Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Datasheet

Tyto alba
(Barn owl)

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Datasheet

Tyto alba (Barn owl)

Summary

  • Last modified
  • 08 November 2018
  • Datasheet Type(s)
  • Invasive Species
  • Natural Enemy
  • Host Animal
  • Preferred Scientific Name
  • Tyto alba
  • Preferred Common Name
  • Barn owl
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Metazoa
  •     Phylum: Chordata
  •       Subphylum: Vertebrata
  •         Class: Aves
  • Summary of Invasiveness
  • T. alba was introduced to the Hawaiian Islands and Seychelles Islands to control invasive rat populations; it has also been introduced to St. Helena. It is known to prey on or compete with native birds in Hawai...

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Pictures

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PictureTitleCaptionCopyright
Tyto alba (Barn owl); perched on a fence-post. Copp Rd, Kula, Maui, Hawaii, USA. June 21, 2007.
TitleAdult perched
CaptionTyto alba (Barn owl); perched on a fence-post. Copp Rd, Kula, Maui, Hawaii, USA. June 21, 2007.
Copyright©Forest Starr & Kim Starr - CC BY 4.0
Tyto alba (Barn owl); perched on a fence-post. Copp Rd, Kula, Maui, Hawaii, USA. June 21, 2007.
Adult perchedTyto alba (Barn owl); perched on a fence-post. Copp Rd, Kula, Maui, Hawaii, USA. June 21, 2007.©Forest Starr & Kim Starr - CC BY 4.0
Adult Barn Owl, (Tyto alba). Sonoran Desert Museum, Arizona, USA.
TitleAdult
CaptionAdult Barn Owl, (Tyto alba). Sonoran Desert Museum, Arizona, USA.
Copyright©Joy Viola/Northeastern University/Bugwood.org - CC BY-NC 3.0 US
Adult Barn Owl, (Tyto alba). Sonoran Desert Museum, Arizona, USA.
AdultAdult Barn Owl, (Tyto alba). Sonoran Desert Museum, Arizona, USA. ©Joy Viola/Northeastern University/Bugwood.org - CC BY-NC 3.0 US
Adult Barn Owl, (Tyto alba). Sonoran Desert Museum, Arizona, USA.
TitleAdult
CaptionAdult Barn Owl, (Tyto alba). Sonoran Desert Museum, Arizona, USA.
Copyright©Joy Viola/Northeastern University/Bugwood.org - CC BY-NC 3.0 US
Adult Barn Owl, (Tyto alba). Sonoran Desert Museum, Arizona, USA.
AdultAdult Barn Owl, (Tyto alba). Sonoran Desert Museum, Arizona, USA.©Joy Viola/Northeastern University/Bugwood.org - CC BY-NC 3.0 US

Identity

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Preferred Scientific Name

  • Tyto alba Scopoli 1769

Preferred Common Name

  • Barn owl

Other Scientific Names

  • Tyto perlata Ridgeway, 1914

International Common Names

  • English: Common Barn owl
  • Spanish: Lechuza Común
  • French: Effraie des clochers

Local Common Names

  • Germany: Schleiereule
  • UK: Demon Owl; Ghost Owl; Lesser Masked owl; Monkey-faced Owl; Night owl; White owl

Summary of Invasiveness

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T. alba was introduced to the Hawaiian Islands and Seychelles Islands to control invasive rat populations; it has also been introduced to St. Helena. It is known to prey on or compete with native birds in Hawaii and the Seychelles; in the Seychelles it nearly exterminated a local race of the White Tern (Gygis alba candida) before control measures were taken. As a native species, it is widely distributed around the world, and is itself a species of conservation concern in parts of its range, being listed as a Species of European Conservation Concern (Eaton et al., 2009) and as endangered in seven U.S. states, a species of concern in seven states, and threatened in three additional states (Marti et al., 2005).

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Metazoa
  •         Phylum: Chordata
  •             Subphylum: Vertebrata
  •                 Class: Aves
  •                     Order: Strigiformes
  •                         Family: Tytonidae
  •                             Genus: Tyto
  •                                 Species: Tyto alba

Notes on Taxonomy and Nomenclature

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There are between 28 and 35 recognized subspecies (the exact number is disputed), and 46 races, although differences between subspecies are understudied and several distinct species may lie within T. alba (Bruce 1999, Dickinson 2003). There are considerable distinctions between subspecies including feather coloration, wing, tail, and leg length; these are thought to be due to adaptation to the local environment.

