THE EPIZOOTIOLOGYAND IMPACT OF AVIAN POX ON HAWAIIAN FOREST BIRDS

CHARLES VAN RIPER III,  SANDRA G. VAN RIPER
AND WALLACE R. HANSEN

¹ Geological Survey, Forest and Rangeland Ecosystem Science Center, Colorado Plateau Field Station, 

² Department of Biological Sciences, Box 5614 Northern Arizona University, Flagstaff, Arizona 86011 USA,

³ US Geological Survey, National Wildlife Health Center, 6006 Schroeder Road, Madison, Wisconsin 53711-6223 USA

Correspondence should be directed to:

Dr. Charles van Riper III, USGS/FRESC Colorado Plateau Field Station, Box 5614, Northern Arizona University, Flagstaff, AZ  86011-5614. 

⁴Email: charles.van.riper@nau.edu

                        ABSTRACT. -  We determined the prevalence and altitudinal distribution of forest birds infected with avian pox at 16 locations on Hawaii, from sea level to tree line in mesic and xeric habitats, from 1977-1980.  Isolates from lesions were cultured in the laboratory for positive identification of Poxvirus avium.   Infected birds from the wild were brought into the laboratory to assess differences in the course of infection in native vs. introduced species.  We also documented distributions and activity cycles of potential avian pox vectors.

Native forest birds were: a) more susceptible to avian pox infection than were introduced species, b) most likely to be infected during the wet season, and, c) found to have a higher prevalence in mesic when compared to xeric forests. Avian pox occurred in forest birds at all elevations, but highest levels were in the mid elevational ranges (circa 1200 m) where vectors and native birds had the greatest overlap.  Temporal and elevational differences in prevalence were apparent throughout the annual cycle.  Avian pox probably did not reach epizootic proportions on Hawaii until after introduction of the mosquito and domestic birds in the early 1800s, and since then has had a negative impact on the population dynamics of native forest birds.  Today, this introduced disease is an important factor that should be considered in future conservation efforts that are directed at the recovery of native forest birds in Hawaii.