Journal of Threatened
Taxa | www.threatenedtaxa.org | 26 September 2023 | 15(9): 23843–23856
ISSN 0974-7907
(Online) | ISSN 0974-7893 (Print)
https://doi.org/10.11609/jott.8149.15.9.23843-23856
#8149 | Received 12
August 2022 | Final received 03 August 2023 | Finally accepted 24 August 2023
Nest
construction and repairing habits of Baya Weaver Ploceus philippinus
(Aves: Passeriformes: Ploceidae) in the agricultural
landscape of Villupuram District, Tamil Nadu, India
M. Pandian
No. F1901, AIS Housing Complex, Natesan Nagar West, Virugambakkam,
Chennai, Tamil Nadu 600092, India.
Editor: H. Byju,
Coimbatore, Tamil Nadu, India. Date of
publication: 26 September 2023 (online & print)
Citation: Pandian, M. (2023).
Nest construction and repairing habits of Baya Weaver
Ploceus philippinus (Aves:
Passeriformes: Ploceidae) in the agricultural
landscape of Villupuram District, Tamil Nadu, India. Journal of
Threatened Taxa 15(9): 23843–23856. https://doi.org/10.11609/jott.8149.15.9.23843-23856
Copyright: © Pandian 2023. 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 M.Sc., Ph.D., in botany and BLIS from University of Madras and Bachelor of Education (B.Ed.) 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, Streaked Weaver and Black-breasted Weaver, Grey Francolins, Indian Flying Fox, munias and Ring-necked Parakeets.
Acknowledgements: I thank D. Balaji (Mailam),
A. Giridharan, S. Kamarajan,
and P. Poornima (Narasingapuram) for data collection
and analysis.
Abstract: The intricate nesting habits of Baya Weaver Ploceus philippinus were studied on two Palmyrah
Palm Borassus flabellifer
trees in Chendur village, Villupuram district, Tamil
Nadu between 20 March and 30 November 2020. Observations concentrated on
sources of fibers, developmental stages of nests,
re-construction & repairing of nests, deposition of clay in the nest walls,
and various threats. A total of 98 nests of various developmental stages (wad
stage—4, helmet stage—31, egg-chamber closed stage—5, and complete nests—58)
were studied on these two nest colonies. The birds used leaf fibers of Indian date Palm Phoenix sylvestris
and Sugarcane Saccharum officinarum
as nest materials, and took 6–48 days for construction
of a complete nest. 95% of helmet stage nests (n = 126) contained clay
deposits. Analysis of plastered clay revealed it was alkaline with pH 9, and
dry weight ranged from 5.1–5.8 g. Males re-constructed new nests from the
remnant stalks attached to tips of palm fronds, and also made repairs on
damaged nests. Anthropogenic factors, wind, rain, and avian predators, such as
House Crow Corvus splendens,
Long-billed Crow Corvus macrorhynchos,
Rufous Treepie Dendocitta vagabunda, and Shikra Accipeter badius
posed threats to Baya Weavers. A total of 42 nests,
11 broken eggs, and 14 dead chicks were found fallen under the two nest
supporting trees. The detailed systematic survey covering entire district,
rapid urbanization, and the anthropogenic pressures will help in drafting an
action plan to conserve local populations of Baya
Weaver.
Keywords: Clay deposit, nest fall, nest
materials, nest re-construction, nest repair, threats.
INTRODUCTION
Baya Weaver Ploceus philippinus (Linnaeus, 1766) is a social, polygamous,
colonial nester. It occurs in the Indian subcontinent (Ali et al. 1956), Java,
Malacca and Sumatra (Blyth 1845; Wood 1926), China, Indonesia, Laos, Myanmar,
Singapore, Thailand, and Vietnam (BirdLife
International 2016). The IUCN Red List of Threatened Species classifies Ploceus philippinus
under ‘Least Concern’ (Birdlife International 2016). In India, the breeding
season of Baya Weaver is from May–November
(Ali & Ripley 1987; Rasmussen & Anderton 2005). While weavers select a variety of
trees for nesting, they most 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). Males usually build partial helmet stage nests
and complete them only after females select them and mate (Ali et al. 1956).
