Discovery of
a possible hybrid of the Critically Endangered Forest Owlet Athene
blewitti and Spotted Owlet Athene
brama (Aves: Strigiformes) from northern Maharashtra, India
Satish A. Pande 1,
Amit P. Pawashe 1, Raju Kasambe 2 & Reuven Yosef2,3
1 Ela
Foundation, C-9 Bhosale Park, Sahakar Nagar-2, Pune, Maharashtra 411009, India
2 Sevadal Mahila Mahavidyalaya,
Sakkardara chowk, Umrer Road, Nagpur, Maharashtra 440009, India
3 International
Birding & Research Centre in Eilat, P.O. Box 774, Eilat 88000, Israel
Email: 3 ryosef@eilatcity.co.il
(corresponding author)
Date
of publication (online): 26 April 2011
Date
of publication (print): 26 April 2011
ISSN
0974-7907 (online) | 0974-7893 (print)
Editor: Boris P. Nikolov
Manuscript
details:
Ms # o2553
Received 28
August 2010
Final received
06 December 2010
Finally
accepted 16 January 2011
Citation: Pande, S.A.,
A.P. Pawashe, R. Kasambe & R. Yosef (2011). Discovery of a possible hybrid of the Critically Endangered Forest
Owlet Athene blewitti and Spotted Owlet Athene brama (Aves:
Strigiformes) from northern Maharashtra, India. Journal of Threatened Taxa 3(4): 1727–1730.
Copyright: © Satish A. Pande, Amit P. Pawashe, Raju Kasambe & Reuven Yosef 2011. 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:We thank Nathaniel J. Moses,
Satish Ranade, Kedar Pawagi, and Tzadok Tzemach for their help in the field;
and the officials and staff of the Indian Forest Department in Nagpur, Pune,
and MTR for their support. Special
mention is due to Mr R. Choudhary, CCF, MTR, Amravati, and Mr Prakash Thosare,
CCF Pune, for their help in making our stay in the remote forest areas
possible. Optics donated by
Swarovski Optics facilitated our fieldwork. We greatly thank our anonymous donor who underwrote the
expenses of the expedition.
For figures, images, videos -- click here
Owls (Strigiformes) are considered to
have the lowest hybridization rate among birds (Mikkola 2003). It is believed that inherent
isolation mechanisms in the owls are relatively effective in explaining the low
frequency of hybridization between sympatric owl species (Mikkola 1983, 2003).
The Forest Owlet Athene blewitti was recently rediscovered after 113
years in western and central India (King & Rasmussen 1998), specifically in
the states of Madhya Pradesh and Maharashtra (Rasmussen & Collar 1998;
Pande et al. 2003; Rithe 2003). Little is known about this endemic species, which has a very limited
distribution in central India, and to date limited studies have been undertaken
on their ecology and behavior (e.g., Rasmussen & Ishtiaq 1999; Ishtiaq et
al. 2002).
The species is considered to be
Critically Endangered and at an extremely high risk of extinction (Collar et al. 1994; del Hoyo et al. 1999). The species is listed under Schedule I
of the Indian Wildlife (Protection) Act and hence we are unable to collect any
kind of samples (feces, pellets, discarded feathers, etc.) or to capture and
sample any of the birds for molecular studies. Hence, our study is based on visual observations (which include
photographic and video 1 & 2) of the individuals reported here.
Study Area and Methods
To further enhance our understanding of
the species’ habitat requirements, the Ela Foundation (ELA) and the
International Birding and Research Centre in Eilat (IBRCE) arranged an
expedition to the Melghat Tiger Reserve (MTR) in early February 2004. In the framework of this project, we
undertook transects in MTR and mapped all known and newly discovered
territories of Forest and Spotted Owlets.
Because of the fact that the species is
Critically Endangered, our activities were constantly monitored by a forest
ranger who also prevented us from collecting any
feather, feces or pellet samples of the owls.
Results and Discussion
During our study we became well
acquainted with the different color morphs and behavioral idiosyncrasies of the
two sympatric species. This
enabled us to discern that a particular territory bordering on Forest and
Spotted Owlet (A.
b. indica)
territories had owls with intermediate plumages, vocalizations, and
behaviors. The family that
defended the territory consisted of two adults and one recently fledged
owlet. Since all our studies were
photographed and videotaped, we were able to compare the two Athene species with this family, and we concluded
that it was a fertile hybrid of the two species. The larger of the two adults was assumed to be the female
and was verified in subsequent days when copulation was observed. All data were obtained from still and
video photographic evidence collated by the authors, and arebased on visual observations in the field (Fig. 1).
