In the 1940s and 1950s, the hunting guide L.S. Quackenbush lived in a cabin in remote Oxbow, Maine. He rented cabins to hunters, cut, stacked and split wood and used his daily walks to keep detailed notes on the spring arrivals of songbirds and the first appearances of flowers and tree leaves.

His journals meticulously documenting the changing seasons grew and grew, eventually totaling more than 5,000 pages. Now they are filling gaps on how trees and migratory birds are responding to a changing climate in northern Maine, where historical data is sparse.

A new paper by the University of Maine’s Caitlin McDonough MacKenzie compares Quackenbush’s journals to recent observations, and suggests bird arrivals may be lagging behind the earlier leaf-out and flowering induced by a warming climate. Flora appears to be more directly responsive to local warming, while migratory bird schedules are more complex.

A growing body of research uses such historical observations to study seasonal timing and cyclical changes in the natural world, a field known as phenology.

So Quackenbush is following in the boot steps of Henry David Thoreau, the proto-hippie philosopher whose detailed nature observations have opened windows into the historic climate near his beloved Walden Pond. In 2008, a pair of Boston University researchers used Thoreau’s nature journals from the 1850s to calculate that plants in Concord, Massachusetts, were flowering a week earlier, on average.

Others have analyzed Sand County Almanac author Aldo Leopold’s Wisconsin journals.

McDonough MacKenzie compared Quackenbush’s observations on leaf-out and flowering of 10 species to temperature data from the National Oceanic and Atmospheric Administration. She found that the average date of leaf-out advanced 2.3 days for each degree Celsius increase in April temperature. This is different from southern New England, where another study found that leaf-out advanced 6.1 days per degree Celsius.

It’s good science from an unlikely source, but the oddest thing is the improbable twists that allowed these journals to fall from obscurity into McDonough MacKenzie’s hands. “Honestly, they landed in my lap in the most incredible way,” she said.

The story started more than a decade ago, when College of the Atlantic lecturer Scott Swann was sorting through the papers of the late ornithologist Bill Drury.

“Hidden in the eaves of the attic, I came across these three boxes of folders of Quackenbush, and I became fascinated,” Swann said. “They are loose-leaf papers, they are the most absolutely unarchivable materials, so it’s sort of a miracle that they have withstood the test of time.”

When Swann heard that Abe Miller-Rushing, science director for Acadia National Park, was looking for historical ecological information, he passed the boxes along. Miller-Rushing asked University of Maine graduate student Adam Derkacz to digitize the files.

MacDonough McKenzie, then a Ph.D. candidate in Richard Primack’s lab at Boston University, was spending the summer at Acadia studying an 1894 account of the flora of Mount Desert Island. Her desk in the archival lab was near Derkacz’s. When they went on long runs together, Derkacz mentioned the tedium of scanning the thousands of pages. But he also noticed the value of the meticulous notes. Miller-Rushing then encouraged McDonough MacKenzie to study the journals.

“I started looking through it, and it was just amazing,” she said. “A treasure trove.” In his later years, Quackenbush had even compiled years of observations into easy-to-read tables.

As it happens, Miller-Rushing and Primack were the researchers who published on Thoreau and phenology in 2008. They are co-authors on the recent paper, which also compares Thoreau’s observations with those of Quackenbush. It appears that dates of first flowering advanced more in warm years in Thoreau’s Massachusetts than in Quackenbush’s Maine.

McDonough MacKenzie also compared Quackenbush’s dates of first arrivals of eight species of migratory birds to 20 years of recent observations in the region by Bill Sheehan, an avid birder. The analysis showed that birds were arriving earlier, but April temperatures had little influence on bird arrivals.

Their methods were different. Quackenbush birded mostly in Oxbow, while Sheehan traveled around northern Maine looking for early arrivals. And although April temperatures were not significantly different in the two time periods, McDonough MacKenzie said, it is possible to draw some general conclusions from the observations.

“We can see very clearly that leaf-out and flowering are correlated to April temperatures, but migratory bird arrivals are not,” McDonough MacKenzie said. “That’s where we have this potential mismatch. Adding in more data today will help us figure out if this is an ongoing trend.”

Miller-Rushing said the journals fill out another piece of the climate puzzle.

“We feel really safe to say that Quackenbush’s observations add to the story that flowering times and tree leaf-out times and bird migration times are all changing,” Miller-Rushing said. “And it’s suggestive that they might be changing a little differently in northern Maine than they are in other areas.”

Miller-Rushing said he would like to find more data sets, to test this hypothesis. This may soon become easier, as a growing number of amateur naturalists are posting their observations online.

Theresa Crimmins, the associate director of the USA National Phenology Network, said the network’s Nature’s Notebook has more than 3,400 active observers. She is pleased that nontraditional data sets such as the Quackenbush journals are coming to light.

“This can help us have a window into the past,” Crimmins said, “and help us put what we’re documenting right now into some historical context.”

But Crimmins said a standardized online system makes using the data “infinitely more feasible” than using entries from nature journals.

Some wonder whether we’re losing something along the way. Sheehan, the birder who contributed observations to the paper, has been birding in northern Maine’s Aroostook County and taking good notes since 1992. But he has recently transitioned from notebooks to the online database eBird.

“These databases are a little too specific. I like the roaming thoughts of Mr. Quackenbush,” he said. “He has a lot of little editorial observations that I think are important.”

“There are so few amateur naturalists. Too many people think it’s something they can’t do,” said Sheehan. “You don’t know what you’re mailing ahead to another generation by taking good notes.”