Radar lab to survey Kauaʻi’s endangered seabirds, monitor declining population

Starting now until the middle of July, the Kaua‘i Endangered Seabird Recovery Project mobile radar lab will be surveying island’s two endangered seabirds all around Kauaʻi.

Monitoring Kauaʻi’s two endangered seabirds ‘A‘o (Newell’s Shearwater) and Ua‘u (Hawaiian Petrel) via radar has been ongoing since 1993. Recent data from 2017, showed a massive decline in populations of these species, according to the state Department of Land and Natural Resources.

The study used truck mounted radar at 15 standard sites around the island. Radar surveys at these sites were started in 1993 by Robert Day and Brian Cooper of ABR Inc., and were continued near-annually by the Kaua‘i Endangered Seabird Recovery Project from 2006 onwards.

According to DLNR, radar is utilized worldwide to study birds and is a key tool to monitor the island’s seabirds as they fly overhead in darkness to and from their breeding colonies and the sea. “The radar allows observers to “see” the birds flying overhead in the darkness as a series of dots passing across the radar screen. By assessing the speed of movement, the direction of travel, and the time that the event is recorded, birds are identified to species,” according to the department.

Using this long-term data, KESRP is able to quantify the change in the movement rates of both species; a proxy for their population size.

Between 1993 and 2020, radar data indicated a 72.8% decline for Hawaiian Petrels (at an average rate of 4.7% a year), with 10 out of 13 sites having drastically reduced numbers of radar targets at an average change of -53.6%, according to state officials.

“Given that Kauaʻi holds 90% of the world’s population of ‘A‘o and a significant proportion of the world’s population of Ua‘u, it is vital that we protect these birds,” DLNR officials said.

Conservation actions to reverse these declines have been implemented in some of the colonies of these species however, populations of both species should be monitored constantly to better understand the impact of these actions, according to the department. To keep up this monitoring, KESRP continues their radar monitoring this year.