Status and Trends of the Land Avifauna on

2008 Hawai`i Conservation Conference

Based on a report to the U.S. Fish and Wildlife Service by R.J. Camp, T.K. Pratt, A.P. Marshall, F. Amidon, and L.L. Williams

Outline

• Introduction • Sampling – Population estimation – Trend estimation • Estimates • Threats • Focal Species – Nightingale Reed-Warbler

Introduction

• Mariana Islands identified as an Endemic Bird Area by BirdLife International – Increasing human population & rampant habitat transformation – Brown Tree (Bogia irregularis) eliminated most on – now reported from Saipan • Faced with large-scale habitat change and an imminent new predator, how are land birds on Saipan fairing?

The Birds

B. Kumiu E. VanderWerf T. Shears Yellow Bittern White-throated Ground-Dove Mariana Fruit-Dove

J. Yue T. Pete

Collared Kingfisher Micronesian The Birds

A. Leishman E. VanderWerf S. Vogt

Rufous Fantail Nightingale Reed-Warbler Bridled White-eye

T. Pete E. VanderWerf

Golden White-eye Micronesian Starling The Birds

S. Vogt E. VanderWerf

Micronesian Megapode Micronesian Swiftlet

T. Rosell L. Kee T. Pete Island Collared-Dove Eurasian Tree Sparrow Orange-cheeked Waxbill

Sampling

• 1982 (Engbring et al.) • 1997 (USFWS) • 2007 (USFWS)

• Standard point- transect sampling – 14 transects – 244-248 stations – 242 resampled

Estimation

• Fit a species specific detection function to account for birds present but missed • Estimate density and variance by species – Global detection function – Account for covariates (eg weather) – Annual estimates generated

Trends

• Determine trend with repeated measures ANOVA – Densities were log + 1 transformed – Compound symmetry variance-covariance structure – Kenward-Roger adjustment to df – Tukey’s adjustment for multiple-comparisons • Increasing, stable or declining trends

Increasing Densities

40 140 35 A B B 120 A A B 30 100 25 80 20 60

Density 15 Density 10 40 5 20 0 0 1980 1985 1990 1995 2000 2005 2010 1980 1985 1990 1995 2000 2005 2010 Year Year Yellow Bittern White-throated Ground-dove

700 300 600 A A B 250 A B C 500 200 400 150 300 Density 200 Density 100 100 50 0 0 1980 1985 1990 1995 2000 2005 2010 1980 1985 1990 1995 2000 2005 2010 Year Year

Micronesian Myzomela Micronesian Starling Increasing Densities

8 7 A B B 6 5 4

Density 3 2 1 0 60 1980 1985 1990 1995 2000 2005 2010 50 A B B Year 40 30 Eurasian Tree Sparrow

Density 20 10 0 1980 1985 1990 1995 2000 2005 2010 6 Year 5 A A B 4 Island Collared-dove 3

Density 2 1 0 1980 1985 1990 1995 2000 2005 2010 Year

Orange-cheeked Waxbill Stable Densities

60 50 A B A 40 30

Density 20 10 0 1980 1985 1990 1995 2000 2005 2010 70 60 A A A Year 50 40 Collared Kingfisher 30 Density 20 10 0 1980 1985 1990 1995 2000 2005 2010 70 60 Year A A A 50 40 30

Mariana Fruit-dove Density 20 10 0 1980 1985 1990 1995 2000 2005 2010 Year

Bridled White-eye Decreasing Densities

1200 2000 1000 A B C A B C 1500 800 600 10% 1000

Density Density 23% 400 41% 500 29% 200 47% 45% 0 0 1980 1985 1990 1995 2000 2005 2010 1980 1985 1990 1995 2000 2005 2010 Year Year

Rufous Fantail Golden White-eye

80 70 A B C 60 50 40 30%

Density 30 20 44% 10 61% 0 1980 1985 1990 1995 2000 2005 2010 Year

Nightingale Reed-Warbler

Other Birds

500 400 A A B 300 200 Density Micronesian Megapode 100 • Very rare species 0 • 1980 1985 1990 1995 2000 2005 2010 Detected 5 1 0 Year • Saipan population declining • Although more common on Micronesian Swiftlet other Mariana Islands • numbers a magnitude smaller • no movement assumption violated • preferentially record near point • distances biased low > overestimates

Rapid human development

• 429% increase between 1980 & 2000; subsequent decline • Coastal plain, southern plateau, Kagman peninsula (70%)

Land class & disturbance Saipan 100 • Introduced Forest 80

60 – 27% Percent 40 • Secondary Forest 20

0 – Forest Secondary Agroforest Nonforest 30% Vegetation Land Class • Agroforest

Saipan – 11%

100 80 • Minimum Disturbed 60

40 – 68% Percent

20 Falanruw et al. 1989

0 Introduced Limestone Casuarina Forest Type Nightingale Reed-Warbler

• Regional Comparisons • Habitat Associations

Photo by CNMI-DFW NIRW Regional Comparisons

• Little development – Suicide – Tanapag • More development – Garapan – Kagman – Susupe – Fadang • Repeated measures ANOVA

NIRW Regional Comparisons

2 Less Development More Development . 1.5

a b b a a b a b b a b c 1 a a a a a b b b 0.5 NIRW Density (SE)

0 1982 1997 2007 1982 1997 2007 1982 1997 2007 1982 1997 2007 1982 1997 2007 1982 1997 2007 Suicide Tanapag Garapan Kagman Susupe Fadang Year and Region

NIRW Habitat Associations

• Suitable habitat – Open, Secondary forest and Tangantangan thicket • Less suitable habitat – Golf course, Limestone forest and Residential • 2-way repeated measures ANOVA

NIRW Habitat Associations

• 58 to 22 birds/km2 Habitat 1982 2007 • Year & Habitat effects Suitable Densities

• Large-scale habitat change Open 37 22 • Imminent new predator – SF 31 25 brown tree snake TT 40 27 • Saipan Upland Mitigation Less Suitable Bank (2002) GC 38 4 • Surveying frequency LF 18 8 • Surveying effort • Demographic studies Res 60 5

Acknowledgements

• Funding: • Data Sets – CNMI Division of Fish – 1982: Engbring, Ramsey & and Wildlife Wildman – U.S. Fish and Wildlife – 1997: USFWS Service • Bird Observers – U.S. Geological – C. Aguon, F. Amidon, P. Survey – PIERC Ashman, J. Engbring, J. Lepson, A. Marshall, G. • Thanks to: Martin, P. Pyle, N. Shema, – M. Gorresen, J. P. Radley, M. Reynolds, & Hatfield, R. Holden, S. L. Williams Kremer, & L. Mehrhoff