I live near the confluence of three canyons. Our yard includes a ridge top separating the smaller from the middle sized canyon. The view from my chair looks west down the middle canyon to where it joins the larger one. To my left, I look out over the middle canyon, toward the wall that separates it from the larger. About 150 feet out is a pair of 60 foot pines whose tops are about level with me. That is the favorite perch of Janis and Slim. When I arrived this morning, one of the two was sitting near the top of one pine. The other soon joined it, and gave me several head bobs in greeting. One of my great pleasures is when Janis flies from that tree top toward me, dipping down to mask her approach behind a sage bush, and then reappearing moments before landing on my finger, expecting to sort through several peanuts. Being a jay, she does that when it suits her. This morning, they were both happy to sit on their pine and watch with me as the sun crawled down canyon walls. After about ten minutes, a different jay approached from the far canyon wall seven hundred feet behind the pines, arcing its path well west of Janis and Slim, who have been know to intercept and harass jays that overfly their territory. As this jay got closer, another from down the canyon joined it and they both landed on the top of a 30 foot oak that stands above my chair. As is typical, this incursion brought both Janis and Slim over and into the oak, where they adjusted the seating arrangements selected by the first two jays. To my right is the smaller canyon. Live oaks block much of my view, but the rim is visible, about fifteen hundred feet away. Three strong calls announce the arrival of two other jays from that direction. Within 20 seconds of the first two jays' arrival, there were at least ten jays in the oak. As they settle in and jostle each other, I call to Janis and put out my finger. She flies out of the middle of the tree and sorts peanuts for a few moments, letting the nut catchers wait. After she selects a nut and carries it back to her pine, I toss one up and out over the canyon. Several jays take off after it, one easily wins the race and carries its prize back up the canyon from where it came.
That is not how all our catching competitions start. Sometimes Flip sees me climbing the hill, and arrives at the oak top as I arrive at my chair. Flip's presence and his catching a peanut is often not enough to bring Janis and Slim over. That may be because Flip's territory is to the north and does not overlap theirs. Or it may be that Flip has been catching peanuts for seven years. Or maybe because Flip is Janis's father. In any event, when Flip catches a peanut, that will often attract another jay from up in the smaller canyon, and that will eventually set off the cascade of jays coming to the tree to compete, play and spend some time with their neighbors.
California jays do not gather in groups very often. The literature indicates that transient jays tend to flock together, and these are typically first year birds who have not yet selected a mate or territory. Last week I encountered a flock of at least twenty five jays in the park near our house. They were on the south face of a large hill, working their way up a crease in the hillside that supported several small bunches of willow trees. They reached the uppermost thicket, about 600 feet up the hill, and hung out there for about twenty minutes, fly catching and foraging. They made several calls while flying back and forth between different trees, and I heard one rattle. They then flew back down toward the canyon floor and across into woods of live oaks.
The very next day I was again fortunate to witness a gathering of a different sort. The resident jay pairs in the territories surrounding our property engaged in a series of very loud interactions over a period of about twenty minutes. Four to six jays would gather near a territory boundary and call back and forth. It was a mix of jay-jay-jay calls (often accompanied by the rattle of a female) and the single screech call that seems common when they communicate across the canyons. They flew back and forth, and often there were jays gathered at three different territory boundaries at the same time. During all this commotion, I recognized and called to Jimmy. He came to my hand for a peanut, and continued his interactions with the others. My guess is that they were discussing territory boundaries, possibly with jays who do not currently have local territory.
The only other gatherings that I've witnessed have been mobbing of predators, with several jays surrounding a hawk or cat while calling. The literature mentions "jay funerals" as another gathering of jays. I hope to never encounter one.