Journal of Threatened Taxa | www.threatenedtaxa.org | 26 September
2019 | 11(12): 14471–14483
Ornithophony in the soundscape of Anaikatty Hills, Coimbatore, Tamil Nadu, India
Chandrasekaran Divyapriya 1 & Padmanabhan Pramod 2
1,2 Nature
Education Division, Sálim Ali Centre for Ornithology
& Natural History (SACON), Anaikatty (P.O.), Coimbatore,
Tamil Nadu 641108, India.
1 Bharathiar University, Marudhamalai
Road, Coimbatore, Tamil Nadu 641046, India.
1 cdp08india@gmail.com
(corresponding author), 2 neosacon@gmail.com
Abstract: An attempt has been made to understand the extent of ornithophony (vocalization of birds) in the soundscape of Anaikatty Hills. The
study was limited to 13 hours of daylight from dawn to dusk (06.00–19.00 h)
between January 2015 and October 2016.
Six replicates of 5-minute bird call recordings were collected from each
hour window in 24 recording spots of the study area. Each 5-minute recording was divided into 150
‘2-sec’ observation units for the detailed analysis of the soundscape. A total
of 78 recordings amounting to 390 minutes of acoustic data allowed a
preliminary analysis of the ornithophony of the
area. A total of 62 bird species were
heard vocalizing during the study period and contributed 8,629 units. A total of 73.75% acoustic space was occupied
by birds, among which the eight dominant species alone contributed to 63.65% of
ornithophony.
The remaining 26% of acoustic space was occupied by other biophonies (12.60%), geophony (5.57%), indistinct sounds
(7.66%), and anthropogenic noise (0.41%).
Passerines dominated the vocalizations with 7,269 (84.24%) and
non-passerines with 1,360 (15.76%) units.
Birds vocalized in all 13 observation windows, with a peak in the first
three hours of the day (06.00–09.00 h).
Vocalizations of non-passerines were prominent in the dusk hours
(18.00–19.00 h).
Keywords: Acoustic community, bird acoustics, bird vocalization,
diurnal singing, ornithophony, soundscape analysis.
doi: https://doi.org/10.11609/jott.4948.11.12.14471-14483
Editor: V.V. Robin, Department of Biology, IISER Tirupati,
India. Date of publication: 26 September 2019
(online & print)
Manuscript details: #4948 | Received 13 March 2019 |
Final received 02 August 2019 | Finally accepted 21 August 2019
Citation: Divyapriya, C. & P. Pramod (2019). Ornithophony in the soundscape of Anaikatty
Hills, Coimbatore, Tamil Nadu, India. Journal of Threatened Taxa 11(12): 14471–14483. https://doi.org/10.11609/jott.4948.11.12.14471-14483
Copyright: © Divyapriya & Pramod 2019. Creative Commons Attribution
4.0 International License. JoTT allows unrestricted use, reproduction, and
distribution of this article in any medium by adequate credit to the author(s)
and the source of publication.
Funding: The study
was self-funded by CD.
Competing interests: The authors declare no competing
interests.
Author details and contribution: C. Divyapriya is a PhD scholar in Nature Education Division, Sálim
Ali Centre for Ornithology & Natural History (SACON). She collected,
curated, analyzed and interpreted the audio recordings of birds and major
contributor in writing the manuscript.
The work is part of her doctoral thesis.
Dr. P. Pramod is a Principal
Scientist, Sálim Ali Centre for Ornithology &
Natural History (SACON) and Head of the Nature Education division. He
conceptualized, supervised the study, reviewed the analysis and edited the
draft. All authors read and approved the
final manuscript.
Acknowledgements:
Authors thank The Cornell Lab of
Ornithology for providing RAVEN Pro 1.4 version with 100% concession. Authors
thank director, Sálim Ali Centre for Ornithology and
Natural History (SACON), Coimbatore for providing facilities and encouragement.
INTRODUCTION
The biological sound produced by vocalizing animals
(e.g., birds and stridulating insects (biophony)),
non-biological sounds such as wind, rain, running stream (geophony) in a forest
or any natural habitat (Hildebrand 2009) constitutes the soundscape of that
area (Pijanowski et al. 2011; Gage & Axel
2014). The man-made sounds produced from
automobile, machinery (technophony or anthrophony)
that dominate in urban settings are rarely detected in forest habitats (Krause
1987; Pijanowski et al. 2011; Gage & Axel
2014). Vocalization of birds (ornithophony) of a terrestrial habitat varies due to the
variations in the dominant vocalizers, number of species involved in vocal
activity and the time specificity of the birds.
It is well known that many species of birds are more vocally active
during dawn and dusk hours as they are active in search of food and / or
attracting a female partner (Slabbekoorn 2004; Brumm, 2006; Catchpole & Slater 2008; Ey & Fischer 2009).
Leaving aside the functionality, ornithophony
is observed as one of the dominant aspects of the soundscape of any natural
ecosystem, especially in forests.
