Nesting on Cell Phone Towers: An Inexplicable Breeding Strategy by Asian Woollynecks Ciconia episcopus in Bangladesh

Abstract

The Asian Woollynecks were once thought to be a rare winter migrant to the wetlands of Bangladesh, and until very recently, only a few incidents of nesting had been observed. New information shows expanding populations across their habitat, though little is known about their movement ecology, breeding ecology and preferences for artificial nest sites. In this paper, we documented some crucial nesting and breeding information on this species. We used camera traps as a means of passive monitoring and identified Large‐billed crow Corvus macrorhynchos and House crow Corvus splendens as potential nest predators. Three nests were found in artificial structures, where anthropogenic activity, like disturbances during cell phone tower maintenance, or predators limit the breeding success of Asian Woollynecks.

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Ecology and Evolution, 2025; 15:e71353
https://doi.org/10.1002/ece3.71353
Ecology and Evolution
NATURE NOTES OPEN ACCESS
Nesting on Cell Phone Towers: An Inexplicable Breeding
Strategy by Asian Woollynecks Ciconia episcopus
in Bangladesh
AllamaShibliSadik1, 2 | AshisKumarDatta2
1Forest Department, Wildlife Center, Gazipur, Bangladesh | 2Department of Zoology, Jahangirnagar Universit y, Savar,Bangladesh
Correspondence: Ashis Kumar Datta (akdatta@juniv.edu)
Received: 9 January 2025 | Revised: 6 April 2025 | Accepted: 11 April 2025
Funding: The authors received no specific funding for this work.
Keywords: breeding biology| Ciconia episcopus| nest predation| nesting ecology
ABSTRACT
The Asian Woollynecks were once thought to be a rare winter migrant to the wetlands of Bangladesh, and until very recently,
only a few incidents of nesting had been observed. New information shows expanding populations across their habitat, though
little is known about their movement ecology, breeding ecology and preferences for artificial nest sites. In this paper, we docu-
mented some crucial nesting and breeding information on this species. We used camera traps as a means of passive monitoring
and identified Large- billed crow Corvus macrorhynchos and House crow Corvus splendens as potential nest predators. Three
nests were found in artificial structures, where anthropogenic activity, like disturbances during cell phone tower maintenance,
or predators limit the breeding success of Asian Woollynecks.
1 | Introduction
Nesting in human- modified environments and use of man- made
structures is a common phenomenon in storks. In a beneficial
standpoint, such man- made structures offer access to perches,
roosting or breeding sites (Mainwaring2015). However, electro-
cution and collisions with powerlines have been documented in
many regions, and a long- term study in Poland found no dif-
ferences in breeding success of stork nests in natural and man-
made structures (Tryjanowski etal.2009). An interesting study
to detect the possible effect of electromagnetic fields on White
Stork Ciconia ciconia productivity, Balmori (2005) in Spain
found that microwaves had an impact on the reproduction of the
white stork.
Asian Woollyneck Ciconia episcopus is a globally near threat-
ened (NT) large wader present across South and South-
east Asian countries (Birdlife International 2020; Birdlife
International2023; Sundar 2020). Recent findings suggest that
Woollyneck has established a stronghold in South Asia, particu-
larly in Nepal, India and Sri Lanka, probably due to agricultural
expansion, land use change and subsequent behavioural plas-
ticity of the stork (Sundar 2020; Ghimire etal. 2021a, 2021b).
Although the species was considered to be negatively influenced
by human presence, new information shows that Asian Woolly-
necked Stork prefers natural a nd artificial wetla nds, paddy fields,
pastures, grasslands, man- made urban structures, nesting on
agro- forestry- related trees amid crop fields, and other agricul-
tural landscapes (Sundar2006; Choudhary etal.2013; Vaghela
etal.2015; Greeshman etal.2018; Kittur and Sundar2021).
The species ha s a large population size and is li kely stable or increas-
ing across its range; however, the population in South- east Asia
has undergone considerable declines due to many anthropogenic
activities (Birdlife International 2020; Kittur and Sundar 2020;
Sundar 2020; Ghimire et al. 2021a; Ghimire et al. 2021b). The
bird is threatened in South- east Asian range countries; it appears
stable or possibly expanding in the South Asian range, such as in
This is a n open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium,
provided the original work is properly cited.
© 2025 The Author(s). Ecology and Evolution published by British E cological Society and John Wiley & Sons Ltd.