Nesting birds prefer Cocos nucifera (Arecaceae)
along the west coast of the Indian peninsula, B. flabellifer
(Arecaceae) along the east coast, and Vachellia nilotica (Fabaceae)
in the arid northwestern region (Sharma 1989). The
breeding biology of this species was studied by Ali & Ambedkar (1956),
Ambedkar (1964), and Mathew (1977). Several researchers have reported
construction of abnormal nests (Ali & Ambedkar 1956; Ambedkar 1964; Crook
1964; Sharma 1989; Pandian 2018). Asokan et al.
(2008) studied the timeline of nest construction. No other detailed
studies have been carried out on the time taken for construction of various
stages of nests, nest repairing, nest reconstruction, and physico-chemical
analysis of clay deposited in the helmet stage nests of this species in Tamil
Nadu. To fill this gap the present study was carried out.
The following
questions were kept in mind: (1) How do weavers select substrata on the trees for
nest construction? (2) What are the sources of nesting material? (3) What are
the developmental stages of nests like wad, helmet, egg-chamber closed and
complete nests, re-construction of nests and repairing of damaged nests? (4)
How much time is taken to build various stages of nests? (5) What is the physico-chemical nature of clay deposits? And, (6) what are
probable threats to weaver populations?
MATERIALS AND METHODS
Study Area
The present
study was carried out in Chendur Village, Tindivanam Taluk, Villupuram District of northeastern Tamil Nadu. The district spreads over 3,715 km2,
with a human population of c. 2,090,000 (Figure 1). Agriculture is the primary
occupation of the people. The major crops of the area are Paddy Oryza sativa,
Jowar Sorghum bicolor, Pearl Millet Pennisetum glaucum,
Finger Millet Eleusine coracana,
Sugarcane Saccharum officinarum,
Groundnut Arachis hypogaea,
and Green Gram Vigna radiata. Three nest-supporting plant species, such
as Palmyrah Palm, Indian Date Palm, and Coconut occur
abundantly in the agricultural lands. Among them, only two individuals of B.
flabellifer were chosen for study, considering
the past history of Baya Weavers selecting these two
trees for nest construction, proximity to road, and location of trees suitable
for study by fixing camera. The maximum and minimum temperatures in the district
are 36oC and 20oC, respectively. The average annual
rainfall is 1,060 mm (Viluppuram 2021).
Methods
With help from field
assistants/informants (4), I identified two B. flabellifer
nesting trees in Chendur village having a history of Baya Weavers constructing nests since 2016. These two
nesting trees were surveyed with the help of field assistants on two shifts,
i.e., one person each from 0600 h to 1200 h and 1200 h to 1800 h on a daily
basis between 20 March and 30 November 2020. All the nests found in these two
trees were treated as nest colony-I and colony-II. The height of the trees, gbh, and distances from nesting trees with source of fibers, distance of source of wet clay, and cultivation of
grains crop were measured using a 100 m measuring tape. The locations of
nesting trees were determined using GPS. Using 10 x 42 field binoculars
(Nikon-Monarch-7), the nests, males plucking nest fibers,
developmental stages of nests, clay deposits on inner wall of helmet stage
nests, and the total number of birds visiting nesting trees were observed. Clay
deposits from helmet stage nests were collected separately from each side of
inner walls of fallen nests and analyzed. The physico-chemical analyses of collected clay samples
including temperature, salinity, dissolved oxygen, oxidation reduction
potential, specific conductivity, electrical conductivity, total dissolved
solids, and other metals & minerals were carried out by using YSI
multiparameter (Model: 600XL-B-O, 650MDS, YSI Incorporated, Yellow Springs,
Ohio 45387, USA) and Perkin Elmer Atomic Absorption Spectrophotometer
Analyst 400. The recorded results were tabulated (SPSS
software). Re-constructions of nests, repairing of damaged nests, fall of
nests, eggs & chicks, and impact of avian predators were recorded and
photographed. Photographs were taken using Nikon P1000 digital camera.