The vocal communication of the birds was well studied,
experimented and the results give insights about the characteristics of avian
vocal signals (Aylor 1971; Morton 1975; Wiley &
Richards 1978; Brenowitz 1982). The environmental factors such as humidity,
temperature, atmospheric turbulence, or vegetation cover influence the signal
transfer through masking, absorption, attenuation, reverberation or signal
scattering effect (Wiley & Richards 1978).
Birds prefer a suitable environmental condition for the effective
long-distant signal transfer (Morton 1975; Kroodsma
1977; Brenowitz 1982). As the vocal communication
consumes significant energy and time (Prestwich 1994; Oberweger
& Goller 2001), animals adapt their vocal signals
spectrally, by altering their syllable structure and usage; or temporally, by
opting for a better daytime hour for signal transfer (Ficken
et al. 1974; Nelson & Marler 1990; Boncoraglio & Saino 2007; Planque & Slabbekoorn 2008; Ey & Fischer 2009; Velásquez
et al. 2018). Birds reduce the
interference and masking effect of other animal signals such as insects
(Stanley et al. 2016), and abiotic noise like wind and water (Klump 1996). Hence,
birds have vocal partitioning or an
‘acoustic niche’ (Brumm 2006; Planque & Slabbekoorn 2008;
Luther 2009; Hart et al. 2015). As dawn
and dusk hours have a favourable environmental conditions (Morton 1975; Slagsvold 1996; Hutchinson 2002) and enhance long-distant
signal transfer (Henwood & Fabrick 1979; Dabelsteen & Mathevon 2002;
Brown & Handford 2003), birds probably prefer
those hours for consistent signal transfer.
The interaction of biological and non-biological
sounds provides the overall framework of the acoustic ecology of a landscape (Pijanowski et al. 2011).
Spectral frequency (Hz) analysis is a valid method for interpreting the
terrestrial soundscape (Irwin 1990; Nowicki & Nelson 1990; Cardoso 2010;
Cardoso & Atwell 2011). Overlapping
of sound frequencies of geophony (such as wind, rain) or technophony
(automobiles) may mask the biophony signals (Qi et
al. 2008; Mullet 2017). Most of the technophony and a few biophonic sounds (birds) occur in
lower frequency range 1–2 kHz.
Passerines species’ frequency ranges between 3 and 6 kHz, whereas
insects occupy a higher range, > 6kHz, and all the geophony are of low
frequency ranging from 1–11 kHz (Napoletano 2004; Qi
et al. 2008; Joo et al. 2011; Kasten et al. 2012; Gage
& Axel 2014).
Biophony of the soundscape can be comprehended by examining
the temporal framework across the daytime from dawn to dusk (Joo 2008; Joo et al. 2011). It also provides valuable insights on species
diversity (Napoletano 2004; Sueur
et al. 2008) and ecosystem (Qi et al. 2008).
This study is a first step to understand the biophony
in the soundscape of Anaikatty Hills through a
community acoustics’ approach on the ornithophony
across daylight hours.
METHODS
Study area
The study area is Anaikatty
Hills (11.090–11.097 0N & 76.778–76.792 0E; Fig. 1),
in Coimbatore District, Tamil Nadu, India, is a part of the Nilgiri
Biosphere Reserve (NBR), approximately 500 to 600 m, lies on the leeward side
of the Western Ghats. It receives an annual rainfall of about 700mm, which is
mainly contributed by the north-east monsoon.
The temperature varies from 17˚ C to 36˚ C (Mukherjee & Bhupathy 2007). It
is a secondary forest area surrounded by dry deciduous forests rich in
biodiversity and forms a part of the Western Ghats, which is one among the 35
biodiversity hotspots of the world (Noss et al.
2015). The study site is dominated by
trees such as Ceylon Tea Cassine glauca, Woolly-leaved Fire-brand Teak Premna tomentosa,
Umbrella Thorn Acacia planifrons, Neem Azadirachta indica,
Ceylon Boxwood Psydrax dicoccos,
Krishna Siris Albizia
amara, Bidi Leaf Tree Bauhinia racemosa, Algaroba Prosopis
juliflora, and shrubs such as Orangeberry Glycosmis
mauritiana, Clausena
dentata, Cat Thorn Scutia myrtina, Siam Weed Chromolaena
odorata, and Lantana Lantana
camara (Balasubramanian et al. 2017). A total of 145 bird species, from 48 families
with 52% of passerine species has been reported from the study site (Ali et al.
2013).
Field methods
The acoustic signals were recorded from 24 different
recording spots (Fig. 1) of the landscape to capture the soundscape from the
maximum microhabitats from January 2015 to October 2016. The study area is a scrub jungle with dry
deciduous forest patches (Ali et al. 2013).
