Weekly round-up: May 23

European common swifts winter in central and southern Africa before migrating north in spring

Swifts are even more swift than scientists thought, with new tracking technology showing the migrating birds cover an average of 570 kilometres (354 miles) per day, 70 kilometres more than previously estimated.

New tracking data also recorded one individual travelling 830 kilometres (516 miles) per day over nine days on the journey between Africa and northern Europe.

The team behind the study, from Lund University, also found that migration was faster and straighter in the spring, while their ability to fly and simultaneously forage for insects is key to a rapid passage – as is their mysterious ability to forecast wind speeds for the journey ahead.

Co-author Susanne Åkesson from Lund University said: “The swifts seem to achieve these high speeds over substantial distances – on average about 8,000 kilometers one way – in spring by using a mixed migration strategy, with fueling at stopover and a fly-and-forage strategy, meaning they feed and fuel a bit each day.

“The strategy will substantially reduce the cost of transport since they do not need to carry so much fuel, which will increase the realized speed of migration.”

Regarding their impressive forecasting abilities, Åkesson suggested they may rely on air pressure from passing weather systems. 

“This means they do not react directly to local winds but to what they expect to find along the route ahead during the next few days.”

However they do it, by selecting their departure date based on likely weather ahead, swifts can gain an extra 20 per cent support from advantageous tailwinds on their journey north in the spring versus the return south in autumn.
Publication iScience

Parrots are commonly sold in the illegal wildlife trade

More attractive or “pretty” parrots are at higher risk of being snatched from the wild and sold on as pets in Indonesia’s illegal wildlife trade, according to a new study.

A team from the Australian National University found several key indicators in the targeting of particular species, including its colour, brightness, size and ability to mimic sounds. The ease with which they could be exported, often mis-labeled as captive-bred, was also a factor.

“High demand for parrots as pets, and their removal from the wild for the trade, have significantly contributed to their severe decline worldwide,” said co-author Professor Rob Heinsohn. “One third of the nearly 400 parrot species are threatened by extinction today. 

“But while the trade is vast, not every parrot species is at equal risk of being traded.”

The team, who analysed two decades worth of data on the illegal parrot trade in southeast Asia, highlighted the need for more efficient law enforcement and prevention strategies, such as nest protection and education.
Publication Biological Conservation

A population of white sharks which spend half the year off the central Californian coast is holding steady at around 300 individuals – but shows some signs of growth.

Between 2011 and 2018 a team led by Oregon State University identified hundreds of adult and subadult white sharks – which are not fully mature but prey on marine mammals. The results showed a slight rise in numbers of adult sharks, while subadult numbers remained steady. 

The presence of a healthy white shark population bodes well for surrounding ecosystems.

“Robust populations of large predators are critical to the health of our coastal marine ecosystem,” said co-author Taylor Chapple, a marine ecologist at Oregon State who specialises in the study of marine predators. “So our findings are not only good news for white sharks, but also for the rich waters just off our shores here.”

The team collected data on the population over 2,500 hours of observation at three sites along the coast.

“Every white shark has a unique dorsal fin. It’s like a fingerprint or a barcode. It’s very distinct,” Chapple said. “We were able to identify every individual over that eight-year period. With that information, we were able to estimate the population as a whole and establish a trend over time.”

White shark numbers worldwide are decreasing due to bycatch and poaching for their fins and teeth, leading them to be classed as Vulnerable to extinction by the IUCN.
Publication Biological Conservation

Genetic differences have been found between great tits living in urban and rural areas

Great tits living in the city are genetically different to individuals of the same species living in the countryside.

A study by Lund University analysed populations of great tits in cities across Europe and compared them with those living in nearby rural areas. They found regardless of the city, genes linked to cognition and behaviours regulated by serotonin, such as aggression and circadian rhythms, were selected for and passed down generations.

“This indicates that these behaviours, and cognition, are very important in order to live in urban environments with a lot of stress in the form of noise pollution, lights at night, air pollution and constant proximity to people,” said Lund University senior lecturer Caroline Isaksson, who led the study together with her former doctoral student Pablo Salmon.
Publication Nature Communications

Human-wildlife conflict is a significant threat to both parties, but researchers have identified the areas most at risk for interactions between people and elephants and lions across Africa – and propose the construction of high-quality fences will be a worthwhile investment.

“We found that 82 per cent of sites containing lions and elephants in Africa are adjacent to areas with considerable human pressure,” said lead author Enrico Di Minin, associate professor at the University of Helsinki

“Areas at severe risk of conflict [defined as areas with high densities of humans, crops, and cattle] comprise nine per cent of the perimeter of these species’ ranges and are found in 18 countries hosting, respectively, approximately 74 per cent and 41 per cent of African lion and elephant populations.”

Interactions between locals and wildlife result in hundreds of human deaths per year, while retaliatory killings of lions and elephants in response to livestock losses and trampled crops respectively threaten each species.

The team proposed the effectiveness of high-quality mitigation fences would offer a sound return on investment, but noted they are expensive to build and maintain. They also highlighted the importance of preventing further habitat fragmentation, a significant threat to numerous species across the continent.
Publication Nature Communications

Endangered reptiles threatened by last year’s oil spill off the coast of Mauritius have successfully bred in a Jersey zoo.

Bojer’s skink, Bouton’s skink and the lesser night gecko were among the myriad species threatened when a Japanese tanker ran aground in July, spilling 1,000 tonnes of oil across part of the island’s pristine coast. The Durrell Wildlife Trust deployed a team to rescue the reptiles, in some cases having only an hour on individual islets to track them down.

So far 52 juveniles Bojer’s skinks and 26 lesser night geckos have been born. The Bouton’s skinks have yet to produce any fertile eggs. However, the team is aiming to raise 180 individuals of each species, a so-called “ark” population, to preserve genetic diversity before returning them to the islands.
Source The Guardian

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