Not sure about this. Also not sure if they will have to give up their right to sue. If your house burns down, the insurance settlement consists of the dwelling as well as the contents. My impression is that there is probably some kind of insurance in place that will quickly reimburse travelers that lose their belongings on a flight whatever the reason for the mishap. If LaGuardia is found to be negligent in some way, then the insurance company that paid the claim can seek the claims they have paid from that source. 155 x $5k is only $775k total, and therefore not much in the scheme of things. Of course, LaGuardia is probably not liable for the birds, and I doubt your can sue Canada (I think they were Canadian geese), so the insurance company will probably eat this money. More likely that the passengers are being asked to sign that the $5,000 will end their claims regarding personal belongings that were lost - just to make sure that nobody claims three laptops, other high end equipment, and $2000 suits.

Of course, I could be wrong too.