Acoustic data was recorded using Sony PCM-M10 portable linear PCM
handheld audio recorder (2009), with an Audio-Technica
ATR-6550 condenser shotgun microphone in .WAV format with 44.1kHz sampling
frequency and 24-bit accuracy rate. The
diel pattern of acoustic behavior of birds was
observed and calls were recorded from 06.00h to 19.00h spanning 13 hours of a
day. The daylight period is segmented
into 13 one-hour slots (from henceforth mentioned as ‘observation window’). Six replicates of 5-minute bird call recordings
were collected from each window, of which each 5-minute call recording is
considered as ‘a sampling unit’. The
first author held the microphone for one minute in each direction to capture
the soundscape. The sampling effort is
six replications of 13h, makes 78 recordings. The average sampling effort per
location was 3.0. The sampling effort is
presented in Table 1. The recording
date, time and location were noted during the recording period. Recordings were not collected during rainy
days. The sunrise and sunset time was
06.00–06.48 h and 17.57–18:51 h, respectively.
The sunrise and sunset data were obtained from the official website of
Indian Meteorological Department, Government of India.
Data analysis
Each 5-min recording was analysed by dividing it into
150 ‘2-sec’ parts (henceforth mentioned as ‘observation unit(s)’). The first author manually investigated each
2-sec unit for capturing the dominant vocalizing bird species. It was a challenging and time-consuming task,
however, it helped to understand the soundscape in a much finer
resolution. About 90% of the species
were identified and the remaining were documented as unidentified species. One second would be too short, whereas 3-sec
part would miss out the short vocal signals, hence, 2-sec unit analysis was
preferred. The term ‘vocal unit’ is used
to refer to any biophony (animal vocalizations)
present in it. The calls/audio signals
of (i) individual birds, (ii) unidentified birds,
(iii) birds which were identified to their genus category, (iv) gap during the
absence of any vocal signal of bird, (v) wind, (vi) vehicle noise, (vii) sound
of other animals like Spotted Deer, Indian Palm Squirrel, goat, and (viii)
other indistinct sounds were also noted in each observation unit. The loud and vocally dominant species in each
observation unit was visually classified and considered for further
analysis. The vocalizations identified
to group level were also considered as separate taxa for broad level classifications,
however, they are not included as separate species while accounting for the
total number of species vocalized.
The 13 daytime hours were classified into morning
(06.00–09.00 h), mid-day (09.00–12.00 h), afternoon (12.00–16.00 h), and
evening (16.00–19.00 h) hours. To study
the variation on the number of bird species and vocal units across 13
observation windows, ANOVA test (Fisher 1925) with random effect was
performed. Kruskal-Wallis test (Kruskal
& Wallis 1952) was performed to show statistical proof for significant
variation between morning and evening hours against mid-day and afternoon
hours. All the statistical tests were
performed using SPSS v.16.0 (SPSS Inc. 2007).
The sound recordings were analyzed for
spectrogram views with the aid of sound analysis software Raven Pro 1.4
(Bioacoustics Research Program 2011) and audio signals were edited using
Audacity 2.0.6. software. The
spectrogram settings in Raven Pro 1.4 (2011) were as follows: Hann 512, 3dB
filter Bandwidth 124Hz, 50% overlap, grid spacing 86.1Hz. The frequency values of bird vocalizations
were measured by visual inspection method (Irwin 1990; Nowicki & Nelson
1990; Baker & Boylan 1995; Cardoso & Atwell 2011; Singh & Price
2015).
RESULTS
Soundscape analysis
The acoustic data collected from the field had 78 recordings
with a total duration of 390 minutes sampled from multiple locations (24) of
the same landscape evenly spread along the 13 different observation
windows. This gives 900 observation
units per window adding to 11,700 units in total. Visual classification of these observation
units yielded a total of 62 bird species’ calls (Tables 2, 3). The checklist of species was prepared
following Praveen et al. (2019).
Passerines dominated all through the 13 day-hours and non-passerines
were more vocalizing during 18.00h to 19.00h.
Especially, the first three hours had 19, 22, and 20 passerine species
(Fig. 2). Thirty-nine passerine species (62.90%) and 23 (37.09%) non-passerine
species (Tables 2, 3) were recorded as the vocalizers of the Anaikatty soundscape.
Among the total 11,700 observation units, birds occupied 8,629 (74%); of
these, passerines occupied 7,269 (84.24%), and non-passerines only 1,360
(15.76%) vocal units (Fig. 3). Of the remaining 26% of the sample, 12.60% was
contributed by biophony of other creature such as
insects and 5.57% by geophony (wind, indistinct noise). Undetectable or
indistinct sounds were 7.66%, and the remaining negligible 0.41% by
anthropogenic noise. ANOVA (Fisher 1925)
showed that the bird species and vocal units significantly varied across the 13
observation windows, i.e., F12,65 = 4.220, p < 0.01 and F12,65
= 2.251, p = 0.019, respectively.
ANOVA (Fisher 1925) showed that the vocalization number of bird species
were significantly varied across 13 hours (random effect in ANOVA).
Bird vocalizations across diurnal hours
The number of species recorded vocalizing was high in
the initial three hours of the day (Fig. 2).
