A review of “Discovery
of possible hybrid of the Critically Endangered Forest Owlet Athene
blewitti and Spotted Owlet Athene
brama from northern Maharashtra”
Girish Jathar 1& Dharmaraj Patil 2
1Foundation for
Ecological Conservation and Sustainable Development, 848/1, Vrindavan Park,
Kalamba Road, Kolhapur, Maharashtra 416007, India
210, Suryanagari
Apt, Opposite Dinosaur Garden, Pimple Gurav, Pune, Maharashtra, India
Email:1 girishjathar@gmail.com (corresponding author), 2 dharmarajraptor@gmail.com
Date
of publication (online): 26 May 2011
Date
of publication (print): 26 May 2011
ISSN
0974-7907 (online) | 0974-7893 (print)
Manuscript details:
Ms # o2801
Received 11 May 2011
Citation: Jathar, G. & D. Patil (2011). A review of “Discovery
of possible hybrid of the Critically Endangered Forest Owlet Athene blewitti and Spotted Owlet Athene brama from northern Maharashtra”. Journal
of Threatened Taxa3(5): 1800–1803.
Copyright: © Girish Jathar & Dharmaraj Patil 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.
Pande et al. (2011) have reported possible
hybrid of the Forest Owlet Heteroglaux blewitti and Spotted Owlet Athene brama. This has begun an intriguing debate on hybridization among
owls. Their claim is based on
field observations; photographic and videotaped evidences however, the
interpretation offered by the authors would seem unlikely. We found several
anomalies in this paper pertaining to identification of the species,
vocalization, behaviour and logic presented for hybridization. There are many points in the
communication that need a well-supported reference.
The first paragraph of the paper describes about
lowest hybridization rate among owls (Mikkola 2003) however authors make a
contradictory statement in the second last paragraph of the paper giving a
reference of del Hoyo et al. (1999) addressing it as a well-known phenomenon.
However, del Hoyo et al. (1999) state (page no 83, Vol.5, HBW) about the
hybridization of Barred Owl and Spotted Owls in Oregon and Washington states of
USA and does not mention anywhere in the text that ‘hybridization is well known
phenomenon’. This indicates
inadequate and false referencing by the authors to prove their point. Moreover, these contradictory
statements create confusion while understanding the justification of the paper.
Literature review
The literature review of the Forest Owlet in
second paragraph is incomplete and mentions about only three studies on the
subject. However, since 1998, 12
papers and several articles, and a book have been published on the ecology,
status and distribution, taxonomy, diet, breeding, behaviour and conservation
of the species. This clearly indicates incomplete literature survey, ignorance,
and lack of scientific temperament amongst authors while addressing a very
serious subject.
In the same paragraph, the authors quote
reference of first author Pande et al. (2003) about presence of Forest Owlet in
Madhya Pradesh and Maharashtra. However, presence of the
species in Madhya Pradesh is reported only by Rasmussen and Collar (1998) and
Rithe (2003). Pande et al.
(2003), page no. 170 mentions a brief note on its absence in Western Ghats and
do not describe anything about the presence of Forest Owlet elsewhere. This indicates sceptical referencing,
by the authors, of their own publication.
In the last paragraph of the introduction the
authors clearly mentions that they could not collect any tissue samples for
molecular studies. In addition,
the owlets were neither colour banded nor monitored
throughout the breeding season. Hence, it is difficult to prove hybridization just with the photographs
of owlets. It is also not clear
whether the individuals photographed were the same or taken elsewhere. The authors should have taken photographs
in a series to confirm the individual identity during the study period.
Study Area and Methodology
There is a serious question about the study area
and methodology used by the authors. In this part of the paper, the authors have not mentioned about the time
spent observing the owlets, name of the village or area, GPS locations and the
area covered. The authors also
mentioned about the territory mapping and transects established for the
study. However, it is not clear
how many transects were laid and how much time was spent on each transect to
monitor the species. This crucial information is instrumental in scientific
rigour and authenticity of data collection.
Results and discussion
In section Results and discussion Pande et al.
