Based on the analysis of eight years of data collected by field biologists, the researchers found that populations of many bird species increased across mountain meadows after restoration strategies successfully improved habitat conditions.
“This paper is the culmination of many years of work monitoring meadows,” said study lead author Brent Campos. “And it definitely increases the amount of evidence we have that one of the most commonly used approaches is having the effects we want.”
Degraded meadows and their streams can be rehabilitated using a “pond and plug” technique to restore the floodplain function. This strategy aims to elevate groundwater levels in the dry season by spreading large flows across the floodplain.
The pond and plug treatment improves water quality, soil moisture, and wetland vegetation – improvements that are extremely beneficial to birds and other wildlife.
In the Sierra Nevada mountains, major projects are underway to restore meadows that have been degraded from overgrazing, agricultural use, and stream channel modifications.
From 2009 to 2017, biologists sampled birds at 31 montane meadows in California that were sites of restoration projects. The study authors used the data to investigate the abundance of 12 bird species from one to 18 years after restoration.
The researchers also analyzed the amount of deciduous shrubs and trees, which is an indicator of bird habitat quality, and assessed the effectiveness of the restoration techniques that were used.
The study revealed that six of the twelve species increased in abundance after restoration, while the numbers of five species remained the same. The amount of deciduous trees and shrubs at a site at the time of restoration was found to be a strong predictor of bird abundance.
According to the researchers, hydrologic measures to fill in stream channels and vegetative measures to plant shrubs and trees were both helpful in creating habitats for birds. The vegetative approach of planting trees and shrubs, including willows and cottonwoods, accelerated the positive impacts of restoration.
Study co-author Helen Loffland is a meadow bird specialist with The Institute for Bird Populations.
“Having access to one of the longest term datasets around for bird monitoring and meadow restoration was really essential to this paper,” said Loffland. “And it was heartening to see such positive responses from the birds in areas where both hydrologic and vegetative restoration measures were used.”
The research will be particularly helpful for restoration practitioners who base their work on published scientific studies.
“We know that restoration practitioners are out there trying to do the best job possible with limited funding,” said Campos. “We hope that this new research will help them in their work restoring meadows’ key functions of fostering biodiversity, reducing downstream flooding, purifying water, and storing carbon.”
The study sites included the Perazzo Meadows, Red Clover Valley near Portola, and a restoration site in Humbug Valley, also known as Tásmam Koyóm.
“It is pretty incredible to visit the Tásmam Koyóm site, which is only 6 years out from the restoration completion and see such an abundance of birds,” said study co-author Ryan Burnet. “To see so many more song sparrows or yellow warblers is really encouraging. Normally, you’d need to wait 10 or even 20 years to see a biological response like that.”
The study is published in the journal Restoration Ecology.