Aloha, Old Coot

Here’s a bit of a bright spot: 50 years of bird surveys suggest that a trio of endangered Hawaiian waterbirds is on the uptick. And making a bit more effort to restore wetlands on several islands could mean even bigger flocks.

The Hawaiian moorhen, Hawaiian coot, and Hawaiian stilt are year-round residents of low-elevation wetlands. By the 1950s, all three species were considered in trouble due to wetland losses and invasions by exotic plants and predators. All three species are now officially listed as endangered species.

Often, a lack of long-term data makes it hard for biologists to tell if efforts to restore declining species are working. In this case, however, researchers had access to a “remarkable” data set built on bird counts stretching back to 1956, a team reports in the journal Population Ecology. Past efforts to slice and dice the data had concluded that the birds had begun to bounce back after being protected in the 1970s, but those studies didn’t use all the available data or differentiate trends on various Hawaiian islands. To sharpen up the picture, J. Michael Reed of Tufts University in Boston, Massachusetts and colleagues used an array of statistical techniques to sift out trends.

“Our analyses show that all three of the endangered Hawaiian waterbirds have increased in population size over the past three decades,” they report. “The Hawaiian moorhen increase has been slower in more recent years than earlier in the survey period, but Hawaiian coot and stilt numbers still exhibit steep increases.”

Flock growth varied by island, however, with “significant population increases” found on two islands – Oahu and Kauai – “where most wetland protection has occurred.” In contrast, they found “weak or no increases” on two islands – Hawaii and Maui – that have few wetlands or less protection.

There’s opportunity in those poor numbers, however. On Maui, in particular, increasing wetland protection and management “would likely result in continued population gains,” they argue, improving the odds of meeting legal thresholds for species recovery. But “given the long-term trend in the Hawaiian Islands of losing wetland habitat from unprotected areas,” the researchers say “protected refuges and conservation easements on private land will continue to be critically important” to future progress. David Malakoff | June 17, 2011

Source: J. Michael Reed • Chris S. Elphick •, & Elena N. Ieno • Alain F. Zuur (2011). Long-term population trends of endangered Hawaiian waterbirds Population Ecology DOI: 10.1007/s10144-011-0262-9

Image: Hawaiian Moorhen, U.S. Fish & Wildlife Service