Description

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T. alba is a medium-sized owl measuring 29-44 cm (variation within each subspecies is less than that across the species as a whole).  Body mass is highly variable between locations, with most ranging from 187-475 g (387- >600 g in Surinam and Malaysia and 400-700 g in North America) (Bruce, 1999).  The wing chord measures 80-95 cm (Mullarney et al., 1999).  Females are generally larger in all measurements except wing chord and tail length, and typically darker than males (Bruce, 1999; Marti et al., 2005).  Taylor (1993) recognized flecking under wings as a reliable marker for sexing T. alba alba: flecking indicated females and absence of flecks indicated males, but accuracy for other subspecies is unknown.

There is considerable plumage variation among subspecies and races (Bruce, 1999).  T. alba lacks the ear tufts common among owls and has a prominent heart-shaped face.  The iris is dark and the eyes small for Strigiformes (Bunn et al., 1982; Marti et al., 2005).  The wing feathers are rounded with 10 primaries, 15 secondaries, and 12 rectrices.  The legs are long and feathered, and the underparts buff with spotting on the wings and breast, although subspecies with primarily seabird diets may have lighter underparts and island subspecies may be darker (Bruce, 1999; Marti et al., 2005).

The young are altricial at hatching, and nidicolous.  They have bare skin on the neck, back, and belly, and thin whitish down on the tarsus, toes, and upperparts with an ivory bill.  Second natal down growth occurs at approximately 14 days (Marti et al., 2005).  The plumage of fledglings is similar to that of adults with more flecking, and may undergo a first prealternate molt prior to reaching adult basic plumage (Taylor, 1993).  Body mass exceeds that of adults during the growth stages and weight is lost prior to flight at 52-56 days, with full-fledging up to eight weeks after flight capability (Ehrlich et al., 1988; Marti et al., 2005).

Distribution

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T. alba is frequently cited as amongst the most cosmopolitan of owl species, with subspecies regionally distributed (Bruce, 1999; Marti, 2005; Konig and Weick, 2010). It is found on all continents except Antarctica. Its range is limited by severe cold due to an inability to store sufficient energy reserves (Marti, 2005). Vagrants are seen in northern regions of Canada, Europe and Russia, and one once reached the sub-Antarctic island of South Georgia (Bruce, 1999).

