Where have all the snow geese gone in Delaware?
Massive flocks of snow geese honking overhead, gliding onto farm fields and feeding in tidal marshes have been a sign of winter in Delaware for more than three decades.
But not this year.
The birds, which normally arrive in late October in numbers so impressive they attract tourists from around the world, didn't show up in October. They weren't really here in November or December, either.
Finally, at the end of January, they started to arrive but not in the huge numbers normally seen in Delaware, Maryland and New Jersey. There aren't many in Pennsylvania either.
No one is certain why the birds appear to be shifting their winter habitat and altering their migration patterns.
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This year, it could be that November and December were much warmer than usual and the birds simply stopped short of Delaware, Maryland and New Jersey. Or it could be that the birds have a wider range and are no longer as dependent on coastal marsh habitats during the winter. They could be moving west of the coast to graze on farm fields and spreading out through the region rather than concentrating in one area.
The impact of the geese bypassing Delaware depends on one's perspective. While tourism takes a hit, farmers, for one, welcome the break from the pesky birds.
When people call Bombay Hook National Wildlife Refuge near Smyrna to see where the snow geese are, outdoor recreation planner Tina Watson has been telling them to come later in December.
"They just haven't been as consistent," she said. And that, she said, "has probably been going on for the last three years."
Where she used to tell people to plan their visits for the end of October, more recently, she's suggested closer to Thanksgiving to get the peak of migration for snow goose and other waterfowl.
This season, it was even later, and the birds are more scarce.
To find the big flocks, you need to look north – to New York.
Whether this will become a trend is unclear. If it is, it won't be the first time snow geese have done a complete northward shift in range.
"Birds don't migrate because they want to," said hunting guide Jerry Kucharski, who specializes in snow goose hunting with his DelBay Guide Service. Birds "migrate because they are forced to migrate."
Snow geese used to be rare in Delaware.
Dave Carter, who grew up hunting the marshes of northern Delaware, recalled a day when he was back in high school.
"I was duck hunting in Hamburger Cove," he said. "This white bird flew over. It was probably 1979."
He didn't know what it was until a buddy told him it was a snow goose.
There are two big data sets that track bird migration over time: One, the Audubon Society's Christmas Bird Count, uses volunteers to tally birds seen at specific locations during December into the first weekend in January. The count is more than 100 years old, but in Delaware, teams have been collecting data over a shorter time frame – starting in earnest sometime around the late 1950s.
Snow geese, especially at that time, were indeed very rare birds here.
There is a second, long-term survey collected during midwinter by state and federal officials as part of a survey of waterfowl. It, too, shows scant snow geese in Delaware four decades ago. That survey came to an end in the winter of 2015.
The story of snow geese has shifted over time. In the early 1900s, the snow goose population was down to a low of several thousands birds. Federal officials stepped in with a management plan in 1981 with the goal that the population – then at 200,000 birds – not slip below 120,000.
The midwinter epicenter was the marshes of Virginia and North Carolina.
With management, the population grew and by 2009; it was estimated at over 1 million birds.
Chris Dwyer, a migratory game bird biologist with the U.S. Fish & Wildlife Service Northeast Region, said it was one of those cases where "the pendulum swings from the rare to the abundant."
The big concern then was what the birds were doing to their Arctic breeding grounds.
Snow geese nest in the far north Arctic area of North Foxe Basin and Central Baffin Island north to Ellesmere Island and into northwest Greenland.
They pluck the vegetation from roots and can cause long-term damage to ecologically fragile habitats.
As the population grew, the birds expanded their traditional wintering range north into Delaware.
Carter, who did marsh studies at Bombay Hook National Wildlife Refuge when he worked for the state Department of Natural Resources and Environmental Control, said there was concern that the birds were also damaging the salt marshes at the refuge.
"We assumed they were just tearing up all the marsh," he said. But what they found instead was that the birds were foraging only on the soft marsh areas that were already weakened and collapsing because of rising sea levels.
Marsh damage was a growing concern and then, the birds started foraging on corn, soybeans and winter wheat fields.
"They have spread out drastically," he said.
Federal officials found that the birds favored the Mid-Atlantic states because there were plenty of grain fields for foraging in the winter.
Watson said hunters tell her the birds taste better now that they are feeding on grain rather than salt marsh grass.
Jesse Baird, a state wildlife biologist, said the birds have been late to arrive this season.
"My guess this year would probably be something related to weather," he said. "Those birds typically don't leave until they have to."
Both November and December were unseasonably mild in Delaware, and that may be part of the story. Others suggest that the federal plan to downsize the population also may be having an impact.
And it could be that the birds just aren't as concentrated as they used to be when they depended on salt marsh grass for food in their wintering habitats.
In fact, Baird said, other migratory waterfowl also were slow to arrive. The November season was very slow, and ducks really didn't start to show up until December into January, he said.
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"My guess" with the snow geese "is they stopped in Pennsylvania and New York," he said.
The reason there is so much guessing is because snow geese, even though they are big, white and congregate in flocks, are notoriously difficult to track.
And that was part of the problem with the earlier population decline.
Dwyer said there wasn't even a comprehensive banding program.
"It's all about timing," he said. "That's the working theory."
The idea is that if conditions are mild in the fall, there won't be a big push south of migratory waterfowl.
These birds, of course, take a big risk when they stay put or stop short during migration.
Dwyer said they saw it last year with black ducks. The birds stayed further north, and then the weather turned dramatically colder.
"Their strategy seems to be to wait out the bad weather," he said.
Birds seem to weigh the risk between staying and migrating, and the main driver seems to be access to food and how much energy they spend getting to that food.
"It costs them a lot of energy to get through the winter," he said.
Snow geese are savvy birds, said hunting guide Kucharski.
A flock of snow geese can clean a field in two days, he said.
And they adapt quickly to changing conditions, hunting pressure and the decoys and tools that guides like Kucharski use.
"An average age is 7 years old," he said. The bird "has seen a lot of decoys and heard a lot of calls."
Reach Molly Murray at (302) 463-3334 or mmurray@delawareonline.com. Follow her on Twitter @MollyMurraytnj.