Published Jan. 13, 2009, in the Wyoming Tribune Eagle, “It’s possible wolves in Yellowstone are having a positive effect on songbirds.”
2015 Update: New studies show that wolves are not the only cog missing in the Yellowstone ecosystem. The park needs its beavers to build dams and recharge the subsurface water so the willows will grow better and the songbirds will multiply. See High Country News, Dec. 8, 2014, Vol. 46, No. 21, “Have returning wolves really saved Yellowstone?” www.hcn.org.
By Barb Gorges
Back in the early 1990s, the National Audubon Society lobbied for the reintroduction of wolves in the Yellowstone ecosystem.
Why, some folks wondered, would an organization with a name equated with bird conservation be interested in wolves?
An Audubon member myself, I agreed with the ecologists who were saying it was important to have all the pieces of an ecosystem, from top dog predator on down to burying beetle and I lobbied for wolves on ecological principles.
There were a couple people who thought wolves shouldn’t be reintroduced because, based on a few anecdotes, wolves might already be present.
If there were wolves in Yellowstone immediately before reintroduction, and not just casual stragglers or hybrids and captives dumped by people, they were nearly invisible, awfully quiet, well behaved and unproductive.
Today, commercial enterprises will take you on a wolf tour (www. wolftracker.com). Reintroduced wolves multiplied so quickly they also became a noticeable nuisance to livestock operators.
Wolves are apparently having an effect on the Yellowstone ecosystem that their predator stand-ins, the coyotes, were not able to achieve between early 20th century wolf eradication programs and wolf reintroduction in 1995. The willows are increasing, which means increasing numbers of songbirds.
Doug Smith, leader of the Yellowstone Wolf Project for Yellowstone National Park, in a reply to my email query, was quick to point out that studies are still ongoing and that some people believe there is more than the wolf at work in the growth of willow shrubs. Papers are in the process of being written and Smith said, “As far as wolf impacts on songbirds, we are on our way to establishing the link that goes through willow and elk.”
Willow grows in riparian zones, the areas along creeks and rivers. A healthy riparian zone, with lots of vegetation, absorbs rainfall and snowmelt like a sponge and releases it slowly into creeks. In an unhealthy situation, with little vegetation present, water runs off quickly, eroding the surface, depositing sediment in the stream where it suffocates fish eggs and the invertebrates that feed fish.
In a healthy riparian zone, vegetation slows the runoff water. Slow water can’t carry as much sediment and organic matter and so it drops it on the plants adjacent to the stream, rather than in the stream. Riparian plants, such as willow, thrive on and grow through the sediment deposits, eventually providing more and more vegetation.
If the lack of vegetation in a riparian zone is from overgrazing by wildlife or livestock, managers can reverse the trend by either fencing the animals out for a period of time, or reducing the number of animals grazing and/or the time and amount they graze.
National park managers have restrictions that prevent them from removing elk, which have kept the willows trimmed too well while the wolves were out of the picture.
However, the willows seem to be recovering and expanding. One theory is that climate change is providing a longer growing season. Another theory is that the Yellowstone fires of 1988 provided a huge increase in forbs (non-woody plants including wildflowers) that elk like better than shrubs and they grazed the willows less.
A third theory is that elk no longer get to graze willows at their leisure since wolves are constantly nipping at their heels and running them off.
Range management scientists have spent years conducting studies of the effects of various grazing schemes and could probably make some predictions, but every ecosystem has its quirks.
Whether the wolves are totally or partly responsible for the regeneration of Yellowstone willows, we can reasonably predict healthier riparian zones.
From my birdwatcher’s perspective, this means more and greater diversity of songbirds which are attracted to the insects associated with the willows, and the shelter their shrubbiness provides. Smith listed willow flycatcher, yellow warbler, common yellowthroat, Lincoln’s sparrow and song sparrow in particular.
Improved riparian habitat means improved fisheries. It also means ephemeral and intermittent streams will flow a little longer each year.
The increase in vegetation can support more critters (even livestock outside the park). Wyoming’s riparian zones are important to something like 70 percent of wildlife species.
Bureaucracy and politics will continue to plague the Yellowstone wolves, but if studies show wolves have helped repair an important part of their ecosystem, reintroduction has been worthwhile.