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

Asia

BahrainPresentNative Not invasive Bruce, 1999
BangladeshPresentNative Not invasive BirdLife International, 2012
CambodiaPresentNative Not invasive Bruce, 1999
ChinaPresentNative Not invasive Bruce, 1999
-SichuanPresentNative Not invasive BirdLife International, 2012
-YunnanPresentNative Not invasive Bruce, 1999
East TimorPresentNative Not invasive Bruce, 1999
Georgia (Republic of)PresentNative Not invasive BirdLife International, 2012
IndiaWidespreadNative Not invasive Konig and Weick, 2010
-Andaman and Nicobar IslandsPresentNative Not invasive Konig and Weick, 2010
-Andhra PradeshPresentNative Not invasive Konig and Weick, 2010
-Arunachal PradeshPresentNative Not invasive Konig and Weick, 2010
-AssamPresentNative Not invasive Konig and Weick, 2010
-BiharPresentNative Not invasive Konig and Weick, 2010
-ChandigarhPresentNative Not invasive Konig and Weick, 2010
-ChhattisgarhPresentNative Not invasive Konig and Weick, 2010
-Dadra and Nagar HaveliPresentNative Not invasive Konig and Weick, 2010
-DamanPresentNative Not invasive Konig and Weick, 2010
-DelhiPresentNative Not invasive Konig and Weick, 2010
-DiuPresentNative Not invasive Konig and Weick, 2010
-GoaPresentNative Not invasive Konig and Weick, 2010
-GujaratPresentNative Not invasive Konig and Weick, 2010
-HaryanaPresentNative Not invasive Konig and Weick, 2010
-Himachal PradeshPresentNative Not invasive Konig and Weick, 2010
-Indian PunjabPresentNative Not invasive Konig and Weick, 2010
-Jammu and KashmirPresentNative Not invasive Konig and Weick, 2010
-JharkhandPresentNative Not invasive Konig and Weick, 2010
-KarnatakaPresentNative Not invasive Konig and Weick, 2010
-KeralaPresentNative Not invasive Konig and Weick, 2010
-LakshadweepPresentNative Not invasive Konig and Weick, 2010
-Madhya PradeshPresentNative Not invasive Konig and Weick, 2010
-MaharashtraPresentNative Not invasive Konig and Weick, 2010
-ManipurPresentNative Not invasive Konig and Weick, 2010
-MeghalayaPresentNative Not invasive Konig and Weick, 2010
-MizoramPresentNative Not invasive Konig and Weick, 2010
-NagalandPresentNative Not invasive Konig and Weick, 2010
-OdishaPresentNative Not invasive Konig and Weick, 2010
-RajasthanPresentNative Not invasive Konig and Weick, 2010
-SikkimPresentNative Not invasive Konig and Weick, 2010
-Tamil NaduPresentNative Not invasive Konig and Weick, 2010
-TripuraPresentNative Not invasive Konig and Weick, 2010
-Uttar PradeshPresentNative Not invasive Konig and Weick, 2010
-UttarakhandPresentNative Not invasive Konig and Weick, 2010
-West BengalPresentNative Not invasive Konig and Weick, 2010
IndonesiaWidespreadNative Not invasive Bruce, 1999
-JavaPresentNative Not invasive Konig and Weick, 2010
-Nusa TenggaraPresentNative Not invasive Bruce, 1999; Bruce, 1999
-SumatraPresentNative Not invasive Konig and Weick, 2010
IranPresentNative Not invasive Konig and Weick, 2010
IraqPresentNative Not invasive Konig and Weick, 2010
IsraelPresentNative Not invasive BirdLife International, 2012
LaosPresentNative Not invasive Konig and Weick, 2010
MalaysiaPresent, few occurrences2002Native Not invasive Wells, 2007
-Peninsular MalaysiaPresent, few occurrences2002Native Not invasive Wells, 2007
MyanmarPresentNative Not invasive Konig and Weick, 2010
NepalPresentNative Not invasive BirdLife International, 2012
OmanPresentNative Not invasive Avibase, 2012
PakistanPresentNative Not invasive Konig and Weick, 2010
QatarPresentNative Not invasive Avibase, 2012
Saudi ArabiaPresentNative Not invasive Konig and Weick, 2010
SingaporePresentNative Not invasive Avibase, 2012
Sri LankaPresentNative Not invasive Konig and Weick, 2010
SyriaPresentNative Not invasive Bruce, 1999
ThailandPresent, few occurrences2002Native Not invasive Wells, 2007
TurkeyWidespread2010Native Not invasive Kirwan, 2010Uncommon despite widespread distribution. One report in East Anatolia
United Arab EmiratesPresent, few occurrencesNative Not invasive Pederson and Aspinall, 2011
VietnamPresentNative Not invasive Konig and Weick, 2010
YemenPresentNative Not invasive Bruce, 1999