Collected data were tabulated, analyzed as total
number of fronds used by the birds, average number of nests per frond and shown
as tables.
RESULTS
It was observed that no old or
torn nests from previous years were found on these two male B. fabellifer trees when the study was commenced on 20
March 2020 (Image 1). Baya Weavers constructed a
total of 98 nests (Wad stage—4, helmet stage—31, egg-chamber closed stage—5,
and complete nests—58) on two male B. fabellifer
trees. Birds failed to continue constructions on four wad stage nests, and 31
helmet stage nests and five egg-chamber closed stage nests. The remaining 58
nests were complete nests with entrance tubes. The study revealed that the
birds built an average of 1.17 nests per palm frond. Nest colony-I contained
62.24% nests (n = 61) and the remaining 37.76% nests (n = 37) were found in
nest colony-II (Table 1).
Commencement of nest construction
All the males had commenced nest
constructions on 02 April 2020. From 20 March to 01 April, no Baya Weaver was observed on these two nesting trees. On 02
April between 0600 h and 0830 h, 16 males with partial plumage first visited on
these two palm trees probably searching for suitable substrata for construction
of nests.
Selection of Palm fronds
Males visited distal ends of palm
fronds randomly, except the lowermost dried and the uppermost partially opened
young fronds. After selection of the distal ends of fronds, they bit the margins
by using their beaks and made the margins serrate/rough and also made punctures
on the leaf blades probably to make the knots strong. Out of 248 leaf tips
studied, the margins of 232 leaf tips was serrate, and 16 leaf tips had serrate as well as punctures. This process of making frond
margins serrate continued for five days, i.e., from 02–06 April and the males
were observed on nesting trees between 0600 h and 0830 h. During these periods,
no activities of nest construction were noted. After 0830 h, they left the
nesting trees for foraging in the crop fields and perching on nearby
tress/shrubs. They did not return to the nesting trees till the next morning.
Sources of fibers
Males plucked fibers
from Indian date palm P. sylvestris trees (n =
6) and Sugarcane crops S. officinarum situated
within c.120 m distance from the nest-supporting trees. Males moved to west to
puck fibers from P. sylvestris
and to all directions to get fibers from S. officinarum crops. The study revealed that the males
had visited P. sylvestris trees daily from
0600 h to 1730 h, perched on rachis/leaflets, made incisions on the margins of
leaflets near the bases and speedily tears off fine fibers
toward the distal ends. The birds tore off fibers in
this manner and carried to the nesting trees. Observations on 100 trips from
the sources of fibers (P. sylvestris
and S. officinarum) to nest-supporting
trees revealed that the birds carried 2–5 fibers per
trip. They selected young fronds for peeling fibers
and avoided the old fronds on the bottom of the tree crown. Study on 10 fronds
from four P. sylvestris trees where birds tore
off fibers revealed that the mean size of fronds was
106 cm (Standard Error of 4.73) and the birds had selected leaflets from the
distal half of rachis, i.e., from middle to distal part of the rachis and never
selected hardened leaflets found on the lower half of rachis, i.e., towards
leaf bases. Similarly, males tore off fibers from
young and green leaf blades of sugarcane crop and no incident of selection of fibers from dried and partly dried leaves were observed
(Image 2).
Behaviour of stealing fibers
Thirty-two incidents of males
stealing fibers from adjacent nests when the resident
birds of the nests were away were observed. Such incidents of stealing fibers from nests of other birds within the colony were
observed throughout the breeding season.
Stages of nest constructions
Four developmental stages of nest
constructions such as wad stage, helmet stage, egg-chamber closed stage, and
complete nest stage were taken into account and
studied in detail (Image 5).
