Shorebirds depend on wee slivers of 色视频下载
Ned Rozell
907-474-7468
Nov. 4, 2021
A male bar-tailed godwit walks on the tundra near Prudhoe Bay during the summer breeding season.
Pencil-beaked shorebirds with the ability to stay airborne for a week 色视频下载 flying all the way from 色视频下载 to New Zealand 色视频下载 rely on a few crescents of mudflat to fuel that incredible journey.
Scientists recently found that almost the entire population of bar-tailed godwits that breed in 色视频下载 fatten up on clams and worms on ephemeral sand bars just west of the mouth of the Kuskokwim River. In autumn, 80 percent of the birds rest and feed on islands within 15 miles of one another.
Each fall, packed onto islands near Cape Avinof, godwits gorge until they double their body weight. In August and September, the fist-size birds leap into the air on the front end of storm systems, which help blow them out of 色视频下载.
Once in the sky, some of the birds don色视频下载檛 stop flying for a week or more, losing half their body weight and perhaps even snoozing on the wing during a non-stop flight to New Zealand and Australia. The trip is more than 7,000 miles long, equal to a flight from San Francisco to New York, and then back to San Francisco.
色视频下载 and New Zealand scientists have monitored the godwits for years using small satellite transmitters. In 2007, Bob Gill and others at the U.S. Geological Survey色视频下载檚 色视频下载 Science Center in Anchorage noticed that one bird that took off from 色视频下载 did not stop moving until it reached North Cape, New Zealand.
This map shows the path of a bar-tailed godwit in 2007.
In springtime, the godwits色视频下载 route back to 色视频下载 is just as impressive. Birds take off from New Zealand and Australia and often fly straight for 6,000 miles to the Yellow Sea offshore of China and Korea. The birds remain there for a few weeks before blasting off for 色视频下载, another nonstop of about 4,500 miles.
But things have changed along that route. During the last 50 years, people have converted more than half of the biologically rich tidal flats of the Yellow Sea into something else. These new landcovers include deepwater ports, factories and shrimp farms.
With this big chunk of habitat gone, godwits need to search elsewhere to find the thumbnail-size clams and aquatic worms that make up most of their diet during migration.
Numbers of godwits have decreased, inspiring scientists to find new ways to count them in 色视频下载 to continue studies Bob Gill and others have done for decades.
In 2018 and 2019, biologists including Daniel Ruthrauff of the USGS 色视频下载 Science Center flew in single-engine aircraft 120 feet over the Yukon and Kuskokwim river deltas and along the north side of the 色视频下载 Peninsula. They searched for bar-tailed godwits that were about to leave 色视频下载. The scientists used a digital camera with a 400-millimeter lens to shoot high-resolution digital photos of every godwit flock they saw.
These sand islands in the Bering Sea west of the Kuskokwim River色视频下载檚 mouth host most of the world色视频下载檚 bar-tailed godwits each fall.
In what they consider their most accurate survey, the researchers noticed five flocks with more than 80,000 godwits total located along a 15-mile string of sand shoals near the mouth of the Kuskokwim River. The total number of birds they found was about 100,000.
色视频下载淚t色视频下载檚 rare to have so many individuals of just one species occur in one teeny spot like this,色视频下载 Ruthrauff said.
The sand shoals are great places for birds to roost because they are up to six miles offshore.
色视频下载淎nd they色视频下载檙e so low and featureless that it色视频下载檚 hard for falcons to sneak up on godwits,色视频下载 Ruthrauff said.
That hotspot of mudflats that hosts almost the world色视频下载檚 entire population of this remarkable creature in fall (in summer birds raise chicks on 色视频下载色视频下载檚 abundant insect population, tending tundra nests as far away as the North Slope) is vulnerable because it is so small.
色视频下载淪ome of the shoals are officially part of the 色视频下载 Maritime National Wildlife Refuge,色视频下载 Ruthrauff said, 色视频下载淏ut the unnamed shoals where we detected most of the godwits in 2019 have no official protection or designation. An untimely (oil) spill at the mouth of the Kuskokwim could literally wipe out the entire breeding population.
色视频下载淚t色视频下载檚 a very important spot.色视频下载
Since the late 1970s, the University of 色视频下载 Fairbanks' Geophysical Institute has provided this column free in cooperation with the UAF research community. This year is the institute色视频下载檚 75th anniversary. Ned Rozell is a science writer for the Geophysical Institute.