also, the availability of a clear line
of sight in all directions afforded by free-hanging cables may allow birds to detect
the approach of predators.
Colony size
The number of nests in each
colony varied 1–82 nests per colony were observed on power cables, whereas 1–73
nests were observed on nest-supporting trees; 12% of nest colonies (n= 3)
observed on power cables were solitary nests, as were 4.8% (n= 2) of nests
observed on trees. Sharma (1989) had recorded 1–250 nests in Rajasthan, 5–24
nests in South Goa (Borkar & Komarpant
2003), 1–30 nests in Nanded (Achegawe et al. 2016),
and 1–61 nests in Vellore district, Tamil Nadu (Pandian 2021a) and hence, the
present observations of 1–82 nests on power cables and 1–73 nests on potential
nest-supporting trees concur with the findings of previous studies (Pandian
2021a). This indicates that there exists no major variation in the number of
nests in a colony either on power cables or nest-supporting trees.
Distance with crop bunds
The distances between nest
colonies (n= 25) and bunds in the vicinity were: one colony was directly over a
bund in Madurapakkam village (11.999oN–79.606oE);
nine colonies were 1–2 m away from the bunds; six colonies at 3–4 m distance; five colonies at 5–6 m; four colonies at >6 m. This indicates that the birds
preferred power cables away from bunds/pathways for construction of nests,
probably to avoid any human disturbances because nests on power cables were
found hanging 4–4.5 m above the ground. The distance from bunds seems not to
apply to potential nest-supporting trees, because all such trees occurred on
crop bunds and nests were attached to palm fronds above 10 m from the ground.
Source of fibres
A study of the source of nest
materials revealed that male Baya Weavers plucked
fibres from leaves of sugarcane, Indian date palm, and narrow leaf cattail,
made incisions on the leaf margins near the bases and tore off fine fibres
toward the distal ends and then carried them to the power cables. They selected
young leaves found around the terminal buds and avoided dried and partly dried
old leaves. The study on 250 trips of males on power cables revealed that males
brought fibres from sugarcane leaves in 241 trips, seven trips from Indian date
palm, and two trips from narrow leaf cattail. The study on 250 trips of
males on nest-supporting trees revealed that the males used fibres from
Sugarcane (112 trips) and Indian date palm (138 trips) for the
construction of nests. However, no instance of carrying fibre from narrow leaf
cattail to nest-supporting trees was observed. This indicates that the
birds used more fibres of sugarcane for the construction of nests on power
cables, whereas more fibres of Indian date palm were used for the
construction of nests on nest-supporting tees. Baya
Weavers were found to have used leaves of Phoenix sp., coarse grass and
paddy leave for the construction of nests in Kolaba
district, Maharashtra (Ali 1931). In the present study, Baya
Weavers used fibres from leaves of sugarcane, Indian date palm, and narrow leaf
cattail, rather than fibres of grass, or paddy as observed by Wood (1926) and
Ali (1931). The birds’ preferential use of more fibres of Sugarcane on power cables
and more fibres of Indian date palm on potential nest-supporting trees for the
construction of nests require further studies.
Developmental stages of nests
In the present study, out of a total of 408
nests counted on power cables, various stages of nests included: wad stage
nests—8.6% (n= 35), Ring stage—5.2% (n= 21), helmet stage nests—55.6% (n= 227),
egg-chamber closed stage nests—12% (n= 49), 5.4% complete nests—5.4% (n= 22),
and abnormal nests—13.2% (n= 54). An
average of 16.3 nests/nest colony was found on power cables. Various stages of
nest developments are given in Image 2 and Figure 3.
On 41 potential nest-supporting
plants, various stages of nests included: wad stage nests—3.71% (n= 27), Ring
stage—2.2% (n= 16), helmet stage nests—24.9% (n= 181), egg-chamber closed stage
nests—25.7% (n= 187), complete nests—33.6% (n= 244), and abnormal nests—9.9%
(n= 72). An average of 17.7 nests/nest colony was observed on nesting trees
(Image 2). Since further development of helmet stage nests depends on pairing,
it was presumed that after being paired with a female, active breeding occurs
in egg-chamber closed stage nests and complete nests. Based on that assumption,
active breeding would occur in 17.4 % of nests (n= 71) attached to power
cables, whereas active breeding would occur in 59.3% of nests (n= 432) on
potential nest-supporting trees. It indicates that a proportionately less
number of active nests were found on power cables when compared to
nest-supporting trees as both occur in the same vicinity, i.e., within 500
radii. Proportionately, reducing the number of active nests (egg-chamber closed
& complete nests) attached to power cables than the potential nest-supporting
trees in the same area during the same breeding period requires further
studies.