Africa

AlgeriaPresentNative Not invasive Bruce, 1999
AngolaPresentNative Not invasive Bruce, 1999
BeninPresentNative Not invasive BirdLife International, 2012
BotswanaPresentNative Not invasive Bruce, 1999
Burkina FasoPresentNative Not invasive Bruce, 1999
BurundiPresentNative Not invasive Bruce, 1999
CameroonPresentNative Not invasive Bruce, 1999
Cape VerdePresentNative Not invasive BirdLife International, 2012
Central African RepublicPresentNative Not invasive Bruce, 1999
ChadPresentNative Not invasive Bruce, 1999
ComorosPresentNative Not invasive Konig and Weick, 2010
CongoPresentNative Not invasive Bruce, 1999
Congo Democratic RepublicPresentNative Not invasive Bruce, 1999
Côte d'IvoirePresentNative Not invasive Bruce, 1999
EgyptPresentNative Not invasive Bruce, 1999
Equatorial GuineaPresentNative Not invasive Bruce, 1999
EritreaPresent, few occurrences2008Native Not invasive Ash and Atkins, 2010Two sightings reported since last publication of T. alba distribution in 1957
EthiopiaWidespread2010Native Not invasive Ash and Atkins, 2010Primarily found throughout the Rift Valley
GabonPresentNative Not invasive Bruce, 1999
GambiaPresentNative Not invasive Bruce, 1999
GhanaPresentNative Not invasive Bruce, 1999
GuineaPresentNative Not invasive Bruce, 1999
Guinea-BissauPresentNative Not invasive Bruce, 1999
KenyaPresentNative Not invasive Bruce, 1999
LesothoPresentNative Not invasive Bruce, 1999
LiberiaPresentNative Not invasive Bruce, 1999
LibyaPresentNative Not invasive Bruce, 1999
MadagascarPresentNative Not invasive Bruce, 1999
MalawiPresentNative Not invasive Bruce, 1999
MaliPresentNative Not invasive Bruce, 1999
MauritaniaPresentNative Not invasive Bruce, 1999
MayottePresentNative Not invasive Bruce, 1999
MoroccoPresentNative Not invasive Bruce, 1999
MozambiquePresentNative Not invasive Bruce, 1999
NamibiaPresentNative Not invasive Bruce, 1999
NigerPresentNative Not invasive Bruce, 1999
NigeriaPresentNative Not invasive Bruce, 1999
Saint HelenaPresentIntroducedLong, 1981Successfully introduced, population unknown
SeychellesLocalisedIntroduced1951 Invasive Long, 1981; Lever, 2010Present on a number of granite islands
Sierra LeonePresentNative Not invasive Bruce, 1999
SomaliaPresentNative Not invasive Bruce, 1999
South AfricaPresentNative Not invasive Bruce, 1999
Spain
-Canary IslandsLocalisedNative Not invasive Bruce, 1999
SudanPresentNative Not invasive Bruce, 1999
SwazilandPresentNative Not invasive Bruce, 1999
TanzaniaPresentNative Not invasive Bruce, 1999
-ZanzibarPresentNative Not invasive Bruce, 1999
TogoPresentNative Not invasive Bruce, 1999
TunisiaPresentNative Not invasive Bruce, 1999
UgandaPresentNative Not invasive Bruce, 1999
ZambiaPresentNative Not invasive Bruce, 1999
ZimbabwePresent, few occurrencesNative Not invasive Bruce, 1999

