I am mostly making a "devil's advocate" argument about bird language here, because I think it's interesting that there's even enough evidence for something like bird grammar to make it a feasible subject of debate.
One last time and I will shut up. The people who should know about it--the linguists, who it seems you don't trust --don't think there really is enough evidence to make it worth debating. It seems to me closer to the Eskimo 8 zillion words for snow error: not exactly true, and even if it was, blown all out of proportion (well, if there was evidence that birds had something like a syntax, then this would be much more significant.
I really don't know whether I think they will ever proove it, but it does seem to make sense to me intuitively--why wouldn't other species have something like language?
And, again, it makes perfect sense. Other species would and do have something LIKE language--various kinds of communication systems. They just show a number of real qualitative differences from human languages: human languages can do many many things they can't. For whatever reason. Presumably evolutionary.