Thursday, February 19, 2009

Non-Native Birds at the Feeder

Photos courtesy of Tom Grey of Tom Grey's Bird Photos.

Looking at results from this year's Great Backyard Bird Count, it's easy to see that some of the most reported birds are non-native species. In Idaho, chances are that a number of non-native species could make an appearance in your backyard, including house sparrow (above), starling, house finch, California quail, rock dove and others.

What does this mean for bird conservation? What impacts are these birds having on native species? Should we be concerned? Should we be doing something?

In some cases, like the house sparrow and the Eurasian starling (above), these birds clearly have a negative impact on native species. Starlings were introduced to New York City's Central Park in 1890 as part of a horribly conceived effort to introduce all the birds mentioned in Shakespeare's works to North America. The starlings quickly spread across the continent and now number some 200 million here. Oddly enough, they are in long-term decline in their native Europe.

But are all non-native species bad? Some conservationists believe so. But the reality is more complex. Some species may be merely filling habitats created by humans. Suburban and urban environments are not suitable for many birds. Is it a bad thing that non-native species have filled the void?
House finches (above) are not native to Idaho. They thrive in backyards. Periodically, an eye disease reduces their numbers. Are they really a problem, or just a new addition to Idaho's bird life?

At least one study has reported that, in most instances, non-native species do not reduce overall biodiversity.

Conservancy biologist Erik Meijaard reports that in Indonesia, despite a tremendous diversity of birds, very few exist around homes--probably because they are not adapted to do so. Is it really worse to have non-native birds in human-altered environments than none at all?

Species move around, with or without humans. Is the fact that they were moved by humans always bad, or just another evolutionary adaptation? Issues around non-native species need more study and thought.

I like watching the California quail that scurry around Boise. They are one of a list of species introduced to Idaho for hunting purposes: chukar, gray partridge, turkey, ring-necked pheasant. One wonders why they were brought here, given that Idaho has so many native species.

On the flip side, these non-natives sometimes live in places where native game birds fare poorly. Pheasants live in farm fields; quail inhabit cities; chukars thrive on cheatgrass.

But that doesn't mean we should introduce more game birds. Certainly in some instances such introductions have been disastrous, particularly in the case of fish. Lake trout illegally thrown into Lake Yellowstone are gobbling up the native cutthroat trout, a horrible loss. Feral pigs released for hunting purposes have become a major nuisance. Hopefully we can learn from our mistakes and not intentionally introduce more animals--there will be plenty enough unintentional introductions.

The Eurasian collared dove( above) population stems from escaped domestic birds. Bird counters noted 9 birds in 2006, 56 in 2007, 83 in 2008 and 311 in 2009. This bears watching. Maybe hunters should be encouraged to take these birds now, to keep populations managed before they become a problem.

Non-native birds are here to stay. Why do some spread and others survive in low numbers? What species are at risk of becoming harmful, and what species actually add to our native diversity? Questions like these don't have easy answers. But hopefully citizen-conservationist projects like the Great Backyard Bird Count can help us better understand our birds, both native and non-native.--Matt Miller

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