Wad stage
The males plait knots round the
margins of leaf blades by using legs and beak called wad stage (Image 5a,b). The study on 98 wad stage nests revealed that the time
taken for construction of wad stage varied and the males took minimum two hours
to maximum of nine days for construction of wads. In an exceptional case, a
male plaited knot continuously for nine days and the wad stage became an
amorphous ball like structure. The males usually plaited knot on one leaf tip,
but in many cases they used up to six leaf tips for
plaiting a knot/wad stage (Image 3). The males built 22.45% wad stage nests (n
= 22) in 1–2 days, 54.09% wad stage nests (n = 53) in 3–4 days, 19.38% wad
stage nests (n = 19) in 5–6 days, and 4.08% wad stage nests (n = 4) in 7–9
days.
Helmet stage
The males
took 1–15 days to construct helmet stage nests. Out of 98 wad stage, 94 were
developed into helmet stage nests (birds abandoned 4 wad stage nests). When the
females reached the nesting colony, the males perched on helmet stage nests and
made loud noises by flapping their wings (Image 4 d). The males built 84%
helmet stage nests (n = 79) in 1–5 days (including 27 nests were built within
one day from dawn to dusk), 13.8% helmet stage nests (n = 13) in 6–10 days, and
2.1% helmet stage nests (n = 2) in 11–15 days.
Egg-chamber closed stage
Out of 94 helmet stage nests, 31
helmet stage nests were abandoned by the males and did not develop further
probably due to non-selection of helmets by females or abandoning by resident
males themselves. The remaining 63 helmet stage nests were developed further into
egg-chamber closed stage nests. After construction of helmet stage nests, males
wait for arrival of females for selection of their helmet stage nests followed
by pairing. Hence, further development of nests depends on the chances of
selection of helmet stage nests by females and time taken for such selection
followed by pairings. My studies revealed that the number of days taken for
development of helmet stage nests including the time taken for arrival of
females, selection of helmets, and followed by pairing were found varied from
one day to 29 days. Out of 63 helmet stage nests, 35 helmet stage nests were
developed into egg-chamber closed stage nests in 1–5 days, followed by 20 nests
in 6–10 days, four nests in 11–15 days, three nests in 16–20 days and one nest
took 29 days (Image 4e).
Complete nests
The birds abandoned five
egg-chamber closed stage nests without any further development. Birds took 1–28
days to complete the construction of entrance tube. Out of 58 complete nests
studied, in 69% nests (n=40), the entrance tubes were constructed in 1–5 days,
while in 12 nests, it took 6–10 days, 11–15 days for four nests, and 21–28 days
for two nests (Image 4f; Table 2). During the entire study period, neither
courtships nor mating were observed on the helmet stage nests or source of fibers or on nest-supporting trees.
Deposition of clay in the nests
After completion of construction
of helmet stage nests and before arrival of females to select such nests, the
males plastered two sides of the inner walls of helmet stage nests with wet
clay. Observation on 132 helmet stage nests (94 first time
built helmet stage nests and 38 re-built helmet stage nests) revealed
that 95 % of nests (n = 126) contained clay deposits. Only a very small
percentage (4.65%; n = 6) did not have clay. My studies revealed that the males
did not take readily available wet clay from the paddy fields, situated c.300 m
from the two nesting trees. Males waited for the frequent spell of rainfall
during south west monsoon. Immediately after rainfall, the next day morning
between 0600 h and 0730 h the males swarmed to the wet fallow land and mud road
situated c.40 m distance from the nesting trees and scooped wet clay through
their beaks in many trips and carried it to helmet stage nests. Continuous
observations revealed that the males did not take clay directly from wet soil
surfaces from all the sites. They selected sites where wet clay was exposed in
tire tracks left by vehicles on mud roads and fallow land. The practice of
males scooping clay after rainfall was observed from April–October 2020 in the
morning between 0600 h and 0730 h. It was not possible to ascertain whether the
birds added clay on the inner walls after closing of egg-chamber and
construction of entrance tube. Dissection of two fallen nests (helmet stage—1
and egg-chamber closed—1) revealed that the males smudged two patches of clay
on each side of the nest. The surface of dried plaster of clay had many beak
marks as scars (Image 5f). It was observed in one egg-chamber closed stage nest
that even after plastering of clay, another layer of fresh fibres was found on
the patches of clay. It indicates that even after smudging clay, males further
added fibres above the layer of clay (Image 6e). No female was seen scooping
clay and carrying to nests (Image 5).
