|MadSci Network: Zoology|
There is probably no good way of excluding one particular species from a feeder. This is especially true for certain species, such as mourning doves, house sparrows, and starlings, that are gregarious, agressive, not picky about what they eat, or some combination thereof. After looking at several websites containg information about seed preferences about the only way to discourage mourning doves via seed preference is by putting out striped sunflower and/or peanuts (shelled and in the shell). Mourning doves "prefer" every other type of seed that is readily available. Another tactic you might try is based on feeding habit rather than food preference. Most doves are ground feeders. Perhaps if you put a helping of seed on the ground, either in a feeder tray or straight on the ground, this might divert the mourning doves from an elevated feeder. However, if the flocks are large enough this may just end up attracting more mourning doves. Unfortunately, mourning doves are one of the species mentioned in an essay in The Birder's Handbook (by Ehrlich, Dobkin, and Wheye) that have benefitted from feeders. They make the point that many populations of mourning doves have stopped seasonal migration and have begun expanding northward due to the availabilty of year-round food supplies at feeders.
Try the links in the MadSci Library for more information on Zoology.