In the first hour of observation, i.e., 06.00–07.00 h, 95% of the time
was occupied by bird calls (858 out of 900 observation units), 10.00–11.00 h
window received the next maxima with 763 bird vocal units, and in the evening
just before the sunset, i.e., 17.00–18.00 h had the next peak with 647 vocal
units. (Fig. 3, 4).
The Kruskal-Wallis test showed no significant
difference across the bird species between mid-day–afternoon hours against
morning–evening hours, χ2 = 3.47, df = 1, p = 0.063
(N = 13). There was no significant
variation in vocal units among the tested groups χ2 = 0.73, df
= 1, p = 0.39 (N = 13). In any one-hour
observational window, a minimum of 16 species was recorded to be vocally
active.
Non-passerines were higher at 06.00–07.00 h and
declined as the day progressed. There
was a peak in their vocalizations during 18.00–19.00 h (Fig. 2). It is to be noted that non-passerine vocal
contribution increased from 15.00h onwards (Fig. 3). Among the 13 hours, Indian Pitta was more
vocal during 18.00–19.00 h. The 15
species that contributed to dusk calls were either producers of low-frequency
calls or harmonics. Totally, 10 species
(Yellow-billed Babbler, Jungle Crow, Common Tailorbird, Indian Peafowl, Indian
Robin, White-browed Bulbul, Spotted Dove, Red-vented Bulbul, Grey Jungle fowl,
and Common Hawk Cuckoo) were observed to be vocalizing both in dawn and dusk
time. The low and high frequency values
of the 62 species are given in Tables 2 and 3.
Dominance in vocalization
Eight species dominated the ornithophony
with 63.65% of vocal units’ contribution (Fig. 5 and their statistical analysis
is provided in Table 4). Of these,
Common Tailorbird, Red-vented Bulbul, Yellow-billed Babbler, Indian Robin, and
White-browed Bulbul had vocalized in all 13-hour observation windows (Fig. 5),
whereas Purple-rumped Sunbird, Grey-breasted Prinia, and Common Iora were
absent in the 18.00–19.00 h window.
Common Tailorbird dominated the soundscape of the study area with 1,619
vocal units (Fig. 5), i.e., 18.76% vocal signal contribution and was present in
74 out of 78 recordings. White-browed
Bulbul’s vocal signals were present in 66 recordings, occupied just 3.97% of
total ornithophony (Table 4). Indian Paradise-flycatcher was found only in
a 5-min recording. They produce several
quick high-pitched notes and hence, occupy several observation units (40) in a
single utterance. The Common Rose-finch,
Blue-bearded Bee-eater, Rose-ringed Parakeet, Indian Golden Oriole, Ashy Drongo, Plum-headed Parakeet, Tawny-bellied Babbler,
Greater Racket-tailed Drongo, and Barn Swallow were
observed in only one of the recordings.
Fifteen non-passerines were recorded vocalizing during
the dawn hour (06.00–07.00 h), after that non-passerine composition declined in
the subsequent hours (Fig. 2). It is to
be noted that non-passerines vocal contribution slightly increased from 15.00h
onwards (Fig. 3). Indian Peafowl, Grey
Francolin, Grey Junglefowl, Red-wattled Lapwing, Jerdon’s Nightjar, and Common Hawk Cuckoo were the dominant
non-passerines during the 18.00–19.00 h window and were at low ebb or almost
nil during other hours. Indian Peafowl
was the only non-passerine to be vocally active in all 13 observation windows,
the Grey Francolins were present in seven out of 13 observation windows, and
the Grey Junglefowl calls were recorded in six observation windows. Indian Pitta being a winter visitor and lower
song rate species had fewer vocal units in the present study. Figure 6 shows the number of bird species’
spread in each observation window. The
06.00–08.00 h window had more bird species, whereas, 18.00–19.00 h had the
least. Figure 7 depicts the vocal units’
data spread. Vocal units at 09.00–10.00
h, 12.00–13.00 h, and 18.00–19.00 h were relatively more variable than other
observation hours.
DISCUSSION
Soundscape analysis
The study area, a scrub jungle in a dry deciduous
landscape, had more of sound than silence in day hours. The sounds of birds dominated 74% of the time
in the study area, especially in the initial three hours. We have recorded other biophony
and indistinct, undetectable sound sources from the study area. The indistinct sounds in the study area could
be relatively short-bursts of wind or sound produced by any other vocalizing
animal. Earlier studies say that the
forest environment has lesser decibel (Aylor 1971;
Marten & Marler 1977; Marten et al. 1977) as
background sound than in urban areas (Brumm & Slabbekoorn 2005; Brumm
2006). The terrestrial habitats are
prone to low-frequency noise caused by air turbulence, rain, running water (Brumm & Slabbekoorn 2005) and
other biotic noises (Slabbekoorn 2004). The omnipresent cicadas and their concert
produce a constant spectrum of background noise (Slabbekoorn
2004). Therein, the biophony
generally ranges between 2kHz and 11kHz (Napoletano
2004; Qi et al. 2008; Joo et al. 2011; Kasten et al.
