Pollution per se, I'm not so sure, but changing habitats have critically devastating effects on migratory birds. This is because they are sensitive to protecting habitat not in one location but protecting habitat along their migratory paths from Canada to the south.
More and more, scientific research is clarifying where those routes are, and that is hopeful, because perhaps we can better preserve these corridors that are essential to the migratory birds. But migratory birds are one of the most affected by habitat destruction because of this reliance on a number of way stations.