North America

BermudaPresentNative Not invasive Bruce, 1999
CanadaLocalised1997Native Not invasive Bruce, 1999
-British ColumbiaPresent, few occurrences1997Native Not invasive Campbell et al., 1997Present in southern portion of province in low numbers
-OntarioPresent, few occurrences1997Native Not invasive Campbell et al., 1997Present in southern portion of province in low numbers
-Yukon TerritoryPresent, few occurrencesSinclair et al., 2003Not reported in species list
MexicoWidespreadNative Not invasive Bruce, 1999
USAWidespreadNative Not invasive Marti et al., 2005
-AlabamaPresentNative Not invasive Marti et al., 2005
-ArizonaPresentNative Not invasive Marti et al., 2005
-ArkansasPresentNative Not invasive Marti et al., 2005
-CaliforniaWidespreadNative Not invasive Marti et al., 2005
-ColoradoPresentNative Not invasive Marti et al., 2005
-ConnecticutPresent, few occurrencesNative Not invasive Marti et al., 2005Endangered at the state level
-DelawarePresentNative Not invasive Marti et al., 2005
-District of ColumbiaPresentNative Not invasive Marti et al., 2005
-FloridaPresentNative Not invasive Marti et al., 2005
-GeorgiaPresentNative Not invasive Marti et al., 2005
-HawaiiWidespread2012Introduced1958Klavitter, 2009
-IdahoPresent, few occurrencesNative Not invasive Marti et al., 2005
-IllinoisPresent, few occurrencesNative Not invasive Marti et al., 2005Endangered at the state level
-IndianaPresent, few occurrencesNative Not invasive Marti et al., 2005
-IowaLocalisedNative Not invasive Marti et al., 2005Endangered at the state level
-KansasPresentNative Not invasive Marti et al., 2005
-KentuckyPresentNative Not invasive Marti et al., 2005
-LouisianaPresentNative Not invasive Marti et al., 2005
-MainePresent, few occurrencesNative Not invasive Marti et al., 2005
-MarylandPresentNative Not invasive Marti et al., 2005
-MassachusettsLocalisedNative Not invasive Marti et al., 2005Species of special concern
-MichiganPresent, few occurrencesNative Not invasive Marti et al., 2005Endangered at the state level
-MinnesotaPresent, few occurrencesNative Not invasive Marti et al., 2005Species of special concern
-MississippiPresentNative Not invasive Marti et al., 2005
-MissouriPresent, few occurrencesNative Not invasive Marti et al., 2005Endangered at the state level
-NebraskaPresentNative Not invasive Marti et al., 2005Species of special concern
-NevadaPresentNative Not invasive Marti et al., 2005
-New HampshirePresent, few occurrencesNative Not invasive Marti et al., 2005
-New JerseyPresentNative Not invasive Marti et al., 2005Species of special concern
-New MexicoPresentNative Not invasive Marti et al., 2005
-New YorkLocalisedNative Not invasive Marti et al., 2005Species of special concern
-North CarolinaPresentNative Not invasive Marti et al., 2005
-North DakotaPresent, few occurrencesNative Not invasive Marti et al., 2005Species of special concern
-OhioPresent, few occurrencesNative Not invasive Marti et al., 2005Endangered at the state level
-OklahomaLocalisedNative Not invasive Marti et al., 2005
-OregonLocalisedNative Not invasive Marti et al., 2005Threatened at the state level
-PennsylvaniaPresent, few occurrencesNative Not invasive Marti et al., 2005Species at risk
-Rhode IslandPresentNative Not invasive Marti et al., 2005
-South CarolinaPresentNative Not invasive Marti et al., 2005
-South DakotaPresent, few occurrencesNative Not invasive Marti et al., 2005Species of special concern
-TennesseePresentNative Not invasive Marti et al., 2005Species at risk
-TexasPresentNative Not invasive Marti et al., 2005
-UtahPresent, few occurrencesNative Not invasive Marti et al., 2005
-VermontPresent, few occurrencesNative Not invasive Marti et al., 2005
-VirginiaPresentNative Not invasive Marti et al., 2005
-WashingtonLocalisedNative Not invasive Marti et al., 2005
-West VirginiaPresentNative Not invasive Marti et al., 2005
-WisconsinPresent, few occurrencesNative Not invasive Marti et al., 2005Endangered at the state level
-WyomingPresent, few occurrencesNative Not invasive Marti et al., 2005

Central America and Caribbean

BahamasPresentNative Not invasive Long, 1981; Marti et al., 2005Colonized historically
BelizePresentNative Not invasive Bruce, 1999
Cayman IslandsPresentNative Not invasive Bruce, 1999
Costa RicaPresentNative Not invasive Bruce, 1999
CubaPresentNative Not invasive Bruce, 1999
CuraçaoPresentNative Not invasive Bruce, 1999
El SalvadorPresentNative Not invasive Bruce, 1999
GuatemalaPresentNative Not invasive Bruce, 1999
HondurasPresentNative Not invasive Bruce, 1999
JamaicaPresentNative Not invasive Bruce, 1999
Netherlands AntillesPresentNative Not invasive Bruce, 1999
NicaraguaPresentNative Not invasive Bruce, 1999
PanamaPresentNative Not invasive Bruce, 1999
Trinidad and TobagoPresentNative Not invasive Bruce, 1999

