Journal of Threatened Taxa |
www.threatenedtaxa.org | 26 July 2023 | 15(7): 23521–23528
ISSN 0974-7907
(Online) | ISSN 0974-7893 (Print)
https://doi.org/10.11609/jott.8214.15.7.23521-23528
#8214 | Received 01
October 2022 | Final received 25 May 2023 | Finally accepted 06 July 2023
Tree cover and built-up area
regulate the territory size in Eurasian Magpie Pica pica in
Ladakh, India
Iqbal Ali Khan 1, Anil
Kumar 2, Dinesh Bhatt 3 &
Prakhar Rawal 4
1,2 Zoological Survey of India,
Northern Regional Centre, Dehradun, Uttarakhand 248195, India.
1,3 Department of Zoology &
Environmental Sciences, Gurukula Kangri (deemed to be
University), Haridwar, Uttarakhand 249404, India.
4 Department of Biology, University
of Turku, FI-20014 Turku, Finland.
1 khanbbt555@gmail.com, 2 anilsonta@gmail.com
(corresponding author), 3 dineshharidwar@gmail.com, 4 prakharrawal95@gmail.com
Abstract: Eurasian Magpie Pica pica is one of the well-studied corvids, but the
majority of our understanding of this species is from Europe. In India, its
distribution is restricted to some valleys of Ladakh
such as the northwestern part of the Indus, Nubra,
Zanskar, Drass, and Suru.
The present study aimed at understanding the territorial behavior of this
species in small urban settlements of Ladakh region.
Twenty-five pairs were studied in March 2020–April 2021. Territories were
outlined for each color-banded individual, and data on habitat variables
(namely built-up, agriculture, and green cover) was extracted. Generalized
linear mixed models were used to study the effect of the habitat structure on
territory size. The territory size (Mean ± SD) was 0.042 ± 0.025 km2,
with tree cover comprising the highest proportion (24.36 ± 15.41 %) of area
within territories. Built-up area was a feature of all territories,
highlighting the affinity of magpies towards human presence. Presence of tree
cover and built-up area significantly (~ <0.002) reduced territory size.
High adaptability, foraging, and nesting opportunities, and protection from
predators have been recognized as the reasons for magpies’ affinity with human
habitation. Foraging opportunities are minimal outside human settlements in
this region, magpies’ territories are largely shaped by the fulfilment of
foraging requirements.
Keywords: Behavior, Corvid,
foraging, Himalaya, territorial, territory sharing, urban settlements.
Editor: Anonymity requested. Date of publication: 26 July 2023 (online &
print)
Citation: Khan, I.A., A. Kumar, D. Bhatt & P. Rawal (2023). Tree cover and built-up area regulate the
territory size in Eurasian Magpie Pica pica in
Ladakh, India. Journal of Threatened Taxa 15(7):
23521–23528. https://doi.org/10.11609/jott.8214.15.7.23521-23528
Copyright: © Khan et al. 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 authors declare no competing interests.
Author details: Iqbal Ali Khan is a PhD scholar from Gurukula Kangri (deemed to be University), Haridwar, working with the Zoological Survey of India, Dehradun. He has been studying trans-Himalayan birds for five years, with a focus on the behavioural ecology of Eurasian Magpie Pica pica in Ladakh. Dr. Anil Kumar is a
senior scientist at the Zoological Survey of India, Dehradun. Over the years he is working on avifauna, behavioural ecology and sociobiology of birds, especially song characteristics and variations in Copsychus robins. Dr. Dinesh Bhatt is an emeritus professor at Gurukula Kangri (deemed to be University), Haridwar. He is a renowned expert on avian bioacoustics, biodiversity and reproduction of birds. Prakhar Rawal is a PhD scholar at the University of Turku, Finland, working on the ecology of wetland birds. In past, he has worked with Dr. Anil Kumar and significantly contributed as a statistical expert.
Author contributions: IAK undertook field surveys, colour-banded the focal individuals of Eurasian Magpie, noted the behavioural data, took the images in the field and collected the literature for manuscript preparation. AK designed and planned the study including interpretation of data and manuscript writing. DB checked the manuscript and provided inputs for improvements. PR undertook the statistical analysis, prepared graphs and provided inputs for the interpretation of the statistical outcome.
Acknowledgements: Authors are grateful to Dr.
Dhriti Banerjee, director, ZSI, Kolkata, for support
and encouragements. First and second authors are thankful to officer-in-charge,
ZSI, Dehradun, for institutional facilities. The first author is grateful to Prof. Dinesh Bhatt (Emeritus professor, Gurukul Kangri
(Deemed to be University), Haridwar), Dr. Anil Kumar,
scientist-E, ZSI, Dehradun, and Prof. D.S. Malik,
head, Department of Zoology and Environmental Science, Gurukul Kangri,
Haridwar, for departmental support to carry out this study. First author is
thankful to Prakhar Rawal for his contribution in this study. First author is
grateful to Ministry of Tribal Affairs (NFST) to grant the Ph.D. fellowship.