Physico-chemical analysis of clay
deposits taken from one helmet and one egg-chamber closed stage nests revealed
it was alkaline (pH 9). The dry weights of the clay ranged 5.1–5.8 g. The other
parameters also showed no major variations. The physical and chemical
properties of clay collected from both walls of two nests matched with the soil
sample collected from the nearby ground where male birds scooped clay (Table
3).
Falling of nests
Of 98 nests constructed during
the study period, 43% (n = 42) of various developmental stages (helmet
stage—22, egg-chamber closed stage—03, and complete nests—17) fell from the
nest-supporting trees due to biotic and abiotic factors. 31 nests fell after
rainfall, and the remaining 11 fell when no rainfall occurred (Table 4).
Re-construction of nests
The males started to rebuild 38
nests from the remnants of wad fibers found attached
to the tips of palm fronds. Twenty-three nests were developed into helmet stage
nests but did not progress further. The remaining 15 nests were successfully
developed into complete nests. When studying the number of days taken to re-built a complete nest revealed that the birds took 6–37
days to re-built complete nests. The study reveals that the birds had
constructed 13 complete nests in 6–25 days and for another two nests took 26
days and 37 days, respectively.
One re-built helmet stage nest
was again felled down on 21 May and a male had started to construct another
helmet stage nest at the same tip of frond on 24 May and completed the
construction of helmet stage nest on 25 May. Later the helmet stage nest did
not develop further. On 30 June, another re-built helmet stage nest was felled
down and a male had again constructed helmet stage nest from the same tip of
palm frond within two days i.e., on 01 and 02 July. Later in nine days, i.e.,
on 11 July and it was developed into a complete nest (Image 6).
Repairing of damaged nests
Incidents of
partial damages to seven nests (egg-chamber closed stage—4, and complete nests—3)
by House Crow and Rufous Treepie were recorded in the study area. In all these
nests the birds brought fresh plant fibers and plait
on the edges of damaged walls. Then the birds had continued further
construction activities and repaired all the nests. The repaired nests
resembled two different colours, i.e., the older part resembled pale colour and
the repaired portion resembled green colour due to the addition of fresh green fibers (Image 7).
Threats
Opportunistic
sightings of predatory birds such as House Crow C. splendens,
Long-billed Crow C. macrorhynchos, Rufous
Treepie D. vagabunda, and Shikra
A. badius were observed on these two nesting
trees. On 24 July at 1240 h, one Shikra had chased
the individuals of Baya Weaver from nesting colony-I
and when seeing the predator, all the individuals of Baya
Weaver fled from the nest colony. One male Baya
became a prey to Shikra and later took the victim to
a nearby shrub and ate it completely, except feathers (Image 8 j). On 11 June,
one Rufous Treepie visited nesting colonies and made punctures on the
egg-chambers. The predator had inserted its head into the egg-chamber but we were unable to ascertain whether it prey upon
the eggs/chicks from the nests. Individuals of House Crow and Large-billed Crow
were found perching on nesting trees and chased the individuals of Baya Weaver but preying adult
birds/chicks were not observed during the study period. On 28 May, a House Crow
plucked fibers from three nests (complete nests-3)
and caused partial damages to the nests (Table 5).
On 30 September, one land holder
had uprooted and removed P. sylvestris trees
(n = 14) found on bunds of fallow lands situated 60 m from nesting trees while
clearing the land for cultivation. The males had plucked fibers
from these trees for construction of nests. A total of 42 fallen nests, 11
broken eggs, and 14 dead chicks were observed under the nesting trees. In one
instance, farmer burnt bushes around nesting tree which caused temporary driven
of birds from nesting tree (Image 9).
