Scientists uncover widespread declines of raptors in Kenya

Scientists uncover widespread declines of raptors in Kenya



A recent study confirms alarming declines in raptor populations in Kenya. Incidental poisoning is a major problem for vultures in particular, depriving ecosystems of the birds’ vital role as scavengers. Conservationists are working with communities to help species recover.

“The population of raptors today bears no resemblance to those numbers we saw a half century ago,” said Simon Thomsett, director of the Kenya Bird of Prey Trust and one of the study’s authors. “And those had already drastically declined 25 years ago before we started to take notice.”

Drawing on road surveys carried out from 2003-2020, as well as historical data from similar surveys done between 1970 and 1977, the researchers found that populations of vultures and large eagle species had all declined. Numbers of previously common small and medium-sized raptors like black-winged kites (Elanus caeruleus) had also fallen sharply.

“The level of decline for many species was huge,” co-lead author Darcy Ogada told Mongabay. “But more surprising was the decline in medium-sized raptors like augur buzzards [Buteo augur] and long-crested eagles [Lophaetus occipitalis] which were once very commonly seen roadside birds and often seen in farms where they are the farmer’s friend because they prey on rodents.”

Encounters with 19 of 22 species studied using road surveys fell, including for the iconic secretary bird (Sagittarius serpentarius), encountered 94% less frequently, hooded vultures (Necrosyrtes monachus, down 88%) and lesser kestrels (Falco naumanni, down 93%). Fourteen of these species showed declines ranging from 20-95% when compared to the 1970s.

Encounters with 19 of 22 species studied using road surveys fell, including for the secretary bird (Sagittarius serpentarius), which was encountered 94% less frequently. Image by Ansie Potgieter via Unsplash.
Encounters with 19 of 22 species studied using road surveys fell, including for the secretary bird (Sagittarius serpentarius), which was encountered 94% less frequently. Image by Ansie Potgieter via Unsplash.

Ogada, who is assistant director for the Peregrine Fund’s Africa program, and her co-lead author, Phil Shaw of the University of St. Andrews in the U.K., led the team of scientists drawn from Kenya, the U.K., France and the U.S., which published the first report on nationwide trends for Kenya’s raptors.

“Given what we know about biodiversity loss in general in Kenya, we wanted to know specifically about the fate of Kenya’s raptors,” she said. “Fortunately, there was already historical data from the 1970s that was collected using the same method [road surveys], which could be used for comparison.”

Each year from 2010, the researchers spent four or five days driving slowly along roads in different parts of the country, identifying how many of each raptor species they saw. One team of scientists covered Laikipia, Samburu and Meru counties in central Kenya, while another team surveyed the southern part of the country, in Kajiado county and the national parks of Amboseli, Tsavo East and Tsavo West.

Raptors have fared better in protected areas, with the overall rate of decline for vultures and large eagles less pronounced in national parks and private conservancies than in unprotected areas. Medium-sized and small raptors like Montagu’s harriers (Circus pygargus) were actually seen more frequently in protected areas in the 2000s than during surveys in the 1970s, but those gains are tempered by an 85% drop outside of protected areas. Ten of the 22 species covered by the surveys are now found almost exclusively within protected areas, underlining the importance of these areas to their continued survival.

Andre Botha, co-chair of the IUCN’s Vulture Specialist Group, who was not involved with the recent study, said the survey method was a sound one.

“The method that was used to conduct the recent assessment is the same as that followed in 2010 [by these researchers] and also similar to approaches to surveys in various other parts of the world, so it is one way to assess populations,” he said. “It was, however, also scientifically important to follow the same method as previously to enable reliable comparison between the two counts.”

Medium-sized and small raptors like Montagu’s harriers (Circus pygargus) were seen more frequently in protected areas in the 2000s than during surveys in the 1970s, but those gains are tempered by an 85% drop outside of protected areas. Image by Radovan Václav via Flickr (CC BY-NC 2.0).
Medium-sized and small raptors like Montagu’s harriers (Circus pygargus) were seen more frequently in protected areas in the 2000s than during surveys in the 1970s, but those gains are tempered by an 85% drop outside of protected areas. Image by Radovan Václav via Flickr (CC BY-NC 2.0).

Grim findings

“Outside of Kenya’s protected area network, there is evidence that populations of many raptors have almost collapsed,” study co-lead Phil Shaw told Mongabay, “and this cuts across species size, diet or ecological requirements. While most species have fared better within protected areas, several large raptor species have shown worrying declines even here, suggesting a need to bolster site protection and connectivity.”

Both the reasons for the decline and possible remedies are well-known.

“Some threats, like raptor electrocutions, can be easily mitigated and some excellent work is being done around the world to reduce raptor mortalities,” said co-author Munir Virani, CEO of the Mohamed Bin Zayed Raptor Conservation Fund. “A case in point is the remediation of power lines done in Mongolia where raptor mortalities from electrocution has been reduced by 98% per year.”