Constant support and encouragements from, wildlife warden Kargil,
and field staff of Wildlife Protection Division, Kargil
is highly acknowledged.
INTRODUCTION
Territory is an area defended by
an organism or a group of organisms for mating, nesting, roosting, and
foraging. During the breeding season, songbirds show territoriality in which
the mated pairs defend the nest and feeding grounds until the young ones fledge
(Alcock 2009). The size of the territory varies,
depending on the habitat quality, structure, and the number of conspecific
neighbors (Jones 2001; Flockhart et al. 2016; Skorupski
et al. 2018). In urban areas, territory size differs in conspecific individuals
depending on their ability to adapt to urban environments (Juarez et al. 2020).
Territory size is crucial for breeding success which plays a major role for the
survival and sustainability of species (Flockhart et al. 2016; Phillips et al.
2020). Hence, understanding of the territorial behavior is not only an
interesting ecological inquiry but can also provide insights to manage
landscapes, particularly urban ones, in a manner that can aid in the
conservation of desired species.
The Eurasian Magpie Pica pica is a medium-sized corvid; an omnivorous bird
with a range that includes Asia, Europe, and parts of northwestern Africa.
Magpies often defend a vast, multi-purpose territory in which they nest,
forage, and spend the majority of their time (Birkhead
1991). Eurasian Magpies are an urban adapter species, capable of invading towns
while also maintaining a wild population in rural and natural habitats (Jokimäki 2017). Although it is one of the most studied
species of corvids with majority of the research conducted in Europe. Studies
on the bird in other continents are still scanty (Benmazouz
et al. 2021). Magpies have a high level of fidelity to their home range,
indicating that their dispersal lengths are quite small (Birkhead
1991).
Ladakh is characterized by large
stretches of uninhabited land interspersed with small human settlements where
magpies can be found. Magpies are known to be sedentary and usually do not
migrate among these villages, and they act as isolated habitats rather than a
gradient, with no individuals observed in between (Newton 2010). The study of
bird territorial behavior in such isolated systems can help us understand how
territorial individuals coexist in small habitats. Studies on magpies from
these high-altitude regions of Ladakh are virtually
absent (Khan et al. 2022).
In this study, we investigated
the territorial behavior of Eurasian Magpies in the small, isolated urban
settlements of Ladakh. Our preliminary findings
revealed that the distribution of the species in Ladakh
is patchy, with most populations confined to areas with human settlements. We
assumed that human settlements might have an impact on the daily activities of
magpies, either directly or indirectly. According to previous research, magpies
are more attracted to man-made food scraps, which reduces magpie hunting and
natural food consumption (Croci et al. 2008; Jokimaki et al. 2017; Salek et
al. 2020). Based on this, we predicted that (1) magpie territory would be
smaller near built-up areas due to increased food provisioning and (2)
territory with a higher proportion of tree cover would be smaller in size
because tree patches provide all essential food resources. We also predicted
that (3) an open area with fewer tree patches would have lower food production
and that the magpie’s territory size would be larger in order to meet the food
requirements.
MATERIALS AND METHODS
Study area
The research was carried out at
two locations, namely Gramthang village of Suru Valley and Bursaika village
of Wakha Valley in the district of Kargil (Image 2), Ladakh of
India. About 8 km2 area at each location was explored for study. Gramthang (34.467-0N, 76.0840E) is
situated about 12 km from Kargil. It is located at an
average elevation of 2750 m and has river-fed well-vegetated lands with a high
concentration of Populus alba, P.
ciliata, P. nigra,
Prunus armeniaca, Salix alba, S.
excelsa, and S. fragilis plantations. Bursaika (34.366-0N, 76.383-0E) is 40
km from Kargil and is part of the Wakha
Valley with an elevation of 3,450 m. The landscape consists of open, arable
cropland, patchy shrublands, a moist meadow with perennial spring water,
and Salix vegetation. The number of Populus trees
plantation in Bursaika are substantially smaller than
in Gramthang due to water constraints and harsh
terrain. Instead, the vegetation is comprised of Salix fragilis
and Sea buckthorn Hippophae rhamnoides shrubs, with fewer P. alba.
The summer temperature in Gramthang ranges from
10°–25° C, while the winter temperature can reach -29° C at its coldest. Bursaika winters are colder, with temperatures dropping to
-35° C during peak winters (Khan et al. 2022).
Behavioral observations and
territory marking
Twenty-five breeding individuals
were caught using bait traps. The method was adopted from a past study (Kautz
& Seamans 1992) and color-banded for individual identification (Image 2).