Roosting
During the
entire breeding period from April–November, no Baya
Weaver was found night roosting on the nest-supporting trees. Between 1745 h
and 1810 h all the birds used to fly away from the
nest colonies and roost on the shrubs found 1–1.5 km from nest colonies and
return to their nest colonies the next morning. Continuous observations
revealed that some females entered their nests during the evening hours did not
come out and stayed in the nests itself. These females might have incubated
their eggs or nestlings.
DISCUSSION
Commencement
of nest construction
The study
revealed that starts of the breeding season of Baya
Weaver vary from area to area in India. For example, date of commencement of
nest construction was 22 May 1930 in Kolaba district
of Maharashtra (Ali 1931), early June in Parbati Hill, Poona city (Ali et al.
1956), mid-June in Chorao Island, Goa (Borges et al.
2002), and mid-April in Rajampet Taluk of Cuddapah district, Andhra Pradesh (Mathew 1972). In the
present study, breeding commences in the first week of April which corroborate
the observation of Mathew (1972). It indicates that the breeding of Baya Weaver is related to South-West monsoon in Tamil Nadu.
Selection
of Palm fronds
Baya Weavers construct nests from the distal ends of midribs of the coconut
palm in South Goa (Borkar & Komarpant
2003). The birds wrap considerable amounts of fibers
around a chosen frond and makes a strong base for further development of the
nest (Wood 1926). Also in the present study nests were
found attached at the distal ends of the midribs of B. flabellifer
fronds. This indicates that the males selected the distal ends of palm fronds
for construction of nests. No nest was found in the middle or basal parts of
fronds in the two nest colonies.
Source of fibers
Except in
northern India, the birds used leaf fibers of C.
nucifera and P. sylvestris for nest
construction in other parts of the country (Dewar 1909). Baya
Weaver used pliant grass and fibers from palm fronds
in the Northern Province of Sri Lanka (Wood 1926), and leaves of Phoenix sp.,
coarse grass and paddy in Kolaba district,
Maharashtra (Ali 1931) as nest materials.
The present
findings of Baya Weaver using fibers
from P. sylvestris for construction of nests
matches with the observations of Dewar (1909), Wood (1926), and Ali (1931).
Apart from that the birds also used sugarcane leaves as nest material in the
study area.
Time taken
for construction of nest
Asokan et al. (2008) stated that the birds took 18 days to construct one
complete nest in Nagapattinam and Tiruvarur
districts of Tamil Nadu. Achegawe et al. (2016) had
also found similar results in Nanded region of Maharashtra. The present study
revealed that the time taken for construction of a complete nest was not
uniform for all the nests. The birds took 6–48 days for construction of
complete nests. The study also revealed that the males had capable of
constructing helmet stage nest in one day, i.e., from dawn to dusk. Hence, the
present findings of number of days taken to construct complete nest in
Villupuram district found differ with the observations of Asokan
et al. (2008)
Plastering of inner nest walls
with wet clay
The habits
of smudging of clay in the nests are observed only in Asian weavers (P. manyar, P. benghalensis, and P.
philippinus) and not found in African weavers and
the quantity of mud varies from region to region in India (Crook 1963; Davis
1973). Plastering of inner walls of nest with wet clay is done when the nest
construction reaches the helmet stage prior to pairing with females (Dewar
1909; Ali 1931; Ambedkar 1964; Borkar & Komarpant 2003).
Davis
(1973) stated that about 18.33% nests did not show presence of mud blobs on the
inner walls of nests in South Goa. He added that females were never found
bringing mud. In the present study also, 4.54 % of helmet stage nests did not
have clay deposits, and no female was observed carrying clay. This matches with
the findings of Davis (1973 ). Ali (1931) had observed
0.5–1 oz of mud in the nest. Davis (1973 ) also found
that the average dry weight of mud deposit per nest was 66.2 g. But in the
present study, the dry weight of clay ranged from 5.1–5.8 g. Average weight of
mud blobs on left side was greater in comparison with right side (Borkar & Komarpant 2003). The
present study on two nests revealed that there was no major variation in the
weight of clay deposited on the right and left side of the inner walls. In the
present study, the clay collected from nests and in the original sites where
birds took clay was found alkaline (pH 9). The exact causes of plastering of
mud in the nest walls require further studies.
