Weekly round-up: April 11

The house sparrow is Britain’s most commonly-spotted bird

A record 1,019,802 people across the UK took part in the RSPB’s Big Garden Birdwatch in January, more than double the number 12 months earlier – recording over 17 million birds across the nation.

The house sparrow remained the most-sighted species for the 18th year running, with the blue tit in second and starling in third, a reversal of last year’s results. There were no new entries to the top ten, with the blackbird, woodpigeon, robin, great tit, goldfinch, magpie and long-tailed tit filling the places.

However, while the boom in participation resulted in a bumper number of sightings, the RSPB stressed that bird numbers are falling – a Defra study last year recorded an 11 per cent decrease in bird populations between 1970 and 2019, while the State of Nature 2019 report recorded a drop of 44 million breeding birds between 1967 and 2009.
Source RSPB

Species endemic to islands and mountains are most at risk from climate change, with a 3C rise in global temperatures predicted to threaten all species in certain areas with extinction, according to a new study.

Assessing 273 biodiversity-rich regions, researchers predicted the negative impacts from climate change were three to ten times greater for endemic species compared with those native or introduced to a region.

Speaking to the i, co-author Dr Mariana Vale said: “We already expected the endemics to be more vulnerable, precisely because they are restricted to a specific geographical region. What is interesting in our study is that we quantified how much they will be affected. What we show is that a small increase in temperature [greatly] increases the threat to biodiversity. We knew that endemic species would be more susceptible, but we didn’t expect it to be to such a degree.”

The team predicted 100 per cent of endemic plant and animal island species would be at risk of extinction, and 84 per cent of endemic mountain species. 

However, a study focusing solely on mammals published this week highlighted the need for more data to better understand how they will respond to climate change.

Almost a quarter of all mammalian species are at risk of extinction, with climate change a significant factor in reproduction and survival rates. Both must be taken into consideration when assessing populations, but in a search of 5,728 terrestrial mammal species, the team found only 106 studies considering both.

Lead author Dr Maria Paniw, from the University of Zurich, said: “Researchers often publish results on the effects of climate on survival or on reproduction – and not both. But only in rare cases does a climatic variable, say, temperature, consistently negatively or positively affect all studied rates of survival and reproduction.” 

For example,while higher temperatures could decrease the number of offspring, if the offspring have a better chance of survival because of less competition, the population size may not be affected. However, if higher temperatures decrease both reproduction and survival, a study of only one of these could underestimate the effects on a population.

In the oceans, warming temperatures are already causing significant population relocation, with a decline in species diversity around the equator.

Researchers examined the distribution of 48,661 marine species since 1955, showing that species richness levels off or declines at latitudes with annual temperatures exceeding 20C, resulting in a more pronounced drop in the range of biodiversity at the equator.

Co-author David Schoeman, a professor at the University of the Sunshine Coast, said: “Although the number of benthic species – organisms attached to the seafloor, like corals, oysters and seaweeds – has not actually declined at the equator, the number of free-swimming pelagic species, like fish, dropped significantly between 1965 and 1985, and had dropped further by 2010.

“The decrease in numbers of species at the equator doesn’t mean that sea life is becoming extinct from the planet. Instead, it means extirpation, or local loss of those species. 

“The ‘missing’ tropical species are likely following their thermal habitat as subtropical waters warm, exactly as we predicted in a paper published in 2016 and as demonstrated in fossil records from 140,000 years ago when global temperatures were as hot as they are now. 

“This results in a process called tropicalisation, where species with warm-water affinities become more common, and those with cool-water affinities become less common.”
Publication Biological Conservation/Journal of Animal Ecology/Proceedings of the National Academy of Sciences

Gorilla’s chest-beating behaviour can help communicate their size and strength (Scientific Reports)

The dramatic display of a gorilla chest beat can be heard from more than a kilometre away, and has long been thought to attract mates and intimidate rivals – a team of researchers has now shown the iconic sound accurately reflects the animal’s size, a key attribute in both.

Larger males emit beats with lower peak frequencies than smaller ones, helping rivals decide whether to engage or retreat, while females may also factor the information into their choice of mate.

Co-author Eric Ndayishimiye, research assistant with the Dian Fossey Gorilla Fund, said: “Conducting this study was challenging because the chest beats are relatively short in duration and the we needed to be in the right place at the right time to obtain the sound recordings, as well as staying clear from these large powerful animals.”

The recordings showed significant variation in the number of beats and duration, suggesting they may also serve as individuals signatures, but further research is required.
Publication Scientific Reports

Officials in Ghana are investigating what caused the death of hundreds of fish and dolphins that have washed up along the coast over the past ten days.

The fishery commission reported it had taken samples of the animals and waters, but the cause remained unknown – the authorities have also asked people who may have consumed the fish to get in contact as part of the investigations.

In Nzema East, around 200km west of Accra, around 200 dolphins washed up on shore – 30 were rescued alive and returned to the sea.
Source The Guardian/CGTN

Read How ropeless fishing gear could help save the North Atlantic right whale 

Watch As sea ice melts earlier each year, hungry polar bears have started to eat seabird eggs – but they’re not very good at it

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