Attempted Verreaux's Eagle Predation on Rüppell's Vulture and Breeding Observations at Lake Kwenia Colony, Kenya

Vulture News 68 July 2015 Attempted Verreaux’s Eagle predation on Rüppell’s Vulture and breeding observations at Lake Kwenia colony, Kenya Simon Thomsett1* and James Aldred 1Ornithology Section. Dept of Zoology, National Museums of Kenya, Nairobi, Kenya *Corresponding author: [email protected] Summary 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. Introduction al. (1992) question if this behaviour is recorded in Rüppell’s Vulture The predation of Cape Vulture (Gyps (Gyps rueppellii). coprotheres) pulli by Verreaux’s Despite observations of Eagle is well-known in South Africa behaviour between Verreaux’s (Mundy et al. 1992, Gargett 1993). Eagles and nesting Rüppell’s These Verreaux’s Eagle individuals Vultures in Kenya, Tanzania and or pairs patrol the Cape Vulture Ethiopia for some 30 years by one of breeding cliffs looking for unfledged the authors (ST), the vocal intensity chicks and even eggs (although described above was not recorded unsuccessfully) on ledges. The Cape despite hundreds of observed Vultures are recorded as having a interactions between the two species. “distinctive and hoarse call” when In contrast, Rüppell’s Vultures paid Verreaux’s Eagles patrol in such a little or no attention to Verreaux’s manner and that “the uproar of these Eagles even if they flew within 10- griffons has to be heard to be 20 metres of their young. Rarely, the believed”. This is accompanied by eagles did appear to have the intent aggressive gesturing, and Mundy et to predate chicks by looking directly 59 Vulture News 68 July 2015 at exposed chicks and banking round part of a long-term study site (Virani to re-inspect the possibilities. Parent et al. 2012), although in 2013 the Rüppell’s Vultures have been seen to colony is threatened by intensive react by opening wings and agriculture and land developers stretching out their heads (but with directly below the cliffs. Some of the minimal vocalisation) to very close- filming required nest-ledge camera flying Verreaux’s Eagles, but these positions to film chicks and a crude events are characterised by their bird-hide was built halfway down the rarity and lack of intensity despite cliff. From these vantage points we ample opportunity. The “distinctive” were able to see into two nest ledges call and anti-predator behaviour with chicks and had a clear view of shown by the Cape Vulture is nearly all roosting and nesting ledges therefore not a distinct part of the running 2km north and 2km south. In behavioural repertoire of Rüppell’s over 10 years no attempted predation Vulture. Another aspect possibly by Verreaux’s Eagles has been influencing behavioural differences witnessed at Kwenia (ST, personal is the close proximity of nests and observation) nor cited in publications synchronous breeding of Cape on this species (Mundy et al. 1992, Vultures, as opposed to the generally Virani et al. 2012). more widely-spaced nesting and During the 15 day intensive asynchronous breeding of the observation, an adult pair of equatorial nesting Rüppell’s Vulture Verreaux’s Eagles known to nest (Virani et al 2012). A group uproar 4km south west of the colony would would be impossible with widely visit the cliffs and were seen on at spaced nests. least four occasions flying very close to the nests. On 22/1/13, three The Kwenia colony vultures were seen to react with alarm at the very close proximity of Between 22/1/13 and 15/2/13, a BBC the eagle pair circling within 4m of film crew was camped on top of an occupied ledge. On 3/2/13 the Kwenia, the largest Rüppell’s pair circled a ledge 20m directly Vulture colony in southern Kenya, below, flying within 1-2m of adult filming a documentary on vultures. Rüppell’s Vultures with young. The Kwenia colony numbers some Although the intent of the pair 150-200 Rüppell’s Vultures, contains seemed focussed on the ledge, no approximately 64 nests and has been vocalisations were heard. A juvenile 60 Vulture News 68 July 2015 1.5-2 year old female Verreaux’s observations if all nests are to be Eagle spent much time on these enumerated. It is plausible that cliffs, perched and flying near the optimum sites (well-shadowed and ledges throughout the 15 day period. discreet) are competed for and used It appeared to be sufficiently far first, and that secondary sites get from the adult pair’s nest but on at occupied later when there is less least four occasions the eagle was choice. This may explain the escorted away by the adult vulture difficulty in detecting active nests pair using a low intensity aggressive