Abnormal nests
Abnormal nests constituted 13.2%
(n= 54) of the total nests (n= 408) and among them, 94.4% (n= 51) of abnormal
nests were found overhanging sugarcane crops and the remaining 5.6% abnormal
nests (n= 3) overhanging a Guava orchard, Foxtail millet crop, and narrow leaf
cattail (Image 2h). Eight different types of abnormal nests were noticed: 35.2%
(n= 19) abnormal nests belonged to 1+1/2 storeyed type, followed by 22.2% (n=
12) 1+1 storeyed type, 16.6% (n= 9) mixed abnormal types, 9.3% (n= 5) ½+½
storeyed, 7.4% (n= 4) fused nests, 5.6% (n= 3) ½+1 storeyed, one multi-stalked,
and one chain-storeyed nest.
Some other species of the genus Ploceus also construct abnormal nests. Black-breasted
Weaver Ploceus benghalensis
constructs an abnormal entrance tube with more than 1-m length (Mishra 2004).
Spectacled Weaver Ploceus ocularis constructs an abnormal entrance tube two
meters in length in southern Africa (Maclean 1985). African Black-headed Weaver
Ploceus cucullatus
constructs kidney-shaped nests with abnormal supernumerary antechamber or with
bottomless nests in Africa (Collias & Collias 1962). Southern Masked Weaver Ploceus
velatus constructs one of the most abnormal nests
among the weaver birds in South Africa, Angola, Zambia, and Mozambique.
Streaked Weaver Ploceus manyar
constructs abnormal nests with short entrance tubes in India and long entrance
tubes in Java (Delacour 1947). Sakalava Weaver Ploceus sakalava
constructs nests with shorter entrance tubes in the arid habitats and long
entrance tubes in the other parts of Madagascar. In India, the abnormal nests
of Baya Weaver were studied by Ali et al. (1956) and
Ambedkar (1958, 1980) in Pune, Maharashtra, and Sharma (1985, 1988, 1995) in
Rajasthan. Thirteen distinct types of abnormal nests were recorded in South Goa
(Borkar & Komarpant
2003). Two-storeyed and three-storeyed types of nests were studied in Nanded,
Maharashtra (Achegawe et al. 2016). Fifteen types of
abnormal nests were recorded in Villupuram district, Tamil Nadu (Pandian 2018).
But in the present study area, only eight different types of abnormal nests
were observed on power cables.
Deposition of clay in the nests
The males have the habit of
plastering wet clay on the inner walls of helmet stage nests, and such
plastering of clay takes place immediately after the construction of helmet
stage nests and before the arrival of females to select such nests. Observation
on 240 helmet stage nests attached to power cables using binoculars revealed
that clay deposits were found on 92.9% (n= 223) nests and the remaining 7.1%
(n= 17) nests were free of clay deposits. It was not possible to view and
ascertain clay deposits in the remaining 168 nests. Dissection of two fallen
nests (helmet stage-1 and egg-chamber closed-1) revealed that patches of clay
were observed on either side of the nests. No females were seen carrying wet
clay to the nests.
Plastering of inner walls of the
nest with wet clay is done when the nest construction reaches the helmet stage
before pairing with females (Dewar 1909; Ali 1931; Ambedkar 1969; Borkar & Komarpant 2003).
Wood (1926) had suggested that plastering of clay helps to stabilize the nest
in strong winds. The mud on either side of the nest may stabilize the swinging
nest in high winds (Crook 1963). He added that female was never found bringing
mud. In the present study also, 7.1% (n= 17) helmet stage nests do not have
clay deposits, and hence this matches with the findings of Davis (1974). The
habits of smudging of clay in the nests were common in three species of Asian
weavers (P. manyar, P. benghalensis,
and P. philippinus) and not found in African
Weaver (Crook 1963; Davis 1974). Hence, the observance of clay deposits in the
present study corroborates the findings of the above authors. Davis (1973) had
recorded that about 18.3% of nests did not show the presence of mud blobs on
the inner walls of nests in South Goa. In the present study also 7.1% of nests
did not show traces of clay and hence it matches with the observations of Davis
(1974) (Image 3ab).
Fallen nests
A total of 285 nests in various
developmental stages (wad stage-63, ring stage-48, helmet stage-86, egg-chamber
closed stage-30, and complete nests-58) had fallen from the nest colonies, and
were found scattered on the ground in sugarcane and other crop fields. Among
the fallen nests, six complete nests contained 11 damaged eggs (Image 3cf).
Rivalry exists among males during the earlier stages of nest construction and
some males had cut down the nests of other males in Poona City, Maharashtra
(Ali et al. 1956). They also stated that many completed nests were blown down
due to recurring spells of bad weather during June–August in the Bombay area
causing mortality to nest colonies. Pandian (2021a) had recorded 458 fallen
nests of various developmental stages under the nest-supporting plants in 26
villages in Arakkonam taluk, Tamil Nadu due to
various biotic and abiotic factors. A male Baya
Weaver had cut down its nest by lacerating the stalk in Villupuram district
(Pandian 2021b). Hence, the observations of 285 fallen nests in the study area
might be due to various biotic/abiotic factors like slippery nature of
aluminium cables, plaiting of weak knots, south-west monsoon, or cutting down
of nests by rival male Baya Weavers as stated by Ali
et al. (1956) and Pandian (2021a,b).
