Vultures

Discussions and information on all Southern African Birds
User avatar
Richprins
Committee Member
Posts: 63794
Joined: Sat May 19, 2012 3:52 pm
Location: NELSPRUIT

Re: Vultures

Post by Richprins » Wed Apr 03, 2019 8:39 am

:shock: :shock: :shock:
Please check Needs Attention pre-booking: https://africawild-forum.com/viewtopic.php?f=322&t=596

User avatar
Lisbeth
Global Moderator
Posts: 51586
Joined: Sat May 19, 2012 12:31 pm
Country: Switzerland
Location: Lugano

Re: Vultures

Post by Lisbeth » Wed Apr 03, 2019 10:18 am

BIG one :shock:
"Education is the most powerful weapon which you can use to change the world." Nelson Mandela
The desire for equality must never exceed the demands of knowledge

Klipspringer
Posts: 514
Joined: Sat Sep 14, 2013 12:34 pm
Country: Germany

Re: Vultures

Post by Klipspringer » Thu Jun 06, 2019 8:18 am

https://africageographic.com/blog/do-el ... -research/

Do elephants affect vulture nesting success? Ongoing research
Posted on 5 June, 2019 by Guest Blogger


Written by Mr Robin Cook (Elephants Alive’s Big Trees Project Manager) and Dr. Michelle Henley (Elephants Alive Director, Co-founder and Principal Researcher)

There is a worrying trend of declining white-backed vulture (Gypis africanus) numbers in Africa, with the major factors being poisonings (Ogada et al. 2016), poaching (McKean et al. 2013), electrocutions (Van Rooyen 2000) and habitat loss (Bamford et al. 2009). These factors primarily influence adult vultures, thereby, having confounding consequences on the vulture populations.

A secondary factor under investigation is a potential shortage of nesting sites. White-backed vultures nest in tall trees in Africa’s savannas, building large nests towards the top of these trees. Concerns have been raised over how African elephants’ (Loxodonta africana) impact may affect white-backed vulture nesting success, and hence, vulture populations (Rushworth et al. 2018).

Elephant impact on big tree species is a widely researched and complex topic, as elephant impact differs between elephant sexes (Greyling 2004) and across tree species (Shannon et al. 2008). However, it is important for long-term research to be carried out on elephants and vultures, so as to understand whether elephants are indeed affecting vulture nesting success.

In the Associated Private Nature Reserves (APNR) of the Greater Kruger National Park, vulture surveys have been carried out by Elephants Alive since 2008. These surveys focus on the survival of vulture nests versus the survival of the trees in which they are nesting. The surveyed reserves included the Klaserie, Timbavati and Umbabat Private Nature Reserves. The first four years of surveys were published by Vogel et al. (2014), with results indicating that vulture nest survival rates decreased far quicker in comparison to the trees in which they nested.

Of all the surveyed trees, 20% had died over the four-year period, in comparison to 80% of the active nests. Furthermore, it was hypothesised that insect borer activity, in combination with elephant impact, was leading to the slow decline of nesting trees within the APNR.

Elephant impact, i.e. bark-striping, increases the likelihood of borers colonising a tree, which may eventually cause the tree to be hollowed out. This leads to dieback of branches within the top canopy of the tree, which may result in eventual vulture nest collapse (M. Henley personal communication).

Elephants Alive’s vulture surveys have continued in the APNR on an annual basis, and as of 2018, Balule Private Nature Reserve was added to the surveyed reserves. This allowed us the opportunity to include trees with vulture nests along the Olifants River.

Our 2018 surveys have recorded a minimum of 156 active white-backed vulture nests within the APNR, as well as 42 intact but inactive nests. The majority of nests were recorded in knobthorn (Senegalia nigrescens) and jackalberry (Diospyros mespiliformis) trees, usually in the tallest individuals of these species. However, a total of 12 different tree species contain vulture nests within the APNR.

