LOL your Izzy sounds exactly like my Stedman - and I do mean EXACT. Literally, when I was reading your post I felt like someone was writing about my Sted, lol.
Stedman will also go nuts when we are on a walk and he see's another dog. Not SO MUCH if the dog is far, far away...but if we are close to one, he FREAKS OUT!! Bark, bark, bark, bark, bark!
He even rears up on his leash trying to get to them.
Also, just like your Izzy - my Stedman sits at home on the arm of the over stuffed chair and stares out our front living room windows. If there is a dog, cat, squirrel, or even PEOPLE that are outside - HE FREAKS. Again, bark, bark, bark, bark, bark LOL.
I am just so used to it though. It really doesn't bother me too much (I don't know if that's a good or a bad thing LOL) as these are the ONLY times he barks. And it's so funny because my Tatum just stands there and looks at him like he is on crack
