The photo above that Dick Tipton shot of the Osprey getting hammered by a Western Kingbird is the epitome of what lengths small birds go to in order to protect their home and family from larger birds, whether the threat is real or not.
There is no way anyone could convince the energetic kingbird that the osprey means no harm. To a small bird with an open nest - such as kingbirds use - larger birds mean trouble as they carry off nestlings and eat them.
But in the long run it isn't all that "bad." Nature almost always generates a surplus, a saving grace during baby times for birds. The osprey, for example, has three young, which is its insurance policy for survival of that gene pool, while the kingbird usually has five nestlings, and often it's the weaker one that gets polished off by predator or tool of natural selection.
Over the millennia during which birds have been reproducing, the rule of thumb has been to lay more eggs than necessary, hatch more babies then necessary and try to help more babies survive than necessary. That keeps Murphy's Law, which states, "Anything that can go wrong, will go wrong," at bay. Barn owls have worked out their insurance policy for survival to a science. When a momma barn owl lays an egg, she begins to incubate it. Over the next week or so, she'll lay three to five eggs, incubating them as they arrive. They hatch in the same order, and by the time the last egg has hatched, the first nestling is already looking for things to eat. If food is scarce, and mom and daddy barn owl cannot keep up with mice to slake the hunger of the largest of the brood - well - you know who/what gets eaten...
Eagles have a similar strategy, only the larger one will literally kick its sibling out of the nest if there's not enough food. Many viewers watching the golden eagle nest on the Wolf Tree web site this spring saw the results of that situation. One day there were two eaglets, and the next day there was one. The other was laying dead at the base of the cliff after the larger one shoved it out of the nest during a squabble over food.
On top of that, crows, ravens, magpies, jays, chipmunks, weasels, snakes, skunks and a lot of other birds, mammals, reptiles and amphibians all eat baby birds.
The nefarious bullfrog eats baby ducks like popcorn. They are not native to Oregon's ponds and lakes, and have no business being here - but they are allowed to breed and raise havoc here because they are a "game animal" with a "season" on them, despite the damages they do to our native amphibians and waterfowl. It's a good thing mallards and our native salamanders lay lots of eggs...
That osprey in the photo above gets hammered from both ends. Smaller birds go after it because it resembles a bird-eating hawk. An osprey wouldn't know what to do with a baby kingbird, even if it was in the water; osprey are fish-eaters. But then, so are bald eagles.
Yep, you guessed it, eagles chase osprey and force them to drop their fish, then the eagle snatches it (sometimes before it hits the water), and the osprey, probably muttering under its breath about the unfairness of it all, has to go back and catch another one, which it does handily.
Nature is always trying to ensure that her creatures are going to survive by making it possible for them to keep up the reproduction rate. In that light, wait 'till you see what happens the next time our lowly little meadow vole decides it's time to crank out a surplus. But that's another story...