Mockingbirds are very territorial. They are also great native birds to have around. Even if you could, I would not discourage them from being in your yard as they have a job to do just like the bluebirds do. If they have been reinforced by getting mealworms so far, you will have to do something to extinguish their behavior. One basic tenet of behavior is "unrewarded behavior eventually extinguishes itself." So, if you make it impossible for them to get any mealworms for a while, they will eventually stop defending the feeder and move on.

One way to do this is to stop feeding the mealworms. The bluebirds don't need the mealworms. The mockingbirds will move on if they don't get any mealworms for a while.

Another way you can do this is to create a feeder that will not allow the mockingbird to feed from it. A feeder that has holes that are too small for the mockingbird to fit in but will allow smaller birds into it would work to accomplish this. I will include a link to some plans. The thing that you will have to do is to train the bluebirds to recognize the new feeder. This will be hard when they are competing with the mockingbirds. You have to link the two feeders in their minds by gradually changing the feeder over so that the bluebirds connect the worms with the new feeder. The only way to do this is to have the new feeder open for a few days until the blues find them. Like I said this will be hard to do when the mockingbird is chasing them away, so I would stop feeding mealworms for a few weeks and then try this and see if the mockingbird forgets about it and moves on to a new source of food.

The other thing you may have a problem with at some point are hawks that will notice the concentration of song birds at the feeder. This seems to be a bigger problem when you feed seeds as you have many more birds frequenting that kind of feeder. This also creates other problems besides hawks, like disease. I have seen enough people end up with hawk problems from artificial feeding to warn you that it could be the next problem you are facing. Hawks are a necessary part of the system as the bluebirds and the mockers, so you should be happy to have them all. The berry bushes in your yard are a natural way to feed everyone, but they double as cover that helps to protect the birds from the larger predators giving them a fighting chance. Just something to think about when you consider artifical feeding.

Here is a link that might be useful: mealworm feeder

Vonyon - thank you for all the info. I am aware of the problems with feeding birds by feeders, i.e. disease and predators, but I live in a new development that was once heavily forested and is now practically treeless. I found several dead birds in my yard in the weeks after they cut down the forest behind me. I can't help but think they could use some help food-wise. Although I have lots of cover and bird-friendly plants, I only have a small yard and my neighbors are not planting anything. Anyway, I do see your point.

can i ask how to get mockingbirds to leave the nest boxes of my bluebirds alone? no matter where i place the boxes mockingbirds try to run of the bluebirds. can u help?