(2011) refers to colour morphs and behaviour idiosyncrasies amongthe Forest Owlet and Spotted Owlet. However, the literature published on Spotted Owlet (Ali & Ripley
1969; Kumar 1985; Rasmussen & Anderton 2005) does not mention about any
colour morphs. The Forest Owlet
shows colour dichromatism (Ishtiaq & Rahmani 2004; Jathar & Rahmani
2004) however, this shouldn’t been mistaken as colour morph. The fledglings, Forest Owlets show
variation in colour and can be mistaken as Spotted Owlets.
The major difference attributed between these
two species is their behaviour which is not considered
by authors. The Spotted Owlet is a
nocturnal (Ali & Ripley 1969; Kumar 1985) whereas the Forest Owlet is
diurnal and crepuscular species (Rasmussen & Ishtiaq 1999; Ishtiaq et al.
2002; Ishtiaq & Rahmani 2004; Mehta et al. 2009; Jathar & Rahmani
2004). Hence, the fledglings of
Forest Owlets were observed perched on trees and giving begging calls
throughout the day (Ishtiaq & Rahmani 2004; Jathar & Rahmani
2004). Whereas, the Spotted Owlet
fledglings hide in trees or in nest cavities during daytime and start calling
and moving in twilight hours (Kumar 1985).
Morphology and identification
The first paragraph of the results and
discussion mentions that “The family defended the territory consisted of two
adults and one recently fledged owlet (as shown in Fig.1 c & d)”. The bird
in the picture ‘c’ – is adult Forest Owlet, showing dark head, neck and
collar, dark primaries, longer primaries and tail, dark grey yellow bill,
blotched upper breast, continuous solid brown band across the breast, white
flanks, and solid brown over all body colour. Whereas the bird in picture ‘d’ – is a fledgling of
about 45–50 days based on light brown head, neck and collar, light brown
continuous breast band, shorter primaries and tail, pale grey yellow bill,
streaks on belly and upper breast and over all pale brown colour. The posture of owlets
in the pictures also indicate the stout and upright adult ‘c’ and a
clumsy juvenile ‘d’. These
self-explanatory pictures depicts that the bird ‘c’ is an adult female Forest
Owlet (later observed mating with male Forest Owlet) and not the fertile hybrid
as described by Pande et al. (2011).
The authors describe the Spotted Owlet as a
subspecies Athene brama indica. However, Ali & Ripley (1969) states distribution of the Spotted
Owlet as “south of 200N latitude, the boundary arbitrarily fixed for
convenience between the northern and southern populations which intergrade
around this parallel”. Therefore,
identifying the Spotted Owlet up to subspecies level is a difficult unless; the
birds are captured and measured for morphometric data. Therefore, identification of Spotted
Owlet as A. b. indica is doubtful.
Copulation
Pande et al. (2011) further mention about the
copulations in subsequent days. It
is difficult to prove that the owlets engaged in copulation were the same
birds, especially when the birds were not colour marked. Secondly, if the pair is already having a fledgling, then why would the female
engage in copulation? It is unlikely that a pair rearing a fledgling would
copulate. The breeding season of
the Forest Owlet is from October to June (Ishtiaq et al. 2002; Ishtiaq &
Rahmani 2004; Jathar & Rahmani 2004). The maximum copulations, i.e. 44% were observed in November and a few 5%
were in February (Jathar & Rahmani 2004) late copulations were the results
of failure in breeding attempt. Pande et al. (2011) state that the breeding was successful with one
fledgling. In this scenario, the pair should not copulate and rear a new brood. If this is extra pair copulation then
the other male should chase off the earlier male and kill the existing
fledgling to induce female for mating. Studies by Ishtiaq & Rahmani (2000) and Jathar and Rahmani (2004)
have comparable observations from their studies, in which the males have killed
the fledglings or destroyed the eggs prior to induce copulation and
renesting. Interestingly, del Hoyo
et al. 1999 mentions that “extra pair copulations are rare among owls (page no.
120, Vol. 5) only recorded in Burrowing Owls, Flammulated Owl, Northern
Long-eared Owls and Eastern Screech Owls which are colonial in habit”. Whereas the Spotted Owlet and Forest
Owlets are not colonial breeders, hence this claim cannot be acceptable without
comparable studies of non-colonial owls.