Fallen
nests
The
practice of male cutting down the nest of rival cock was common when the owner
had gone to fetch building materials (Ali et al. 1956). Pandian (2021) had
observed that male Baya Weaver cut down a complete
nest occupied by White-rumped Munia Lonchura striata in
Villupuram district. In the present study, 42.85% nests (n = 42) of various
developmental stages were found fallen under the nest-supporting trees. Apart
from rain and wind, these might have also occurred due to rival males as stated
by Ali et al. (1956). Falling of such a great number of nests (42.85%) from two
nest colonies in a single breeding season is of great concern and it needs
further study.
Re-construction
of nests
The study
indicates that the birds are capable of constructing complete nests from the
same stalks from where the earlier nests were detached. It was not possible to
differentiate whether the same male commences construction of nest from the
torn stalk or different male uses the stalk for further construction of nest. However the birds have the intelligent to re-construct their
nests from the stalk of detached nests.
Repairing
of damaged nests
Baya Weavers have the capacity to repair their damaged nests with fresh
green strips of fibers, i.e., various types of
artificial nest mutilations (Ali & Ambedkar 1957; Collias
& Collias 1959, 1962). In the present study also the birds had repaired heavily damaged nests by using
fresh fibers and hence it matches with the findings
of Ali & Ambedkar (1957) and Collias & Collias (1959, 1962).
Threats
Ali (1931) had stated that
agitated behaviour of Baya Weaver was observed when
Crow Pheasants Centropus sinensis appeared in close proximity of the nesting
tree. He also observed a Shikra making an
unsuccessful stoop on nest colony. In the present study also, Baya Weaver had exhibited agitated behaviours when House
Crows visited nesting trees and all birds fled away from tree crown when they
saw Shikra and a Rufous Treepie near the nesting
trees.
Ali et al. (1956) had observed
that many completed nests were blown down due to recurring spells of bad
weather during June–August in Bombay area and was major natural mortality
factor of nest colonies. He also noted accidental drowning of chicks from
nests. Similarly in the present study also, 31 nests
were found fallen down immediately after rainfall. Out of 14 dead chicks, five
were found under the nesting trees after rain and wind. Hence, the present
observations match with the findings of Ali et al. (1956).
CONCLUSION
This is a systematic study on the
nesting habits on Baya Weaver on two Palmyrah Palm trees in a confined geographical area of one
village in Villupuram district. Increasing urbanization by conversion of
cultivated lands into residential areas, expansion of roads, abandoning
cultivations along with indiscriminate felling of principal nest-supporting palm
plants, such as Palmyrah Palm B. flabellifer, Coconut C. nucifera, and Indian
Date Palm P. sylvestris that are vital for Baya Weaver is a conservation issue in this landscape.
Increasing practices of monoculture of Casuarina, Sugarcane, and flower
crops, declining areas of cultivation of cereals and millets also causes
shortage of grains to birds. Fall of viable nests due to various anthropogenic
factors, winds, rain and avian predators cause severe stress on the breeding of
Baya Weaver. Therefore, it is essential to conduct
sustained surveys and monitor the nesting sites during the subsequent breeding
seasons and efforts should be taken to create suitable nesting habitats by not
destroying the nesting trees. Based on the above the following could be options
for securing the bird’s habitat from the area.
Establish a special management
plan for the area, considering the anthropogenic and natural stresses that the
habitat is currently subjected to.
Local community, particularly
land holders, and agricultural workers should be sensitized to understand the
need to preserve the precious nesting sites.
The detailed systematic survey
covering the entire Villupuram district will help in drafting an action plan to
conserve the populations of Baya Weaver.
The impact of abiotic factors
such as rain and wind on the nest fall need further studies.
The exact causes of males
depositing wet clay on the inner walls of nests during helmet stage, fall of
large number of nests, and mortality to chicks require further studies.