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India, Pakistan and Nepal (Kittur and Sundar2020; Sundar2020).
The IUCN Red List has downlisted Asian Woollynecks from
Vulnerable to Near Threatened in response to criticism over its
sudden unsubstantiated uplisting alongside recent ecological
data from across its range. In Bangladesh, this stork is consid-
ered a critically endangered (CR) rare winter migrant distributed
mostly in landmasses resulting from the accretion of sediments
(locally known as chars) and wetlands of the Rajshahi Division
(along Padma River) and mud- banks of the northeast region of the
country (IUCN Bangladesh2015). Only a handful of observations
were recorded till 2013; since then, sightings of Woollynecks are
now reported sporadically in Padma riverine areas (ebird 2021;
Figure1). However, we still lack population data. There were few
anecdotal breeding records of woolly- necked storks in Bangladesh
(Khan 1987), until recently, Hasan and Ghimire (2020) con-
firmed the first breeding of this species from the Rajshahi and
Chapainawabganj districts. Herein, we present additional breed-
ing records from a recent survey alongside detailed observations
on nests to understand aspects, such as nesting ecology, human
disturbances and nest predation.
1.1 | Study Area
Based on published information of Woollynecks nesting on large
and medium- sized trees, man- made or urban structures, such as
cell phone towers (Vaghela etal.2015; Hasan and Ghimire2020;
Kittur and Sundar2021), we surveyed five districts viz. Pabna,
Natore (Chalon beel area), Rajshahi, Chapainawabganj and
part of Naogaon for potential nesting sites (Figure 2). Except
Naogaon, all four districts are situated on the banks of the river
Padma, the distributary of the river Ganges in Bangladesh.
Large waders can be observed in seasonally accreted land-
masses, small channels, grasslands and further upstream along
the Padma in these districts during winter. The waders include
Painted Stork Mycteria leucocephala, Black Stork Ciconia nigra,
Asian Openbill Anastomus oscitans, Asian Woollyneck Stork
and large multi- species congregations of migratory waterfowl
(Thompson2021).
2 | Methods
The study was carried out from 5 October 2021 to 30 October
2023. We actively searched for possible nesting sites by walking,
engine boat or by motor bike as feasible to inspect cell phone
towers. The vast majority of the study area was urban, with
patches of more natural habitat, including seasonally accreted
lands, riverbanks, homestead plantations, agricultural fields
and especially man- made structures like buildings and cell
phone towers.
Surveys included the sites where Woollyneck storks had nested
in previous years (Hasan and Ghimire2020). To obtain a more
FIGUR E  | Recent observations of Asian Woollynecks in Bangladesh (Date sources: ebird 2021, and personal observations).

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comprehensive coverage of stork nesting on cell phone towers,
we consulted three major mobile network provider companies,
viz., Teletalk, Banglalink and Robi, who altogether maintain
990 towers in our survey areas. Instead of physically inspecting
the tops of all the towers, we interviewed people living around
the towers and cell phone tower maintenance crew to document
potential nesting sites of Asian Woollynecks. Once nest building
was completed, we installed cameras (camera model: GardePro)
for an average of 74 days on two nests. Camera traps were in-
stalled on the nests with assistance from cell phone tower main-
tenance crews. They were given hands- on training on installing
and operating camera traps prior to that. Camera information
was used alongside direct visual observation (using binoculars)
and by drone (used once for a single nest to avoid disturbances).
All breeding activities were documented with minimal distur-
bances. During the survey, we conducted focus group discus-
sions and interviews with local community members. The sole
purpose of these interviews was to find nesting information and
their perception on conserving colonial waterbirds, especially
storks, in the study area. We did not collect any individual data
to protect their identity.
A nest was defined as successful when it produced at least one
fledgling. For other nests, nest failure was confirmed using egg-
shell (suggesting predation) or dead nestlings. Fledging success
was calculated as the proportion of eggs in a clutch that survived
to fledging (Cornell etal. 2011). Nest building materials were
identified after the birds left the nests and from photographs
taken using the camera traps (Figure3). Due to small sample
size, we did not perform any statistical tests but provided de-
scriptive summaries. The study area map was produced by
ArcGIS 10.3.
3 | Results
After surveying over 230 km throughout the study area
(Figure 1), we observed eight Asian Woollynecks in 2022 and
six in 2023. Three nests of Asian Woollynecks were found
during 2022, and all of these nests were built on cell phone tow-
ers (Figure 2). Nest 1 and Nest 3 were newly described nesting
sites. Nest 2 in the Bijoynagar area has been known to have
Asian Woollynecks nesting in the past. Nest 1 was predated by
a Large- billed Crow Corvus macrorhynchos. In between egg lay-
ing and predation, the Crows were recorded six times. On 2 July
2022, the tower maintenance (welding) started at 11:57 AM and
lasted till 1:43 PM, where the predation event was recorded at
12:05 PM.
Likewise, Nest 2 was abandoned with eggs predated by a House
Crow Corvus splendens. Before the predation event took place
on 26 May 2022, at 2:26 PM, the House crow was seen at least 10
times near nests. Both nesting pairs appeared in the towers sev-
eral times after predation events. Afterwards, the pair from Nest
FIGUR E  | Map showing study area and confirmed breeding sites of Asian Woollyneck in Rajshahi districts, Bangladesh.

