Mao Gymnomyza samoensis Species Report May 2020 U.S. Fish and Wildlife Service Pacific Islands Fish and Wildlife Office Honolulu, HI Cover Photo Credits Mao, Gymnomyza samoensis photographs courtesy R. Stirnemann. Suggested Citation USFWS. 2020. Species Status Assessment for Mao (Gymnomyza samoensis). May 2020 (Version 1.1). U.S. Fish and Wildlife Service, Pacific Islands Fish and Wildlife Office, Honolulu, HI. 46 pp. Primary Authors Version 1.1 of this document was prepared by Fred Amidon and James Kwon of the Pacific Islands Fish and Wildlife Office, Honolulu, Hawaii. Preparation and review was conducted by Gregory Koob, Megan Laut, and Stephen E. Miller of the Pacific Islands Fish and Wildlife Office. ii Executive Summary The Mao or Ma‘oma‘o (Gymnomyza samoensis) is a large endangered honeyeater (Family Meliphagidae) endemic to the Samoa archipelago. Historically, the species occurred on the islands of Savai‘i and ‘Upolu in the independent nation of Samoa, and on the island of Tutuila in American Samoa, an unincorporated territory of the United States. Historical population estimates are unknown but the species was considered widespread in forested habitats on Savai‘i and ‘Upolu. Currently the species is only known to occur on the islands of Savai‘i and ‘Upolu and the total population is estimated to be around 500 individuals. The range restriction and population declines are believed to be associated with the loss and degradation of Mao habitat and high rates of nest failure and fledgling depredations. Mao habitat loss and degradation is related to human development (.e.g, agriculture and logging), increase in the distribution and number of invasive plant species, increase in number of feral ungulates, and forest impacts from naturally occurring tropical cyclones (hurricanes). Increased nest failures and fledgling depredations are related to nest predation by introduced rats, depredation of juveniles by feral cats, and nest loss due to naturally occurring tropical cyclones (hurricanes). This Species Report evaluates the viability of the Mao, defined as the likelihood that it will persist over time. Viability is assessed by the resiliency, representation, and redundancy of the Mao populations. Each of these terms, and the Mao’s resultant viability, under current conditions are described below. Currently, there are no known Mao in American Samoa. Resiliency is the capacity of a population to withstand stochastic disturbance events. There are no historical population estimates, but the species was considered widespread in forested habitats on Savai‘i and ‘Upolu. Currently, the Savai‘i, ‘Upolu, and Tutuila populations have low to moderate, low, and no resiliency, respectively. The Tutuila population is believed extirpated and both the Savai‘i and ‘Upolu populations have experienced population restrictions and declines. These trends are expected to continue if the threats to the species continue at current levels or worsen. Representation is having one or more populations of a species occupying the full range of habitat types used by the species. Currently, the species is considered to have low to moderate representation due to range restrictions on Savai‘i and ‘Upolu and the extirpation of the Tutuila population. These range restrictions are expected to continue if the threats to the species continue at current levels or worsen. Redundancy is minimizing the risk of extinction of the species by establishing multiple populations across a landscape so some populations will always survive catastrophic events. Currently, the species is considered to have moderate redundancy as the species still occurs in two of the three original populations. Redundancy is expected to decrease in the future if threats to the species continue at current levels or worsen, potentially resulting in the extirpation of one or both of the two remaining populations. iii Table of Contents Cover Photo Credits ........................................................................................................................ ii Suggested Citation .......................................................................................................................... ii Primary Authors .............................................................................................................................. ii Executive Summary ....................................................................................................................... iii List of Figures ................................................................................................................................. v List of Tables ................................................................................................................................. vi Introduction ..................................................................................................................................... 1 Regulatory History .......................................................................................................................... 1 Methodology ................................................................................................................................ 1 Part 1. Life History and Historical Status ....................................................................................... 4 Geography ................................................................................................................................... 4 Species Description ................................................................................................................... 12 Life History................................................................................................................................ 14 Historical Range, Distribution, and Population Status .............................................................. 18 Part 2. Current Conditions and Species Status.............................................................................. 20 Current Range and Distribution ................................................................................................. 20 Factors Affecting Viability ........................................................................................................ 22 Resiliency, Representation, and Redundancy of the Species ....................................................... 30 Resiliency of Current Populations ............................................................................................. 30 Current Representation and Redundancy of the Species ........................................................... 30 Literature Cited ............................................................................................................................. 32 iv List of Figures Figure 1. The three conservation biology principles of resiliency, redundancy, and representation, or the “3Rs”. ........................................................................................................... 2 Figure 2. Islands of the Samoan archipelago. ................................................................................. 5 Figure 3. Monthly mean precipitation for selected areas of the Samoan archipelago. All data from PCCSP (2019). ....................................................................................................................... 6 Figure 4. Monthly mean temperatures for selected areas of the Samoan archipelago. All data from PCCSP (2019). ....................................................................................................................... 7 Figure 5. Cyclone (hurricane) tracks for the central South Pacific from 1898 to 2019. All data from Knapp et al. (2010) and NOAA IBTrACS (2019). ................................................................ 7 Figure 6. Locations of roads in the Samoan archipelago. ............................................................... 9 Figure 7. Vegetation land cover on American Samoa (from data by Meyer et al., 2017). ........... 10 Figure 8. Vegetation land cover for Samoa (from data by LINZ, 2015a-i). ................................. 11 Figure 9. Photograph of an adult Mao by R. Stirnemann. ............................................................ 13 Figure 10. Beak, wing, tarsus, and tail measurements from Mao in Western Samoa (Stirnemann et al., 2015a, p. 381). ..................................................................................................................... 13 Figure 11. Breeding cycle of the Mao (from data in Stirnemann et al., 2015b, pp.5-7) ............... 15 Figure 12. Generalized life stages of the Mao. ............................................................................. 17 Figure 13. The estimated historical range of the Mao. ................................................................. 19 Figure 14. Sites where Mao where observed in Samoa from 1987 to 2000. (Land cover from MNRE, 2006, p. 3). ....................................................................................................................... 20 Figure 15. Locations in 2005-2006 where Mao were detected (●) and not detected (+) (MNRE 2006, p. 4; Tipamaa 2007, in litt., cited in Birdlife International 2012). Land cover from MNRE, 2006, p. 4....................................................................................................................................... 21 Figure 16. Estimated forest cover in Samoa from 1954 to 1999 (MNRE 2014, in litt.; FAO 2005, in litt.) Maps from Figures 4-6