Table 1. Details of nest colonies
of Baya Weaver on Borassus flabellifer trees in Chendur
village, Villupuram district.
|
Nesting trees with GPS |
Height (m) |
GBH (cm) |
Total no. of fronds found in
the crown |
No. of fronds without nests |
No. of fronds used by birds for
construction of nests |
Total no. of nests (including
all developmental stages) counted |
Average no. of nests per frond |
|
Borassus flabellifer (colony-I) (12.123446 N 79.591657 E) |
7.5 |
78 |
54 |
30 |
24 |
61 |
0.88 |
|
Borassus flabellifer (colony-II) (12.113396 N 79.580264 E) |
9.5 |
82 |
61 |
25 |
18 |
37 |
1.64 |
|
Total |
115 |
55 |
42 |
98 |
1.17 (average) |
||
Table 2. Details of number of
days taken by the birds to construct complete nests.
|
Number of complete nests |
Percentage (%) |
Number of days taken |
|
02 |
3.4 |
1–5 |
|
18 |
31 |
06–10 |
|
20 |
34.4 |
11–15 |
|
08 |
13.8 |
16–20 |
|
03 |
5.1 |
21–25 |
|
7 |
12 |
Above 26 |
Table 3. Details of properties of
clay deposited in the nests.
|
Parameters |
Soil sample collected from the site where Baya
Weaver took soil |
Egg-chamber closed stage (Left wall) |
Egg-chamber closed stage (Right wall) |
Helmet stage (Left wall) |
Helmet stage (Right wall) |
|
Weight (g) |
25 |
5.1 |
5.2 |
5.4 |
5.8 |
|
Temperature (oC) |
25.91 |
26.01 |
25.93 |
26.02 |
25.92 |
|
Specific Conductance (Ms/Cm) |
0.048 |
0.048 |
0.035 |
0.051 |
0.024 |
|
Conductivity (Ms/Cm) |
0.049 |
0.049 |
0.036 |
0.051 |
0.025 |
|
Resistivity (Ω Cm) |
22193.3 |
19805.2 |
27440.7 |
19490.3 |
40131.3 |
|
Total Dissolved Solids (TDS %) |
0.031 |
0.033 |
0.023 |
0.032 |
0.016 |
|
Salinity (Sal) |
0.02 |
0.02 |
0.02 |
0.02 |
0.01 |
|
Dissolved Oxygen (DO %) |
32.4 |
37.2 |
23.7 |
30.7 |
19.4 |
|
Dissolved Oxygen milligrams per
litre (DO Mg/L) |
2.72 |
2.94 |
1.94 |
2.42 |
1.89 |
|
Dissolved Oxygen charge (DO Ch) |
15.5 |
16.5 |
13.5 |
15.5 |
12.4 |
|
Potential of Hydrogen (pH) |
9.36 |
9.30 |
9.30 |
9.23 |
9.30 |
|
Potential of Hydrogen in Milli Volt (pHml/) |
-179.3 |
-175.0 |
-175.9 |
-172.4 |
-176.4 |
|
Oxidation Reduction Potential
(ORP) |
-110.4 |
-103.5 |
-103.4 |
-99.7 |
-102.1 |
Table 4. Details of month-wise
nest fall from two nesting trees.
|
Month |
No. of nests felled down |
|
May 2020 |
11 |
|
June 2020 |
13 |
|
July 2020 |
17 |
|
August 2020 |
1 |
|
Total |
42 |
Table 5. Details of impact of
avian predators on Baya Weaver colonies in Chendur village.
|
|
Name of the
predator |
No. of sightings
noted |
No. of nests
damaged |
No. of Baya
Weaver killed |
|
1 |
Corvus splendens |
72 |
3 |
0 |
|
2 |
Corvus macrorhynchos |
27 |
0 |
0 |
|
3 |
Dendrocitta vagabunda |
4 |
4 |
0 |
|
4 |
Accipiter badius |
7 |
0 |
1 |
|
Total |
110 |
7 |
1 |
|
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