Parkview, South Africa
Parkview, South Africa

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Monadjem A.,University of Swaziland | Kane A.,Trinity College Dublin | Botha A.,Birds of Prey Programme | Dalton D.,National Zoological Gardens of South Africa | And 3 more authors.
PLoS ONE | Year: 2012

Investigating the ecology of long lived birds is particularly challenging owing to the time scales involved. Here an analysis is presented of a long term study of the survival and population dynamics of the marabou stork (Leptoptilos crumeniferus), a wide ranging scavenging bird from Sub-Saharan Africa. Using resightings data of tagged nestlings and free flying birds we show that the stork population can be divided into three general life stages with unique survival probabilities and fecundities. Fecundity of the storks is inversely related to rainfall during their breeding season. Corroborative evidence for a metapopulation structure is discussed highlighting the impact of the Swaziland birds on the ecology of the species in the broader region. The importance of tag loss or illegibility over time is highlighted. Clearly, any attempt at conserving a species will require a detailed understanding of its population structure, of the sort examined here. © 2012 Monadjem et al.


Monadjem A.,University of Swaziland | Botha A.,Birds of Prey Programme | Murn C.,Hawk Conservancy Trust andover
African Journal of Ecology | Year: 2013

Old World vultures are in decline across their entire range. Although critical for the formulation of effective conservation measures, neither survival nor movement patterns of African vultures are adequately known. This paper presents survival and movement data on the African white-backed vultures (Gyps africanus) from South Africa. Survival estimates were modelled on resightings of tagged vultures. Birds were captured en masse and resighted between November 2005 and December 2010. A total of 93 adult and subadult birds were fitted with uniquely numbered patagial tags, which were resighted 3707 times(mean of 39.8 resightings per bird). The programme MARK was used to estimate survival. The best model was one where survival and recaptures varied only with time (e.g. year). However, owing to the fading (illegibility) of tags in later years, the relationship with time is probably spurious. The second best model was one where survival and recaptures varied with age and time. Annual survival estimates increased from 85.2% in second-year birds to 99.9% in adults. This corresponds well with the survival of two other Gyps vultures that have been studied to date and underscores the point that additional mortality of adults in these long-lived species will result in rapid population declines. © 2012 Blackwell Publishing Ltd.


Jenkins A.R.,University of Cape Town | Shaw J.M.,University of Cape Town | Smallie J.J.,Wildlife and Energy Programme | Gibbons B.,African Crane Conservation Programme | And 2 more authors.
Bird Conservation International | Year: 2011

Ludwig"s Bustard Neotis ludwigii, endemic to Africa"s south-west arid zone, is susceptible to collisions with overhead power lines. Limited data from the south-eastern part of its range suggest that this factor may threaten its survival. We estimated transmission line collision rates for Ludwig"s Bustard across its South African range to assess the effect of this mortality on the population. Conservatively, collision rates averaged at least 0.63 ± 0.12 fatal collisions per km of transmission line per year, with relatively little regional variation. Despite being less abundant, the larger males were more collision-prone than females, which might account for the female-biased population. Extrapolating collision rates across the range of the species suggests that 4,000-11,900 birds are killed annually on high-voltage transmission lines. Actual mortality on overhead lines is probably much greater, given biases in carcass detection (crippling, scavenging and habitat biases), as well as the fact that our estimate excludes mortality on lower voltage distribution lines and telephone wires. Given an estimated global population of 56,000-81,000 birds in the late 1980s, the demographic invariant method suggests that such mortality is unsustainable. This result supports the recent upgrading of the conservation status of Ludwig"s Bustard from "Least Concern" to "Endangered", and highlights the need for further research on this problem. Copyright © 2011 BirdLife International.


