UPDATE 7:30 PM SATURDAY:
Aliy Zirkle snatched the Iditarod lead away from Martin Buser on Saturday evening.
Zirkle, last year's runnerup, was the seventh musher to reach Kaltag but the first to leave. She dropped two dogs during her brief 19-minute stay in Kaltag before heading to the Norton Sound coast with a team of 11 dogs.
Buser has been in Kaltag for about four hours. He got there at 2:24 p.m. By 5 p.m., five others had joined him -- Mitch Seavey (3:37 p.m. arrival), Aaron Burmeister (4:07), Jake Berkowitz (4:09), Jessie Royer (4:24 p.m.), Joar Leifseth Ulsom (4:42 p.m.).
Zirkle arrived at 5:52 p.m.
UPDATE 5 PM SATURDAY:
Martin Buser's five-hour lead in the Iditarod shrank to 73 minutes Saturday afternoon.
Buser was the first musher to reach Kaltag after a brutal trip down a wind-swept Yukon River trail.
He had the checkpoint to himself for 73 minutes before Mitch Seavey showed up. Half an hour later, Aaron Burmeister and Jake Berkowitz were there too.
Buser's lead is vanishing quickly as teams behind him make better speed, possibly because their dogs have conserved energy while Buser's used up a bunch on their dash to Rohn to begin the race a week ago.
Buser broke trail on the 50-mile run from Eagle Island to Kaltag, making the trip in 11 hours, 42 minutes.
His pursuers were significantly faster.
Seavey made the trip in 9:17 and arrived at 3:37 p.m. Burmeister arrived at 4:07 after a run that took him 9:23, and Berkowitz arrived at 4:09 p.m. after a run of 9:21.
UPDATE 3:10 PM SATURDAY:
After breaking a wind-swept trail littered with overflow for 140 miles, Martin Buser pulled his team off the frozen Yukon River on Saturday afternoon with a lead that seems to be heading in the wrong direction.
“It felt like I was going backwards,” said Buser, sporting a white wind breaker.
At 2:24 p.m., Rosie Fletcher and Quick led Buser’s team of 11 dogs into the village of Kaltag, a junction where the Yukon River bends east upstream and mushers head west toward the Bering Sea. Rosie and Quick are trying to help their 54-year-old master complete a mission to match Rick Swenson’s five Iditarod championships. But getting that elusive fifth trophy won’t be another walk in the dog yard.
A chase pack of at least five mushers are close enough to suggest they are beginning to reel in the musher from Big Lake. According to the GPS trackers, a pack led by Mitch Seavey will soon pull into Kaltag and join Buser and his team.
Seavey is traveling with Aliy Zirkle of Two Rivers, Aaron Burmeister of Nome, Jessie Royer of Montana, Jake Berkowitz of Big Lake and Joar leifseth Ulsom of Norway.
Behind them is a huge pack that left Eagle Island all within the span of four hours on Saturday morning. This pack is led by Nicolas Petit of Girdwood, followed by Sonny Lindner of Fairbanks, Lance Mackey of Fairbanks, Ray Redington Jr. of Wasilla, Dallas Seavey of Willow, DeeDee Jonrowe of Willow, Jeff King of Denali Park, Paul Gebhardt of Kasilof, and Ken Anderson of Two Rivers.
Buser, who called the trail “horrible,” made the slow, lonely 60-mile run from the previous checkpoint of Eagle Island to Kaltag in 11 hours, 43 minutes. The 60-mile run before that from Grayling to Eagle Island, Buser completed in 9:03, nearly two hours slower than Dallas Seavey (7:04).
Buser said he has no idea where the other mushers are. He wasn’t able to see where other mushers are from Eagle Island, so he said he’s racing blind.
Asked if he saw headlamps behind him, Buser said he “didn’t look back.”
As far as his strategy is working out, Buser said his dogs are young, mostly two and a half years old. If the Willow-to-Rohn plan doesn’t end up working out, he said he will at least have an older, more experienced team to race for that fifth title next year.
UPDATE 12:00 PM SATURDAY:
Overflow and spring-like weather weren’t the only concerns mushers faced Saturday morning as they headed up the Yukon River.
Reports surfaced on Friday that poor flying weather were going to keep drop bags from getting into the checkpoint of Eagle Island. News of this apparently spread to Grayling, which sent mushers, including race leader Martin Buser, scrambling to find extra pounds of kibble and packing it into their sleds just in case rumors were true.
Iditarod volunteers upriver in Kaltag were scrambling themselves Friday evening, said race judge Rhodi Davidson. They loaded snowmachines with drop bags and made two trips to supply Eagle Island, an outpost located roughly halfway down the 140-mile Yukon River route that begins in Anvik.
“Everybody’s got what they need out there,” said Davidson. “They prioritized the bags and sent out the ones they needed.”
Four Iditarod Air Force planes left for Eagle Island at first light Saturday morning, Davidson said. But out of the four, only one was able to land and drop off supplies.
Mushers prepare drop bags — filled with dog food, human food, dog booties and other important supplies — well in advance before the Iditarod begins. They were required to drop off the bags in Anchorage by the middle of February.
But poor weather around Unalakleet, the main aviation hub for getting supplies to Kaltag and Eagle Island, had kept flights grounded for days. It wasn’t until Friday when flights were able to send supplies inland to Kaltag.
