I’m sorry but we don’t really have any research on this topic. There are various trap makers around the country and over the years we’ve learned that some traps work and some don’t. When we find out about any one style of trap, we typically bring them in and see if they work basing much of our decision on what happens after some are used out in the field. The Grackle Traps we carry have proven to work which is why we continue to sell them. If we learn something isn’t working, we either drop them or get another model/style to replace it. As a reseller that carries over 100 models of live traps, we’ve learned if something doesn’t work there is no need to carry it for the same reasons you cited.
That being established I do know we have been selling this trap for many years and I have not fielded any question or complaint that couldn’t be handled. The key to this trap being successful (as is true with most any repeating bird type trap) is that you must both keep it filled with bait and remove trapped birds daily. This will keep the ones caught both content and well fed so they are inclined to lure more inside. Remember, food is a BIG motivator for most any animal. I personally have been able to lure a wide range of birds to feed out of my hand including crows so they might be smart but they are basically motivated by the same thing as most any other animal.

By removing trapped birds daily you don’t run the risk of having other birds see something bad happening “in the cage”. When you outside and start shooting birds, it doesn’t take long for them to figure out that “person” =’s “bad” because there is a “sequence” of events when you arrive. First, they see you, then they hear a “bang” and then they see other birds dropping dead. Before long they equate seeing you to dead birds. The same thing can happen if you leave birds in the cage too long and some die. The others will become afraid of it so by removing them daily, you should be able to minimize this problem that can lead to trap shyness.

In most cases these animals will not quit and move on without some strong “persuasion”. This means you’ll need to trap and relocate them. As you’re probably learning, they can cause quite a bit of damage to docks. They will mostly chew the styrofoam and/or plastic floats doing permanent damage. They can also chew the dock itself depending on the kind of wood used to construct it. The Easy Set Live Beaver Trap is a good option for this type of problem but you could use some other devices we have featured in our beaver control article.