In 2019 and 2020, the same individuals were seen at the sites, indicating
little to no migration. Territorial observations were made in the months of
March and April when the birds were nesting. Observations were carried out in
2020 and 2021 at sites Bursaika and Gramthang, respectively. Behavioral observations were made
with field binoculars or with the naked eyes, depending on the
situation. Nesting locations of territory owners were also discovered
prior to egg laying by simply looking for birds carrying nest material. This
was relatively easy in the early part of the season before the trees went into
leaf in the summer (May–June). Since magpies are diurnal, each focal individual
was tracked from a safe distance (about 10–30 m) for almost the whole day from
early morning emergence time (0600–0630 h) to late roosting time (1830–1900 h).
The locations visited by magpies for foraging, roosting, water drinking, and
playing (Image 3, 4) were all tracked and marked using GPS (Garmin Etrex 30) shortly after the bird left the spot.
Variable extractions
Territorial variables included
territory size, number of foraging points & the amount of tree cover,
cultivated area, built-up area, and miscellaneous area (shrubland, rock
terrain, river stream, and grassy meadow) within the territory were extracted
using polygons in Google Earth Pro software (version 7.3.6.9345). We determined
the total area of the territory by connecting all the GPS points used by the
focal pair of magpies during the breeding season, plotting all the points in
the Google Earth satellite imagery and tracing out the total territory of the
magpie by connecting all the points and forming a polygon. Other variables
within the territory, such as tree patches, cultivated area, built-up area, and
other miscellaneous areas were also traced using polygons. Multiple polygons
were traced in one territory, and then all the polygons were combined to
identify the different variable areas. Field notes and Google satellite images
were used to cross-check all the sites and areas, and a high-resolution territories
map was created. We studied the influence of neighbors by extracting the
proportion of their territory which overlapped with the territory of other
individuals.
Data analysis
The analysis was carried out
using R version 4.2.2. As the territory size was not normally distributed
(Shapiro-Wilk normality test, p = 0.01), and individuals were selected from two
different sites, we used Generalized Linear Mixed Models (GLMM) to study the
influence of the proportion of different land cover type on the territory size
using the package lmerTest (Kuznetsova et al. 2017).
Based on a correlation matrix, we removed the highly correlated (r > |0.4|)
variables and selected 4 variables for the analysis – tree, agricultural,
built-up cover, and neighbor presence. Their proportions were used, rather than
the absolute area. The response variable was territory size in m2,
but the results are presented in km2 for clarity. Sites (Gramthang & Bursaika) were
taken as the random effects. We ran multiple models using different families
and selected the best model based on AIC values. Regression plots were
created using model results with the help of package effects (Fox &
Weisberg 2019).
RESULTS
Descriptions of territories
We collected territorial data of
25 breeding pairs of Eurasian Magpies and observations showed that the magpie
territory is almost circular in shape, with the nest being located close to the
center. The breeding territory size of magpies varies from a minimum of 0.0094
km2 to a maximum of 0.1049 km2 (mean: 0.0415 ± 0.0248 km2,
n = 25) for all territories in the two sites. Magpie territories overlapped
heavily, seen at both study sites, and magpies actively defended only the close
proximity of the nesting tree (~ <20 m radius). Juveniles and non-breeding
individuals (floaters) were occasionally spotted foraging in groups inside
breeding territories of nesting pairs. Tree cover composed the highest amount
of territory cover (mean proportion of territory for all individuals: 24.36 ±
15.41 %), followed by agricultural land (22.32 ± 15.51 %), and built-up areas
(14.12 ± 9.73 %). All magpie territories in both sites feature human presence
(mean proportion of territory for all individuals: 36.4 ± 19.13 %), either in
the form of agricultural land or built-up areas, or both. Magpie territories in
Bursaika were smaller (mean: 0.0212 ± 0.0084 km2)
and showed greater overlapping, with seven of the 10 individuals sharing more
than 75 % of their territories (mean territory shared: 73.3 ± 30.5 %). The
distance between nests at this site was also smaller, with an average distance
of 81 m to the nearest nest. On the other hand, territories at Gramthang were larger (0.055 ± 0.0219 km2) and
with relatively lower territory sharing (55.6 ± 28.5 %). The average distance
to the nearest nest was also larger at this site (134 m). The majority of the
nests were located on Populus (9.22
± 1.64 m; n = 9) and willow trees (6.62 ± 0.74 m; n = 8), followed by apricot
(6.75 ± 0.95 m; n = 4), mulberry (8.5 ± 0.7 m; n = 2), and sea-buckthorn shrub
(3.00 m; n = 1). Only one of the 25 nests was found on an artificial structure,
an electric tower (in Gramthang). Nearly all nests
(except a single nest on sea-buckthorn shrub), were constructed at a height
>5 m.
