Workers in Butte, Montana, have been trying for years to save birds by stopping them settling on a mile-long toxic lake.
If any birds settle at former copper mine for more than a few hours, the acidic conditions effectively disintegrate them from the inside out. The deadly water is the result of sulphuric acid and heavy metals being released from rocks in the pit, following the closure of the site and shutting down of its pumps in 1982, 27 years after the site started operations. Now it is a tourist attraction, with a gift shop and a fee to use a viewing platform.
Western Grebe is one of many species which must constantly be driven away from the toxic water (Alexander Viduetsky).
Mark Mariano works as a Waterfowl Protection Specialist for Rampart Solutions, tasked by the mining company with protecting migrating birds visiting the water at Berkeley Pit. He said: "I wake up without an alarm every morning and I'm happy to go literally rescue birds. And most days you go home with your head held high."
The site is frequently visited by migrating birds in spring and autumn, with Butte sitting in the overlap zone of the Pacific and Central Flyways of North America. After 60,000 Snow Geese settled on the lake in 2016, resulting in the deaths of 3,000 of the birds, ornithologists were employed to assess bird movements at the pit. A smaller scale event where at least 342 geese died occurred in 1995, with disputed post-mortem results.
Snow Geese died in their thousands at Berkeley Pit in the autumn of 2016 (Derek Moore).
Since then, a multi-million dollar range of high-tech solutions have been employed to safeguard the migrating birds visiting the site, as different methods must be used to drive away the various species which drop in.
Four sound devices called "wailers" periodically play loud noises, even at night to disuade nocturnal migrants from settling. During the day, propane cannons fire at regular intervals. If this first line of 'defence' doesn't work, rifle shots are used in combination with custom-built drones with 3D-printed elements, and lasers.
The latest addition to the toolkit of the Waterfowl Protection Specialist is a remote-controlled, 3D-printed boat known as the 'WaterDog' which drives birds off the water. A rifle shot is usually enough to drive them off the site once the birds are in the air.
Bird protection measures conducted from the 'bird shack', the hut which used to direct trucks rather than bird-saving boats, has certainly become more sophisticated in recent years. Originally, rifle shots were the only tool at the disposal of the bird guardians.
Mr Mariono is a self-confessed wildfowl fanatic, but also enjoys hunting ducks and geese. He said: "I'm a big waterfowl hunter as well and what that has taught me about protecting waterfowl at the pit is just priceless."
A €19 million water treatment facility was completed in 2019 to make water from the pit safe before it contaminated local groundwater.