top of page

Our Publications

Variation in monthly sizes of home-ranges of Hooded Vultures Necrosyrtes monachus in western, eastern and southern Africa

Lindy J. Thompson, David R. Barber, Marc J. Bechard, André J. Botha, Kerri Wolter, Walter Neser, Evan R. Buechley, Richard Reading, Rebecca A. Garbett, Pete Hancock, Glyn Maude, Munir Z. Virani, Simon Thomsett, Hansoo Lee, Darcy Ogada, Clive R. Barlow, Keith L. Bildstein 

Hooded vulture

IBIS Volume 162, Issue 4, October 2020, Pages 1324-1338


Tracking studies are often used to inform conservation plans and actions. However, species have frequently only been tracked in one or a few localities, whereas space use can be remarkably flexible, especially in long-lived species with advanced learning abilities. We assessed variability in space use in the Critically Endangered Hooded Vulture Necrosyrtes monachus by pooling movement data from three populations across the species’ sub-Saharan range (in South Africa, Botswana, Ethiopia, Kenya, The Gambia and Mozambique). We estimated minimum convex polygons and kernel density estimators (KDEs) and compared monthly home-range sizes between breeding and non-breeding seasons, age-classes and subspecies, accounting for uneven sampling within groups. Mean (± sd) monthly home-range sizes (95% KDEs) for adult Hooded Vultures from southern (12 453 ± 21 188 km2, n = 82) and eastern Africa (3735 ± 3652 km2, n = 24) were 103 and 31 times larger than those of conspecifics from western Africa (121 ± 98 km2, n = 48). This may relate partly to subspecific differences, and individuals with small home-ranges in western Africa and Ethiopia were trapped in urban environments. Regional variation in space use by Hooded Vultures may be linked to flexibility in feeding behaviour (degree of commensalism) which may arise in response to resource availability and persecution in different areas. Age-class also affected monthly home-range sizes, with immature birds generally having larger monthly home-range size estimates than adults. Our results highlight the flexibility of Hooded Vultures in terms of their home-range sizes and suggest that home-range sizes differ between populations and individuals, depending on the extent of human commensalism. Our results also reaffirm the importance of international co-operation in conservation efforts aimed at protecting this wide-ranging, non-migratory species.

Spatial and temporal movement of the Bearded Vulture using GPS telemetry in the Himalayas of Nepal

Tulsi R. Subedi, Juan M. Pérez-García, Shahrul A.M. Sah, Sandesh Gurung, Hem S. Baral, Laxman P. Poudyal, Hansoo Lee, Simon Thomsett, Munir Z. Virani, José D. Anadón


IBIS Volume 162, Issue 2, Special Issue: Avian Migration and Movement Special Issue, Pages 563-571


This study addresses for the first time the movement patterns of the globally near-threatened Bearded Vulture Gypaetus barbatus in its most important stronghold, the high-altitude mountain ranges of Asia. Tracked individuals (n = 8) in the Annapurna Himalayan range (Nepal) foraged over a vast range of 60 715.9 km2 and our results indicated age-class differences in the use of space. Territorial adults showed very small annual home-ranges (K90 = 150.3 km2), whereas immatures wandered extensively and covered vast ranges of the mountains (K90 = 23 930.8 km2). For adults and immatures, these values are notably larger than the other two studied populations in the world (Pyrenees and South Africa). This suggests that the studied Annapurna population might exhibit lower breeding density than in the Pyrenees or South Africa, possibly due to lower food availability.

Prey Item Selection and Prey Delivery of Indian Spotted Eagle 
during Chick‐Rearing Period in Nepal

Sandesh Gurung, Tulsi Ram Subedi, Munir Virani, Ralph Buij, Simon Thomsett, Hem Sagar Baral, Dheeraj Chaudhary 


Proceeding of The 11th Asian Raptor Research and Conservation Network (ARRCN) in Udayana University, Denpasar, Bali – Indonesia, 10 – 11 October 2019


The Indian Spotted Eagle (Clanga hastata) is a vulnerable species and distributed largely limited within the Indian  sub‐continent. This species is recently separated from Lesser  Spotted  Eagle  (Clanga pomarina) and little information exists on the species’ ecology and prey item selection. Here we present the first ever study on the diet of Indian Spotted Eagle during breeding season in lowlands of Nepal. In 2018, we conducted 720 hrs. observation on active nests (n = 3) during chick‐rearing period (June – August) to record prey items delivery. In each day, observation was conducted from dawn to dusk that allowed us to record all deliveries of the day. We reported a  total of 132 prey deliveries; frogs contributed the highest (70.3%) proportion among the selected prey items, followed by small mammals (14.41%), birds (7.58%), lizards (0.73%), and a small proportion of unidentified (6.93%) prey items. Male Indian Spotted Eagle delivered most of the prey items (94.70%) and female mostly fed the eaglets. The most preferred feeding time to the eaglet was between 16:00 – 17:00 hrs, followed by 08:00 – 09:00 hrs. Average daily delivery rate of prey was 2.21 ± 0.73 (range = 0 – 3). Binomial test showed no significant difference in the deliverance of prey items before and after the noon time among in all active nests. Although this area is rich on several species of prey items their preference of frogs in a diet during breeding season could have two possible reasons. First, in our study area chick‐rearing period of Indian Spotted Eagle occurs in the middle of monsoon season that favors the growth of frogs in the flooded fields making them easier to be hunted. Second, frogs’ meat is softer than other prey items and nestlings of Indian Spotted Eagle might have preferred than others.  

