The study found that the breeding success of the hornbills collapsed over a decade-long monitoring period (2008 – 2019), corresponding with rapid warming due to climate change. During the monitoring period, sub-lethal effects of high temperatures, including compromised foraging, provisioning, and body mass maintenance, reduced the chance of hornbills breeding successfully or even breeding at all.

“These temperature effects occurred even in good rainfall years,” said Nicholas Pattinson, a researcher at UCT’s FitzPatrick Institute of African Ornithology.

“While drought did negatively affect breeding success, our findings suggested that the rapid warming in the region was responsible for the collapse in breeding success: temperatures have been rising but drought return rates have remained stable in this area.”

The hornbills have an incredible breeding strategy, whereby the female actually seals herself inside the nest and moults all of her flight feathers. This strategy helps them avoid predation, and while it is common to many hornbills, it is a truly remarkable method of breeding.

Writing in the Frontiers in Ecology and Evolution journal, Pattinson said the study supports the proposition that even in the absence of large-scale mortality events associated with heat waves, cumulative sub-lethal consequences of increasing temperatures can and will likely cause population declines and even local extinctions.

Pattinson and his colleagues were surprised by how rapid climate warming acted so quickly on the breeding success of the hornbills.

“Within just a single decade we see a collapse in breeding success, correlating to the warming in the region and related to the inability of the hornbills to breed successfully at high temperatures. The most surprising thing is the finding that the hornbills, as we were monitoring, were fighting extirpation,” he said.

Commenting on the findings, Pattinson said there is rapidly growing evidence for the negative effects of high temperatures on the behaviour, physiology, breeding and survival of various bird, mammal, and reptile species around the world.

“Heat-related mass die-off events over the period of a few days are increasingly being recorded, which no doubt pose a threat to population persistence and ecosystem function,” he said. A team of researchers monitored the breeding of a population of the hornbills breeding in nest boxes at a study site in the Kalahari Desert from 2008 to 2019. They analysed the breeding success at the scale of entire breeding seasons and individual breeding attempts within seasons and correlated those with weather variables. The team also analysed South African Weather Service data for the Kalahari region to look at long term temperature and rainfall patterns to determine the onset and rate of warming due to climate change.

Out of the 118 breeding attempts the team monitored over the decade period, not a single attempt succeeded where the average air temperature during the attempt was equal to or greater than 35.7 °C. According to Pattinson, this shows a clear, dramatic negative effect of high temperatures on the breeding success of the hornbills.

“Current climate change predictions make it very unlikely that hornbills will persist across the hottest parts of their range even over the next decade. However, if they are going to occur anywhere across their current distribution in the future, the temperatures will have to remain below this threshold of 35.7 °C during their breeding,” he said.

This study may be about the hornbills in the Kalahari Desert, but it is relevant to people and systems worldwide, said Pattinson.

“Much of the public perception of the effects of climate change is related to scenarios calculated for 2050 and beyond. This renders the concept of the effects of climate change abstract to much of the general public not directly affected by extreme weather events, given that the effects are considered to concern future generations,” he said.

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Issued by: UCT Communication and Marketing Department
Photo: Marc/Unsplash

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• A new study has found that hornbills, vultures and eagles are being hunted for bushmeat in Cameroon in much greater numbers than previously thought.
• Researchers estimate that people living around the proposed Ebo National Park in Cameroon’s Littoral region consumed an average of 29 hornbills and eight raptors per month.
• But they remain unsure how the current levels of hunting are affecting the bird populations, given that so little is known about the latter.

Hornbills, vultures and eagles are being hunted for bushmeat in Cameroon in much greater numbers than previously thought, a new study has found.

Previous research has shown that relatively few birds are sold in Cameroon’s markets compared to mammals and reptiles. However, market surveys can be biased toward commercially valuable wildlife, missing animals that are killed by hunters for consumption in their hunting camps, Robin C. Whytock, a doctoral researcher at the University of Stirling in Scotland, and his colleagues found in a study published in 2016. Whytock’s team surveyed discarded animal remains at hunting camps in the Ebo forest (proposed Ebo National Park) in Cameroon’s Littoral region, and found that people were hunting about three hornbills every month on average.