Vocalization
It is not clear from the description that, which
type of calls were listened and compared for analysis. The Spotted Owlet
produces two types of basic calls (Ali & Ripley 1969) and other variants of
syllables resulting in four types of calls (Kumar 1985; Rasmussen &
Anderton 2005) whereas; the Forest Owlet emits six types of calls (Rasmussen
& Ishtiaq 1999; Jathar & Rahmani 2004). The published literature shows that call duration in both
the species range between 0.07 sec to 3.37s (Rasmussen
& Ishtiaq 1999; Ishtiaq & Rahmani 2004; Rasmussen & Anderton 2005;
Jathar & Rahmani 2004). Pande
et al. (2011) mention that the call duration range is 3s for Forest Owlet, 9s
for Spotted Owlet and 6s for hybrid. However, Table 1. describes acoustics studies
of both the species in comparison with Pande et al. (2011).
Secondly, the authors are not aware about terms
used for vocalization such as a ‘bout’ and a ‘call’. In both the species, the
bouts can vary from a single call of milliseconds to series of calls of 15–30
minutes. Moreover, the authors
have not used any bioacoustics programme to prove the validity of the calls on
spectrograph. Therefore, the
observations on vocalization do not stand sound scientifically.
Table. 1. Comparison of the
acoustics studies of the Forest Owlet and Spotted Owlet
Species |
Call duration Pande et al. (2011) |
Call duration Rasmussen &
Ishtiaq (1999), Ishtiaq & Rahmani (2004), Jathar & Rahmani (2004) |
Forest Owlet Heteroglaux blewitti |
3s (± 0.8, N = 73) |
Song - 0.15 - 0.45sec Territorial call - 0.07sec Alarm call - 0.45sec Threat call - 0.17sec Contact call - 1.52sec Hissing call - 3.37sec |
Spotted Owlet Athene brama |
9s (± 1.3, N = 11) |
Rasmussen & Anderton (2005) Song - 0.2sec Contact 0.1secc Uncommon Call -0.4sec Other call -0.2-0.4sec |
Hybrid |
6s (± 0.9, N = 34) |
Authentic data on hybrid not
available as its existence is not proved on sound scientific basis |
Hybridization Logic
Logic i & ii – Limited geographically
to the satpuda range, Altitudinaly to higher, forested parts – The Forest Owlet
is known to be found from Orissa to north western Maharashtra in Satpuda-Maikal
Mountain range which is spread across 1,18,867km2. Along with this
they are restricted to 300m to 750m altitude (Ishtiaq
& Rahmani 2004; Jathar & Rahmani 2004; Mehta et al. 2009). These factors do not result in
geographical isolation of the individual Forest Owlets whichmight lead premating or postmating isolation and subsequent hybridization with
Spotted Owlet. There is ample of
niche, spatiotemporally, for the Forest Owlet (about 11,000km2;
Jathar et al. in prep.) therefore it cannot force the Forest Owlet to cross the
species limit.
Logic iii - limited to habitats in the proximity of
humans and resulting clearings that facilitate foraging (Yosef et al. submitted) – This logic is
based on a single observation in Melghat Tiger Reserve and it is not a
widespread phenomenon all over the range of the Forest Owlet. Earlier studies (Ishtiaq et al. 2000;
Ishtiaq & Rahmani 2004; Jathar & Rahamni 2004; Mehta et al. 2009;
Jathar et al. in prep.) suggests that anthropogenic
activities are detrimental to the habitat and Forest Owlets shift their sites
in case of disturbances. This
logic cannot be instrumental in hybridization.
Logic iv & v -
limited demographically to low population levels wherein neighbouring
territories are located far apart, leads us to assume hybridization with the
far more common Spotted Owlet – This statement requires a study
of population density in given area, which is not been carried out in the
current study. The authors also
claim that they have mapped the territories of Forest Owlet and Spotted Owlet
but did not mention about how far they were spaced. In February 2004, Bombay Natural History Society carried out
survey in the same area at same time and could locate five pairs of the Forest
Owlet and one pair of Spotted Owlet in a stretch of 3km of Malur Village
(Jathar & Rahmani 2004). This study contradicts
Pande et al. (2010) and confirms abundance of the Forest Owlet in the area. Further Jathar
& Rahamni (2004) confirm presence of 69 individual Forest Owlets and Mehta
et al. (2009) report seven individuals in entire Chaurakund Range of the
Melghat Tiger Reserve. Therefore,
chances for hybridizations stands remote as there are
potential mates available in landscape.
