The exhausted travelers were just about out of gas, so they pulled over to the only rest stop they could find in the fog.

The Wisconsin Department of Natural Resources workers aboard the research vessel Coregonus wondered why so many migrating warblers were suddenly landing on their boat 16 miles off the Lake Michigan shore from Port Washington. The pooped birds didn't care where they landed, as long as it was dry.

To the warblers lost in the fog, the boat probably looked like a giant floating life preserver.

"Most of them were just dead-tired," DNR fisheries technician Tim Kroeff said Tuesday.

American redstart, magnolia and palm warblers were among the species landing on the boat, as well as at least one vesper sparrow.

"Some were so tired I could catch them with my hand and bring them into the cabin. Some of them would land and it was almost like they were in hypothermia, they were shivering," said Kroeff, a DNR fisheries technician for three decades.

Warblers migrating from tropical climates to Wisconsin to breed or pass through on their way to Canada visit stopover sites, which ornithologists have dubbed fire escapes, convenience stores and full-service hotels, depending on habitat and availability of food. On this day in late May, the Coregonus was a fire escape - a vital rescue stop the birds happened upon that likely saved their lives.

"It happens in the Great Lakes and the Gulf of Mexico; there are amazing stories from people on ships," said Noel Cutright, founder of Western Great Lakes Bird and Bat Observatory in Ozaukee County. "They're always looking for some place to sit down."

In the 1960s a fishing boat captain on Lake Michigan and Lake Superior harbored so many migratory birds seeking a refuge on his boat he brought aboard potted plants and trees for the birds. Cutright heard of a fishing boat that carried a Christmas tree for the birds to perch on.

Wisconsin is home to 30 migratory warbler species who travel here from the Caribbean, Central and South America at various times throughout the spring. They usually travel at night, and "when it gets light they say, 'Uh-oh, I'm over water. I need to find land.' That's why the western shore of Lake Michigan is so important for migrant birds," Cutright said.

The DNR fisheries crew was traveling out to nets they had set a day earlier to assess the lake trout and burbot populations. Tom Burzynski, a DNR fisheries technician for 25 years, said that as the boat hit a fog bank, it must have passed near a flock of migrating warblers that were very tired and getting harassed by gulls.

The warblers began landing on the boat, and when the cabin door opened, about half a dozen flew inside. Some looked as if they were taking naps, while others began to grab lunch, snapping up black flies inside the cabin.

"The birds took advantage of the flies; one of them even got a large moth. That was good fuel," Burzynski said. "It was unusual to see that many at one time. It was nice to have some take a ride back to shore with us."

Many of the warblers stopped for a short rest and flew off into the fog. Their fate is unknown. But the birds that sought shelter inside the boat cabin made the trip to shore via internal combustion engine instead of their wings. The fisheries crew was happy to serve as a taxi and grateful the birds took care of the pesky lake flies inside the cabin. However, the birds did leave behind deposits on the boat.

"So we had to do some cleaning up," Kroeff said. "But it was pretty easy, and the birds were very entertaining."