But that seems to have been an underestimate, Whytock concluded in a recent study published in Biological Conservation.

Through a survey of 240 men from 19 villages around the Ebo forest, Whytock and his colleagues estimated that people in the region were consuming an average of 29 hornbills and eight raptors per month.

The researchers worry that large birds like hornbills could be especially sensitive to hunting since these birds reproduce slowly and have slow population growth. But they’re not sure how the current levels of hunting affect Ebo forest’s birds.

“It is difficult to quantify the implications of these numbers without having population estimates for the affected species,” Whytock told Mongabay. “My guess is that hornbills and raptors especially are declining in Cameroon’s unprotected forests, but we need to do more work on this.”

However, identifying the number of birds that are killed is the first step to understanding how bushmeat hunting can affect birds like hornbills and eagles, Whytock added.

“I think birds such as crowned eagles are particularly threatened by hunting in Cameroon, both because of direct persecution and because their prey base has been depleted by hunting,” he said in a statement. “These and other similar large-bodied birds that reproduce slowly are therefore a conservation priority.”

The team also found that bird hunting in Ebo forest peaked during the dry season, from February to March, with another peak in June. This trend is concerning, Whytock said, because many birds begin to breed during the dry season in Cameroon, and their “populations are at their most vulnerable to unsustainable offtake.”

The researchers were also interested in finding out if hunting behavior varied with levels of education. However, those who hunt can be hesitant to talk about their hunting activities because of fear of prosecution for the often illegal nature of their activities.

So the researchers deployed two methods of questioning. They asked 675 people direct questions to find out how many of their meals in the past week contained meat from different wild species. They also used an indirect method of questioning called unmatched count technique that grants anonymity for people’s identities and responses, and improves the chances of getting more truthful answers to potentially incriminatory questions, such as those about hunting activities.

The results of the surveys were unexpected, Whytock said.

The indirect line of questioning revealed that better-educated hunters tended to hunt more. But direct questioning showed the opposite: better-educated hunters reported consuming fewer wild birds. This suggests that without the cover of anonymity, they were inclined to give evasive answers.

“I was surprised that the indirect questioning revealed bird hunting was higher among better educated hunters, even though we did know anecdotally that some of the most prolific hunters are relatively well-educated,” Whytock said. “The result shows the value of accounting for ‘social desirability bias’ when conducting questionnaire surveys, as people will try to hide illegal behaviour.”

Overall, hornbills, such as the black-casqued hornbill (Ceratogymna atrata) and the white-thighed hornbill (Bycanistes albotibialis), were among the most consumed birds, followed by raptors like the palm-nut vulture (Gypohierax angolensis) and a few eagles.

However, given how little is currently known about the population status of forest birds in Cameroon, there’s an urgent need to assess their populations and quantify how many are being hunted, the authors write in the study.

“Pending further assessment in other locations and in light of other threats such as habitat loss, we recommend that palm-nut vulture, black casqued hornbill and white-thighed hornbill are re-classified as Data Deficient (from Least Concern) by the International Union for the Conservation of Nature’s Red List of Threatened Species,” the researchers add.

Featured image: Black-casqued hornbill. Photo by Bernard DUPONT via Flickr (CC BY-SA 2.0).
Article published by Shreya Dasgupta
Source: https://news.mongabay.com

Citation:

• Whytock, R.C. et al. (2018). Quantifying the scale and socioeconomic drivers of bird hunting in Central African forest communities. Biological Conservation. 218 (2018) 18–25. https://doi.org/10.1016/j.biocon.2017.11.034.

The post Bushmeat hunting threatens hornbills and raptors in Cameroon’s forests, study finds appeared first on African Conservation Foundation.