That's because of Duck Typing [1]. I really like Python for how quick and easy it is to make small pieces of software, but I fully agree that Duck Typing can become more of a hindrance on larger projects.
It'd be great to have more static duck typing. I suppose that's the point of traits and mixins, to some extent. But it'd be nice to have on-the-fly constraints created and enforced.
Unless you're referring to type-inferencing when you use the term static duck-typing. The term duck-typing was never meant to refer to type-inferencing - duck-typing is type-opacity right into the runtime. The whole point of duck-typing is that objects can be referred to generically even in cases where their underlying type would be undecidable.
Type-inferencing gives you some of the source-level flexibility of not having to refer directly to an object's type much like duck-typing, but without many of the crazy runtime disasters that you can get with duck-typing.
I guess the conclusion is that the definition of duck typing is fuzzy and misleading.
public dynamic DoDynamicStuff(dynamic wooDynamix)
{
Console.WriteLine(wooDynamix.DynamicProperty1);
}