South America

ArgentinaPresentNative Not invasive Bruce, 1999
BoliviaPresentNative Not invasive Bruce, 1999
BrazilPresentNative Not invasive Bruce, 1999
-AcrePresentNative Not invasive Bruce, 1999
-AlagoasPresentNative Not invasive Bruce, 1999
-AmapaPresentNative Not invasive Bruce, 1999
-AmazonasPresentNative Not invasive Bruce, 1999
-BahiaPresentNative Not invasive Bruce, 1999
-CearaPresentNative Not invasive Bruce, 1999
-Espirito SantoPresentNative Not invasive Bruce, 1999
-Fernando de NoronhaPresentNative Not invasive Bruce, 1999
-GoiasPresentNative Not invasive Bruce, 1999
-MaranhaoPresentNative Not invasive Bruce, 1999
-Mato GrossoPresentNative Not invasive Bruce, 1999
-Mato Grosso do SulPresentNative Not invasive Bruce, 1999
-Minas GeraisPresentNative Not invasive Bruce, 1999
-ParaPresentNative Not invasive Bruce, 1999
-ParaibaPresentNative Not invasive Bruce, 1999
-ParanaPresentNative Not invasive Bruce, 1999
-PernambucoPresentNative Not invasive Bruce, 1999
-PiauiPresentNative Not invasive Bruce, 1999
-Rio de JaneiroPresentNative Not invasive Bruce, 1999
-Rio Grande do NortePresentNative Not invasive Bruce, 1999
-Rio Grande do SulPresentNative Not invasive Bruce, 1999
-RondoniaPresentNative Not invasive Bruce, 1999
-RoraimaPresentNative Not invasive Bruce, 1999
-Santa CatarinaPresentNative Not invasive Bruce, 1999
-Sao PauloPresentNative Not invasive Bruce, 1999
-SergipePresentNative Not invasive Bruce, 1999
-TocantinsPresentNative Not invasive Bruce, 1999
ChilePresentNative Not invasive Bruce, 1999
ColombiaPresentNative Not invasive Bruce, 1999
EcuadorPresentNative Not invasive Bruce, 1999
Falkland IslandsPresent, few occurrencesNative Not invasive Bruce, 1999
French GuianaPresentNative Not invasive Bruce, 1999
GuyanaPresentNative Not invasive Bruce, 1999
ParaguayPresentNative Not invasive Bruce, 1999
PeruPresentNative Not invasive Bruce, 1999
South Georgia and the South Sandwich IslandsPresent, few occurrencesNative Not invasive Bruce, 1999
SurinamePresentNative Not invasive Bruce, 1999
UruguayPresentNative Not invasive Bruce, 1999
VenezuelaPresentNative Not invasive Bruce, 1999

Europe

AlbaniaPresentNative Not invasive Bruce, 1999
AndorraPresentNative Not invasive Bruce, 1999
AustriaPresentNative Not invasive Bruce, 1999
BelarusPresentNative Not invasive Bruce, 1999
BelgiumPresentNative Not invasive Bruce, 1999
Bosnia-HercegovinaPresentNative Not invasive Bruce, 1999
BulgariaPresentNative Not invasive Bruce, 1999; Golemanski et al., 2011
CroatiaPresentNative Not invasive Bruce, 1999
CyprusPresentNative Not invasive Bruce, 1999
Czech RepublicPresentNative Not invasive Bruce, 1999
Czechoslovakia (former)PresentNative Not invasive Bruce, 1999
DenmarkPresentNative Not invasive Bruce, 1999
EstoniaPresent, few occurrences Not invasive IUCN, 2012Vagrant
FinlandPresent, few occurrences Not invasive IUCN, 2012Vagrant
FrancePresentNative Not invasive Bruce, 1999
-CorsicaPresentNative Not invasive Bruce, 1999
GermanyPresentNative Not invasive Bruce, 1999
GibraltarPresentNative Not invasive Bruce, 1999
GreecePresentNative Not invasive Bruce, 1999
HungaryPresentNative Not invasive Bruce, 1999
IrelandWidespread2004Native Not invasive Parkin and Knox, 2009May be declining; nest box efforts underway showing success in recruiting breeding individuals
ItalyPresentNative Not invasive Bruce, 1999
LatviaPresentNative Not invasive Bruce, 1999
LiechtensteinPresentNative Not invasive Bruce, 1999
LithuaniaPresentNative Not invasive Bruce, 1999
LuxembourgPresentNative Not invasive Bruce, 1999
MacedoniaPresentNative Not invasive Bruce, 1999
MaltaPresentNative Not invasive Bruce, 1999
MoldovaPresentNative Not invasive Bruce, 1999
MonacoPresentNative Not invasive Bruce, 1999
MontenegroPresentNative Not invasive Bruce, 1999
NetherlandsPresentNative Not invasive Bruce, 1999
NorwayPresent, few occurrences Not invasive IUCN, 2012Vagrant
PolandPresentNative Not invasive Bruce, 1999
PortugalPresentNative Not invasive Bruce, 1999
-MadeiraPresentNative Not invasive Bruce, 1999
RomaniaPresentNative Not invasive Bruce, 1999
Russian FederationPresentNativeBirdLife International, 2012
San MarinoPresentNative Not invasive Bruce, 1999
SerbiaPresentNative Not invasive Bruce, 1999
SlovakiaPresentNative Not invasive Bruce, 1999
SloveniaPresentNative Not invasive Bruce, 1999
SpainPresentNative Not invasive Bruce, 1999
-Balearic IslandsPresentNative Not invasive Bruce, 1999
Svalbard and Jan MayenPresent, few occurrences Not invasive Bruce, 1999Vagrant
SwitzerlandPresentNative Not invasive Bruce, 1999
UKWidespreadNative Not invasive Parkin and Knox, 2009May be declining; nest box efforts underway showing success in recruiting breeding individuals
-Channel IslandsPresentNative Not invasive Bruce, 1999
UkrainePresentNative Not invasive Bruce, 1999
Yugoslavia (former)PresentNative Not invasive Bruce, 1999
Yugoslavia (Serbia and Montenegro)PresentNative Not invasive Bruce, 1999