Elephant impact levels also differ amongst the tree species containing vulture nests. This highlights that the tree species may influence the likelihood of a tree with a vulture nest receiving elephant impact. Both knobthorn and marula (Sclerocarya birrea subsp. caffra) trees had the highest levels of elephant impact, whilst significantly lower impact levels were recorded on the riverine-based jackalberry and apple leaf (Philenoptera violacea) trees.

However, our results still indicate that there is no clear relationship between the number of dilapidated nests and dead trees. Between 2014 and 2018, 50 trees containing vulture nests have subsequently died, in comparison to 110 dilapidated vulture nests.

What is of importance to the future prospects of vulture nesting success is the availability of suitable trees for nesting success. In Kenya’s Masai Mara National Reserve, Kendall et al. (2018) showed that tree availability exceeded the nesting needs for vultures. Our current research will explore this in further depth within the APNR. Furthermore, tree recruitment rate and the survival rate of seedlings is a key factor in availability of nesting sites in future (Helm et al. 2011).

Whilst our results are indicating that there is no direct relationship between elephant impact and vulture nest survival, we still need to explore how the combination of both elephant impact and borer activity lead to the dieback of upper canopy branches and potential nest collapse. This can only be determined through long term studies such as these in the APNR.

What is encouraging for us is that within the reserves where we have over a decade’s worth of data on trees containing vulture nests, the number of recorded active vulture nests within the APNR has increased over the years. Between 2014 and 2018, Klaserie’s active vulture nests have increased from 63 to 85, whilst the Timbavati have witnessed an increase from 34 to 47 active nests. With the addition of Balule Private Nature Reserve, we will also be able to understand the relationship between vultures and elephants at a greater scale so as to aid management in understanding how elephant may impact vultures, and the potential management told which can be put in place for protecting these trees (Derham et al. 2016; Cook et al. 2018).


References

• Bamford, A. J., Monadjem, A., Diekmann, M., & Hardy, I. C. (2009). Development of non-explosive-based methods for mass capture of vultures. South African Journal of Wildlife Research-24- month delayed open access, 39(2), 202-208.
• Cook, R. M., Parrini, F., King, L. E., Witkowski, E. T. F., & Henley, M. D. (2018). African honeybees as a mitigation method for elephant impact on trees. Biological Conservation, 217, 329-336.
• Derham, K., Henley, M. D., & Schulte, B. A. (2016). Wire netting reduces African elephant (Loxodonta africana) impact to selected trees in South Africa. Koedoe, 58(1), 1-7.
• Greyling, M. D. (2010). Sex and age related distinctions in the feeding ecology of the African elephant, PhD thesis, University of the Witwatersrand, Johannesburg.
• Helm, C. V., Scott, S. L., & Witkowski, E. T. F. (2011). Reproductive potential and seed fate of Sclerocarya birrea subsp. caffra (marula) in the low altitude savannas of South Africa. South African Journal of Botany, 77(3), 650-664.
• Kendall, C. J., Rubenstein, D. I., Slater, P. L., & Monadjem, A. (2018). An assessment of tree availability as a possible cause of population declines in scavenging raptors. Journal of Avian Biology, 49(1), jav-01497.
• McKean, S., Mander, M., Diederichs, N., Ntuli, L., Mavundla, K., Williams, V., & Wakelin, J. (2013). The impact of traditional use on vultures in South Africa. Vulture News, 65(1), 15-36.
• Ogada, D., Shaw, P., Beyers, R.L., Buij, R., Murn, C., Thiollay, J.M., Beale, C.M., Holdo, R.M., Pomeroy, D., Baker, N. and Krüger, S.C., 2016. Another continental vulture crisis: Africa’s vultures collapsing toward extinction. Conservation Letters, 9(2), 89-97.
• Rushworth, I. A., Druce, D., Craigie, J., & Coverdale, B. (2018). Vulnerability of vulture populations to elephant impacts in KwaZulu-Natal. Bothalia-African Biodiversity & Conservation, 48(2), 1-10.
• Shannon, G., Druce, D. J., Page, B. R., Eckhardt, H. C., Grant, R., & Slotow, R. (2008). The utilization of large savanna trees by elephant in southern Kruger National Park. Journal of Tropical Ecology, 24(3), 281-289.
• Van Rooyen C.S. 2000. An overview of vulture electrocutions in South Africa. Vulture News 43, 5-22.
• Vogel, S. M., Henley, M. D., Rode, S. C., van de Vyver, D., Meares, K. F., Simmons, G., & de Boer, W. F. (2014). Elephant (Loxodonta africana) impact on trees used by nesting vultures and raptors in South Africa. African Journal of Ecology, 52(4), 458-465.

