Minnesota and the Mississippi River Valley are special places in North America. As the mighty river drains water southward from nearly half the continent, it also provides a crucial flyway for migratory birds. Nearly half of North American bird species spend at least part of their life in the Mississippi River flyway.

Migratory birds include familiar species like Baltimore orioles and hummingbirds, and perhaps less familiar birds like many colorful warbler species. These birds may be less familiar to Minnesotans, because they breed far to the north. Still, Minnesota provides critical migratory habitat for these long-distance travelers.

One of the hazards migratory birds face is collision with human-made structures, in particular windows. Songbirds, as nighttime migrants, are especially at risk from window collisions. A large area of glass on a building can appear as a safe corridor to fly through. Reflections of trees or other natural features can present confusing obstacles for birds.

The new Vikings stadium is a perfect example of just such a structure. The striking glass facade makes an appealing design. However, for birds, this design may prove deadly. Because it is located less than a mile from the Mississippi River, tens of thousands of birds will migrate past this facility.

To their credit, the Vikings have agreed to implement mitigation lighting procedures "when possible." Modifying lighting, especially turning off interior lights at night, is a good start. However, large numbers of birds migrate in the fall, when the stadium is likely to be lit up like a beacon for nighttime games. Our concern is that lighting procedures will not be enough to limit significant bird strikes on the new stadium.

We are glad that Audubon Minnesota has been working with the Vikings for more than a year, encouraging them to implement more substantial measures to deter bird strikes. In particular, Audubon Minnesota is recommending bird-safe glass, which can reduce bird strikes by 75 percent or more. The Vikings say that the stadium budget does not accommodate the additional cost to incorporate bird-safe glass, an estimated $1.1 million.

Here at the National Eagle Center, thousands of birds migrate past our facility on the banks of the Mississippi in Wabasha. Indeed, with two sides of the building nearly all glass, we see some bird strikes. During peak migration times, we implement a number of procedures to limit collisions. None are fail-safe against bird collisions, but they are what we can do at this point. Were we to do it over again, we would surely incorporate the newest technology, which would now include using bird-safe glass in the construction.

Indeed, this is where environmentally sustainable design is headed. LEED certification encourages measures to deter bird collisions, and state guidelines require bird-safe glass on projects involving bonding money. Though the state guidelines may not technically apply, these standards should guide the Vikings in the construction of their landmark facility.

And if the Vikings think that it's just a few "bird nerds" who are concerned, they should think again. The people of Minnesota are paying for a significant chunk of this stadium and do not want their money going for something that will kill thousands of birds. Wildlife viewing, including bird-watching, represents a major industry in the state. A recent study in Wisconsin found that wildlife viewing was the No. 1 outdoor recreational activity, engaging more people than hunting, fishing and bicycling.

If the Vikings cannot be persuaded to meet state guidelines for bird safety — or to do it because it is the right thing to do — they ought to consider the economic and public-relations repercussions of dismissing the impact of their new facility on one of Minnesota's treasured resources.

We encourage the Vikings to reconsider their position and include bird-safe glass in the new stadium plans.

Rolf Thompson is executive director of the National Eagle Center in Wabasha, Minn.