Diet and space use of the Martial Eagle (Polemaetus bellicosus) in the Maasai Mara region of Kenya

Richard Stratton Hatfield

Martial Eagle on Hare (Stratton Hatfield).JPG

Master's Thesis, University of Kentucky, 2018


Eagle Hill, the study site of the late Leslie Brown, was first surveyed over 60 years ago in 1948. The demise of its eagle population was near-complete less than 50 years later, but significantly, the majority of these losses occurred in the space of a few years
in the late 1970s. Unfortunately, human densities and land use changes are poorly known, and thus poor correlation can be made between that and eagle declines. Tolerant local attitudes and land use practices certainly played a significant role in
protecting the eagles while human populations began to grow. But at a certain point it would seem that changed human attitudes and population density quickly tipped the balance against eagles.

Eagle Hill, Kenya: changes over 60 years

Simon Thomsett


Scopus 34: 24–30, January 2015


Eagle Hill, the study site of the late Leslie Brown, was first surveyed over 60 years ago in 1948. The demise of its eagle population was near-complete less than 50 years later, but significantly, the majority of these losses occurred in the space of a few years
in the late 1970s. Unfortunately, human densities and land use changes are poorly known, and thus poor correlation can be made between that and eagle declines. Tolerant local attitudes and land use practices certainly played a significant role in
protecting the eagles while human populations began to grow. But at a certain point it would seem that changed human attitudes and population density quickly tipped the balance against eagles.

Attempted Verreaux’s Eagle predation on Rüppell’s Vulture and breeding observations at Lake Kwenia colony, Kenya

Simon Thomsett, James Aldred

Kwenia 2.jpg

African Journals Online, Vol. 68 No. 1 (2015)


A Verreaux’s Eagle (Aquila verreauxii) was observed to attack in mid-air a fully grown juvenile Rüppell’s Vulture (Gyps rueppellii). This event including observations on the breeding of these vultures at Kwenia are presented. Other notes are given for the nesting of Rüppell’s Vultures at this site.

Two recent records of Cassin’s Hawk Eagle Spizaetus africanus
from Imenti Forest, Kenya

Darcy Ogada, Brian Finch, Shiv Kapila, Peter Wairasho, Benson Mugambi, Simon Thomsett

Copyright Nick Trent Cassin_s Front.JPG

Scopus 35: 44–46, July 2015


Cassin’s Hawk Eagle, Spizaetus  africanus, is a little-known forest-dependent species that occurs mainly in West and Central Africa (Brown et al. 1982). The species was considered a Guineo-Congolian near endemic whose eastern-most distribution was the forests of western Uganda, but some recent reports suggest that it was once more widespread in the highland forests of East Africa (Clark & Edelstam 2001, Jones 2007). The discovery of an adult Cassin’s Hawk Eagle in Ndundulu Forest of the Udzungwa Mountains, southern Tanzania, represents the eastern-most confirmed record of this species (Jones 2007). This, along with other observations in the Udzungwa Mountains of species of flora and fauna with Guineo-Congolian affinities, indicates an historical link between the Afromontane forests of southern Tanzania and the lowland Guineo-Congolian forests  (Jones 2007). The first record of Cassin’s Hawk Eagle in Kenya, a bird collected in the highland forests of Mt Elgon (Clark & Edelstam 2001), suggests a wider link that includes the Afromontane forests of Kenya. 

Mechanisms of co-existence in vultures: Understanding the Patterns of Vulture Abundance at Carcasses in Masai Mara National Reserve, Kenya.

Kendall, C., Virani, M.Z., Kirui, P., Thomsett, S., and M. Githiru.


2012,Condor 114:523-53.


