Missouri River Institute symposium: As cottonwoods fall, birds fly away
VERMILLION -- The next 100 years for birds along the Missouri River will likely be much different from what birdwatchers along the river have traditionally seen, thanks to the change in the cottonwood forests along the river.
Those are the research results of Chris Merkord, a post-doctoral research associate with the Biology department at the University of South Dakota. His examination of the 39-mile segment of the Missouri National Recreational River between the Fort Randall Dam and Running Water -- the small South Dakota community on the river southwest of Springfield -- shows the changing nature of the cottonwood forests along the river will impact what types of birds are able to find habitat. The cottonwood forests are not growing back, in part, because of the lack of sandbars that foster forest growth and there's less naturally filling sediment in that area of the river.
Merkord presented his findings Thursday as part of the Missouri River Institute's annual symposium held at the Al Neuharth Media Center on the USD campus.
"We don't have the sediment coming through the (Fort Randall) Dam," Merkord said. "We have the erosion going on and we don't have any sediment coming in from upstream to replace it, so the river is sort of eating itself into its current banks. The further down it gets, the less chance it has to meander into its floodplain."
Cottonwoods along the river best grow in bare, moist sediment areas but those opportunities are limited, Merkord said.
In particular, species like ovenbird and hairy woodpeckers could see the largest population decreases -- in some cases 40 percent over the next 100 years -- along the river because the life of the cottonwood forests has changed since the day the area was settled. The northern flicker and baltimore oriole species were also identified for reduced populations. The impact of agriculture, deforestation and the damming of the Missouri River have also made a difference with forests, he said.
"We know there's a problem with cottonwood forests in general and that's been shown in years of research," Merkord said. "It's gone on for a long time along the Missouri River. If you realize that we're losing our cottonwood forests, the next question is finding out what that means for other species that use the forest."
Thursday's event included presentations from faculty, students and local government bodies from the region and across the country. The Missouri River and its cottonwood forests were a hot topic, along with the invasive plant species and bird migration in the river area.
"We really do try to run the gamut on all things related to the river," Missouri River Institute Director Tim Cowman said.
The invasion of plants like saltcedar, purple loosestrife and cattail marshes have since filled in. Even though it is vegetation, it doesn't help the bird population with habitat.
The species change is not all bad news.
Merkord's projections show birds like the common yellowthroat, indigo bunting, blue jay and song sparrow would benefit from the next generation of forest that would succeed the cottonwood, such as potential ash, elm and box elder tree species. The hummingbird species will still be around but not in numbers that have been seen in cottonwood forests.
"The diversity of the birds along the river is going to follow the health of the cottonwood forests," Cowman said. "If we see the decrease in the forests along the river, that's certainly going to have an impact on the bird species that we see along the river."
Another presentation examined the stopover habitat for migrating birds and whether or not the three- or four-acre woodlots that are built on farms across the region would be suitable, compared to the traditional riverside habitats for birds who are making 150- to 200-mile trips during spring and fall migration.
USD biology department professor Dave Swanson led a two-year project, which sampled the blood of migrating birds and found key indicators in the birds' blood that shows both woodlots and riverside tree habitats are proving suitable for birds to "fatten up" before they migrate.
Cowman said the concern about the cottonwood forests has been realized by scientists and researchers, but realistic options for how to regrow cottonwood forests are still being looked at. Merkord said it's possible to plant cottonwood forests, but the question of how effective they would be still remains and it would not be cheap.
"You can plant cottonwood forests," he said. "You can turn an empty row crop field into a cottonwood forest if you want. It takes some money but it's an option, and there would be a question if it would be as good as a regular forest."
Merkord said the projected change in birds carries over to other species that call the river home.
"The forests are changing and they're becoming less diverse and there's fewer species in them," he said. "That has effects that ripple through the whole community and what we do about that has an impact in the whole social, political and cultural communities. Everyone has different values but I think understanding the whole system is changing is the first step."