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2 relocated to Nest 3, which was 60 m away, and laid a single
egg. The pair also moved nesting materials from Nest 2 to Nest
3. One egg in Nest 3 successfully hatched and fledged during the
2022 breeding season (Figure3E). The clutch sizes of the three
nests were five, four and one.
We find that our observed Nest 1 and Nest 2 were distressed
because of the frequent presence of maintenance crews of the
tower. The breeding pair was away from the nest for a few hours
because of maintena nce workers. Both the nests were aba ndoned
and subsequently predated by House Crow and Large- billed
Crows, respectively. Our camera trap photograph revealed the
incidents (Figure 4). Additionally, the photograph showed that
five eggs in Nest 1 were almost ready to hatch on the basis of the
appearance of the dead hatchlings (Figure4B).
In the 2023 breeding season, the pairs did not return to their
nesting tower. However, one pair started building a nest on the
previously used Nest 3 in the Bijoynagar area. The nest was
nearly completed in the middle of June 2023 but was destroyed
during maintenance work on the cell phone tower on 16 June.
For nesting, Asian Woollynecks used green leaves and sticks of
Acacia auriculiformis, Dalbergia sissoo, Swietenia macrophylla,
Eucalyptus sp., Mangifera indica and a few unidentified grass
species. In Table1, we have summarised all of the information
related to the three observed nests for easy reading.
4 | Discussion
During our 2- year breeding sur vey, where we covered an exten-
sive area over two consecutive years, we found very few nests,
and all of these were on cell phone towers. The previous study
in Bangladesh by Hasan and Ghimire(2020) also observed nests
only on cell phone towers. Use of mobile towers for nesting
FIGUR E  | Camera trap and drone photograph of breeding activities of Asian Woollynecks in study area [(A) nest building by Woollyneck pair,
(B) egg incubation, (C) Nest 2 with complete clutch of four eggs, (D) Nest 1 with five eggs, (E) Woollyneck pair with a chick at Nest 3].

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by Asian Woollynecks has been observed in several locations
(Vaghela et al. 2015; Hasan and Ghimire 2020; Sundar 2020;
Kittur and Sundar 2021). Most of these studies provide anec-
dotal observation and have surmised that storks use towers for
increased visibility, height, avoidance of human disturbances
and stronger nest substrates. However, the extensive study on
breeding ecology by Kittur and Sundar(2021) showed use of arti-
ficial substrates (electricity pylons) in an agriculture- dominated
landscape by Asian Woollynecks to be minimal (8%–13% of
nests each year). The study area lacks larger trees; however, the
urbanised landscape is predominantly agricultural, along with
larger waterbodies. Clearly, the use of artificial sites appears to
be a behaviour regulated by local conditions, and it is not clear
why the storks in Bangladesh are using cell phone towers over
trees all the time.
We observed that Asian Woollynecks initiated nesting in April
or May, which is later relative to previous nesting records in
Bangladesh (September—November; Hasan and Ghimire2020)
but overlapped with observations in India (May—October;
Kittur and Sundar 2021). In the lowlands of Nepal, the onset
of breeding is observed from March to November (spanning
summer- monsoon) where the nesting period coincides with
the monsoon (Ghimire et al. 2022). Most studies on Asian
Woollynecks are short- term, making it difficult to know for sure
the nesting period, and the only multi- year study in north India
showed that the nesting period was consistently between May
and October (Kittur and Sundar 2021), and our observations
over 2 years also show some inter- annual consistency of nesting
with nests observed between April and May (this study). With
the available information, it appears that there is a variation in
the nesting season of the Asian Woollynecks across its range.
Deposition of green plant material in a nest is a quite common in
birds, but their function is not properly known, as in the case of
Asian Woollynecks in this study. Similar to Woollynecks, other
stork species, such as Asian Openbill (Anastomus oscitans) and
Wood Stork (Mycteria americana) are also seen to use green
nesting materials to line the inner surface of the nest (Rodgers
Jr etal. 1988). It is believed that green Eucalyptus trees have
FIGUR E  | Nest predation attempt [(A) by House Crow] and nest predation [(B) by Large- billed Crow] of Asian Woollynecks in Bangladesh.

