Monday, March 23, 2015

Reducing Avian Predation of Salmonids by Cormorants

Probably my least favorite topic of conservation discussion is predator and pest management. In most cases, this means the lethal removal of an animal that is simply doing what mother nature programmed it to do in order to survive. I've grown up being taught to respect the earth's creatures and never kill anything I didn't intend to nourish my own body with. However, my thoughts on this kind of management have evolved a great deal in the past few years. The tough decisions to lethally remove predators and pests in order to improve ecosystems have changed my perspective.

Bald Cypress can reach 600 years of age. Their roots, which
protrude the surface of wetland areas are called "knees" that allow
them take in oxygen when the trunk is submerged in standing water.
(Photo by Tommy Lawler)
I grew up in the lowlands of Alabama, hunting white-tailed deer, fishing for bass and catfish in swamplands covered in beautiful cypress forests with eerie Spanish moss cascading from the canopy above. When I first saw the bird commonly known as a cormorant, the locals referred to them as "water turkeys." They are not table-fare, and some would deem them hardly worth of the cost of a shotgun shell to remove them from the equation. They were simply tolerated as a non-game migratory species until U.S. Fish and Game intervened and began implementing removal programs. In it's most efficient removal program, the South Carolina Department of Natural Resources permitted hunts on lake Marion and Moultrie, that resulted in hunters removing nearly 12,000 birds within a month. Meanwhile, the National Wildlife Federation, Audobon Society and Humane Society expressed discontent for this practice. As an outdoor conservationist and environment writer, I'll wear the label of "tree-hugger." But what's the cost of letting nature run it's course? In the case of cormorant nesting, lack of intervention could results in the loss of 600 year old bald cypress trees.

Beyond ravaging vegetation necessary for maintaining water quality, the compounding effect of their acidic feces building up at roosting sites alters the soil chemistry, wiping out ancient bog forests and destroying it's recovery potential. Trees struggling to survive are stripped of their leaves to be used for nesting material, and the nesting sites burden branches with weight, breaking limbs. The loss of these trees and vegetation perpetuates erosion, causing further destruction to delicate wetland habitat.

These removal programs also benefit other bird species. Cormorants are drawn to similar habitat where other water birds reside. Roosts of cormorants compete for nesting areas with waterfowl, herons, egrets and other birds, in some cases even destroying the nesting habitat of particular species by destroying the vegetation in the understory of cypress forests.

Double crested cormorant colony
Photo taken by Lindsay Adrean of ODFW
In relevance to the Pacific Northwest, the removal programs protect fish, and in some cases, endangered fish. Salmonids comprise most of the cormorant's diet on the Columbia River. While their primary food source is easy to identify through field studies, the quantifiable impact of cormorants on fisheries is significant, but a little more difficult to determine. It is estimated that nearly fifteen thousand breeding pairs of cormorants on East Sand Island consumed eighteen million federally protected juvenile salmon and steelhead smolts traveling through the estuary in 2013. That's nearly 15% of the population. Sand Island's breeding colony of cormorants has grown from 100 breeding pairs in 1989 to the largest known colony of these birds in North America, comprising 40% of the total population in the Western United States. In addition to fish that are consumed, fish that prove to be unsuccessful meals for cormorants are wounded and more likely to carry disease or die from infection.

The National Oceanic and Atmospheric Administration has suggested that the number of cormorants at the mouth of the estuary be reduced to six thousand. The U.S. Army Corps of Engineers plan lethal removal of 11,000 birds from the population, as well as oiling 15,000 eggs, a method of blocking the intake of oxygen to prevent the unborn chicks from hatching.

Lethal management methods draw their fair share of criticism. The Portland District U.S. Army Corps of Engineers Environmental Impact Statement declares that,

Wildlife management is fundamentally a human concept that aims to manage the needs or goals of humans with the needs of wildlife. Thus, there is a large “human dimension” component to wildlife management, as individuals with an interest in the outcome of the management plan do not all share common values, nor would any one management action or alternative appease all stakeholders. The issues presented in this Final Environmental Impact Statement pose a complex problem that spans a diverse range of stakeholders, and the importance of the “human dimension” in making a decision cannot be overstated.

During a public comment period, the Corps received 150,000 comments on it's drafted plan, estimating all but a thousand of those comments came from two opposition campaigns developed by Care2 and the Audobon Society.

Tunnel and observation blinds used by researchers.
Photo taken by Lindsay Adrean of ODFW
It's important to understand that these removal programs are part of management plans set in place to offset the impact of dams operated by the Corps of Engineers under an agreement with the National Marine Fisheries Service. These management plans require the Corps of Engineers to protect runs of fish listed under the Endangered Species Act. The obstacles to the recovery of these fish are complex. "Avian predation upon Columbia River Salmon stocks has grown to become the single-largest, unchecked impact on their sustainability," says Columbia River Intertribal Fish Commission Executive Director Paul Lumley. "While this management is warranted, it may not be enough to reduce the staggering fish losses."

East Sand Island in June 2012. Photo taken by Lindsay Adrean of ODFW
Hazing and reducing habitat through netting and structures that make it difficult for birds to find areas to land are also included in the plan, although non-lethal efforts to disperse the colony from the estuary have had virtually no success deterring them from returning to the estuary as their roosting area. One tactic, "social attraction," or setting up decoys and playing back audio of calls from nesting birds, was attempted at 5 alternative nesting sites, none of which successfully drew colonies of birds.

These programs are designed to manage populations, not eradicate them. The proposed actions are part of an Environmental Impact Statement reviewed to balance protection of both the fish and the birds, a stewardship mission to protect all species that use the Columbia River system. These migratory birds have large populations that cover a wide range of the planet, but these particular roosting areas threaten smolts traveling out to the salt, drawing focus on the responsibility of protecting threatened salmon and steelhead.

This article was published by The Good Men Project on March 21st, 2015

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