Effect of habitat variables on
territory size
We found that both increased
built-up area and tree cover proportions within the territory had a
significantly strong negative effect on the territory size of magpies, meaning
that magpie territories are smaller near urban areas and greater tree cover
(Figure 1). This is likely due to the high availability of resources near trees
and urban areas, removing the need to defend large territories. Agriculture
area had no significant effect, indicating limited feeding opportunities in
agricultural fields during the study period. The presence of neighbors is also
found to not have any significant effect, which is in-line with previous
studies which have shown magpies to share feeding grounds. Table 1 summarizes
the GLMM results describing the individual contributions of habitat variables
in predicting territory size.
DISCUSSION
The current study describes the
territorial behavior of Eurasian Magpies, and how territory size varies with
habitat variables in the sparse urban settlements of the Himalayas.
Characteristics of magpie territories, including choice of nesting sites, territory
size, and territory sharing behavior, are largely similar to those observed in
previous studies from other parts of the world. Previous studies have found
magpie territory sizes to be 5 ha on average (Moller 1982; Birkhead
1991), but the mean can range anywhere from 1 ha–7.5 ha (Reese & Kadlec
1985; Dhindsa & Boag
1991). The mean territory size in our sites also lies within the expected
range, with a mean of 4.15 ha. Although, only part of the territory close to
the nest (~ within a 20 m radius of the nest) is actively defended by the
breeding pair, other individuals entering this space aggressively pushed away.
Magpie territories appear to be less rigidly defined, as both breeders and
non-breeders can be found in the same spaces on subsequent visits. During
breeding seasons, magpies were frequently seen chasing each other and calling
from prominent perches with aggressive wing-fluttering. Although magpies are
primarily territorial during breeding seasons, they are known to flock for
‘ceremonial gatherings’ (Baeyens 1979), roosting
(Moller 1985), and feeding (Vogrin 1998). Magpies in
our sites shared territories primary for feeding, gathering to feed at a few
selected points where food waste was dumped. Magpies are likely to feed
together, even during the breeding season, most probably owing to the limited
food resources in this landscape, largely restricted to these small urban
settlements. This claim is further strengthened by the fact that magpies formed
smaller territories and stayed closer to neighbors at the site, i.e., Wakha, pointing to the need for magpies to stay close to
human habitation, even at the cost of sharing feeding spaces. Magpies have
previously been observed to form feeding flocks when the resources are
localized and clumped (Eden 1987).
Although magpies are widely known
to be able to nest on artificial structures (Birkhead
1991; Takeishi 1994), they prefer to nest on trees, and only choose artificial
nesting sites in case the tree density is low (Nakahara 2015). Additionally, in
human habitations magpies construct their nests at greater heights (usually
over 5 m), primarily to avoid human disturbance and predation (Antonov 2002, 2003; Salek 2020).
Both Populus and willow trees, which were
majorly used for nesting in the region, are tall trees providing suitable
nesting sites for magpies (growing up to ~30 m) and have previously been shown
to be preferred tree species for nesting of magpies (Antonov
2002). Moreover, large artificial structures are absent in the sparse urban
settlements of this region, limiting opportunities for nesting on artificial
structures. Therefore, all (except one) nests were constructed on trees. The
sole nest constructed on an electric tower was away from housing, with no trees
in close proximity.
Trees are not only an absolute
necessity for nesting in these sites, but they may also be provisioning
important food resources, like insects, butterfly/moth larvae at these sites.
The other primary food source in magpie territories was human-dumped waste
sites, as explained earlier. Urban adapter species are known to form smaller
territories near human habitation due to high availability of resources in
close proximity, such as waste dump (Juarez et al. 2020). Hence, in line with
our predictions, we found the presence of both tree cover and built-up area to
have a significant negative effect on territory size (Table 1). Additionally,
due to the localization of resources to these small sites, magpies are willing
to share feeding sites even during the breeding season. Therefore, in these
sites the presence of neighboring magpies does not significantly affect
territory size, indicating that the major driver of territory size in these
isolated urban settlements is resource availability, rather than interspecific
interactions. Tatner (1982) previously found no
association between magpie density and breeding success in urban areas, as long
as the territory is resourceful. Magpies have previously been shown to prefer
urban areas with suitable nesting sites and trees from different parts of the
world (Wang et al. 2008; Salek et al. 2020), and we
add to the existing knowledge from the isolated urban settlements of the
Himalaya, for the first time.
Table 1. Summary of GLMM results
with values of coefficients, standard errors (SE) and p-value for the selected
variables.
|
Variables |
Coefficient |
SE |
P value |
|
Intercept estimate |
11.15 |
0.33 |
<0.001 |
|
Tree cover |
- 1.44 |
0.41 |
<0.001 |
|
Built-up |
- 1.87 |
0.62 |
0.002 |
|
Agriculture |
- 0.41 |
0.36 |
0.26 |
|
Neighbor |
-0.05 |
0.19 |
0.79 |
For
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