My bird feeders have been sort of a neutral zone all Spring. There has been a wide variety of birds frequenting them and there have been very few skirmishes. Not at all like the hummingbird feeders which are the scene of daily wars between the various hummers. The seed and suet feeders have been relatively peaceful. Of course, there have been some issues. Some as simple as the bigger birds chase off the smaller birds, but even that was relatively calm. I have not seen much really aggresive behavior.
That all changed when the first mockingbird fledgling appeared. All at once the parent mockingbirds have claimed the feeders. No other birds are allowed to feed without being harassed. That includes the seed feeders which the mockingbirds don't use. Any chickadee or titmouse that dares to try to feed will get a fast rush from one of the parent mockingbirds. The rush is like a bullet. It is the fastest flight I have seen by them at any other time. The suet feeders, which the mockingbirds do use, are in the middle of the seed feeders but they don't care if the other birds are on the seed feeders or the suet feeders, the offending birds are chased away.
Their viligance is not continuous. There are long periods of time when the mockingbirds are not in sight. So the feeders are still available for most of the day, but when the mockingbirds return, they stay at least a few minutes chasing the other birds away. Once the other birds quit trying to feed the mockingbirds fly off. The mockingbirds are there fairly constantly during early morning feeding times and near dusk. Inbetween running the other birds off, they spend a fair amount of time feeding the fledglings. The fledglings fly to the parents and bob their heads up and down while making a soft screeching sound as they wait for the parent to drop some food into their mouths.