January 28, 2020
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    Climate change is causing birds to shrink, study suggests

    December 05, 2019

    The researchers analysed 52 different species of migratory birds As the climate warms, birds are shrinking and their wingspans are growing, according to a new study.Researchers analysed 70,716 specimens from 52 North American migratory bird species collected over 40 years.The birds had died after colliding with buildings in Chicago, Illinois.The authors say the study is the largest of its kind and that the findings are important to understanding how animals will adapt to climate change."We found almost all of the species were getting smaller," said lead author Brian Weeks, an assistant professor at the school for environment and sustainability at the University of Michigan."The species were pretty diverse, but responding in a similar way," he said. "The consistency was shocking."He said studies of animal responses to climate change often focus on shifts in geographical range or timing of life events, like migration and birth. But this study suggests body morphology is a crucial third aspect.
    All measurements were taken by one researcher, Dave Willard, over the 40-year period"That's one major implication," he said. "It's hard to understand how species will adapt without taking all three of these things into consideration."The findings showed that from 1978 to 2016, the length of the birds' lower leg bone - a common measure of body size - shortened by 2.4%. Over the same time, the wings lengthened by 1.3%.The evidence suggests warming temperatures caused the decrease in body size, which in turn caused the increase in wing length."Migration is an incredibly taxing thing they do," Mr Weeks said, explaining that the smaller body size means less energy available for the birds to complete their long journeys.He says the birds most likely to survive migration were the ones with longer wingspans that compensated for their smaller bodies.The scientists aren't exactly sure why warmer temperatures cause birds to shrink. One theory is that smaller animals are better at cooling off, losing body heat more quickly due to their larger surface-area-to-volume ratios.Mr Weeks said the body of specimens was the result of a "herculean effort" by Dave Willard, co-author of the study and an ornithologist at the Field Museum in Chicago.
    Dave Willard stands with the Field Museum's vast collection of bird specimens in 1999
    In 1978, he started walking around buildings in the mornings during spring and fall migration to collect birds that had collided with buildings.Birds usually migrate at night and are attracted to the artificial light from buildings, causing fatal collisions with windows. Hundreds of millions of birds are estimated to be killed in building collisions each year."He didn't have this study in mind," Mr Weeks said. "He just thought it could be useful in the future."Over the years, many volunteers and scientists contributed to the collection efforts.Mr Willard measured all 70,716 specimens himself using the same methods, "the gold standard" for this type of data, according to Mr Weeks.The paper was published in the journal Ecology Letters.
    It builds on a growing body of evidence that suggests animals are shrinking as the climate warms.In 2014, researchers found that alpine goats appeared to be shrinking due to warming temperatures. The same year, another study found salamanders had shrunk rapidly in response to climate change.

    Plastic pollution has killed half a million hermit crabs, study says
    Researchers said they found 526 hermit crabs had been trapped inside one container An estimated 570,000 hermit crabs have been killed after being trapped in plastic debris, a new study has said.The researchers said piles of plastic on beaches create physical barriers and "deadly traps" for the crabs.The study looked at strawberry hermit crab populations on two remote tropical island locations.The scientists say more research is needed into how plastic pollution is affecting wildlife populations worldwide, especially on land."The potential for plastics on beaches and in other terrestrial ecosystems to cause harm is under-acknowledged," said co-author Alex Bond, a senior curator in the department of life sciences at the Natural History Museum in London.He says plastic in the ocean entangles and is ingested by wildlife, but on land it acts as a trap and a barrier to species going about their daily lives.The researchers surveyed sites on the Cocos (Keeling) Islands in the Indian Ocean and Henderson Island in the South Pacific. They say both locations are littered with millions of pieces of plastic.They say crabs had crawled into plastic containers and were unable to get out, eventually dying. The containers had openings that allowed the crabs to enter, but were positioned with the opening facing an upward angle, making it so the crabs would have difficulty crawling back out.
    A bottle on a littered beach with shells from hermit crabs that were trapped inside
    The researchers counted how many hazardous containers there were and how many contained trapped crabs, and extrapolated their findings to estimate totals for the islands."These results are shocking but perhaps not surprising," said lead researcher Jennifer Lavers from the institute for marine and Antarctic studies at the University of Tasmania in Australia."It is inevitable that these creatures will interact with and be affected by plastic pollution," she said.The problem is worsened by the fact that hermit crabs don't have a shell of their own. As they grow, they need to move into larger shells. When one crab dies, it emits a smell that tells another crab a new shell is available.Meaning, "the very mechanism that evolved to ensure hermit crabs could replace their shells, has resulted in a lethal lure," according to the paper.In one container, researchers found 526 hermit crabs. They also found containers with both dead and living crabs, the latter presumably drawn in by the former.The authors say hermit crabs play an important role in the ecosystem. They fertilise and aerate soil, and disperse seeds. They also play a role in tourism - an important source of employment on the islands - by giving visitors a chance to observe native wildlife.Though the study was conducted on remote islands, Mr Bond says plastic pollution is global, and that this is likely to be an issue anywhere hermit crabs live alongside debris.

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