Black Eagle Project Roodekrans
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Black Eagle Project Roodekrans 19th September 2013 - # 3 Our third weekly eagle info page – if there is anything you would like to have clarified and or discussed, give me a shout on 079 505 6419 or send me an email on [email protected] The eagles...are now into their 6th week of incubation – 35 days on Thursday 18th September – or 37 & 38 days on Saturday and Sunday respectively. The weekend after this will conclude the incubation period and some will “look forward” to the first egg hatching on Saturday 28 th September with the second on 2nd July. Having already felt that there wasn’t much notice of spring, we entered summer virtually immediately with temperatures rising rapidly. Undoubtedly, this scenario bothers me immensely in that if we are already experiencing soaring temperatures in September and October through to December will be the adult eagles’ biggest test yet! Keeping the chick/juvenile cool is one thing, but keeping themselves cool too upon the excruciatingly hot rock-face nest will be something even I would rather not witness. Observing both adults and their young hyperventilating throughout the summer months is something the eagles may live to regret yet! Its early days yet and I’m only sketching the possible scenario that is likely to follow and hopefully, prey will be bountiful and equally interesting is how the eagles will tolerate our Highveld thunderstorms with a youngster on the nest. The coolness after a summer downpour will be welcomed by the trio and there too, the youngster will require adult protection until it is at least into its final month on the nest before it fledges on New Year’s eve…or there about ☺ Below, I have included an interview that Markus Jais did with well-known Black Eagle authority, Rob Davies, who obtained his doctorate on the studies executed on 21 Black Eagle pairs in the mountains surrounding Beaufort West (Northern Cape Province). Enjoy! Eagle Greetings, Bo van der Lecq BEPR The Verreaux’s Eagle – an interview with Dr Rob Davies Rob Davies I first met Rob Davies in 1995 at the bird’s collection at the Nairobi Museum where he was researching for his project with Bill Clark on developing a raptor book for Africa. He has been a tremendous inspiration to many artists and raptor biologists around the world and I had the great privilege of staying with him in Midrand South Africa during the WWGBP Meeting there in 1998. Rob interest in birds of prey developed by watching kestrels and peregrines along the Pembrokeshire coastline. He studied zoology at the University of Exeter, and then moved to South Africa in 1982 where he studied the majestic Verreaux’s Eagle in the Karoo National Park for his PhD through Pretoria University. He is one of the finest artists I know and an excellent raptor biologist. He is meticulous in his work, soft spoken and a great person to be with in the field. In this interview, Rob talks passionately to Markus Jais about the status, threats and conservation issues facing the Verreaux’s Eagle. This interview was made possible by the efforts of Markus Jais. - Munir Virani 1) What is the current status of the Verreaux’s Eagle in Africa? Favourable: on the IUCN Red List, Verreaux’s Eagle is classified as least concern. The species has a huge geographic range given as over 4 million square kilometres, encompassing much of sub-Saharan Africa and extending up the Rift Valley, just reaching the Middle East. But more important than range is the area of occupancy and density within those areas. Fortunately Verreaux’s Eagles can exist at quite high density for a large eagle species where prey populations permit (with territories as small as 10km2) and they live in mountains and in remote places so they have been less affected by human development pressures than other eagle species. Total population estimate given by Birdlife is 10k – 100k but this has not yet been based on sound measurement of their mountain habitat and there may be as many as 2000 pairs just in the Cape Province of South Africa (now known as Northern and Western Cape). 