User avatar
Richprins
Committee Member
Posts: 63794
Joined: Sat May 19, 2012 3:52 pm
Location: NELSPRUIT

Re: Vultures

Post by Richprins » Thu Jun 06, 2019 9:13 am

@#$
Please check Needs Attention pre-booking: https://africawild-forum.com/viewtopic.php?f=322&t=596

User avatar
Lisbeth
Global Moderator
Posts: 51586
Joined: Sat May 19, 2012 12:31 pm
Country: Switzerland
Location: Lugano

Re: Vultures

Post by Lisbeth » Thu Jun 06, 2019 10:28 am

Also vultures most likely are suffering from the advancement of human activities all over the place. They are doing well in the nature reserves, so what is left -O-
"Education is the most powerful weapon which you can use to change the world." Nelson Mandela
The desire for equality must never exceed the demands of knowledge

Klipspringer
Posts: 514
Joined: Sat Sep 14, 2013 12:34 pm
Country: Germany

Re: Vultures

Post by Klipspringer » Thu Jun 06, 2019 11:23 am

Vultures and other birds who use large trees for nesting suffer also in Protected areas because the large trees are in decline and tree recruitment does not occur for a lot of species.

Elephants are to blame, but not only I think.

The area around Satara used to be a woodland and the decline of the canopy started long before elephant numbers exploded. :-?

User avatar
Richprins
Committee Member
Posts: 63794
Joined: Sat May 19, 2012 3:52 pm
Location: NELSPRUIT

Re: Vultures

Post by Richprins » Thu Jun 06, 2019 11:25 am

Fire also plays a role! ..0..
Please check Needs Attention pre-booking: https://africawild-forum.com/viewtopic.php?f=322&t=596

Klipspringer
Posts: 514
Joined: Sat Sep 14, 2013 12:34 pm
Country: Germany

Re: Vultures

Post by Klipspringer » Thu Jun 06, 2019 12:18 pm

Another more scientific article about vultures and elephants in KZN with remarks to KNP. Long read!

