Hi Mac,
I'm currently working on cottontail rabbits at a few different city gardens for a municipality near me. They are decimating the annual flower plantings as soon as the gardeners put them in. I too, am limited to cage traps due to city ordinance and heavy public traffic. Of course, this time of year, rabbits are much more difficult to cage trap than in the Winter, as they have much more food available to them. I will list some things that have worked for me, but bear in mind that my costs for these baits and lures are passed along to my customer, so basically, price is not an issue for me personally.
First, I seem to have better success with a covered cage trap - I make my own covers from wood, but also use the Safeguard brand traps along with their factory plastic covers, and even burlap bags.I like to offer the rabbits a 'smorgasbord' of different food items and/or smells. Lately, I have been using a large piece of cabbage leaf ( for eye appeal ), an alfalfa cube, a piece of celery, carrot, pear & apple ( slices ), an 'apple flavor horse treat' wafer along with some commercial food-based woodchuck lure or paste bait. Lures & baits that have worked well for me recently are Blackie's "Numchuck" (that I got from Bogmaster), Jameson's Formula One & Two, and Erickson's "Garden Fresh" in conjunction with the food baits mentioned previously. I will also disturb the dirt where I am placing the trap, if possible - fresh digging is attractive to them and I always scratch out a little dirt pattern in front of the cage as well. I have used apple juice/cider in a spray bottle and spray the inside of the trap, and used it as a trailing scent as well. Salt is good too - rock salt, softener salt or those round rabbit salt licks, but they're hard on the cages and it kills nearby plantings, so I generally avoid it. Urine is a great attractor, perhaps because of the salt content - use rabbit urine if you can get it, but I have caught rabbits with nothing more than fox urine ( yes... fox urine ) sprayed on a piece lettuce or cabbage leaf. Seems that I will usually catch at least two squirrels, or more, for every rabbit caught, so I set real heavy - lots of traps - but I'm doing it for pay.
In a nutshell, caging rabbits in the Summer is a real pain, and I avoid it like the plague, with exceptions for good customers. We have had a real population explosion of rabbits the last few years, so reluctantly, I have had to deal with them. I hope that some of these ideas will help you with your particular rabbit situation.
Regards & best wishes,
Mike Tucker