The Spotted Owlet (Fig. 1a) has a
heavily spotted crown, a darkish facial disc bordered by white around its
sides; and curved white eyebrows (del Hoyo et al. 1999; this study). Its ear coverts are white. The dorsal side is gray-brown with
scattered white spots. Its tail is
short and has a conspicuous white-tip; the white tail bars are narrow. The breast is creamy white with short
gray to brownish bars, and has a broad white gorget. Tail wagging is vertical (up and down) only. The duration of its call is 9s (± 1.3,
N = 11) and it vocalizes all night (Fig. 2).
In contrast, the Forest Owlet (Fig. 1b)
has a mostly white facial disc with fine light brown to dark-brown barring (del
Hoyo et al. 1999; this study). Its
white facial disc is almost invisible in the field and its face appears
brown. The head is very sparsely
spotted and in many individuals it appears unspotted, as are the mantle and the
back. Interestingly, it has an
obsolete hind-collar, thin white eyebrows, and its flight feathers and
rectrices have broad white bars. The tail is short and has a broad, white terminal bar that is visible
below the wings when the owl is perched. The Forest Owlet’s ventral region is mostly white with a dark chocolate brown bar across the neck and a broad lateral
band on the top third of its chest. The lateral lower breast and upper flanks
are broadly barred and the central ventral region is white, in the shape of an
inverted “U”. To date, juvenile
owlets have not been fully characterized. The juvenile owlet that we observed had a buff-colored central breast;
in adults the lower abdomen is white. Tail wagging is lateral(sideways) only. The duration of
its call is ca. 3s (± 0.8, N = 73; Fig. 2) and it vocalizes only during the
day. When it vocalizes, its head is extended and the thin white gular band is
visible.
In addition, we also discovered
individuals which displayed a combination of the markings of the two species
and whose vocalizations were intermediate. This has led us to believe that these are most probably
hybrids of the Forest and Spotted owlets that coexist in the forests.
As expected, the hybrid individuals
displayed characteristics that were intermediate to the two species described
above (Fig. 1c). Two of the three
birds had a few faint white spots on the head, a thin white-eye ring and
eyebrows, but no white on the ear coverts. A thin white throat band was visible when it was resting and
also when the bird stretched its neck or was engaged in vocalizing. The upper part of the chest
was dark brown but fainter than in the Forest Owlet and the lower two-thirds of
the chest had streaks shaped like inverted arrowheads on a white
background. Notably, barring on
the flanks was absent. The portion
of the tail that protruded beyond the wings had a sub-terminal dark band and a
white terminal band. Appreciable
spotting on the wings was noted when the owl was viewed from the side or behind
(Fig. 1d). Its dorsal color was
brown and paler than that of the Forest Owlet, and was characterized by a
grayish tinge and significant white spotting. The primaries were black. Surprisingly, the characteristic
that alerted us to the possibility of these being hybrids was the tail wagging,
which was lateral and horizontal. The duration of its call was ca. 6s (± 0.9, N = 34) and it vocalized
during the day (0500-1100 hr) and from after noon until early night (1600-1900
hr). These findings are similar to
that reported for hybrids between the Barred (Strix occidentalis) and Spotted Owls (S. varia) that give calls that are intermediate between the typical
calls of the two species (del Hoyo et al. 1999).
The differences described above also
puzzled the local indigenous guide, from the Korku Adivasi tribe, who has been well-acquainted with the owls of the region for several
decades, thus suggesting that this was a unique or infrequent situation. Also, RK showed a photograph of a
similar individual in 2002, photographed in the same area, but unfortunately he
was unable to identify it conclusively. This suggests that the hybrids may have a much wider distribution that
could equal or surpass the very limited one of the Forest Owlet.
Hybridization is comparatively well
known in owls (del Hoyo et al. 1999). We assume that several demographic factors have influenced the
populations involved and allowed them to cross the species-limit barrier and
for hybridization to occur. The
logic that the Forest Owlet is (i) limited geographically to the Satpura Range,
(ii) attitudinally to the higher, forested parts, (iii) limited to habitats in
the proximity of humans and resulting clearings that facilitate foraging (Yosef
et al. submitted), and (iv) limited demographically to low population levels
wherein (v) neighbouring territories are located far apart, leads us to assume
hybridization with the far more common Spotted Owlet. It is possible that dispersing individuals that do not find
conspecifics set up territories and mate with the abundant Spotted Owlets.
Our observations strongly suggest that
the hybrids are fertile; the female was subsequently observed (and filmed)
while engaged in extra-pair copulation (EPC) with the neighboring male Forest
Owlet. The biological implications
of our discovery regarding conservation and our detailed description of the
hybrids of the Critically Endangered Forest Owlet, thus confirming their
existence, is of great interest in light of the fact that hybridization is rare
in owls, but its consequences can be far-reaching and grave (Haig et al.
2004). Many a wild species have
been known to loose their identity and legal protection, owing to genetic
contamination, making their continued conservation a philosophically
problematic question that could result in chaos (Sutherland 2000).
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