http://www.scielo.org.za/pdf/babc/v48n2/03.pdf
Vulture populations in KZN are small, declining and already at
risk of extinction. In KZN, 94.2% of tree-nesting vulture nests occur in areas with elephant;
this could increase to 99.5% in the near future if proposed land-use change takes place.
Anthropogenic impacts in the broader landscape mean that there are limited opportunities for
vultures to nest elsewhere, and we hypothesise that loss of suitable nesting habitat in existing
areas, including through impact of elephant on large trees, could result in declines and even
extirpation of these species as breeding residents. Given the demonstrated and potential
impacts of elephants on large trees necessary for vulture nesting, it is essential that the role
of protected areas and extensive wildlife systems for vultures be adequately taken into account
when managing elephant populations.
Tree selection by vultures
A brief summary of vulture tree selection for nesting based
on local studies is provided. In Hluhluwe–iMfolozi Park,
the following trees are selected by Lappet-faced and Whiteheaded vultures within which to nest: Senegalia (Acacia)
nigrescens, Senegalia (Acacia) burkei, Vachellia (Acacia) robusta
and at times Schotia brachypetala, Balanites maughamii and
Ficus sp. (D. Druce pers. obs.). African White-backed Vultures
utilise Ficus sycomorus (36.4% of nests, n = 242), Vachellia
(Acacia) robusta (33.1%), Schotia brachypetala (14.9%),
Spirostachys africana (9.9%), Senegalia (Acacia) nigrescens (2.5%)
and Senegalia (Acacia) burkei (1.7%) (Whateley 1986).
In Phongolo Nature Reserve, there is a definite preference by
African White-backed Vultures for Senegalia (Acacia) nigrescens
trees with 27 of 28 recorded nests occurring in mature
Senegalia (Acacia) nigrescens trees, and one nest in an Vachellia
(Acacia) tortilis (James Wakelin, unpublished data). The single
Lappet-faced Vulture nest at Ithala Game Reserve in 2005
was in a Vachellia (Acacia) tortilis tree (Rushworth, Wakelin &
Bawden 2007).
In the Kruger National Park, the heights of the nests of African
White-backed Vultures were 10 m – 25 m above ground (large
trees), with the most important species used being Senegalia
(Acacia) nigrescens 29%, Vachellia (Acacia) robusta 19%, Senegalia
(Acacia) welwitchii sub sp. delagoensis 17%, Ficus sycamorus 12%
and Diospyros mespiliformis 9% (n = 106) (Kemp & Kemp 1975).
Vogel et al. (2014) found that a larger proportion of vulture
nests were present on trees with lower elephant impact.
However, they observed that further investigation is required
as to whether vultures are selecting trees with low elephant
impact – thus avoiding trees with signs of a shortened
lifespan – or are abandoning trees when elephant impact
increases over time. They did observe however that some
new vulture nests were established in trees with high
elephant impact. Vulture nests are more likely to persist for
longer in larger trees (Vogel et al. 2014).
African White-backed Vultures tend to nest in large trees
close to perennial rivers and smaller drainage lines but also
nest away from watercourses (Howells, Craigie & Nänni
2010; Kemp & Kemp 1975; Whateley 1986). After massive
floods destroy favoured nesting trees on perennial rivers,
vultures may relocate their nests to unaffected tributaries
(Whateley 1986). Lappet-faced and White-headed Vultures
tend to nest in the interfluves away from drainage lines
(Howells et al. 2010; Kemp & Kemp 1975).