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TABLE  | Details of nest locations of three Asian Woollyneck nests in Bangladesh.
Nesting parameters 2022 2023
Nest pumber Nest 1 Nest 2 Nest 3 Nest 1 Nest 2 Nest 3
Nest location In a paddy field at
Bidirpur Bazar
Inside cultivable
land at Bijoynagar
In a paddy field
at Bijoy nagar
No nest
found
No nest
found
In a paddy field at Bijoynagar
Onset of nest building 3 March 2022 22 April 2022 26 may (carried nest
materials from Nest 2)
— — Tower demolished and nest destroyed
Substrate/tree Cell phone tower Cell phone tower Cell phone tower — — Cell phone tower
Height from ground (m) 52 42 42 — — 42
Distance to nearest road (m) 20 25 10 — — 10
Distance to nearest Tree
(> 10 m)
50 300 300 — — 300
Distance to Padma River m 330 1146 1160 — — 1160
Nest diameter (total length)
in cm
63.5 61.8 Not measured — — Not measured
Nest diameter (core area) in
cm
45.5 43.4 Not measured — — Not measured
Breeding parameters
Date of laying of first egg 27 May 2022 21 May 2022 26 May 2022 — — —
Last egg laid 6 June 2022 Not known Not known — — —
Clutch size 5 4 1 — — —
Incubation period Not completed Not completed — — — —
Nest predation/egg lost 5 4 None — — —
Nest fate Predated
(2 July 2022)
Abandoned and
predated
Successfully fledged — — —

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volatile chemicals that are known to repel or even kill ectopara-
sites (Gwinner etal.2000). However, in the case of Wood Stork
(Mycteria americana) role of green leaves in repelling nest ecto-
parasites was not evident (Rodgers Jr etal.1988). Clutch sizes
of Asian Woollynecks in north India, determined from fledged
chicks, were 3–5 (average of 3.1), with one pair fledging six
chicks (Sundar2020; Kittur and Sundar2021). Our findings of a
single egg in a nest and the subsequent fledging of the hatchling
from this egg are unusual.
The primary reason for nest disturbance and abandonment that
led to egg predation was due to di sturbance caused by ma intenance
workers. Nest abandonment due to mobile tower maintenance
workers was also reported from the same study area (Hasan and
Ghimire2020). We believe this to also be the reason why storks
avoided nesting on the towers in 2023. Asian Woollyneck showed
high nest site fidelity in north India despite year- long human pres -
ence (44% of 166 unique sites were used more than once; Kittur
and Sundar 2021) (Kittur and Sundar 2021). In Bangladesh,
Asian Woollynecks abandoned nest sites after disturbance by hu-
mans, as Hasan and Ghimire(2020) reported, and our observa-
tions also indicate the same. Observations in Bangladesh suggest
that Asian Woollynecks face enormous disturbances when nest-
ing on cell phone towers. It is unclear, therefore, why all the nests
of this species found in Bangladesh are on cell phone towers. Such
continued disturbance by humans is likely to cause storks to start
nesting on trees where regular human visits are unlikely, except
perhaps by hunters. The contradictory situation of very high nest
disturbance by humans on cell phone towers and no nests being
found on trees is, as yet, inexplicable. Ghimire etal.(2020) identi-
fied Yellow- throated Martin Martes f lavigula, a mammalian nest
predator for Asian Woollyneck in Nepal; in this study, we iden-
tified large- billed crow Corvus macrorhynchos and House crow
Corvus splendens as competent nest predators.
Habitat and nest protection is suggested to be a likely require-
ment for Asian Woollyneck survival in South- East Asia (Birdlife
International2023). Protecting nests in cell phone towers during
the breeding season appears to be a critical requirement in
Bangladesh as well. Working with cell phone providers to under-
stand how workers can minimise disturbances during the Asian
Woollyneck breeding season is an important requirement. The
study concludes that studies on the habitat suitability analysis,
long- term viability of nesting on cell phone towers, the role of
electromagnetic radiation, and predator–prey interactions in
these habitats should be carried out immediately to conserve
Asian Woollynecks in Bangladesh.
Author Contributions
Allama Shibli Sadik: conceptualization (equal), data curation (sup-
porting), funding acquisition (lead), investigation (equal), methodology
(equal), project administration (lead), writing – original draft (sup-
porting). Ashis Kumar Datta: data curation (equal), formal analysis
(lead), methodology (equal), supervision (equal), writing – original
draft (lead), writing – review and editing (lead).
Acknowledgments
We are thankful to Bangladesh Forest Department for funding the re-
search entitled ‘The Status Distribution and Conservation of Colonial
Waterbirds in Bangladesh’ through SUFAL Innovation Grant (SIG- 1),
of SUFAL Project. We convey our appreciation to Sher- E- Afgan, Rima
Akter, Mojirul Islam, Jahangir Kabir and Kayes for their support in
monitoring the field sites. Our sincere gratitude to Dr. Gopi Sundar as
he provided initial feedback on the manuscript. We would like to thank
the mobile tower maintenance crews and local community people for
their cooperation during our field survey.
Conflicts of Interest
The authors declare no conflicts of interest.
Data Availability Statement
Data collected for this research are available in Table 1 of this
manuscript.
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Supporting Information
Additional supporting information can be found online in the
Supporting Information section.