Predation threats
Opportunistic sightings of
predatory birds, such as House Crow Corvus splendens, Large-billed Crow Corvus
macrorhynchos, Rufous Treepie Dendrocitta
vagabunda, and Shikra Accipiter
badius were made in the vicinity of nest colonies
attached to power cables during the study period. But no incident of predation
of adult birds was observed. Whenever predators landed on nest-bearing power
cables, all the birds deserted the nesting sites to roost on adjacent sugarcane
crops or Prosopis juliflora trees. Eight
incidents of nest damages by three avian predators, viz., House Crow,
Large-billed Crow, and Rufous Treepie were observed during the study period.
Rufous Treepie made puncture by creating a circular hole near the brood chamber
of one complete nest and it was not possible to ascertain whether Rufous
Treepie predated eggs/chicks or not (Image 3de). Among 408 nests, 32 nests
(egg-chamber closed stage-9, complete nests-16, and abnormal nests-7) in the
colonies were found damaged. Ali (1931) had stated that agitated behaviours of
birds were observed when Crow Pheasants Centropus
sinensis appeared in close proximity of nesting
bearing trees in Kolaba district, Maharashtra, and
also observed Shikra making an unsuccessful stoop on
nest colony. In the present study also individuals of Baya
Weaver had exhibited agitated behaviour when House Crows, Large-Billed Crow, Shikra, and Rufous Treepie visited nesting sites as stated
by Ali (1931). Nest predation by the treepie was reported in Arakkonam Taluk, Tamil Nadu (Pandian 2021a). Hence, the
present observation of agitated behaviour of birds when sighting avian
predators and 32 damaged nests including a hole on the egg-chamber matches with
the observations of Ali (1931) and Pandian (2021a) (Table 3).
CONCLUSION
This is the first systematic study on the
preference of Baya Weaver towards power transmission
cables as nesting substrata, stages of nests, abnormal nests, and probable
threats to the nests on such cables in the study area. The survey revealed that
Baya Weavers preferred electric cables and avoided
readily available species of palms, such as B. flabellifer,
C. nucifera, and P. sylvestris for
nesting. Among the three palm species, the birds proportionately preferred P.
sylvestris over the other two palms. However,
this species seems to be in low availability in the study area. Hence it is suggested
that planting more P. sylvestris and
preventing felling the same can create more habitats for Baya
Weavers. These three palms are an integral part of rural areas and they are
also associated with rural cottage industries. Increasing urbanization by
conversion of cultivated lands into residential areas, industrialization,
widening of roads along with indiscriminate felling of these principal
nest-supporting plants that are vital for Baya Weaver
is a conservation issue in this landscape. The increasing practice of
monoculture of Casuarina, sugarcane, vegetables, and flower crops,
declining areas of cultivation of cereals and millets cause a shortage of food
grains to adult birds. Destruction of viable nests due to various anthropogenic
factors and abiotic factors (monsoon winds and rains) also causes severe stress
on the breeding of Baya Weaver. They preferred power
cables away from bunds/pathways in the croplands for the construction of nests
probably to avoid any human disturbances. Abnormal nests constituted 13.2% of
total nests and 92.9% of helmet stage nests contained clay depots on inner
walls. House Crow, Large-billed Crow, and Rufous Treepie had damaged nests of Baya Weaver. The breeding period of this bird was found
varied on power cables and potential nest-supporting trees. The survey is
limited to 10 villages, but this is part of a larger geographical area that has
a potential for a high nesting population of Baya
Weaver which, however, faces threats from the changing rural landscape. Local
communities, particularly landholders, agricultural workers, and school
students should be sensitized to understand the need to preserve the
populations of this species.
Table 1. Details of villages, GPS coordinates of a
nest bearing power cables, number of individuals of Baya Weaver and
nests in the study area as on fourth week of September 2021.