“We’ve had all sorts of snow squalls,” said Ferno Tweto, the station manager for ERA Alaska in Unalakleet and avid follower of the Iditarod. “When I did see those small planes flying the last couple days I couldn’t believe they were actually flying inland. We weren’t going that way and we’re familiar with the area.”
According to Joe Runyan, an Iditarod Insider reporter, the drop bags “just barely” reached Eagle Island before the arrival of Martin Buser on Friday at 9:55 p.m. Nevertheless, that doesn’t make up for the fact that he and others traveled the 60 miles from Grayling to Eagle Island loaded with extra weight.
Buser, 54, needs all the speed he can muster. He is down to 11 dogs after leaving two at Eagle Island early Saturday morning. Some race analysts have speculated that the four-time Iditarod champion might be running out of gas.
Once Buser reaches Kaltag later this afternoon, he’ll have the dog lot to himself. Well, that is from the pack of six who are trying to catch him. Surely he’ll have a pack of reporters and videographers waiting for him and wanting to know just how much of that magic he and his dogs have left in the tank.
The Big Lake musher clocked a nine-hour run from Grayling to Eagle Island, while the closest six teams chasing him did the 60-mile run in less than eight hours. Was it the poor trail conditions? Extra weight in the sled? A mix of both?
“The trail is really bad,” Davidson said. “It’s almost bank-to-bank overflow. There’s no place to put in a good trail. It’s going to be a slow slog.
“The trail is marked all the way,” she added. “The trailbreakers did their job, but they’re exhausted.”
Kathy Buser, Martin’s wife who is traveling the trail via snowmachine, reported from Kaltag that trail conditions have deteriorated. She thwarted overflow pockets of broken ice with water beneath. Iditarod Insider’s Sebastian Schnuelle said he had trouble with his wide-track snowmachine and not only got it stuck, but sunk it too.
“Last night I could have needed one which floats,” Schnuelle wrote on his Facebook page. “The weather is ugly. Rain, snow rain, snow, blowing snow, overflow, crusty stuff. All the good things mother nature has in store to make life interesting.”
Between Kaltag and Unalakleet, mushers are expected to face weather that could slow them down. Tonight's forecast calls for snow accumulation of up to three inches, with areas of blowing snow and winds up to 25 mph.
“That trail is going to be really crappy,” Tweto said.
In Unalakleet, the east-to-west winds have been so fierce recently that it blew all the ice in the bay out to sea, Tweto said.
“As far as I can see it’s all water out there,” she said. “You can look out and see nothing but dark water.”
Those infamous Unalakleet winds are expected to turn north toward Shaktoolik, the final village before mushers cross the iced-over Norton Bay toward Koyuk.
“Once it turns north,” Tweto said, “that Shaktoolik wind is going to be wicked.”
UPDATE 6:30 AM SATURDAY:
Out in Yukon River territory, driving dogs in a direction that almost always pummels mushers with a headwind, Martin Buser maintained control of the Iditarod Trail Sled Dog Race on Saturday morning.
The Big Lake musher checked into the tiny outpost of Eagle Island at 9:55 p.m., Friday. He rested there almost five hours, dropped two dogs and took off at 2:41 a.m. with his pursuers apparently content to let him lead.
Buser had Eagle Island all to himself during the night until Aliy Zirkle pulled in at 1:42 a.m. A Two Rivers musher who finished second last year, Zirkle pulled out of Eagle Island around 6 a.m. She will have some catching up to do.
Buser has built himself a sizable lead since checking out with 11 dogs. According to the satellite tracking device on his sled, Buser is about 20 miles outside Eagle Island, one of the most remote and inhospitable places along the 1,000-mile trail. The GPS device is also registering a balmy 31 degrees.
Between Eagle Island and Kaltag, where the trail breaks west for the Bering Sea coast, there isn’t much to amuse mushers except for the wind and the snow-covered river that meanders north for roughly 60 miles.
A chase pack of at least a half-dozen teams formed at the Eagle Island checkpoint overnight in hopes of reeling in Buser and keeping the 54-year-old from winning his fifth Iditarod championship.
About a half hour after Zirkle arrived, Mitch Seavey of Sterling was the first of seven teams that reached Eagle Island within the span of an hour. All but two of them — Jeff King of Denali Park and Jessie Royer of Montana — had served their mandatory eight-hour break, which must be accomplished somewhere along the Yukon.
Among that chase pack are some surprises, such as Nicolas Petit of Girdwood, Norwegian rookie Joar Leifseth Ulsom, and Big Lake’s Jake Berkowitz. The three combined have only four years of Iditarod experience: Petit (29th place in 2012 and 28th in 2011) and Berkowitz (31st in 2009 and 65th in 2008).
Petit, who grew up in France but moved to the U.S. when he was a teenager, earned rookie-of-the-year honors in 2011. Last year, he raced the Iditarod with a team of dogs taken from five kennels.
This year the 33-year-old Petit is racing a team that belongs to 12-year Iditarod veteran Raymie Redington, the father of Ray Redington Jr., who was the 12th musher to arrive at Eagle Island this morning.More Iditarod coverage 
By KEVIN KLOTT, KYLE HOPKINS and BETH BRAGG
Anchorage Daily News