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Title: Radar Study of Seabirds and Bats on Windward Hawai'i 
Author: Reynolds, Michelle H.; Cooper, Brian A.; Day, Robert H.
Date: 1997-01
Publisher: University of Hawaii Press
Citation: Reynolds MH, Cooper BA, Day RH. 1997. Radar study of seabirds and bats on Windward Hawai'i. Pac Sci 51(1): 97-106.
Abstract: Modified marine surveillance radar was used to study the presence/
absence, abundance, and flight activity of four nocturnal species: Hawaiian darkrumped
petrel [Pterodroma phaeopygia sandwichensis (Ridgeway)], Newell's shearwater
[Puffinus auricularis newelli (Henshaw)], Band-rumped storm-petrel [Oceanodroma
castro (Harcourt)), and Hawaiian hoary bat (Lasiurus cinereus semotus
Sanborn & Crespo). Hawaiian seabirds were recorded flying to or from inland
nesting colonies at seven sampling sites on the windward side of the island of
Hawai'i. In total, 527 radar "targets" identified as petrel or shearwater-type on the
basis of speed, flight behavior, and radar signal strength were observed during eight
nights of sampling. Mean movement rates (targets per minute) for seabird targets
were 0.1, 0.1,0.3, 3.8, 0.9, and 2.2 for surveys at Kahakai, Kapoho, Mauna Loa,
Pali Uli, Pu'ulena Crater, and Waipi'o Valley, respectively. Two percent of the petrel
and shearwater-type targets detected on radar were confirmed visually or aurally.
Flight paths for seabird targets showed strong directionality at six sampling sites.
Mean flight speed for seabird targets (n = 524) was 61 km/hr for all survey areas.
Peak detection times for seabirds were from 0430 to 0530 hours for birds flying to
sea and 2000 to 2150 hours for birds returning to colonies. Most inland, low elevation
sampling sites could not be surveyed reliably for seabirds during the
evening activity periods because of radar interference from insects and rapidly flying
bats. At those inland sites predawn sampling was the best time for using radar to
detect Hawaiian seabirds moving seaward. Hawaiian hoary bats were recorded at
eight sampling sites. Eighty-six to 89 radar targets that exhibited erratic flight
behavior were identified as "batlike" targets; 17% of these batlike radar targets
were confirmed visually. Band-rumped storm-petrels were not identified during
our surveys.
ISSN: 0030-8870

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