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Millerbird Acrocephalus familiaris

IUCN Red List Criteria

Critically Endangered B1ac(iv) 
Endangered B1ac(iv) 
Vulnerable B1ac(iv);D1+2 

IUCN Red List history

Year Category
2012 Critically Endangered
2010 Critically Endangered
2009 Critically Endangered
2008 Critically Endangered
2004 Critically Endangered
2000 Critically Endangered
1996 Vulnerable
1994 Vulnerable
1988 Threatened

Species attributes

Migratory status not a migrant Forest dependency Does not normally occur in forest
Land mass type   Average mass 18.3 g

Distribution

  Estimate Data quality
Extent of Occurrence breeding/resident (km2) 2 medium
Number of locations 1 -
Fragmentation -

Population & trend

  Estimate Data quality Derivation Year of estimate
No. of mature individuals 250-999 good Estimated 2011
Population trend Stable medium -
Number of subpopulations 1 - - -
Largest subpopulation 250-999 - - -
Generation length (yrs) 4.4 - - -
Population justification: The population was estimated at 507 ± 295  individuals in September 2010 and 775 ± 298 individuals in September 2011 (Kohley et al. 2010 VanderWerf et al. 2011). Considering the population appears to fluctuate, the band 250-999 mature individuals seems appropriate. This estimate equates to 375-1,499 individuals in total, rounded here to 350-1,500 individuals.
Trend justification: Although there is a lack of precision over the monitoring methods, the existing data does suggest that Millerbird numbers on Nihoa have experienced pronounced fluctuations and have likely ranged between fewer than 50 and more than 800 individuals (VanderWerf et al. 2011).

Country/Territory distribution

Country/Territory Occurrence status Presence Breeding Non-breeding Passage Resident
USA Native Extant       Yes

Important Bird Areas where this species has triggered the IBA criteria

Country/Territory IBA Name IBA link
USA Northwestern Hawaiian Islands site factsheet

Habitats & altitude

Habitat (level 1) Habitat (level 2) Importance Occurrence
Shrubland Subtropical/Tropical Moist major resident
Altitude 0 - 0 m Occasional altitudinal limits  

Threats & impact

Threat (level 1) Threat (level 2) Impact and Stresses
Climate change & severe weather Droughts Timing Scope Severity Impact
Past, Likely to Return Whole (>90%) Rapid Declines Past Impact
Stresses
Ecosystem degradation, Species mortality
Climate change & severe weather Habitat shifting & alteration Timing Scope Severity Impact
Future Whole (>90%) Unknown Unknown
Stresses
Indirect ecosystem effects, Ecosystem degradation
Climate change & severe weather Storms & flooding Timing Scope Severity Impact
Ongoing Whole (>90%) Causing/Could cause fluct Medium Impact: 7
Stresses
Ecosystem degradation, Species mortality
Invasive and other problematic species, genes & diseases Invasive non-native/alien species/diseases / European Rabbit (Oryctolagus cuniculus) Timing Scope Severity Impact
Future Whole (>90%) Rapid Declines Medium Impact: 6
Stresses
Ecosystem degradation
Invasive and other problematic species, genes & diseases Invasive non-native/alien species/diseases / Gray Bird Grasshopper (Schistocerca nitens) Timing Scope Severity Impact
Ongoing Majority (50-90%) Slow, Significant Decline Medium Impact: 6
Stresses
Indirect ecosystem effects, Ecosystem degradation
Invasive and other problematic species, genes & diseases Invasive non-native/alien species/diseases / Unspecified rats (Rattus spp.) Timing Scope Severity Impact
Future Whole (>90%) Rapid Declines Medium Impact: 6
Stresses
Reduced reproductive success
Invasive and other problematic species, genes & diseases Invasive non-native/alien species/diseases / Unspecified species Timing Scope Severity Impact
Future Whole (>90%) Slow, Significant Decline Low Impact: 5
Stresses
Species mortality
Invasive and other problematic species, genes & diseases Invasive non-native/alien species/diseases / Unspecified species Timing Scope Severity Impact
Ongoing Minority (<50%) Negligible declines Low Impact: 4
Stresses
Ecosystem degradation
Invasive and other problematic species, genes & diseases Problematic native species/diseases Timing Scope Severity Impact
Unknown Minority (<50%) Negligible declines Unknown
Stresses
Reduced reproductive success, Species mortality
Invasive and other problematic species, genes & diseases Problematic species/disease of unknown origin / Unspecified species Timing Scope Severity Impact
Future Majority (50-90%) Rapid Declines Low Impact: 5
Stresses
Reduced reproductive success, Species mortality
Natural system modifications Fire & fire suppression / Trend Unknown/Unrecorded Timing Scope Severity Impact
Past, Likely to Return Majority (50-90%) Rapid Declines Past Impact
Stresses
Ecosystem degradation

Recommended citation
BirdLife International (2014) Species factsheet: Acrocephalus familiaris. Downloaded from http://www.birdlife.org on 27/08/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 27/08/2014.

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

To provide new information to update this factsheet or to correct any errors, please email BirdLife

To contribute to discussions on the evaluation of the IUCN Red List status of Globally Threatened Birds, please visit BirdLife's Globally Threatened Bird Forums.

Key facts
Current IUCN Red List category Critically Endangered
Family Sylviidae (Old World warblers)
Species name author (Rothschild, 1892)
Population size 250-999 mature individuals
Population trend Stable
Distribution size (breeding/resident) 2 km2
Country endemic? Yes
Links to further information
- Summary information on this species