Introduction: The Pacific Bird Migration Route (Pacific Flyway) drought is frequent, the energy supply of migratory birds is urgent, and in the process of finding fresh water, the birds are getting weaker and weaker, and some even infected with diseases.
Written by: Jane Kay
The long-billed dowitcher, which is in the breeding season, has plump feathers, but when it stops at the migration stop, its feathers retreat a lot. Without wing feathers, they cannot fly long distances or avoid predators.
Photo by TIM FITZHARRIS, MINDEN/National Geographic
The Kern National Wildlife Refuge in California's San Joaquin Valley attracts flocks of black-crowned night herons to stop each year. The reserve once had the largest freshwater wetland in the continental United States, but now most of the water supply is supplied to farms and cities, and the wetlands are nearly dry.
Photo by The Bakersfield Californian, ZUMAPRESS.COM/CORBIS
In Pacific City, Oregon, the dead Cassin's auklet was washed ashore, and volunteers recorded their numbers and marked them. There were also such mass deaths last fall, with starvation and countless birds dying along the Pacific coast.
Photography: J. FORSYTHE/, COASST
Pintail ducks flying along the Pacific migration route are about to reach California, but what awaits them is depleted waterways and barren wetlands.
Photo by FRANS LANTING, National Geographic
Southern California's Salton Sea is also on the Pacific migration route, with pelicans being one of 400 bird species stopping each year when flocks migrate.
Photographed by PETER MCBRIDE, NATIONAL GEOGRAPHIC
Suisun City, Calif., where melting snow from California transit stations has been rushing into rivers over the past few years, with lush vegetation and insect abundance on both sides, where long-billed dowitchers flying from Alaska have been able to get plenty of food supplies.
But now that the snow fields of Sierra Nevada have disappeared, rainfall from clouds is limited, and there are few transit points left to feed the shorebirds along the Pacific migration route. Experts say the sandpiper will face a severe test after arriving in the Central Valley this month.
The Pacific Migration Route, which is more than 6,400 kilometres long, is one of the four major migration routes in North America, with up to 6 million waterfowl migrating along the route each year, featuring ducks, geese and swans, who travel long distances from the fertile habitats of Alaska, Canada or Siberia in search of warm wintering grounds. Subsequently, millions of shorebirds, songbirds and seabirds will join the vast migration procession, including the ultimate king of endurance, the arctic tern.
California's disaster this year has been so severe that wetlands have become "drylands." Many insects, fish and plants have disappeared. Due to food shortages, migratory birds that come to rest here face either death or reproductive challenges. Thousands of ducks and geese are crammed into depleted rivers and swamps, and they are suffering from cholera and botulism.
Waterfowl on pacific migration routes
California's water scarcity has a direct impact on flocks of birds along the Pacific migration route. Take a closer look at the drought at the Lower Klamath National Wildlife Refuge and the Central Valley, and you'll see what determines the success or failure of bird migration during a drought.
LAUREN E. JAMES, National Geographic employee
Source: The Nature Conservancy
Droughts and floods were part of California's natural cycle, but migratory birds have migrated along the Pacific migration route since the Pleistocene ice sheet began to melt, which has now lasted for thousands of years. Today's global warming has led to frequent droughts, and they have to adapt to human-managed water supply systems.
"The worst part is the prolonged drought. Initially, the lack of energy supplies caused by too little food will only affect the weak birds or young birds. In the event of a series of droughts, even the strongest birds are pushed to their limits," said Blake Barbaree, an ornithologist at Point Blue Conservation Science, a nonprofit research center in Petaluma, California.
Trickle
The Pacific Migration Route runs parallel to the California coastline, and the habitats along the route have lost their original appearance after four years of severe drought and decades of irrigation diversion.
Sandhill cranes and greater yellowlegs flying from Anchorage, Alaska, will soon arrive at the Kern National Wildlife Refuge, where they are only to find a trickle.
California's endemic tricolored blackbird has moved from permanent swamps to farms, but their nests are destroyed during harvest season. Half a century ago, there were millions of tricolours in the San Joaquin Valley, a plummeting of about 75 percent since 2011, and were listed on the endangered species list by the state government last December.
Mono Lake in the Eastern Sierra, the terminus of Wilson's phalaropes and tundra swans, has dropped by nearly a metre in depth over the past four years. Southern California's Salton Sea, once a haven for pelicans and several other birds, is also facing a near-drying up as the tributaries at the end of the Colorado River supply less and less water. Cassin's auklet, which hatched in the Farallon Islands, was devastated by hunger. As the water temperature rises, the krill all hide in the depths of the ocean, thus avoiding seabird catches. The carcasses of the little puffins washed up on the beach are estimated to be in the tens of thousands.
Weighing only 28 grams, the western sandpiper spends a day or two each year on its way from Alaska to the Central Valley to the "Everglades of the West" in the Klamath Basin to forage for energy. But they haven't been able to rest here since last year, says John Takekawa, a biologist who worked at the U.S. Geological Survey and now works for the National Audubon Society.
The less water there is, the fewer migratory birds
Drought has ravaged, and water reserves at the Lower Klamath National Wildlife Refuge have been depleted, forcing migratory birds to find water elsewhere. In recent years, droughts have occurred frequently, and fewer migratory birds have come to the reserve to stop. Over the past 15 years, seasonal changes have also affected the amount of water in the reserve. There are now fewer and fewer alpine snow fields, and most waterfowl choose to dock at the Lower Keramas National Wildlife National Reserve in the spring. By autumn, the reserves are largely depleted.