Because of the high, albeit seasonal, availability of carcasses, the Mara-Serengeti ecosystem, Kenya, has a high diversity of scavengers, leading to considerable competition between species. From patterns of occurrence of vultures at 163 carcasses over an 8-year period in the Masai Mara National Reserve, we were able to identify some mechanisms that may reduce competition. Species are associated on the basis of similar dietary needs and beak morphology, and they are highly interdependent, showing little evidence of disassociation. Social vultures (genus Gyps) dominated the vulture scene at the reserve; they were more abundant at carcasses when migratory ungulates were present in the dry season, when more carcasses are likely to be available, than when migratory ungulates were absent. In addition, regardless of the predator's identity, presence of a predator reduced the number of vultures, suggesting that vultures prefer carrion not killed by predators where available. Comparisons between past and current counts of carcasses suggest a substantial shift in Gyps vultures with an increase in the relative abundance of Rüppell's Vulture (G. rueppellii) with respect to that of the White-backed Vulture (G. africanus). In addition, our findings suggest that as changing land use in the Mara-Serengeti ecosystem leads to reductions of large ungulates, social vultures will be the most adversely affected.

Seasonal variation in breeding Rüppell’s Vultures Gyps rueppellii at Kwenia, southern Kenya and implications for conservation.

Virani, M.Z., Monadjem, A., Thomsett, S. and C. Kendall.

Ruppell's Vultures - Gyps rueppelli.jpg

2012; Bird Conservation International


Vulture populations have been declining globally and regionally within Africa. Rüppell’s Vulture Gyps rueppellii is currently listed as ‘Near Threatened’ and numbers of the species, along with African White-backed Vultures G. africanus, have declined by 52% in and around the MaraSerengeti ecosystem. A large breeding colony of Rüppell’s Vulture at Kwenia, southern Kenya, was monitored between 2002 and 2009. Around 150–200 adults were present on each visit, with up to 64 simultaneously active nests. The date of egg-laying differed considerably between years, with two discrete breeding attempts in some years. Nests were not positioned randomly across the cliff face and the number of active nests was related to rainfall in the previous year. The large ungulate migration of the Mara-Serengeti provides a vital foraging ground for the species. Conservation implications of the loss of vultures are discussed.

Major declines in the abundance of vultures and other scavenging raptors in and around the Masai Mara ecosystem, Kenya

Munir Z.Virani, CorinneKendall, PeterNjoroge, SimonThomsett

1 Vulture - Ruppell's Vulture Close-up.jpg

Biological Conservation, Volume 144, Issue 2, February 2011, Pages 746-752

Vulture population declines have been noted in West and Southern Africa, but have not been assessed in East Africa. Roadside transects conducted in 1976 and 1988 were compared with surveys done from 2003–2005 in and around Masai Mara National Reserve, Kenya. Staggering declines in abundance were found for seven of eight scavenging raptors surveyed. No Egyptian vultures were seen during recent transects. We compared trends between the ungulate migration and non-migration season among three land use types (reserve, buffer, and grazed) and among the species surveyed to establish the causes of declines in scavenging raptors. Large declines during the ungulate migratory period suggest that most scavenging raptor species are declining well beyond the area of study. For all species, except Hooded vultures, substantial declines outside of the reserve indicate an important role of land use change in causing observed declines. In addition, significant declines of populations of Gyps species in the reserve itself, especially during the migration season, provide evidence that human activities occurring in other parts of the species’ range such as poisoning of carcasses may be causing their decline. Declines found in this study suggest that at a minimum African white-backed, Rüppell’s, and Hooded vultures should be relisted as Vulnerable. Management actions that limit land use change around the reserve combined with a countrywide ban on carbamate pesticides will be important for conserving keystone members of the scavenging guild. Future research should further examine possible causes of these declines and quantify the effect of reduced scavenging raptor abundance on scavenging efficiency.

Nesting status of African White-backed Vultures Gyps africanus in the Masai Mara National Reserve, Kenya

Munir Virani, Paul Kirui, Ara Monadjem, Simon Thomsett, Mwangi Githiru

White-backed, Ruppell_s.jpg

Journal of African Ornithology, Volume 81, 2010 - Issue 3. Pages 205-209

AbstractVulture populations have declined globally as well as regionally within Africa. Little is known about the status of the African White-backed Vulture Gyps africanus in Kenya, but ongoing studies indicate that its population has declined over the last two decades. A total of 32 African White-backed Vulture nests were monitored in the Masai Mara National Reserve over a five-year period between 2003 and 2007. Mean nesting success was 59%, which is comparable to that of populations from southern Africa. Nearest neighbour distances were significantly closer in wooded habitats (‘trees and shrubs savanna’) than in more open grassland habitats (‘open low shrubs’). Based on nearest neighbour distances, the estimated total breeding population within the Masai Mara National Reserve is 1 106 pairs, a figure that may be an overestimate and requires ground-truthing. Collecting baseline data on numbers of breeding pairs and regular nest monitoring are essential in order to assess the impact of various threats to vultures in Kenya, which include growing threats (elephant-mediated habitat disturbance and fire) as well as emerging threats (such as poisoning with the carbamate-based pesticide Furadan™).

bottom of page