Oceania

American SamoaPresentNative Not invasive Bruce, 1999
AustraliaPresentNative Not invasive Long, 1981; Bruce, 1999Colonized in 1910
-Australian Northern TerritoryPresentNative Not invasive Bruce, 1999
-New South WalesPresentNative Not invasive Bruce, 1999
-QueenslandPresentNative Not invasive Bruce, 1999
-South AustraliaPresentNative Not invasive Bruce, 1999
-TasmaniaPresentNative Not invasive Bruce, 1999
-VictoriaPresentNative Not invasive Bruce, 1999
-Western AustraliaPresentNative Not invasive Bruce, 1999
FijiPresentNative Not invasive Bruce, 1999
New CaledoniaPresentNative Not invasive Bruce, 1999
New ZealandPresent, few occurrencesHyde et al., 2009; Hyde et al., 2013One breeding pair in recent years; means of arrival uncertain.
NiuePresentNative Not invasive BirdLife International, 2012
Papua New GuineaPresentNative Not invasive Bruce, 1999
SamoaPresentNative Not invasive Bruce, 1999
Solomon IslandsPresentNative Not invasive Bruce, 1999
TongaPresentNative Not invasive Bruce, 1999
VanuatuLocalisedNative Not invasive Bruce, 1999

History of Introduction and Spread

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T. alba was introduced to the Hawaiian Islands, USA, to control rats and mice causing damage to sugarcane plantations. During 1958-1963 the Hawaii Commissioners of Agriculture released 86 individuals from California and Texas. Although not an effective biocontrol agent, itbecame widespread throughout the state by 1966 (Foster, 2009).

T. alba was introduced to Mahé Island of the Seychelles in 1951-1952 with 27 individuals brought from South Africa. They were introduced to control the Black Rat (Rattus rattus), but failed to control rat populations. Except for an unsuccessful introduction on Isle Platt in 1949, T. alba established and spread throughout the islands and became abundant due to high availability of native seabird chicks (Lever, 2010).

T. alba was also introduced to Saint Helena Island in the South Atlantic around 1937 and is established there (Long, 1981), but little information is available regarding impacts and current population on the island.

The species was unsuccessfully introduced to New Zealand in 1899 and Lord Howe Island (Australia) during 1922-1950, in both cases for control of introduced, invasive rats (Long, 1981).

Introductions

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Introduced toIntroduced fromYearReasonIntroduced byEstablished in wild throughReferencesNotes
Natural reproductionContinuous restocking
Hawaii USA 1958-1963 Biological control (pathway cause) Yes Klavitter (2009); Pitt and Witmer (2007) Widespread across state; population size unknown
Saint Helena   Yes Long (1981)
Seychelles South Africa 1951-1952 Biological control (pathway cause) Yes Lever (2010); Long (1981) Control efforts have reduced population size on several islands

Risk of Introduction

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Intentional introduction is the only documented form of introduction; unintentional introduction is unlikely to occur, given the large size of this raptor (although according to Hyde et al. (2013), some individuals are known or suspected to have reached New Zealand as stowaways on aircraft or ships). T. alba is among the most cosmopolitan raptor species, and occurs throughout much of the world.  Extensive literature examining the impacts of T. alba on native species and its limited ability to control small mammal populations make future introduction of this species very unlikely.