|
|
District |
Name of the Village |
GPS coordinates of power cables bearing nests |
Crops underneath the power
cables |
Total no. of birds counted |
Total no. of nests |
Developmental stages of nests |
|||||
|
Wad stage |
Ring stage |
Helmet stage stage |
Egg chamber closed stage |
Complete nests |
Abnormal nests |
|||||||
|
1 |
Cuddalore |
Sundaripalayam |
11.896o N–79.549oE |
Sugarcane |
6 |
16 |
0 |
0 |
6 |
7 |
1 |
2 |
|
11.887oN–79.548oE |
Sugarcane |
10 |
3 |
0 |
0 |
2 |
1 |
0 |
0 |
|||
|
V. Agaram |
11.882o N–79.549oE |
Sugarcane |
7 |
5 |
0 |
0 |
3 |
0 |
0 |
2 |
||
|
11.882o N–79.549oE |
Sugarcane |
48 |
29 |
5 |
4 |
12 |
3 |
2 |
3 |
|||
|
AK Kuchipalayam |
11.860o N–79.550oE |
Sugarcane |
64 |
52 |
3 |
3 |
23 |
9 |
7 |
7 |
||
|
11.859oN–79.551oE |
Foxtail millet |
22 |
20 |
2 |
4 |
9 |
5 |
0 |
0 |
|||
|
11.859oN–79.551oE |
Sugarcane |
5 |
5 |
0 |
0 |
4 |
0 |
1 |
0 |
|||
|
11.858o N–79.551oE |
Sugarcane |
4 |
3 |
0 |
0 |
2 |
1 |
0 |
0 |
|||
|
11.857oN–79.556oE |
Sugarcane |
62 |
54 |
1 |
0 |
30 |
6 |
4 |
13 |
|||
|
Kallipattu |
11.855oN–79.553o E |
Narrow leaf Catttail |
1 |
3 |
1 |
0 |
2 |
0 |
0 |
0 |
||
|
11.852oN–79.552oE |
Sugarcane |
1 |
1 |
0 |
0 |
0 |
0 |
0 |
1 |
|||
|
Varinjipakkam |
11.816oN–79.530oE |
Guava |
3 |
10 |
0 |
0 |
6 |
1 |
0 |
3 |
||
|
Poondi |
11.825oN–79.530o E |
Sugarcane |
6 |
6 |
3 |
0 |
1 |
0 |
0 |
2 |
||
|
11.825oN–79.531oE |
Sugarcane |
1 |
1 |
0 |
0 |
1 |
0 |
0 |
0 |
|||
|
11.825oN–79.530oE |
Sugarcane |
2 |
2 |
0 |
0 |
1 |
0 |
0 |
1 |
|||
|
Kandrakottai |
11.834o N–79.557oE |
Sugarcane |
10 |
10 |
0 |
1 |
5 |
0 |
0 |
4 |
||
|
2. |
Villupuram |
Mozhiyanur |
12.132oN–79.570oE |
Sugarcane |
6 |
2 |
0 |
0 |
2 |
0 |
0 |
0 |
|
12.134o N–79.571oE |
Sugarcane |
9 |
8 |
0 |
0 |
8 |
0 |
0 |
0 |
|||
|
12.130o N–79.569o E |
Sugarcane |
1 |
1 |
0 |
0 |
1 |
0 |
0 |
0 |
|||
|
Madurapakkam |
11.999oN–79.606o E |
Sugarcane |
38 |
57 |
0 |
0 |
41 |
9 |
4 |
3 |
||
|
12.000o N–79.606o E |
Sugarcane |
12 |
16 |
8 |
4 |
4 |
0 |
0 |
0 |
|||
|
12.001oN–79.606o E |
Sugarcane |
17 |
17 |
0 |
0 |
11 |
3 |
0 |
3 |
|||
|
11.996oN–79.624oE |
Sugarcane |
68 |
82 |
12 |
5 |
48 |
4 |
3 |
10 |
|||
|
|
11.995o N–79.607o E |
Sugarcane |
4 |
3 |
0 |
0 |
3 |
0 |
0 |
0 |
||
|
3. |
Puducherry |
Kunichampet |
11.999oN–79.625oE |
Sugarcane |
4 |
2 |
0 |
0 |
2 |
0 |
0 |
0 |
|
|
Total |
10 villages |
25 sites |
25 crop sites |
411 |
408 |
35 |
21 |
227 |
49 |
22 |
54 |
Table 2. Details of proportions of nest-supporting
trees selected from available trees around 500m radii from nest bearing cables.
|
Nest-supporting trees |
Total no. of trees found within 500 m radii from
nest bearing cables |
Total no. of trees selected for nesting |
The proportion of trees selected for nesting (%) |
|
Cocos nucifera |
1856 |
33 |
1.78 |
|
Borassus flabellifer |
409 |
6 |
1.47 |
|
Phoenix sylvestris |
31 |
2 |
6.45 |
|
Total |
2296 |
41 |
- |
Table 3. Details of avian predators were observed in
the vicinity of nesting colony in the study area.
|
|
Name of the predator |
No. of sightings noted |
Damages caused to nests |
|
1 |
House Crow |
45 |
2 |
|
2 |
Large-billed Crow |
21 |
5 |
|
3 |
Shikra |
5 |
0 |
|
4 |
Rufous Treepie |
6 |
1 |
|
|
Total |
77 |
8 |
For figures &
images - - click here
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