Elephant–tree interactions
Concern has been expressed over an observed decline in
large tree abundance in protected savannah areas linked to
the destruction of vegetation by large herbivores, particularly
elephant (e.g. Coetzee et al. 1979; Cumming et al. 1997;
Eltringham 1980; Jacobs & Biggs 2002; O’Connor, Goodman
& Clegg 2007). It is not the intention here to provide an
extensive review of elephant–vegetation interactions, but
some key local studies investigating elephant impacts on
large trees are summarised.
In Hluhluwe–iMfolozi Park in KZN, elephant are having a
marked impact on certain less common tree species and larger
tree size classes (Boundja & Midgley 2010). However, the
nature of the elephant impact data currently available does
not allow a clear differentiation between various factors
(elephants, fire, shrub encroachment and interactions between
fire and elephant) driving vegetation change (Druce et al.
2017). Total woody plant density between 1999 and 2007
remained little changed, but there was a shift in representation
of different height classes. Density in trees taller than 8 m
remained unchanged between 1999 and 2007. Representation
of trees between 4 m and 8 m declined by 31%, while the
representation of trees less than 4 m increased from 61% to
71% over the same time period (Druce et al. 2017). Among the
common trees species, a decline in the number of trees in the
taller height classes (4 m – 10 m) was observed for Senegalia
(Acacia) burkei, Senegalia (Acacia) nigrescens, Sclerocarya birrea
and Vachellia (Acacia) robusta (Druce et al. 2017). Senegalia
(Acacia) burkei declined from 1.55 individual trees per plot in
1999 to 0.76 trees per plot in 2007, while Senegalia (Acacia)
nigrescens declined from 2.96 to 1.59 trees per plot, Vachellia
(Acacia) robusta declined from 1.41 to 0.60 trees per plot and
Sclerocarya birrea declined from 0.69 to 0.29 trees per plot in
the same period (unpublished data). The most selected
tree species in Hluhluwe–iMfolozi Park include Cussonia
spp. (0.60 Jacobs index), Albizia versicolor (0.53) and Ficus
spp. (0.53) (Druce et al. 2017). Species selected by Lappetfaced and White-headed vultures as nesting trees also show
high levels of selection by elephant, for example Senegalia
(Acacia) burkei (0.37 Jacobs index), Vachellia (Acacia) robusta
(0.35) and Schotia brachypetala (0.35) (Druce et al. 2017).
Although Senegalia (Acacia) nigrescens does not show high
selection by elephant overall, this species falls within the list
of trees with the highest percentage of bark stripping by
elephant, with 1.1% of all individuals recorded showing signs
of debarking by elephant; 1.1% of all Vachellia (Acacia) robusta,
Senegalia (Acacia) burkei and Vachellia (Acacia) nilotica had
been toppled by elephant by 2007 (Druce et al. 2017). In
summary, in addition to evidence of elephant selecting some
preferred nesting trees, there has been an overall decline in
density of some preferred nesting trees and there are
indications of a recruitment bottleneck into the mature size
class developing (intermediate size trees declining).
In Ithala Game Reserve (KZN), elephant had a
disproportionately large impact on tree mortality, with
elephant responsible for 38% of all tree mortality at a time
when elephant density was one-third of current levels;
damage accumulated over the years as elephants revisited the
trees (Wiseman, Page & O’Connor 2004). In Tembe Elephant
Park (KZN), elephant may be affecting the sand forest and
they have already changed plant cover significantly, but not
the species composition (Gaugris et al. 2004).
In the Kruger National Park (South Africa), the interaction
between elephant browsing and fire is resulting in a decline
in large tree density (Trollope et al. 1998), with mortality
higher than recruitment into the ≥ 5 m height class (Shannon
et al. 2011). In Swaziland, high densities of elephant in
small fenced enclosures resulted in mortality of virtually all
Senegalia (Acacia) nigrescens trees, and the absence of African
White-backed Vulture nests in these enclosures was attributed
to this mortality of preferred nesting trees (Monadjem &
Garcelon 2005). In Chobe National Park (Botswana), tree
density, cover and volume had increased over time
throughout the area, caused by a combination of an increase
of trees in lower size classes and a decrease in larger size
classes; the decrease of large trees is attributed to a growing
elephant population (Kalwij et al. 2010).
Elephant impact on large trees is often mediated through
synergistic interaction effects with fire (Moncrieff, Kruger &
Midgley 2008; Shannon et al. 2011; Trollope et al. 1998) and
browsing by other herbivores (O’Kane et al. 2011; Wiseman
et al. 2004), while in other cases it is not possible to clearly
disentangle the drivers (Druce et al. 2017). Trees with high
elephant impact have a higher likelihood of insect and fungus
establishment (Vogel et al. 2014). Hence, in addition to
making trees more susceptible to fire, elephant could be
influencing the survival of trees indirectly through opening
the bark and facilitating the colonisation by fungus and
insects (Hatcher 1995; Vogel et al. 2014). Older trees had
more accumulated elephant damage, and the accumulated
elephant impact on older trees could render them unsuitable
as potential nesting sites if arthropod and fungus invasions
increased over time (Vogel et al. 2014).
While there is no evidence at this
stage to suggest that suitable nesting trees are becoming
limiting, there is evidence of a reduction in density, and further
evidence of a developing recruitment bottleneck, of preferred
nesting trees in the most important areas for vultures in KZN.
Although it is complex to fully understand the interacting
drivers of change, there is evidence that elephant are at least a
contributory factor in these vegetation changes. We predict
that if an appropriate balance between elephant numbers
and vegetation is not achieved in existing areas with elephant,
this could conceivably lead, in the long term, to the complete
or almost complete loss of tree-nesting vultures as breeding
residents from KZN.

User avatar
Lisbeth
Global Moderator
Posts: 51586
Joined: Sat May 19, 2012 12:31 pm
Country: Switzerland
Location: Lugano

Re: Vultures

Post by Lisbeth » Wed Jun 12, 2019 8:22 pm

With a little help from some humans (?) they will be exsticnt even earlier. Ignorance is killing our planet 0*\ :evil:
"Education is the most powerful weapon which you can use to change the world." Nelson Mandela
The desire for equality must never exceed the demands of knowledge

Return to “Birds”