2012; Gage & Axel 2014). Mullet et
al. (2016) clarify that the high-frequency vocalizing passerines can be
effectively distinguished from low-frequency producers through a spectrogram
analysis. To avoid the biological or
non-biological sound frequency overlap, birds utilize different acoustic niches
to broadcast the information (Krause 1987; Qi et al. 2008; Luther 2009).
This acoustic diversity study assessed the ornithophony distribution across day hours. Anaikatty
soundscape has 86.60% of biophony. Gage & Axel’s
(2014) soundscape power analysis study of Cheboygan County soundscape showed
that the biological sounds attributed to 80% of total eco-acoustics. The
frequency-dependent acoustic analysis corroborates that ornithophony
occupies the 2–8 kHz of spectral bandwidth (Napoletano
2004; Qi et al. 2008; Gage & Axel 2014).
Thus, acoustic diversity study across the day hours will assess the ornithophony distribution and assess the soundscape
framework of a habitat.
Bird vocalizations across diurnal hours
More number of species showed acoustic activity in
dawn and dusk hours; however, the vocal units were not significantly different
across 13 hours. The soundscape of the
study area had higher bird vocalizations in the early three hours (0600–09.00
h). The temperature, wind, humidity is
more advantageous with least atmospheric turbulence and less background noise
during dawn, thus enhancing the signal transmission (Morton 1975; Kroodsma 1977; Krebs & Davies 1981; Slagsvold
1996; Hutchinson 2002; Luther 2009; Hart et al. 2015). Early hour bird
vocalizations were observed in Arizona and in Kutai
Nature Reserve, Borneo (Henwood & Fabrick 1979),
deciduous forest in Denmark (Dabelsteen & Mathevon 2002), open grassland and closed forest habitat in
Ontario (Brown & Handford 2003), and upland
pasture at New York (Brenowitz 1982). Moreover, the dawn (and dusk) chorus gives
the advantage to use the energy reserve unused since the previous night
(McNamara et al. 1987; Hutchinson 2002).
Dawn chorus also has reproductive benefits such as attracting a mate and
deter other potent males to get access to the partner (Slagsvold
1996; Catchpole & Slater 2008), to defend territory and nest site from
conspecific males (Slagsvold 1996).
Low frequency and/or harmonic producing birds’
vocalizations dominated the dusk hour (18.00–19.00 h; Tables 2,3). Low frequency vocalizations of birds and
amphibians dominated during the night at Cheboygan County, Michigan (Gage &
Axel 2014). Harmonics increases the difficulty in locating the calling bird
(Blindfolded birdwatching 2010), thus avoiding predatory attacks. As the visual cues are undependable during
the sunset hour (Kacelnik 1979), low frequency gives
an advantage for long-distance signal propagation (Aylor
1971; Morton 1975; Marten & Marler 1977; Martenet al. 1977; Wiley & Richards 1982; Wiley
1991). Song activity at dusk increases
the pair-bonding behavior in American Robins (Slagsvold 1996), and in Blackbird (Cuthill
& Macdonald 1990). A peak in dawn
and dusk vocal activity suggest that these hours are important for a male to
guard the mate and nest site (Sturkie 1976; Mace
1986, 1987; Cuthill & Macdonald 1990). Soundscape peaked at dawn chorus (06.00–07.00
h), then dropped shortly after sunrise, till evening and once again raised
during dusk hours and reached second maxima at 20.00h in Cheboygan County,
Michigan (Gage & Axel 2014).
Dominance in vocalization
The Common Tailorbird was the most dominant vocalizer
of the landscape as their calls were louder and have a higher song rate, i.e.,
the number of call syllables produced in a minute. All the eight dominant species vocalize continuously. The passerines are louder and are continuous
vocalizers (Garamszegi & Møller
2004; Catchpole & Slater 2008; Cardoso 2010). Seven of the dominant species are forage
generalists and were vocally active all through the day yielding a higher vocal
unit. The early hours had uniform vocal
units’ contribution per observation window.
Increased variability of vocal units during 09.00–10.00 h, 12.00–13.00
h, 14.00–15.00 h, and 18.00–19.00 h could be attributed to relatively variable
number of vocalizers (Fig. 7). This
might also show the need of more sampling efforts.
The 16.00–17.00 h observation window had more
non-passerines (11 species) yielding fewer vocal units, whereas, passerines
were predominant in the study area with more vocal units. More vocal units and complexity exhibits the
versatility of passerine birds (Garamszegi & Møller 2004; Boncaraglio & Saino 2007; Catchpole & Slater 2008; Cardoso 2010), as
they are louder (Calder 1990; Cardoso & Mota
2009; Cardoso 2010) and are continuous vocalizers (Hartley & Suthers 1989; Irwin 1990; Podos
1997; Forstmeier et al. 2002). This makes passerines to occupy a larger
portion of the soundscape of Anaikatty Hills in
general.
