I don't know if there's a danger to whole seeds but what I found after doing an extensive google search on grapes because I wanted to feed mine leftover pulp from making juice is that technically the seeds like with most other plants contain a toxin. However every site and research paper agreed that they would have to eat a lot of seeds to have any bad effects. Unless your giving your chickens handfuls of grapes each a day it shouldn't effect them. Just like apple seeds contain a chemical which turns into cyanide but you'd have to eat entire cupfuls of just seeds to actually poison yourself.
Grapes do occasionally poison dogs for unknown reasons. It isn't every grape or often but odd cases have shown up and noone is sure why. It could even be something on the grape like pesticides. They haven't figured it out. As far as I know it hasn't been seen in other animals and it's not common but it's something to keep in mind if your feeding grapes to any animal.
Our wild eastern turkeys love our grape vines and pick em themselves. I would say they have a natural instinct for edibles.
As far as dogs, I read those studies too and my personal feeling is there must have been other predisposing/genetic factors that affected those dogs. My dog ate grapes and raisins on a pretty regular basis and lived to 14 years - ripe old age for a labrador retriever.
Here are some pictures I took at an animal sanctuary. All these guys were rescued from the most horrible situations. They LOOOOVE grapes. The have to throw a decoy before you open the gate and they go running, a stampede of turkeys and chickens
This poor girl can't pick up the grapes because her whole beak was choped off, you have to hand feed her.