Vulture post from my old website (2000?) at http://www.geocities.ws/laksingh33/new.html

 

 

Years back, about 25 years past (from 2000), I took a photograph of vultures attending a cattle on the roadside while returning to home in Puri. Somehow, it had aroused my curiosity perhaps a stimulation coming from the new Minolta Camera I was handling then. At that time I was not aware that such a sight shall ever be rare in future because vultures were neither very much liked nor in any manner in demand by the people.

Thus, it used to be a common sight then to find vultures attending carcasses. That used to be nature's own way of keeping the area clean and also perhaps to compensate the 'inappropriate systems of carcass-disposal' by humans.

The last such congregations of vultures I ever saw was in the banks of river Chambal during 1983-1985. Everytime, on our return trips to Rajghat from a day-long search for radio-fitted gharial, we used to see the vultures bathing, cleaning their wings and drying these spread open in the afternoon sun. Of course, they had some specified spots where they congregated.

After coming to Similipal in 1987, sighting a congregation of over 30 vultures have never been possible. As such, Similipal Tiger Reserve doesn't have any vultures. That has made it difficult to impossible to locate any animal-kill made by the carnivores. We have been linking the situation to the thick ground vegetation through which the vultures find it impossible to locate carcass and thus have remained off the 2750 sq.km area of the sanctuary.

Surveys outside the sanctuary, in the transitional zone of the Similipal Biosphere Reserve and outside it have indicated that vulture populations are on the decline.
Three species of vultures have been on record from the periphery of Similipal. These are the Black or King Vulture (Sarcogyps calvus), Indian White backed Vulture. (Gyps bengalensis) and Indian Long-billed Vulture (Gyps i. indicus). All three have become rare. This has been our own experience, and recently confirmed by a survey conducted by the Bombay Natural History Society.

DISCUSSION

Vultures are on the decline : it is a well realised fact. When I am asked about the reason for their decline, I can see the niche having been taken over by human scavengers. Man is a competitor with wildlife everywhere for everything, even for carcass. Man has learnt to use the skin and bones of dead cattle and even dogs. That is one reason why the city-outskirts or even the streets are easily swept clean of carcasses. With human habitations growing all around, leaving little space for vultures to survey and come down to ground, scavenging humans are perhaps doing the right service. When ecosystems are turning into "human systems", vultures have no other option but to give way to human system to 'prosper'. 

Postscript (28 October 2021)

(1) I understand new vulture species have been added to Similipal (Mayurbhanj). Prominent is, the Cinereous Vulture, may be an accidental migrant.

(2) Today, attended as Chairperson a webinar session of Rewa Science  College. The topic was on Vulture conservation in India, by Dr Anil Chhangani from Bikaner, Rajasthan. It was a very good talk, educative and eye-opening. Very few opinion may have gone for reasons for vulture decline, beyond diclofenac and nimesulide. But Dr Chhagani gave photo evidences of vulture deaths due to road accident, rail accident, cutting down of nesting trees (this was known), loss of water availability, and mining(!) etc. 

(3) Medicines will not be a problem, if sufficient water is available, he said. Yes, right. In Chambal we made notes on vultures from 1983-2016 along with other large birds. Six species of vultures have been recorded. Egyptian Vulture the most abundant. The trend may get published next month in Journal of Threatened Taxa.

(4) Dr Sudhakar Kar mentioned about 1000s of vultures coming to Bhitarkanika in 1970s, and now none. I feel, the change in water characteristics (salinity), removal of carcasses (food of vulture) for man-run industries, growth of human population and village amenities and cleanliness, are some of the reasons. 

It will be an interesting research topic to trace the history, fate and future of vulture in and around Bhitarkanika.  

 

GHARIAL: MAIDEN CLUTCH AND NEST SITE STRATEGY

Background to this blog. On May 19, 2021 28 gharial hatchlings were observed with a female in Satkoshia Gorge of river Mahanadi, Odisha state. The river stretch is in Satkoshia Gorge Sanctuary (1976) that was constituted under and a part of the national crocodile conservation project of Government of India launched with support from UNDP/FAO. 

While I congratulated the officers who have ensured to regulate habitat disturbances by people, I also mentioned that 28 hatchlings mean it is not the maiden clutch, and that the reproductive effort of the female in previous year(s) had remained unnoticed. 

This prompted me to look back on my data and interpretations on two subjects: 

(A) What is the minimum clutch size?  (1.) In my PhD dissertation (Singh 1978, Table-11) I provided data on 27 nests from rivers Narayani and Kali, Nepal relating to the years 1976 and 1977. Out of these, six nests had less than twenty-five eggs. As a practice in hatchery incubation, nest-wise we examine all unhatched eggs. There were three completely infertile nests with 10, 16 and 24 eggs. Out of the remaining three nests with 12, 18 and 16 eggs, the hatching success were 75, 16.7 and 50%.

(2.) Sunil L. Rajbhandari and Paras M. Acharya (2015, Report to Rufford) have reported the smallest clutch with just 6 eggs in 2014 and 18 in 2013, both at different places in Narayani river.

(3.) Tirrtha M. Maskey (PhD thesis, 1989), studying in Nepal, reported the smallest egg clutch of 16 in 1977, 18 in 1978, 14 in 1979, 14 in 1980, 30 in 1981, 31 in 1987. So, some movement or pushing out of the main congregation may be occurring to reduce competition in resource partitioning.

(4.) Khadka et al (2020, Herpetologica) have provide data on 151 Gharial nests over 17 years in sand banks along the Narayani (n = 94 nests) and Rapti (n = 57 nests) Rivers in Chitwan. Based on the range of clutch size given, the year-wise smallest clutch was with 21 eggs (2003), 11 eggs (2004), 23 (2006), 19 eggs (2010), 23 (2011), 7 (2012), 23 (2013), 6 (2014), 12 (2015), 16 (2016), 19 (2017),

(5.) Our team in Chambal observed 17 and 24 eggs as small clutches around a communal nesting site in 1985 (Rao and Singh 1992), but had not traced the season when they might have joined the congregation.

(B) Where does the gharial lay maiden clutch of eggs?   A mother gharial with her maiden clutch is smaller in size and lower in the hierarchical order. Such mothers may not find access to better nesting locations or communal nesting stretches used by mother gharials larger in size.

Such territorial behaviour at nesting site is seen from the time the ‘trial pits’ are dug before actual nest holes and laying of eggs. At a communal nesting site, the dominant mother takes possession of all hatchlings; others remain around, and the dominant male also joins in creche guarding. Perhaps it takes a couple of nesting seasons before a maiden mother is able to join the communal site.

 A two-year study in captivity at Ramatirtha in the outskirts of Similipal Tiger Reserve started in 1989 demonstrated strong territorial resource partitioning with mugger crocodiles when they go for basking day after day, or nesting year after year.

Conclusion  The clutch size can be as small as 6. Small clutches with 75% hatching success can be 12. Such small clutches will in all probability be away from communal nesting sites, for behavioural reasons and for reproductive success by the young females in the hierarchal order among gharials.

KEY WORDS: Gharial, Gavialis gangeticus, minimum clutch size, adaptation by young breeding female, hierarchal pattern