Conservation
In the end Pande et al.
(2011) talk about the biological implications and conservation of hybrid (if
they exists) owlets without considering its impact on current conservation
efforts. This might take entire conservation efforts in wrong direction as it
happened with Edible-nest Swiftlet Collocalia fuciphaga (Sankaran & Sheshnarayan 2008). This will be a major impediment to the
conservation of the Critically Endangered Forest Owlet.
Unfortunately, the lack of - identification
skills, coherence, scientific temperament, and rigour has lead authors to this
publication. Moreover, our
justifications of bird not being hybrid stand scientifically sound over ‘Possible
Hybrid’ claim of the authors.
References
Ali, S. & S.D.
Ripley (1969). Handbook of the Birds of India and Pakistan together with those of
Nepal, Sikkim, Bhutan and Ceylon, Compact Edition. Oxford University Press,
737pp.
del Hoyo, J., A. Elliott
& J. Sargatal ( 1999). Handbok of the Birds
of The World—Vol. 5. Barn-Owls to Hummingbirds, Lynx
Edicions, Barcelona.
Ishtiaq, F. and A.R.
Rahmani (2000). Cronism in the Forest Owlet Athene blewitti. Forktail 16: 172–173.
Ishtiaq, F. & A.R. Rahmani (2004): The Forest Owlet Heteroglaux
blewitti: vocalization, breeding biology and conservation. Ibis 147(1): 197–205.
Ishtiaq, F., P.C.
Rasmuseen & A.R. Rahmani (2002). Ecology
and behavior of the Forest Owlet, pp. 80–88. In: Newton, I., R.
Kavanagh, J. Osleon & I. Taylor (eds.). Ecology and Conservation of Owls. CSIRO
publishing, Australia.
Jathar, G.A. &
A.R. Rahmani (2004). Ecological studies of the Forest Spotted Owlet Athene (Heteroglaux) blewitti.Final Report. Bombay Natural History Society, Mumbai, India,
77pp.
Kumar, S. (1985). The life
history of the Spotted Owlet (Athene brama brama, Temminck) in the Andhra Pradesh. Raptor
Research Centre Monogr. Publ. No. 4 , Hyderabad,
India.
Mikkola, H. (2003). Strangers in the dark: hybridization between owl species, pp.
82-87. In: Duncan, J.R. (ed.). Owls of the World. Key Porter books, Ltd.,
Toronto, Canada, 319pp.
Mehta, P., J. Kulkarni & D. Patil (2009). A survey
of the Critically Endangered Forest Owlet Heteroglaux blewitti in Central India. Birding Asia 10: 77–87.
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.
Pande, S., S. Tambe,
C.M. Francis & N. Sant (2003). Birds of Western Ghats, Konkan and Malabar (including birds of
Goa). Oxford University Press, Pune, India, 375pp.
Rasmussen, P.C. &
N.J. Collar (1998). Identification, distribution and status of
Forest Owlet Athene(Hetroglaux)blewitti. Forktail 14: 41–49.
Rasmussen, P.C. & F. Ishtiaq (1999). Vocalization
and behaviour of the Forest Owlet Athene(Heteroglaux)blewitti. Forktail 15: 61–65.
Rasmussen, P.C. & J.C. Anderton (2005). Birds of South Asia. The Ripley Guide. Vols. 1 and 2. Smithsonian Institution
and Lynx Edicions, Washington, D. C. and Barcelona.
Rithe, K. (2003). Saving the Forest Owlet. Sanctuary Asia February: 30–33.
Sankaran, R. &
M.S. Seshnarayan (2008). Conservation of the Edible-nest Swiftlet Collocalia fuciphagain the
Andaman and Nicobar Islands. Sálim Ali Centre for Ornithology & Natural
History, 31pp.
Yosef, R., S.A. Pande & R. Kasambe (submitted). Anthropogenic activity aids
habitat selection and survival of the Critically Endangered Forest Owlet (Athene blewitti). Journal of Threatened Taxa.