Attwater's prairie chicken
The Attwater's prairie chicken once numbered about a million in Texas and Louisiana, but their current population has been reduced to less than 50 birds due to the loss of 99% of their original habitat--coastal prairie.
The tallest of North American birds is the whooping crane, which once had a range of over two-thirds of the U.S., but now there are just an estimated 145 cranes in the wild due to loss of habitat; they migrate each year from Canada to Texas--a 2,700 mile trip.
The California condor nearly became extinct from poaching, lead poisoning, and habitat loss, but conservation efforts saved the species, with perhaps a few more than 300 existing--half of those in captivity.
The loss of its habitat and people collecting the last remaining birds as "trophies" critically endangered the ivory-billed woodpecker to where it was believed to be extinct, but recent evidence points to small numbers of the species living in the heavily forested regions of the eastern portions of Arkansas.
The Kirtland's warbler is dependent on particular types of pine trees. As these trees were harvested, the bird struggled to thrive; efforts to preserve its habitat paid off, as there are currently around 1,200 in the state of Michigan.