Bird conservation efforts in the last few decades mainly focused on wetlands. See DDT, national wildlife refuges, and the duck stamp.
So, it's not like the decline is inexorable. But it's not going to fix itself.
They interpret it to only prohibit intentionally killing protected birds. So, if you wanted to, say, drain a wetland that migratory birds depended on to build a parking lot, which would wipe out nesting grounds and lead to a lot of bird deaths--that would be fine under the Trump interpretation as long as you aren't building the parking lot to intentionally kill the birds.
This has already started having an effect. The US Fish and Wildlife Service, for instance, no longer stops loggers from cutting down trees with nests of protected birds in them, killing eggs or chicks.