Climate crisis drives yellow-billed hornbill to local extinction


Southern Yellow-billed Hornbill at the study site. Credit: Nicholas Pattinson

The yellow-billed hornbill, cousin of fan-favorite Zazu from The Lion King, is facing local extinction due to the climate crisis. Researchers studied the effects of high air temperature and drought on the breeding success of southern yellow-billed hornbills in the Kalahari Desert between 2008 and 2019. This study is one of the first to investigate the impact of the climate crisis on reproductive success at the population level. on a longer time scale.

The climate crisis is aggravating the harsh conditions of extreme climates, such as high temperatures and the frequency and intensity of droughts associated with arid regions.

The animals that inhabit these regions are already suffering the consequences. For example, previous research has shown that the breeding success of several bird species is affected by global warming. They reproduce earlier and for a shorter duration.

“There is growing evidence of the negative effects of high temperatures on the behavior, physiology, reproduction and survival of various species of birds, mammals and reptiles around the world,” said the first author, Dr Nicholas Pattinson, University of Cape Town. City.

“For example, heat-related mass mortality events over a period of days are increasingly being recorded, which undoubtedly poses a threat to population persistence and ecosystem function.”

Pattinson and his colleagues investigated whether rapid global warming influenced the breeding success of the southern yellow-billed hornbill, an arid zone bird, over a 10-year period. The study was published in Frontiers in Ecology and Evolution.

The yellow-billed hornbill

The southern yellow-billed hornbill’s distribution includes most of southern Africa, much of it being in the Kalahari Desert. Their population is believed to be declining.

Known for its particular breeding and nesting strategy, the southern yellow-billed hornbill is a socially monogamous species. They are cavity nesters; the female seals herself in the nest cavity and stays there for an average of 50 days to brood and care for the chicks. The only opening is a narrow vertical slit, through which the male feeds the female and the chicks.

This type of nesting largely protects against predation, which means that breeding success mainly depends on other factors such as climate and food availability. For example, yellow-billed hornbills initiate breeding in response to rainfall, which corresponds to the hottest days of the year. It is therefore difficult for them to move breeding dates outside of the hottest periods.

Demographic collapse

Pattinson and his team studied a population of southern yellow-billed hornbills in the Kuruman River Reserve in the southern Kalahari Desert, South Africa, between 2008 and 2019. Data was exclusively collected from pairs breeding in wooden nest boxes. They examined breeding success at both broad and fine scales (long-term trends and individual breeding attempts, respectively). The team also analyzed climate trends in the region.

The results showed that livestock production plummeted during the monitoring period (2008-2019) due to the increase in maximum air temperature.

“During the monitoring period, the sublethal effects of high temperatures (including compromised foraging, provisioning and maintenance of body mass) reduced the chances of hornbills breeding successfully or even breeding at all. “, explained Pattinson.

By comparing the first three seasons (between 2008 and 2011) to the last three (between 2016 and 2019), the researchers found that the average percentage of occupied nest boxes fell from 52% to 12%, nest success (rearing and fledging less than one chick) decreased from 58% to 17%, and the average number of chicks produced per breeding attempt decreased from 1.1 to 0.4.

No successful breeding attempts have been recorded above the air temperature threshold of 35.7°C. Breeding output was negatively correlated with increasing the number of days that maximum air temperature exceeded the threshold at which hornbills displayed heat dissipation behavior and normal breeding and nesting behavior. These effects were present even in drought-free years.

Rapid climate crisis

The study shows that the rapid pace at which the climate crisis is unfolding is having severe negative effects on charismatic species over alarming time periods. Current warming predictions at the study site show that the hornbill’s threshold for successful breeding will be exceeded throughout the breeding season of approximately 2027.

“Much of the public perception of the effects of the climate crisis is tied to calculated scenarios for 2050 and beyond,” Pattinson continued. “Yet the effects of the climate crisis are present and can manifest not just within our lifetime, but even over a single decade.”

“Despite the absence of large mass mortality events, our prediction in this study is that southern yellow-billed hornbills could disappear from the warmer parts of their range as early as 2027.”

“The sub-lethal consequences of high temperatures can lead to local extinctions by leading to recruitment failure (i.e. no young animals joining the population) and changes to the ecosystems on which we all depend.”

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More information:
Frontiers in Ecology and Evolution (2022). DOI: 10.3389/fevo.2022.842264, … evo.2022.842264/full

Climate crisis drives yellow-billed hornbill to local extinction (2022, May 19)
retrieved 19 May 2022

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