2) How has the population developed during the last decades? It is hard to say because monitoring has only been carried out at a few localities. The Rock Hyrax prey base of Verreaux’s Eagles may be one of the most stable food supplies of any large eagle because hyrax do not fluctuate as widely in numbers as say rabbits, game birds or rodents. This is largely because hyraxes do not create their own refuges – they use rocky crevices which are fixed over time and the stable mountainous territories of these long-lived eagles are maintained around this fixed rocky habitat. David Allan noted that Verreaux’s Eagles in the Magaliesberg breed more successfully during drought years than high rainfall years – this paradox arises from the hyrax need to move farther from their rocky shelters to find food when it gets dry and become more exposed to predation. But hyrax numbers can show a fourfold decline after extended drought. So the eagle population will have oscillated slightly over the last few decades with natural fluctuations in rainfall which in Africa are often linked to El Nino events. However some studies have detected a harmful human influence on eagle populations in high density community areas where the human population has depleted the hyrax prey base through hunting and possibly also over-grazing. Community-owned land in Transkei, Lesotho and in areas adjoining the Matobo Hills National Park in Zimbabwe are examples of this. So there is likely to have been some loss of breeding pairs over the last decades but there are still vast tracts of Africa where Verreaux’s Eagles are not heavily persecuted and are still doing very well. 3) What is known about the species in the Western Palearctic? Is it still a regular breeding species there? The range of Verreaux’s Eagles follows the distribution of Rock Hyrax in mountainous terrain and extends across the Red Sea into southern Saudi Arabia, Yemen, Oman, Israel and Jordan. It is considered a ‘Rum speciality’ for birders visiting Jordan. But outside of Africa it is not a common species and there are only a handful of known breeding sites in the Middle East. In parts of Africa, Verreaux’s Eagle meets their ecological counterpart from the Northern hemisphere, the Golden Eagle. In Ethiopia both species nest in the Bale Mountains and maintain exclusive territories from one another. Verreaux’s Eagles extend westward as far as the Air Mountains in Western Niger but they are absent from rocky habitats with hyrax in the Sahel. 4) How does habitat destruction affect the Verreaux’s Eagles? Fortunately it is difficult for humans to destroy mountains and rocks so the habitat for Verreaux’s Eagles and their prey is largely unchanged. I have mentioned the loss of prey populations from high density community areas and urban development may also have displaced prey populations but urban development affects only a tiny fraction of Verreaux’s Eagle range. 5) What are the main threats to the Verreaux’s Eagle in Africa? The principal threat is the loss of prey populations through hunting by humans and displacement of hyrax from their rocky habitats. There is a long history of eagle persecution in sheep farming areas of southern Africa and at one stage the governments paid bounties for this. The levels of persecution were very high – on a par with the killing of Golden Eagles in the States and Wedge-tailed Eagles in Australia – and would have created localised population ‘sinks’. Fortunately those days are largely gone now and most farmers in southern Africa have become enlightened about the beneficial effects of having eagles on the farm. It is easy for the situation to slip and so it is important for conservation and education programmes to be ongoing. However, because they live in remote places, and because they prefer to catch live prey rather than scavenge, Verreaux’s Eagles have not suffered as badly as other large eagles through persecution and poisoning. Rob collecting data on Verreaux's Eagles at his site in the Karoo A new and worrying threat to Verreaux’s Eagles in Africa will be the provision of wind farms to provide energy. These structures, like unsafe electricity pylons before, are known causes of mortality for large raptors. It is very likely that electricity companies will want to put up wind farms in high lift areas on African mountains and ridges and these areas will converge with where Verreaux’s Eagles prefer to fly. Stringent environmental impact assessments need to be carried out to minimise this threat but it is hard to see how wind farms will not have a harmful effect on this eagle if there is an uptake in Africa along the lines seen in parts of Europe. 6) Verreaux’s Eagle is known to feed a lot on rock hyraxes? Are there places where the Verreaux’s Eagle does not depend on those mammals on feeds only on other prey like other medium sized mammals and birds? Gustaf Rudebeck (who studied bird migration) once said to me he thought Verreaux’s Eagles were ‘more evolved’ than the similar Golden Eagle. I didn’t know what he meant initially but I have come to learn that Verreaux’s Eagles are indeed highly specialised at what they do. They are mountain specialists first and foremost and have a high aspect ratio wing design suited to slope lift.