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Currently there is a campaign to eradicate the European Starling from North America because of its threat to other species. Are there actual data regarding the extent of the ecological risk to native species, and are there data on the effects of the current eradication programs (are they working)?

Background

In North America, there an estimated 140 million European Starlings, or about 45% of the global total. The species was introduced to the continent over 100 years ago when only 120 or so were released in the New York area. Those few have quickly spread across the whole continent, competing easily with other native birds of similar type, especially for nesting holes, because they are naturally far more aggressive. It is currently listed in the IUCN List of the world's 100 worst invasive species. Annually, the US kills over 1 million of them with the sole purpose being extermination. There is even a specific poison commercially available. However I am having difficulty finding data to show how invasive the Starling really is in North America and the extent of the ecological risk to native species because of their presence. I would also be interested in data showing the impact of current control methods (do they actually reduce the impact on native species?).

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    $\begingroup$ Australia has also taken great measures to eradicate the species from their country. $\endgroup$ – fredsbend Apr 11 '17 at 21:38
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    $\begingroup$ For the record, I shoot Starlings all the time. Just got one today. First of the season, which prompted the question (should I actually be doing this?). I'm fairly confident the US killing of 1 million of them doesn't bother me. $\endgroup$ – fredsbend Apr 11 '17 at 23:31
  • $\begingroup$ @fredsbend: Perhaps surprisingly, starlings are edible, and supposedly quite tasty. $\endgroup$ – jamesqf Apr 12 '17 at 6:00
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    $\begingroup$ @Alex I think you might be letting an emotional response (mass killings of innocent lives?) affect your conclusions. That's a little to close to philosophy rather than biology. Science is amoral. The question is about the Starlings impact and whether control methods mitigate that. Whether we should attempt mitigation at all is not a biology question. I must confess, your opinion on this is the first I've heard like it. I take it as a given of preservation practices that invasive species that negatively impact native species must be controlled. $\endgroup$ – fredsbend Apr 12 '17 at 16:12
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    $\begingroup$ @AlexDeLarge NP. I found an interesting claim: "About 42% of the species on the Threatened or Endangered species lists are at risk primarily because of alien-invasive species." Is this not concerning to you, that nearly half of endangered species are because we've introduced foreign species? $\endgroup$ – fredsbend Apr 12 '17 at 21:36
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First, for the record, I do not know the North American Starling situation well. However, I know of one study (Koenig, 2003) that failed to find strong effects of Starlings on other cavity nesters (i.e. looking at effects from cavity competition). When trying to control for other effects, only one species was potentially negatively effected by Starlings.

Starlings cause quite large economic effects though (Linz et al, 2007), and it wouldn't surprise me if this is the main reason for the control measures. The paper refers to a previous study which estimates that Starlings cause crop damage costs of \$800 million/year as well as \$800 million/year in health costs, due to disease transmission to livestock and humans (both figures from Pimentel et al., 2000).

So my feeling, based on a couple papers and some quick searches, is that the ecological impacts are uncertain (or to a large extent unknown) but that the economic impacts are quite large. Given the North American population sizes of European Starlings it would however surprise me a lot if there weren't any ecological effects on other species (negative and positive). These issues are hard to study though, especially without long-term data of high quality.

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  • $\begingroup$ Very good point. I did not think of the economical impact being the motivation for control measures. I'm surprised that I didn't, considering most control measures are economically motivated, or at least, environmentally motivated control measures remain underfunded and under implemented. $\endgroup$ – fredsbend Feb 28 '18 at 15:25
  • $\begingroup$ Yes, that might explain the control measures. Since they are on the IUCN top-100 list I would have expected them to also cause well-known ecological problems though. Maybe there are other papers or reports that show this. In the ones I've seen (after brief searching) it is mostly the study by Koenig that is cited though. $\endgroup$ – fileunderwater Feb 28 '18 at 15:39

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