when only a small number of birds pursuit. The sub-adult often sat like a are nesting. sentinel on outcrops overlooking nesting ledges or made sorties to Description of the attempted circle and craned its neck at vulture predation chicks in the nest with obvious intent and interest in unattended vulture At 12PM on 14/2/13, JA was filming chicks. halfway down the cliff and heard a At that time there was a low loud rushing and flapping sound occupancy of nests with six young above. Upon turning three large birds ranging from 50-100 days and one were seen tumbling to the ground pair incubating. Significantly, these some 150m out from the cliff face. chicks were not visible from the Two hit the very steep scree some ground even with the best optical and 110m below, followed immediately photographic equipment and were by an adult Rüppell’s Vulture. only detected after days of intense What followed was videoed some observation from the hide placed five seconds after impact and is here halfway down the cliff or by described. The dense tangle of climbing to nesting ledges. Methods commifera made the video unusable previously employed to survey this for the documentary, but it shows cliff by the authors and colleagues that on impact with the ground the (Virani. et al 2012), could easily eagle disengaged from the juvenile have overlooked these nests from the vulture, which was seen on its back ground survey. For absolute and was 3m down a steep slope. 2m accuracy this emphasises the need away up slope was an adult for intense observation methods Rüppell’s Vulture, possibly the coupled with close cliff ledge access parent. Immediately the eagle had and/or distant multiday behavioural three Rock Hyrax (Procavia 61 Vulture News 68 July 2015 johnstoni) running away from it. (seen riding on its nape!). The eagle After four seconds the eagle turned perched on a tree immediately above toward the juvenile vulture and the vulture, where it was persistently jumped onto it with both feet taking attacked by the Drongos. The eagle it by the head. This rotated the was aware of the cameraman above vulture onto its chest. A few seconds and this, plus the Drongos and the later the adult vulture, itself defensive hyrax, combined to make threatened by an attack, turned and it fly away. The eagle remained flew away, presumably accepting the patrolling above. After some 30 futility of its ability to protect the minutes a troop of Olive Baboons young vulture. The eagle was on its (Padio anubis) were seen moving tibio-tarsal pads, wings partly spread towards the scene in a deliberate and for balance with the vulture head curious manner. down out of sight under the sprawled A decision was made to rescue body, convulsively gripping the head the vulture as a stalemate had with its feet. For some 15 seconds occurred in which our presence was the vulture lay motionless except for influencing the outcome with an when the eagle made occasional increased probability of it being kneading clutches. The vulture was found by baboons and killed. Given apparently being suffocated, and had that the species is Endangered, and only moments to live, when three we could rescue it easily, a co- large Rock Hyrax appeared and ordinated effort was made by local bounded toward the eagle. The eagle Masai community members radioed was alarmed and left the vulture, below, and by abseiling to the moving 4m down slope; it stayed for ground. The vulture was found to five seconds before flying away. The have a shattered humerus either from eagle may also have been wary of impact by the eagle in the sky or the cameraman immediately above it when it hit the ground. It had blood on the cliff. The vulture recovered coming out of the mouth and a small somewhat and after a minute tried to but deep hole in the top of the skull. move but rolled helplessly on its The bird showed no downy tufts back down slope, a broken wing on its flight or contour feathers. Its hindering its ability to right itself. worn tail tips with protruding un- After five minutes the Verreaux’s feathered 2.5cm spines and the Eagle flew back overhead, mobbed presence of some abraded tips on by a pair of Fork-tailed Drongos secondaries indicated that it had 62 Vulture News 68 July 2015 fledged at least a month or more The Verreaux’s Eagle continued previously. The down on the head to survey the cliffs and if it indeed was full and uniform indicating it specialised in taking chicks on had not fed at carcasses. The bird ledges or flying young vultures, its was taken for surgery by Sarah impact would be very significant.

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