Jenkins A.R.,University of Cape Town | De Goede K.H.,Birds of Prey Programme | Sebele L.,Avisense Consulting | Diamond M.,Wildlife and Energy Programme
Bird Conservation International | Year: 2013

In the Karoo region of South Africa, eagles nesting on high voltage power pylons are responsible for frequent short-circuits or faults, which reduce the quality of commercial power supply and escalate costs to the country's energy supplier, Eskom. Between 2002 and 2006 we conducted annual helicopter surveys of eagle nests on 1,400 km of power line and located 139 large nest structures, making up 96 eagle territories occupied by three species: Martial Eagle Polemaetus bellicosus (66 pairs), Verreaux's Eagle Aquila verreauxii (13 pairs) and Tawny Eagle Aquila rapax (17 pairs), and detailed 357 pair-years of breeding activity, including 241 breeding attempts. Roost sites and active nests were associated with line faulting, and more so at particular pylon configurations. We developed a three-step management plan to reduce eagle-related faulting while still accommodating eagles on the power lines: (i) all (potentially) problematic nests were relocated from high-risk positions above the power conductors, to specially provided platforms placed below the conductors; (ii) perch deterrents were installed above the conductors on all nest pylons and on high-risk pylons up to 10 structures on both sides of each nest tower; and (iii) the welfare of the eagles was monitored before and after management. In this way, line faulting was reduced on actively managed lines by > 75%, with no obvious deleterious effects on the eagle population. The study revealed that: (i) power lines can support substantial breeding populations of threatened large raptors, (ii) these birds can be a source of commercially significant line faulting, and (iii) nest relocations and perch deterrents are effective in reducing faulting without negatively impacting eagle populations. Copyright © BirdLife International 2013 Â.


Breeding population estimates for three vulture species in Kruger National Park (KNP), South Africa, were made in 2013 using data from aerial censuses and a plotless density estimator (PDE). PDEs are distance-based methods used to assess sparse populations unsuitable for plot-based methods. A correction factor was applied to the 2013 estimates to reflect the difference between the survey counts and the PDE figures. We flew additional censuses across most of KNP and counted all visible nests to assess the 2013 estimates. Survey counts were within 95% confidence limits of corrected PDE estimates for White-backed Vulture Gyps africanus (count: 892; estimate: 904 [95% CI ±162]), at the limit of confidence for White-headed Vulture Trigonoceps occipitalis (count: 48; estimate: 60 [±13]) and outside confidence limits for Lappet-faced Vulture Torgos tracheliotos (count: 44; estimate: 78 [±18]). Uncorrected PDE estimates accurately reflected White-headed and Lappet-faced Vulture nest counts. The clustered patterns of White-backed Vulture nests and dispersed patterns of White-headed and Lappet-faced Vulture nests offer an explanation for these results and means that corrected PDE densities are inaccurate for estimating dispersed nests but accurate for estimating clustered nests. Using PDE methods, aerial surveys over ∼35% of KNP are probably sufficient to assess changes in these vulture populations over time. Our results highlight these globally important breeding populations. © 2016 NISC (Pty) Ltd


Amar A.,University of Cape Town | Cloete D.,University of Cape Town | Whittington M.,Birds of Prey Programme
Ostrich | Year: 2016

Repeat monitoring is vital to measure biodiversity change. However, monitoring protocols may change, as survey techniques improve or different questions are asked. Such modifications may cause difficulties when examining changes in wildlife populations. The Southern African Bird Atlas Project (SABAP) 1 and 2 are repeat national bird surveys undertaken 20 years apart. These surveys therefore offer unrivalled potential to examine bird population changes in an African context. However, changes in protocols, both spatially and temporally, between the two surveys have raised concerns over using these data to infer population changes. In this study we use independ- ent nest survey data to test whether changes in reporting rates of Martial Eagles in the Kalahari Gemsbok National Park between the two SABAP surveys were reflected in real change in numbers of nesting pairs. From 11 quarter degree squares (QDS), covering c. 8 000 km2, both SABAP and nest surveys suggested a near identical 44% decline. Levels of agreement were weaker at the individual QDS scale, although in 67% of cases the direction of change was the same using both surveys. These results suggest that comparisons in the reporting rates between SABAP 1 and SABAP 2 accurately reflect changes in the breeding population size of this species. © 2016 NISC (Pty) Ltd.

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