• Choose the missing prepositions from the drop-down menus below.
  • Click the button at the bottom to check your answers.
  • Press the "refresh" button on your browser to play again.

   by      by      by      from      in      in      of      of      of      of      of      of      of      on      out      out      under      up      up      with  
High-tech drones are flying to the defence tortoises in California's Mojave Desert. The desert tortoises the western Mojave are threat of being wiped out ravens. The raven is a larger version the crow. Its population in the Mojave has increased more than 700 per cent in the past 25 years and this is having a catastrophic impact the desert tortoises. Allison Fedrick, a local conservationist, observed that some places, "where there used to be 10 ravens, there are now 15,000". Ms Fedrick noted that if nothing was done to help the tortoises, they would be completely wiped . Their numbers have plummeted more than 90 per cent since 1990.

Technology is coming to the rescue the tortoises. A team biologists and drone operators has come with a strategy to reduce the raven population. They are using drones and the use the method of "egg oiling". This involves flying drones to the ravens' nests, removing fertilized eggs, coating them a film of corn oil, and then replacing them. The oil blocks oxygen entering the egg, effectively ending the life the embryo inside. Biologist Mercy Vaughn said: "If ravens figure that their eggs are rotten, they are likely to eat them and nest someplace else." Conservationist John Griffin said oiling was justified as "part a comprehensive approach that...addresses all other factors".

Back to the ravens lesson.

Share this lesson

More Free Sites by Sean Banville

Online Activities