The child constructor always calls one of the parent constructors*; if you leave out the call to "super(...)" one will be added implicitly without any arguments. This whole process of a child class constructor calling its super class constructor is called constructor chaining, and it will only end when Object's non-argument constructor is called.
In this case, the parent constructor can throw an exception so the child constructor must, as always, either catch it or declare throw it. Since the first statement must always be a call to "super(...)" or "this(...)" (as said before, if you don't add it the compiler will) catching is not allowed so the only option is to throw it.
* Or another constructor of the same class if the first call is to "this(...)".