Song rate analysis is beyond the scope of this present
study, however, any trained ears could relatively understand the song rate of
bird calls. The study which aimed at
understanding the vocal activity pattern of diurnal birds illustrates that the
soundscape of Anaikatty is largely occupied by birds
in those hours.
CONCLUSIONS
Birds occupy 73.75% of acoustic space in the
soundscape of Anaikatty Hills and the remaining
26.25% includes the vocal activity of insects, other indistinct sounds or
complete silence. Thirty-nine passerine
species (62.90%) and 23 non-passerine species (37.09%) vocalized in the sampled
soundscape of the study area. The eight
dominant species constitutes 63.65% of ornithophony
of the study area. Out of the total
sampled ornithophony, passerines occupied 84.35% and
non-passerines 14.74% of the vocal units.
Birds vocalized in all 13 daylight hours, with a peak in the first three
hours of the day (06.00–09.00 h).
Passerines dominated the soundscape in all hours except the dusk 18.00–19.00
h.
Limitation of the study
The sampling effort was done to answer the preliminary
account of ornithophony of the soundscape of the
region. Though the researcher
intentionally did not direct the microphone towards the vocalizing bird, the
usage of shotgun microphone might have had an effect on the calling bird. Though the researcher had sampled the 5-min
by directing the microphone in all directions, the shotgun microphone was a
limitation for the soundscape study compared to the omnidirectional microphone.
Table
1. Sampling effort of the study in Anaikatty Hills.
|
13 hrs/ 24 loc |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
15 |
16 |
17 |
18 |
19 |
20 |
21 |
22 |
23 |
24 |
|
6–7 h |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
7-8 h |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
8–9 h |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
9–10 h |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
10–11 h |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
11–12 h |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
12–13 h |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
13–14 h |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
14–15 h |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
15–16 h |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
16–17 h |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
17–18 h |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
18–19 h |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
The
sampling effort was distributed across 13 hours in 24 locations to capture the
soundscape of the study area.
Table
2. List of passerine species of Anaikatty Hills
recorded during the study. Birds with harmonics are marked with an
asterisk (*). Sample size of the low and high frequencies are 10, except # -
sample size 5; ^ - sample size 4.
|
|
Bird
species /Family |
Scientific
name |
Low-frequency
values (in
Hz) (Mean ± S.D.) |
High-frequency
values (in
Hz) (Mean ± S.D.) |
|
|
Pittidae |
|
|
|
|
1 |
Indian
Pitta |
Pitta
brachyura |
1662.5 ±
289.5 |
4662.9
±3353.1 |
|
|
Oriolidae |
|
|
|
|
2 |
Black-hooded
Oriole |
Oriolus xanthornus |
1465.97 ±
798.58 |
2229.97 ±
564.44 |
|
3 |
Eurasian
Golden Oriole |
Oriolus oriolus |
1099.7 ±
408.8 |
7825.8 ±
6266.1 |
|
|
Aegithinidae |
|
|
|
|
4 |
Common Iora |
Aegithina tiphia |
1589.54 ±
301.49 |
3432.68 ±
682.08 |
|
|
Dicruridae |
|
|
|
|
5 |
Ashy Drongo* |
Dicrurus leucophaeus |
1661.9 ±
329.3 |
10420.0 ±
3202.1 |