EMILY M. ENG, NG STAFF; VICTORIA SGARRO
Source: Department of Fisheries and Wildlife Conservation
"For migratory birds to migrate successfully, the three elements of time, location and food are indispensable," Takekawa said. "Now they have fewer and fewer stopovers."
Many scientists have speculated that when migratory birds can't find food at a stop on their way, there is a lag effect: less adaptability and lower reproduction rates, Takekawa said.
"It feels desolate"
The effects of the drought are already beginning to be felt, especially at several important transit stations. In 2012, when precipitation was abundant, Barbaree and other scientists counted the number of long-billed sandpipers in a wetland in the Klamath Basin, about 4,000. Between July and August, the long-billed sandpiper spends at least 30 days in the wetlands, foraging, resting and feathering, after which they fly to a warmer central valley.
In 2013, Indian tribes seized water rights to maintain the number of salmon downstream, and the water supply at the Lower Klamath National Wildlife Refuge was in emergency. For six weeks between August and September, the reserve was lifeless, and thousands of western sandpipers, greater white-fronted geese, snow geese and northern shovelers who would have visited at this time did not show up. "Without a drop of water, the reserve is surprisingly quiet." Barbaree said. "It's really desolate."
Long-billed sandpipers and other birds flock to the upper Klamath River in search of food. Avian botulism in birds began to spread, a disease caused by bacteria. "We watched the birds die. They can't fly or swim. The scene was unbearable. "Mallard ducks during the moulting period can't fly, and they can't escape this disaster."
Last year, drought hit the Klamath Basin again. This summer, the wildlife sanctuary near the Klamath basin will face another water crisis. Protected areas are at the bottom of the water right, and to change the status quo, legislative protection will need to wait for approval by the U.S. Congress.
Get ready for this year's migration
Sacramento National Wildlife Refuge, the heart of the Central Valley, suffered a similar situation last year, said Dan Frisk, who manages five protected areas 110 kilometers north of Sacramento. This year, there will be fewer rice farmers, lower irrigation rates, and waterfowl will be deprived of food and water.
Last year was really a "year of disasters," he said. The amount of water allocated in protected areas has been reduced by 25 per cent, and the use of water for agriculture has also been reduced by 25 per cent. Frisk needs to decide when to ask for assistance from the nearby Shasta Lake Reservoir. He is working with growers, private landowners and environmental groups to find water. "Last year, there was an inadequate food supply for birds. This year, we have advanced the irrigation period a lot and hope to make energy reserves for the upcoming flock of birds," Frisk said.
Last summer, the reserve first welcomed pintail ducks, whose tail feathers are like needles and unusually elegant. Then flocks of snow geese and gooselets arrived. The scene was spectacular. When we irrigated the aquatic weeds, the insects jumped out. The birds began their carnival feast. Frisk said.
How did the waterfowl habitat in the Central Valley disappear?
Waterfowl that winter in the Central Valley mainly rely on three main types of habitat: artificially managed wetlands with abundant water in autumn; At present, 59% of migratory bird habitats have been lost, and the food supply of waterfowl in different types of habitats has also been reduced by 33% to 50%.
Source: MARK PETRIE, DUCKS UNLIMITED
Frisk was particularly worried about the situation this year when the Sutter Bypass Wildlife Area in the Sacramento Valley was also plagued by drought and didn't rain until December.
"Migratory birds will find that there is no water here at all and continue to search for water. When they fly back to breeding areas in Alaska or Canada, they're definitely in bad physical condition. If you are weak, you will be susceptible to getting sick. Some birds may not be able to reproduce as a result. Frisk said.
Ducks in Central Park don't have access to an adequate food supply
With normal water volumes, the Central Valley habitat is able to meet the energy needs of the ducks, except in late March. In autumn, the abundance of habitats plummets, and in mid-winter the bird's food supply is interrupted, at which point duck populations peak.
The total energy requirement is calculated based on the bird's mouth and the energy demand of each bird.
Total energy supply is extrapolated based on foraging habitats and the biomass and nutrient levels in the area.
On the last day of April, josiah Clark, a first-rate bird hunter, and his companion Rob Furrow set off from the Santa Cruz Mountains and rode 210 kilometers to San Francisco Bay. They traveled along the coastal strip of the Pacific Migration Route, spotting 187 bird species along the way, setting a record for birding-on-bicycle competitions in the Northern Hemisphere. But the vegetation along the way is clearly water-deficient, less vibrant and vibrant in the spring, Clark says.
They found cinnamon teal and hummingbirds off the coast, both of which were supposed to stay inland, with the western sandpiper and black-bellied sandlin not in insect-rich flooded meadows, but on beaches covered with seaweed. "This reflects their adaptability, natural selection, survival of the fittest, and those birds that are not adaptable will eventually be eliminated by the environment."
Hope is seen in the rebuild
Although the situation is difficult now, we can still see a glimmer of hope: during the drought, rebuilding the coastal area of the broken embankment, or rebuilding the salt production plant in the tidal marsh can compensate for the flocks of birds. Last December, the San Francisco Bay waters breached the embankment, which partly alleviated the drought, causing pintail, wild ducks ( wigeons ) , Canvasback and ruddy ducks to stop here , said Joy Albertson, director of the Don Edwards National Wildlife Refuge.
"In 2015, the Marina welcomed tens of thousands of migratory birds, compared to just 20 last year," she said. "It's like a giant lake with abundant products. There are so many visiting birds that we can't even count how many there are. ”
(Translator: Strange Flowers Blossom)