I've been monitoring them at one site in Belgium for four years. So far I've not noticed any impact. Of course there could be a subtle influence I've not noticed. The nesting holes they use are so big that few other birds would use them. Perhaps only other tree nesting ducks would compete, but the only other tree nesting ducks in our area are also aliens. They perhaps compete with other alien geese for grazing and space on water. Perhaps, the combined impact of all the alien ducks and geese have a significant impact. However, at the site I study the eutrophication and other anthropogenic impacts are so great that without the aliens we would probably just have fewer geese and ducks.

More on its (presumed) impact in Belgium: http://ias.biodiversity.be/species/show/19

I also attach a risk analysis from Holland and a study from Great Britain.

Another speculative account. There are many more.

Dear Balázs, thanks for pointing out those reports they're very interesting. It is very difficult to separate causation and fact from speculation in these reports and I look forward to the results of Jamie's research.

The issue of aggression is often mentioned, so in the park where I study geese I started counting the number of acts of aggression I noticed between humans and geese. Over three years I've still not see a goose attack anyone, but I stopped counting after the 30th time I saw children chasing geese.

That is not to say that geese are not aggressive. Internecine aggression is common place and sometimes quite violent, but aggression towards other species is quite rare. The strongest aggression I've ever see to another species is hissing, but only from Canada geese. Egyptian geese are much more shy.

Nest site competition sounds like a plausible impact.

Eutrophication is also plausible, but it is difficult to assign causation. It might be because people like to feed geese.

I don't know of any systematic studies on this matter, but I have seen video footage of adult egyptian geese attacking and killing the young of other wildfowl, namely shellduck, in at least 4 separate occasions, all filmed in The Netherlands. They seem to agressively defend foraging territories for their young and the videos showed egyptian geese aggresively pecking young (

Thank you all for your responses, all very interesting.  Of course, once I have results I'll release them.  Usefully I'm using the entire BTO WeBS dataset for all of England, so if there any impacts, I should (hopefully) be able to identify any impacts.  Although, as mentioned, one of the problems will be separating any effect by the Egyptian Goose from the impacts of the other alien species.  Balázs, thank you for posting those reports, all very interesting. 

Pedro, that is interesting, I don't believe there have been many reports of Egyptian Geese actually killing other wildfowl (irrespective of age).  There have been reports of them attacking both people and other birds in South Africa, but nowhere else.