Climate crisis is driving yellow hornbills to local extinction

The climate crisis threatens the local extinction of the yellow-billed Hornbill, a relative of Zazu from The Lion King. Researchers studied the impact of drought and high temperatures on breeding success of southern yellow hornbills in Kalahari Desert, between 2008 and 2019. This is the first study to examine the effects of climate change on breeding success at the population level over a longer period of time.

The climate crisis is causing extreme climate conditions to worsen, such as high temperatures and drought periods that are frequent and intense in arid areas.

These regions already have the consequences for animals who live in them. Research has shown that warming climates can affect the breeding success of many bird species. They breed earlier and for shorter periods of time.

Dr. Nicholas Pattinson of the University of Cape Town, the first author, stated that there is increasing evidence of the negative effects of high temperatures.

“For example, heat-related mass death-off events that occur over a short period of time are becoming more common, which is no doubt a threat to ecosystem function and population persistence.”

Pattinson and colleagues investigated whether climate warming has influenced the breeding success for the southern yellow-bill 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 distribution of the southern yellow-billed Hornbill is extensive. A large portion of it lives within the Kalahari Desert. Their numbers are believed to be declining.

The southern yellow-billed, monogamous species of hornbills is known for its unusual breeding and nesting strategy. They nest in cavities. The female seals her nest cavity and remains there for approximately 50 days to raise and care for chicks. The male feeds the female, and chicks through the narrow vertical slit.

This type nesting is largely protective against predation. Therefore, breeding success depends primarily upon other factors such as climate and availability of food. Yellow-billed Hornbills, for example, breed in response to rainfall. This corresponds with the hottest days. This makes it difficult to shift breeding dates from the hottest times.

Population collapse

Pattinson and his colleagues studied a population south-yellow-billed hornbills in South Africa’s Kuruman River Reserve. The study was conducted between 2008 & 2019. Only data was collected from pairs that were breeding in wooden nest boxes. They evaluated the breeding success at both broad and fine scales (long-term trends, individual breeding attempts) The team also examined climate trends for the region.

The increased maximum air temperature caused a collapse in breeding output during the monitoring period 2008-2019, according to the results.

Pattinson explained that “sub-lethal effects from high temperatures (including compromised foraging and provisioning) decreased the chances of hornbills breeching successfully or even at all” during the monitoring period.

Comparing the first three seasons, 2008-2011, to the last three, 2016-2019, the researchers found that nest success (successfully raising and hatching at least one chicken) dropped from 52% down to 17%. The average number of chicks produced for each breeding attempt fell from 1.1 up to 0.4.

No successful breeding attempts were recorded above the threshold air temperature of 35.7°C. There was a negative correlation between breeding output and days where the maximum temperature exceeded the threshold at the point when hornbills showed heat dissipation and normal breeding or nesting behavior. These effects were also present in years that were not drought-prone.

Climate crisis in rapid pace

The study shows how the climate crisis is accelerating is having adverse effects on charismatic species for alarmingly short times. Current warming predictions from the study site indicate that the threshold for successful breeding for the hornbill will be exceeded in the entire breeding season by around 2027.

Pattinson said, “Much of public perception of climate crisis’s effects is related to scenarios that were calculated for 2050 or beyond.” “Yet the consequences of the climate crisis are still being felt,” Pattinson said. Climate crisisThese are current and can manifest in our lifetimes, or even over a single decade.

“Despite not experiencing large-scale die-offs, our prediction in this research is that southern yellow-billed Hornbills could be extinct from the hottest parts their range as soon as 2027.”

“Sub-lethal consequences may result from high temperatures by causing local extinctions (i.e., no young animal joining the population) or changes to the ecosystems that we all depend.