More complicated is eliminating the use of pesticides used on crops and medicine given to livestock, both of which harm raptors’ health.

“Mitigation in the form of banning the veterinary drug diclofenac, which was responsible for the decline of up to 99% of populations of vulture species in Asia, has dramatically lowered additional mortality in these populations,” Ogada said. “In the U.S., banning of the chemical DDT also led to national resurgence of the country’s national bird, the bald eagle, such that populations today are growing at 10% per year.”

Other threats faced by raptors include habitat destruction caused by expanding agriculture and logging, being trapped or shot (including for use in traditional medicine), and poisoning. Vultures in particular are vulnerable to poisoned carcasses targetting other predators.

A lesser kestrel (Falco naumanni). Some threats, like raptor electrocutions, can be easily mitigated and some excellent work is being done around the world to reduce raptor mortalities, say experts. Image by Sergey Pisarevskiy via Flickr (CC BY-NC-SA 2.0).
A lesser kestrel (Falco naumanni). Some threats, like raptor electrocutions, can be easily mitigated and some excellent work is being done around the world to reduce raptor mortalities, say experts. Image by Sergey Pisarevskiy via Flickr (CC BY-NC-SA 2.0).

Helping vultures recover

Responding to the worrying collapse in vulture populations, the Peregrine Fund, Nature Kenya, BirdLife International, the Kenya Bird of Prey Trust and others are working to reduce cases of poisoning by tagging and tracking vultures, training people in the raptors’ range to help protect and rescue birds from poison, and building predator-proof livestock sheds as an alternative to poisoning.

Conservationists have documented cases of poisoning across the country to map hotspot zones.

“Keeping the records of poisoning incidences help us map the hotspot zones in areas where conflicts are rife so that awareness can be increased,” said Vincent Otieno, vulture conservation program coordinator with Nature Kenya. “From our records, such areas prone to poisoning are those that border conservancies and national parks.”

In Narok and Kajiado counties, at the southern end of the Rift Valley, community volunteers have been trained to respond quickly to vulture poisoning incidents. Equipped with rubber gloves, face masks, plastic containers, and fuel, they bag and burn poisoned carcasses so more vultures don’t gather and gorge themselves on a deadly meal.

They can also bring stricken birds to raptor centers at Naivasha and Soysambu, clinics set up to treat poisoned vultures. Once the birds recover, they are fitted with GPS trackers and released.

Vultures that died from poisoning in Maasai Mara, Kenya. Image courtesy of Nature Kenya.
Vultures that died from poisoning in Maasai Mara, Kenya. Image courtesy of Nature Kenya.
Several conservation organizations are working to reduce cases of poisoning by tagging and tracking vultures, training people in the raptors’ range to help protect and rescue birds from poison, and building predator-proof livestock enclosure as an alternative to poisoning. Image courtesy of Caroline Chebet.
Several conservation organizations are working to reduce cases of poisoning by tagging and tracking vultures, training people in the raptors’ range to help protect and rescue birds from poison, and building predator-proof livestock enclosure as an alternative to poisoning. Image courtesy of Caroline Chebet.

“Tagging these vultures with GPS trackers helps us map out the areas where they spent most of the times,” said study co-author Shiv Kapila, from the Kenya Bird of Prey Trust. “The information we get helps when conducting anti-poisoning campaigns and education.”

Similar work with communities is taking place in the central counties of Laikipia and Samburu. In addition to training volunteers to respond to poisoning incidents, the Peregrine Fund is working alongside conservation nonprofit Lion Landscapes to construct predator-proof bomas, offering herders an alternative to way to protect their livestock from lions than leaving poisoned carcasses where the big cats — as well as vultures, hyenas and other scavengers — will find them.

Conservation groups have also trained rangers, police officers and Kenya Wildlife Service officers.

Botha, who is also the program manager of the Endangered Wildlife Trust’s Vultures for Africa program, noted that conservationists in Kenya and South Africa have been working together for almost 15 years, training thousands of people across 15 African countries to reduce wildlife poisoning.

“We continually communicate and share expertise between countries and beyond, but the uptake of certain interventions are done with different degrees of success, largely due to different circumstances in-country and limited resources that are always a challenge,” he said.

Citation:

Ogada, D., Virani, M. Z., Thiollay, J. M., Kendall, C. J., Thomsett, S., Odino, M., … Shaw, P. (2022). Evidence of widespread declines in Kenya’s raptor populations over a 40-year period. Biological Conservation, 266, 109361. doi:10.1016/j.biocon.2021.109361

This article by Caroline Chebet was first published by Mongabay.com on 17 May 2022. Lead Image: A hooded vulture (Necrosyrtes monachus). Image by MarnixR via Wikimedia Commons (CC BY-SA 3.0).


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