Mass mortality event

In March 1904, 1.5 million migrating birds died in Minnesota and Iowa Large during a snowstorm.[5] According to The Guardian, this was the largest avian mortality event on record in the region.[5] Records of MME have been kept since the 1880s.[5] MMEs of this size—such as the 1904 mass dieoff of migratory birds—are rare and few were as big as this one. According to the records, MMEs "are always associated with extreme weather events such as a drop in temperature, snowstorm or hailstorm".[5]

In 1984, about 10,000 caribou of the George River caribou herd—one of Canada's Migratory woodland caribou herds—drowned during their bi-annual crossing of the Caniapiscau River when James Bay Hydro Project flooded the region.[6]

In 1988, the death of 20,000 harbour seals in the North Sea was found to be due to phocine distemper virus. Ten years later two bacteria were implicated in the death of 1600 New Zealand sea lions. On Marion Island in 2007, some 250–300 adult male Subantarctic fur seal died in a two-week period. It was suggested but not proven that this gender-biased mortality was caused by Streptococcus sanguinis which was carried by the house mouse, an alien species accidentally introduced in the 1800s.[7]

In the Inyo National Forest there are several records of large numbers of migrating mule deer falling to their deaths by slipping on ice while crossing mountain passes. This has occurred when heavy snowfalls have persisted until fall, and have been turned to ice by frequent thawing and freezing.[8] In 2003 a rain-on-snow event encased the ground in ice, resulting in the starvation of 20,000 muskoxen on Banks Island in the Canadian Arctic.[9][10]

In the final week of December, 83,000 dead and dying drum fish washed up along a 20-mile stretch of the Arkansas River, about 100 miles west of Beebe, Arkansas. The cause was speculated to be disease while full test results were expected after one month.[11]

Shortly before midnight on New Year's Eve between 3,000 and 5,000 red-winged blackbirds fell from the sky in Beebe. Most were dead on the ground but some were living but dazed. Laboratory tests have been performed and the Arkansas Livestock and Poultry Commission, the National Wildlife Health Center in Madison, Wisconsin as well as the University of Georgia's wildlife disease study group have procured specimens of the dead birds. In addition to the blackbirds a few grackles and starlings also fell from the sky in the same incident. A test report from the state poultry lab concluded that the birds had died from blunt trauma. An unlicensed fireworks discharge was the likely cause.[12][13]

The months-long Deepwater Horizon oil spill that began in April 2010 in the coastal waters of Gulf of Mexico, resulted in about 600, 000 to 800, 000 bird mortalities.[14] Dolphins and other marine life continued to die in record numbers into 2013.[15]

The Beebe bird deaths were repeated again on New Year's Eve of the following year, 2011, with the reported number of dead birds being 5,000.[16]

On 3 January 2011, more than five hundred starlings, red-winged blackbirds and sparrows fell dead in Pointe Coupee Parish, Louisiana, US.[17]

On 5 January, "hundreds" of dead turtle doves were found at Faenza, Italy.[18] According to Italian news agencies, a huge number of the birds were found to have blue stains on their beaks that could be caused by paint or hypoxia.[19]

Over the weekend of 8–9 January, "over a hundred" dead birds were found clustered together on a California Highway, while "thousands of dead gizzard shad" (a species of fish) turned up in the harbors of Chicago.[20][21]

Between 28 December 2010 and 3 January 2011, 100 tons of dead fish washed ashore on the Brazilian coast.[22]

On 3 January, an estimated two million dead fish were found floating in the Chesapeake Bay in Maryland, US.[23]

On 7 March, millions of small fish, including anchovies, sardines, and mackerel were found dead in the area of King Harbor at Redondo Beach, California, U.S. An investigation by the authorities within the area concluded that the sardines had become trapped within the harbor, depleted the ambient oxygen, which resulted in the deaths. The authorities stated that the event was "unusual, but not unexplainable."[24]

On 14 January, approximately two hundred cows were found dead in a field in Stockton, Wisconsin. The owner of the cattle has told deputies that he suspected the animals died of infectious bovine rhinotracheitis (IBR), or bovine virus diarrhea (BVD). The authorities in Wisconsin sent samples from the carcasses to labs in Madison, to determine cause of death.[25]

In 2015, some 200,000 saiga antelope died within a period of one week in a 20 km² area of the Betpak-Dala desert region of Kazakhstan. They had gathered in large groups for their annual calving. It was determined that warm and humid temperatures had caused Pasteurella multocida, a bacteria that normally live harmlessly in their tonsils, to cross into their bloodstream and cause Hemorrhagic septicemia. This event wiped out 60% of the population of this critically endangered species. Mass mortality events are not uncommon for saiga. In 1981, 70,000 died, in 1988 there were 200,000 deaths and more recently in 2010 12,000 died.[26][2]

Starting in the summer of 2015, through the spring of 2016, about 62,000 dead or dying birds were found on Pacific Ocean beaches from California to Alaska. Some researchers believe that as many as one million common murres, could have died in the massive die-off.[27]

In May 2016, the Los Angeles Times reported that millions of fish had washed ashore along the coast of north-central Vietnam stretching over 125 miles of beaches.[28] This included the shoreline in the Phu Loc district, in Thua Thien Hue province.[28] Possible causes included industrial pollution as government researchers had found that "toxic elements" had caused the "unprecedented" fish mortalities.[28] Concerns were raised about a "massive Taiwanese-owned steel plant" that was allegedly "pumping untreated wastewater" into the ocean.[28]

In 2019, an extreme heatwave with temperatures exceeding 42 °C in central Australia, lead to the death of approximately 40 brumbies.[29]

In 2014, and 2018, heatwaves in Australia have killed significant portion of bat population.

In August 2020, observers reported that hundreds of dead migratory birds heading south for the winter had been found at the White Sands Missile Range in New Mexico.[5] By September the number had increased to tens of thousands, and the die-off had spread across at least New Mexico, Colorado, Texas, Arizona and farther north into Nebraska.[5][30] The birds were migrating species, including "owls, warblers, hummingbirds, loons, flycatchers, and woodpeckers".[30] The seemed to be emaciated as if they had just kept on flying until they dropped.[30] Possible cause of deaths include climate crisis and wildfires, according to The Guardian.[5]