Critter behavior

What do Blue Jays have against squirrels?
I just saw three of them ganging up on one very fast squirrel. Why?  
Squirrels don't bother eggs do they? Jays aren't predators are they?
What do they have against it?

They both eat acorns.

M Ljin wrote:They both eat acorns.

It's spring and they were in maples. No oak trees within 500 yards.
?

The kind of Blue Jays we have are omnivores although primarily vegetable matter and insect eaters. Yes, they compete with squirrels for nuts, but squirrels here are known for stealing eggs and hatchlings, and may compete for good nest sites.

If food is scarce and they've got babies to feed, that may increase their aggression towards competitors.

Blue Jays are groupies and may hang in multigenerational groups, so mutual defense seems in character.

Pearl Sutton wrote: It's spring and they were in maples. No oak trees within 500 yards.     ?

Are maple keys fattening up in your ecosystem? I'm not sure I've seen either squirrels or jays eat them, but Steve Thorn has observed the squirrels feasting:
https://permies.com/t/110456/raining-maple-seeds-squirrels

Actually we warmed up then froze again exactly at the time to kill the buds the maple helicopters come out of. There will be zero helicopters this year in this area.
The trees fully leafed out way early due to all this.

what a timely thing. the day before yesterday I was putting up pea brush and noticed three birds (maybe ovenbirds? robin-sized brown birds, very normal birds around here) ganging up on another of the same kind. Actually I heard some weird peeping and it was the injured bird- it was pinned on its belly, its back feathers had mostly been pulled out and it was bleeding. They were on the roof of the house next door. When I stood up to get a better look they all stopped the attack and stared at me (at which point I thought "oh crap". they did not come for me, though, at least not yet....). Then they all flew away, including the bird being attacked! It was very, very strange.

Pearl Sutton wrote:Actually we warmed up then froze again exactly at the time to kill the buds the maple helicopters come out of. There will be zero helicopters this year in this area.  

I recall you have a lot of Maple trees around, so that may mean that you now have a bird/squirrel food shortage situation. It will be interesting how things all work out.

Generally, animals only fight if they feel they need to. It consumes energy and risks injury. You may never know what really started the squabble you observed, but I expect that one side or the other had clear reasons. We will never be sure what they were.

They do compete for the same foods, but squirrels often get too close to their nests. Jay's are extremely protective of their babies. Most birds are.

Pearl Sutton wrote:What do Blue Jays have against squirrels?
I just saw three of them ganging up on one very fast squirrel. Why?  
Squirrels don't bother eggs do they? Jays aren't predators are they?
What do they have against it?

Rats eat eggs and hatchlings; in fact they can be so predatory on nests that they exterminate the birds. I have personally witnessed an invasion of roof rats completely eliminate a formerly-vibrant songbird population. Squirrels are basically just furry rats, and if they don't also eat eggs and hatchlings, I'd be astonished.

Rats, not feral cats, are the primary predator on urban birds. If you have rats but you don't have cats, the rats will take over and destroy all the nests, and that's what happened where I lived. (Neighbor's dog killed all the cats, rats moved in, birds vanished.)

There was a study (cameras watching nests) on predation of ground-nesting birds. They expected the primary predators would be weasels, mink, raccoons, and the like. Instead, 60% of the predation was by ... whitetail deer. And there exists video of a deer hunting and consuming birds.

Everything likes concentrated protein, when they can get it. I have also seen sheep nibble on a sheep carcass, and woe betide the dog food if the horses discover it!

Generally, animals only fight if they feel they need to. It consumes energy and risks injury.

Animals fight, a lot. We don't see it so much with domestic animals because we define territory for them, and we provide food and mates (or sterilize them, mostly so they don't fight as much), and we select against interpersonal aggression (which is inherited behavior). Wild animals have to do all that for themselves, there's considerable selection FOR individuals who will fight, and they fight over those resources and sometimes just because they don't like someone. Chimpanzees and spotted hyenas have been observed waging deliberate war on neighboring populations, and the leading cause of death in hyenas is other hyenas. My well-fed free-range chickens would sometimes decide one of their number had to go, and that hen would be chased down and receive a sound thrashing for no visible reason (my roosters didn't fight, but my hens did, regularly). Most dogs LOVE a good fight; the only reason we don't see more fights is that we've bred it out of them. It's not at all unusual for animals to fight, within their own species or against a competing species, and sometimes the reason is evidently "I don't like your face."

Yay! Wild bird questions! I love Blue Jays but they are kind of jerks and eat eggs, baby birds and baby squirrels. Basically anything they can. They also store nuts and eat them later and steal hidden squirrel stashes as well. We have a gang of them that fly around like everyone owes them money. The squirrels hate them for this. But don't feel to bad for the squirrels cause they also eat eggs, baby birds and small animals. They also find and eat the secret nuts the Blue Jays hide. Basically they are both kinda jerks and don't like that the other is a jerk so they tend to fight alot. But the energy they spend fighting each other keeps them away from the small song birds. If you want to see an interesting relation you should see is how crows piss off grackles just for the fun of it! I suspect the squirrels and Blue Jays also enjoy there squabbles.

Sam Potter wrote:If you want to see an interesting relation you should see is how crows piss off grackles just for the fun of it! I suspect the squirrels and Blue Jays also enjoy there squabbles.

When I had ravens, I didn't have starlings, because the ravens had no end of fun harassing away any stray starlings. Friend had a horse that just loved tormenting the sheep (chase them around and yank mouthfuls of wool). And we've all had dogs and cats that ding at each other, just for fun. Animals are generally jerks. :D