A hopeful new study shows the Endangered Species Act has been extremely successful in stabilizing and increasing threatened or endangered bird populations, including two Pacific Island species that have been in the care of Chicago-area institutions since the mid-1980s.

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The nonprofit Center for Biological Diversity released its report titled "A Wild Success" in June. Among the findings: 85 percent of birds protected by the Endangered Species Act have recovered in the continental U.S. Populations in the Pacific Islands have also shown recovery, but to a lesser degree at 61 percent.

Roughly three decades ago, the Lincoln Park Zoo and Brookfield Zoo set up critical captive breeding populations of two bird species native to the Pacific Island of Guam – the Guam rail and Guam kingfisher. These birds “would have been lost to extinction if not for dedicated captive-propagation programs,” the report states.

The Lincoln Park Zoo currently has four Guam kingfishers and one Guam rail in captivity. There are 16 Guam kingfishers at the Brookfield Zoo.

Experimental programs to reintroduce these birds in the wild are under way, specifically on the islands of Rota and Cocos near Guam. However, the wild populations aren’t yet well established, which is why the birds are still classified as extinct in the wild by the International Union for Conservation of Nature.

Megan Ross, Lincoln Park Zoo's vice president of animal care and the Species Survival Plan coordinator for Guam rails from 2002 to 2012, participated in two such efforts to reintroduce the Guam rail species to the wild; one in the early 2000s and another in 2012. The bird was singled out in a Center for Biological Diversity press release as a Endangered Species Act success story.

The population of Guam kingfishers has not rebounded as successfully.

"The Guam rail was a ground bird primarily that occupied a number of different habitats," said Loyal Mehrhoff, the Center for Biological Diversity's endangered species recovery director and one of the study's authors. "The kingfisher, not as much. They prefer better limestone forests on Guam. The Guam rail is much more adaptable."

Tim Snyder, Brookfield Zoo's curator of birds, said two Guam kingfishers – a male and a female – hatched last year at the zoo. Three adult females at the zoo are in breeding programs, Snyder said, and plans are being worked out to reintroduce at least some of the birds to the wild, a project similar to those Ross has participated in.

"Within the next five years, once their captive population reaches 200, we're going to start sending birds to some of the smaller islands around Guam," Snyder said.

The International Union for Conservation of Nature estimates that as of 2013, there are 124 Guam kingfishers in captivity.

The prevalence of invasive species that prey on native birds is one reason populations in the Pacific Island region aren’t recovering as robustly as their U.S. counterparts, according to the study. There is also the matter of funding: Programs supporting bird populations on the mainland get more dollars than those focused on Pacific Island birds.

"I think it's just that they're so far away from Washington, D.C., to be honest," said Mehrhoff. "There's less of an impetus to put money into those [Pacific Island] species."

The invasive brown tree snake is responsible for the decline of the birds in their native habitat, according to the study. Shortly after WWII, the snake was accidentally introduced to the island, probably by stowing away on a Guam-bound aircraft or ship, according to the U.S. Geological Survey. The last wild Guam kingfisher died in 1986; the last wild Guam rail died the following year.

"The brown tree snake [preyed] on nests, birds and chicks, drastically reducing the population," said Ross. "Since [the birds] are island-dwelling species, they did not have the necessary instincts for this type of predator."

Tickets can be purchased online or in person to see the Brookfield Zoo's Guam kingfishers. You can visit Lincoln Park Zoo's Guam rail and Guam kingfishers at their McCormick Bird House for free, although parking rates do apply.

Follow Evan Garcia on Twitter: @EvanRGarcia

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