|
6 |
Greater
Racket-tailed Drongo |
Dicrurus paradiseus |
1673.6 ±
118.9 |
2741.6 ±
53.9 |
|
|
Laniidae |
|
|
|
|
7 |
Brown
Shrike* |
Lanius cristatus |
2166.9 ±
504.1 |
10701.9
±1479.1 |
|
|
Corvidae |
|
|
|
|
8 |
Rufous
Treepie* |
Dendrocitta vagabunda |
815.2 ±
272.5 |
18059.0 ±
1996.3 |
|
9 |
House Crow* |
Corvus splendens |
1205.1 ±
955.5 |
3136.6 ±
1317.2 |
|
10 |
Large-billed
Crow* |
Corvus macrorhynchos |
1193.6 ±
690.6 |
2298.2 ±
658.7 |
|
|
Monarchidae |
|
|
|
|
11 |
Indian
Paradise-flycatcher* |
Terpsiphone paradisi |
1231.56 ±
262.78 |
13764.35 ±
1550.62 |
|
|
Dicaeidae |
|
|
|
|
12 |
Thick-billed
Flowerpecker |
Dicaeum
agile |
2562.6 ±
602.4 |
14147.4 ±
592.3 |
|
13 |
Pale-billed
Flowerpecker |
Dicaeum erythrorhynchos |
3721.5 ±
549.8 |
11403.5 ±
567.2 |
|
|
Nectariniidae |
|
|
|
|
14 |
Purple-rumped Sunbird |
Leptocoma zeylonica |
3581.8 ±
461.5 |
6273.3 ±
1006.4 |
|
15 |
Purple
Sunbird |
Cinnyris asiaticus |
4145.5 ±
1099.1 |
7016 ±
734.1 |
|
16 |
Loten's
Sunbird |
Cinnyris lotenius |
4145.5 ±
662.3 |
6643.9
±1530.6 |
|
|
Chloropseidae |
|
|
|
|
17 |
Jerdon's
Leafbird* |
Chloropsis jerdoni |
1844.6 ±
460.3 |
7736.8 ±
5421.0 |
|
|
Fringillidae |
|
|
|
|
18 |
Common Rosefinch# |
Carpodacus erythrinus |
2060.1 ±
146.1 |
6003.3 ±
166.8 |
|
|
Paridae |
|
|
|
|
19 |
Cinereous
Tit |
Parus cinereus |
2835.5 ±
350.4 |
8553.6 ±
427.4 |
|
|
Cisticolidae |
|
|
|
|
20 |
Grey-breasted
Prinia |
Prinia hodgsonii |
3002.7 ±
329.6 |
7107.9 ±
325.6 |
|
21 |
Jungle Prinia |
Prinia
sylvatica |
2705.6 ±
244.5 |
6545.5 ±
600.1 |
|
22 |
Ashy Prinia |
Prinia socialis |
2821.5 ±
530.2 |
6394.2 ±
611.4 |
|
23 |
Common
Tailorbird |
Orthotomus sutorius |
2604.27 ±
1153.85 |
5840.91 ±
833.58 |
|
|
Acrocephalidae |
|
|
|
|
24 |
Blyth's
Reed Warbler |
Acrocephalus dumetorum |
2663.7 ±
505.34 |
7379.51 ±
335.14 |
|
|
Hirundinidae |
|
|
|
|
25 |
Red-rumped Swallow* |
Cecropis daurica |
2719.4 ±
196.9 |
7807.4 ±
1334.1 |
|
26 |
Barn
Swallow* |
Hirundo rustica |
2587.8 ±
597.3 |
8021.2 ±
2566.4 |
|
|
Pycnonotidae |
|
|
|
|
27 |
Red-whiskered
Bulbul |
Pycnonotus jocosus |
1703.8 ±
509.9 |
3667.3 ±
488.7 |
|
28 |
Red-vented
Bulbul |
Pycnonotus cafer |
1562.8 ±
194.1 |
3062.5 ±
393.1 |
|
29 |
White-browed
Bulbul |
Pycnonotus luteolus |
1256.8 ±
227.8 |
3707.7 ±
504.8 |
|
|
Phylloscopidae |
|
|
|
|
30 |
Greenish
Leaf Warbler |
Phylloscopus trochiloides |
3438.2 ±
716.6 |
7505.9 ±
1717.6 |
|
|
Timaliidae |
|
|
|
|
31 |
Indian
Scimitar Babbler*^ |
Pomatorhinus horsfieldii |
622.7 ±
116.9 |
1300.2 ±
248.2 |
|
32 |
Tawny-bellied
Babbler |
Dumetia hyperythra |
3475.0 ±
554.3 |
6443.7 ±
193.6 |
|
|
Leiothrichidae |
|
|
|
|
33 |
Yellow-billed
Babbler* |
Turdoides affinis |
3702.7 ±
518.8 |
9946.6 ±
2710.5 |
|
|
Sturnidae |
|
|
|
|
34 |
Common Myna* |
Acridotheres tristis |
1399.8 ±
393.8 |
10244.5
±3148.6 |
|
35 |
Jungle Myna* |
Acridotheres fuscus |
1368.7 ±
204.5 |
9803.4 ±
3469.0 |
|
|
Muscicapidae |
|
|
|
|
36 |
Indian
Robin |
Saxicoloides fulicatus |
5034.9 ±
1375.7 |
7261.5 ±
642.1 |
|
37 |
Oriental
Magpie Robin* |
Copsychus saularis |
2399.4 ±
320.9 |
6770.0 ±
2349.3 |
|
38 |
Tickell's
Blue flycatcher |
Cyornis tickelliae |
3095.0 ±
206.8 |
7318.3 ±
1788.8 |
|
39 |
Pied Bushchat |
Saxicola caprata |
2037.4 ±
349.7 |
5089.6 ±
849.5 |
Table
3. List of non-passerine species of Anaikatty Hills
recorded during the study. Birds with harmonics are marked with an
asterisk (*). The sample size for low and frequencies of the species are ten,
except ^ - sample size is 8.
