Dozens of wildlife biologists will take to Hawai'i's wetlands tomorrow for a statewide waterbird survey that happens twice a year.

The state Department of Land and Natural Resources' Division of Forestry and Wildlife staff and volunteers will set out as early as 6 a.m. to survey more than 250 wetland sites where waterbirds are known to gather — including marshes, reservoirs, golf course canals, prawn farms, sewage treatment plants and the Honolulu International Airport's reef runway.

O'ahu sites that will be surveyed include Hamakua Marsh, Kawainui Marsh, He'eia Wetlands, Pouhala Marsh, Ke'ehi Lagoon and the North Shore taro lo'i and lotus fields where endangered gallinules, coots and stilts are found.

DLNR Chairwoman Laura H. Thielen said the surveys have gone on for 30 years. "Counting birds gives us important insight on the status of different species statewide, and helps us to better manage our endangered waterbird populations," she said.

Earlier counts showed the Hawaiian stilt population at its highest level in more than 10 years, said Paul Conry, administrator of the DLNR's Division of Forestry and Wildlife. "On O'ahu, the number of Hawaiian stilts has gone from 553 counted in 1997 to over 860 stilts counted in 2007."

Steps taken to improve the stilts' habitats and control predators at nesting and foraging sites are helping more of the birds survive, Conry said.

Data collected during the surveys are used by the state, the U.S. Fish and Wildlife Service and other partner organizations to determine population trends and habitat use of four endangered waterbird species — the Hawaiian stilt, Hawaiian moor-hen, Hawaiian coot and Hawaiian duck.

All bird species at a survey area are also recorded, as are weather and area conditions.

People who want to volunteer to help can contact the state wildlife biologists coordinating the survey: O'ahu, Jason Misaki, 973-9786; Kaua'i, Thomas Kaiakapu, 808-274-3440; Maui County, Fern Duvall, 808-873-3502; Big Island, Joey Mello, 808-974-4229.