Had they consulted with anyone who actually dealt with birds in a non-commercial way (ie: not the people who are selling them the "trained" pigeons), those birds might have been saved and not used.
The fact of the matter is that training pigeons to return is not something that you can do on the spur of the moment. These birds would have had to have been trained for months and even then, would have suffered some losses on the way back. The fact that the birds are drowning in nearby water pools and being attacked by animals only reinforces the fact that they are lost and confused, and that proper training time was not spent.
This same thing happens at weddings all the time. Someone gets it into their head that releasing a flock of doves or white pigeons would be beautiful, and hires a "dove trainer" (note the quotations used for sarcasm) to deliver doves to the wedding. Unfortunently, these doves tend to fly about 30 yards or so from where they are released, then crash to the ground, for two reasons -- first, their wing muscles are not developed enough to sustain long flight because they're cooped up in cages or 8'x 12' flight cages all their lives and haven't been able to properly fly, and secondly, because their homing instinct doesn't work without vigorous training. It's cheaper for the "dove trainers" to simply purchase more doves at $10 a dove, than it is to recapture them all.
I know this because I've dealt with mistreated doves that this has happened to.
As a hobbyist dove owner and handler/rehabilitator, things like this annoy me. I wonder how the 9/11 families who have had victims, from a result of human stupidity, would react to knowing that those symbolic, beautiful white pigeons that were released, are drowning in fountains, being torn apart by animals, hit by cars, and starving to death, because of human stupidity as well.
Anyone who would be willing to "rent" animals as designer items without the animal's benefit in mind, should be questioned thoroughly.