|
|
Bird
species /Family |
Scientific
name |
Low-frequency
values (in Hz) (Mean ± S.D.) |
High-frequency
values (in
Hz) (Mean ± S.D.) |
|
|
Phasianidae |
|
|
|
|
1 |
Indian
Peafowl* |
Pavo cristatus |
551.36 ±
84.9 |
10284.2 ±
891.5 |
|
2 |
Grey
Francolin* |
Francolinus pondicerianus |
1908.2 ±
106.1 |
6700.1 ±
1873.2 |
|
3 |
Grey
Junglefowl* |
Gallus
sonneratii |
763.5 ±
647.6 |
8009.7 ±
4212.4 |
|
|
Columbidae |
|
|
|
|
4 |
Spotted
Dove |
Streptopelia chinensis |
569.0 ±
44.2 |
837.9 ±
39.6 |
|
5 |
Laughing
Dove |
Streptopelia
senegalensis |
640.8 ±
26.4 |
886.1 ±
22.9 |
|
|
Caprimulgidae |
|
|
|
|
6 |
Jerdon's
Nightjar |
Caprimulgus atripennis |
574.9 ±
41.2 |
1476.0 ±
30.8 |
|
|
Cuculidae |
|
|
|
|
7 |
Greater Coucal |
Centropus sinensis |
398.0 ±
102.5 |
870.5 ±
233.4 |
|
8 |
Asian Koel* |
Eudynamys scolopaceus |
982.3 ±
75.49 |
10473.3 ±
4694.39 |
|
9 |
Common Hawk
Cuckoo |
Hierococcyx varius |
1510.81 ±
357.50 |
2225.95 ±
280.65 |
|
|
Charadriidae |
|
|
|
|
10 |
Red-wattled Lapwing* |
Vanellus
indicus |
1490.9 ±
431.3 |
8282.1 ±
4678.9 |
|
|
Accipitridae |
|
|
|
|
11 |
Crested
Serpent Eagle* |
Spilornis cheela |
1806.7 ±
91.9 |
6317.6 +
1242.54 |
|
12 |
Shikra* |
Accipiter
badius |
1472.9 ±
453.0 |
13709.4 ±
1980.1 |
|
|
Upupidae |
|
|
|
|
13 |
Common
Hoopoe |
Upupa epops |
795.0 ±
410.2 |
1621.1 ±
1052.1 |
|
|
Megalaimidae |
|
|
|
|
14 |
White-cheeked
Barbet |
Psilopogon viridis |
940.8 ±
61.7 |
1307.6 ±
40.2 |
|
15 |
Coppersmith
Barbet |
Psilopogon haemacephalus |
633.8 ±
25.1 |
898.1 ±
25.4 |
|
|
Meropidae |
|
|
|
|
16 |
Blue-bearded
Bee-eater |
Nyctyornis athertoni |
586.17 ±
80.15 |
3740.23 ±
695.06 |
|
17 |
Green
Bee-eater |
Merops orientalis |
2781.7 ±
219.5 |
4373.6 ±
241.5 |
|
18 |
Chestnut-headed
Bee-eater |
Merops leschenaulti |
2538.88 ±
113.84 |
3590.01 ±
215.33 |
|
|
Alcedinidae |
|
|
|
|
19 |
White-throated
Kingfisher* |
Halcyon
smyrnensis |
2436.2 ±
105.3 |
7272.7 ±
2739.7 |
|
|
Psittaculidae |
|
|
|
|
20 |
Plum-headed
Parakeet*^ |
Psittacula cyanocephala |
1828.0 ±
468.1 |
6735.8 ±
1347.2 |
|
21 |
Malabar
Parakeet* |
Psittacula columboides |
2571.6 ±
165.1 |
4199.9 ±
277.9 |
|
22 |
Rose-ringed
Parakeet* |
Psittacula krameri |
2047.4 ±
798.9 |
8566.3 ±
1257.9 |
|
23 |
Vernal
Hanging Parrot* |
Loriculus vernalis |
6261.7 ±
571.0 |
7948.1 ±
179.5 |
Table
4. Descriptive statistics of the eight most vocalizing passerines of the study
area.
|
Bird
sp. |
Mean |
Std.
Dev. |
Co-efficient
of Variation (CV) |
Min |
Max |
No.
of presence among 78 recordings |
No.
of vocal units |
|
Common
Tailorbird |
20.76 |
15.43 |
74.32 |
1.00 |
61.00 |
74 |
1619 |
|
Red-vented
Bulbul |
10.73 |
10.36 |
96.53 |
1.00 |
45.00 |
69 |
837 |
|
Common Iora |
10.42 |
16.47 |
158.06 |
1.00 |
63.00 |
52 |
813 |
|
Yellow-billed
Babbler |
7.13 |
10.47 |
146.83 |
1.00 |
58.00 |
54 |
556 |
|
Purple-rumped Sunbird |
7.09 |
11.61 |
163.72 |
1.00 |
68.00 |
52 |
553 |
|
Indian
Robin |
5.31 |
7.99 |
150.55 |
1.00 |
36.00 |
55 |
414 |
|
Grey-breasted
Prinia |
4.59 |
9.60 |
209.14 |
1.00 |
41.00 |
29 |
358 |
|
White-browed
Bulbul |
4.40 |
4.19 |
95.38 |
1.00 |
18.00 |
66 |
343 |
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