High-tech drones are flying to the [offence / defence] of tortoises in California's Mojave desert. The [desert / dessert] tortoises in the western Mojave are under threat of being wiped [in / out] by ravens. The raven is a larger [version / verse] of the crow. Its population in the Mojave has increased [by / at] more than 700 per cent in the past 25 years and this is having a [catastrophe / catastrophic] impact on the desert tortoises. Allison Fedrick, a local conservationist, [reserved / observed] that in some places, "where there used to be 10 ravens, there are now 15,000". Ms Fedrick [notation / noted] that if nothing was done to help the tortoises, they would be [completely / complete] wiped out. Their numbers have [plumed / plummeted] by more than 90 per cent since 1990.
Technology is coming [to / up] the rescue of the tortoises. A team of biologists and drone operators has come up with a [strategic / strategy] to reduce the raven population. They are [usage / using] drones and the use of the method of "egg oiling". This [involves / revolves] flying drones up to the ravens' nests, removing fertilized eggs, [roasting / coating] them with a film of corn oil, and then replacing [it / them] . The oil blocks oxygen from entering the egg, effectively ending the life of the [embryo / embryonic] inside. Biologist Mercy Vaughn said: "If ravens [number / figure] out that their eggs are rotten, they are likely to eat them and [nest / next] someplace else." Conservationist John Griffin said oiling was justified as "part of a comprehensive approach that...[addresses / stamps] all other factors".