Population and roosting behaviour of
Barn Swallows Hirundo rusticawintering in Jamshedpur, Jharkhand, India
SushantKumar Verma
At & P.O. - Harharguttu, Near TRF Colony, Jamshedpur, Jharkhand 831002,
India
Email: vermasushant2008@gmail.com
Date of
publication (online): 26 February 2010
Date of
publication (print): 26 February 2010
ISSN 0974-7907
(online) | 0974-7893 (print)
Editor: Rajah Jayapal
Manuscript
details:
Ms # o2161
Received 18
March 2009
Final received
24 September 2009
Finally accepted
09 February 2010
Citation: Verma, S.K. (2010). Population and
roosting behaviour of Barn Swallows Hirundo rusticawintering in Jamshedpur, Jharkhand, India. Journal of Threatened Taxa 2(2): 721-723.
Copyright: © Sushant Kumar Verma 2010.
Creative Commons Attribution 3.0 Unported License. JoTT allows unrestricted use of this article in any medium
for non-profit purposes, reproduction and distribution by providing adequate
credit to the authors and the source of publication.
Acknowledgements:The
author is thankful to Dr. A. Alim, Department of
Zoology, Jamshedpur Co-operative College, Jamshedpur, for valuable suggestions.
The author expresses his sincere gratitude to Miss Ghazala Sabih and Mr. Abhishek Raj
for generous help, encouragement and inspiration.
For Figures, Images and Tables
- - click here
The Barn SwallowHirundo rusticais the most widespread species of swallows in the world (Turner et al.
1989). It breeds from the central and
eastern Himalaya to Japan and Korea and winters across tropical Asia from India
and Sri Lanka east to Indonesia and New Guinea (Turner et al. 1989). Its preferred habitat during breeding season
is open country with low vegetation. Sinclair et al. (2002) found that they become cosmopolitan during winter
avoiding dense forests and deserts. Winter roost-sites are typically in reed-beds close to rivers and lakes
(Curry-Lindahl 1963; Nutall2000). In addition to reed-beds, maize
or sugarcane fields are also used for roosting (Cramp 1988). Medway (1973) found that in western Malaysia
Barn Swallows roosted extensively not only in Phragmites beds, but also on overhead wires in 26 towns. Similar observations were
made by George (1965) in Mumbai (India), where he found that besides using
sugarcane plantations and mangrove swamps as their traditional roosting place,
thousands of Barn Swallows also roosted on overhead wires in certain crowded
parts near the city. In Honshu, the Barn
Swallow is more an urban bird, with the Red-rumpedSwallow Cecropis dauricareplacing it in rural landscape (Turner et al. 1989). Their gregarious roosting behaviourhelps to reduce predation risk (Bijlsma & van den
Brink 2005) and to conserve energy (Rudebeck 1955).
The Barn SwallowHirundo rusticais a non-breeding winter visitor to Jamshedpur, Jharkhand (India). There is lack of information about the roostingbehaviour of Barn Swallows wintering in Jamshedpur,
hence the present study.
Methods
The roosting
pattern of Barn Swallows was studied from September 2006 to April 2008. This study was carried out on a major
communal roosting area in Jamshedpur, India (22046’20.12”N & 86011’32.66”E)
in a commercial area adjacent to Tatanagar Railway
Station. The approximate population of H.rustica during the entire roosting period was
determined by random counting. For
random counting, the average number of Barn Swallows settled on 1m wire was
determined which was then multiplied by the total length of wire. Ten such samplings were done on every
fifteenth day of each month throughout the study period.
Roost was
watched for five days in each month to record presence and activities of
predatory birds. Monitoring was done for
four hours after the birds settled on wires.
Mean roosting
time (relative to sunset) for each month was calculated to trace out any
fluctuation in relation to available time period between sunset and the end of
twilight. Sunset time is defined here as
the time when the upper arc of the sun was on the true horizon.
Results
First appearance
of Barn Swallows was noted in early September in both years of the study. Seasonal increase in number was observed from
September to a peak in December (Fig. 1). Departure of birds starts from late March and continues to middle of
April. Roosting time relative to sunset
was significantly late in February and March. A correlation exists between roosting time and cloud cover. Birds roosted early in the evening (around 13
to 17 minutes after sunset) when the weather was cloudy. Almost in all evenings when the sky was clear
birds roosted much late (24 to 28 minutes after sunset). Mean time of roosting
in minutes after sunset for each month is given in Table 1. Time interval between roosting of the early
and last bird usually spanned 10 to 17 minutes. It was noted that 10 to 12 roosting swallows occupied 1m of electricity
wire (Image 1). Such occurrence was more
or less uniform across the entire roost colony which enabled me to extrapolate
total population from random samples. A
uniform spacing of about 8cm was noted between two individual roosting swallows
(Image 2). No patterns could be observed
in the direction of facing of birds during roosting. On seeing any predator like Barn Owl or cat,
large numbers would fly off and settle at the same place after a while.
Discussion and
Conclusion
The non-breeding
winter visitor Hirundo rusticaexhibits gregarious, communal roost outside the breeding season in Jamshedpur,
Jharkhand (India). The site of roosting
remained highly illuminated with artificial lights throughout the night.
Possible reasons for selection of such sites for roosting by Barn Swallows may
be: (a) presence of artificial lighting to ward off predatory birds, especially
owls (b) higher thermal gradients in urban agglomerates for generating warmth,
and (c) availability of insects attracted towards artificial lights being
substantial food source. However,
availability of food insects appears to be a low priority factor for urban
roosting of H. rustica. A concomitant increase in the number of
predatory birds indicates the risk of predation. As communal roosting benefits individuals as
a means of reducing predation risk due to improved vigilance for predators
(Pulliam & Caraco 1984; Bijlsma& van den Brink 2005), H. rustica also
resorts to communal roosting.
It was observed
that Barn Swallows roosted significantly later (relative to sunset) in February-April
than in September- January. Giller (1955) reported that roosting time of H. rustica may be influenced by rain and low temperature.
Similar observations were made by Loske (1984). Early roosting in cloudy weather and during
the months of February-April and late roosting in clear weather and during the
months of September-January proves that availability of light is an important
factor.
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