Habitat

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T. alba is a generalist species residing in nearly all climes worldwide except the Sahara Desert, heavily forested or mountainous areas, and locations with mean winter temperatures significantly below 0°C (Bruce, 1999).  It prefers grasslands, deserts, marshlands and wetlands, agricultural areas, other open lowland areas and human-modified landscapes (Bruce, 1999; Marti et al., 2005).

Habitat List

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CategoryHabitatPresenceStatus
Littoral
Coastal areas Present, no further details Natural
Coastal dunes Present, no further details Natural
Salt marshes Present, no further details Natural
Terrestrial-managed
Buildings Secondary/tolerated habitat Natural
Cultivated / agricultural land Principal habitat Natural
Disturbed areas Principal habitat Natural
Managed forests, plantations and orchards Principal habitat Natural
Managed grasslands (grazing systems) Principal habitat Natural
Rail / roadsides Secondary/tolerated habitat Natural
Urban / peri-urban areas Secondary/tolerated habitat Natural
Terrestrial-natural/semi-natural
Deserts Principal habitat Natural
Natural grasslands Principal habitat Natural
Riverbanks Principal habitat Natural
Scrub / shrublands Secondary/tolerated habitat Natural
Wetlands Principal habitat Natural

Biology and Ecology

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Genetics

T. alba has ninety-two diploid chromosomes (Belterman and Boer, 1984).

The number of subspecies is unresolved and several may constitute distinct species from T. alba.

Reproductive Biology

T. alba mates for life, although pairs roost separately until nesting begins (Ehrlich et al., 1982; Marti et al., 2005). It uses natural and manmade cavities for nesting, except for one report of nest burrowing in Colorado and New Mexico, USA (Millsap and Millsap, 1987; Bruce, 1999). The primary breeding season in the northern hemisphere occurs in March-July, although nests are documented throughout the year in various regions of North America. Flexible reproductive timing allows for adaptation to small mammal population fluctuations, and the timing of nesting likely occurs for the fledgling stage to correspond with peak numbers of prey (Marti et al., 2005). Two to three clutches may be laid during periods with large rodent populations (Konig and Weick, 2010). Clutch size is typically 4-7 eggs, but reportedly ranges from 2-16 during periods of reduced or greater prey abundance (Bruce, 1999). The incubation period, at least in the UK, is typically about 32 days and the fledging period 53-61 days (Robinson, 2013). Moulting follows breeding from July-September in the northern hemisphere (Marti et al., 2005).

Physiology and Phenology

There are no documented physiological differences in T. alba populations between native and introduced ranges. Females may abstain from nesting during periods of reduced prey abundance and during cold winters, and nestling reduction has been observed in experimental manipulations (Roulin et al., 1999; Marti et al., 2005). The species readily adapts to human environments and its common name originates from its frequent use of barns as roosting and nesting sites. High mortality caused by starvationis probably due to a high metabolism and inability to store sufficient fat reserves to persist through cold winters, which is uncommon among Tyto species (Marti et al., 2005).

Longevity

T. alba have a short lifespan of approximately 21 months owing to a variety of factors including cold temperatures and human-induced disturbance, with individuals eight years or more considered long-lived; the oldest in the wild was documented at 34 years of age (Marti et al., 2005; Lynch 2007). In the UK the typical lifespan is longer at about 4 years; the maximum recorded lifespan in the wild is 15 years (Robinson, 2013).

Activity Patterns

Migration by T. alba is known to occur primarily among juveniles and is dispersal-related. Adults are generally residents except at range limits, where they move to warmer climes for nesting and overwintering (Marti et al., 2005).

Population Size and Density

Population size is unknown and density varies greatly with habitat quality (Bruce, 1999; Marti et al., 2005). There is a general trend of decline in United States and across Europe, although no threat to the species is considered to exist given its widespread global distribution (BirdLife International, 2012). Active nest-box erection projects throughout the Midwest and Northeast USA provide additional nesting habitat and appear to be helping increase the population (Marti et al., 2005). Information regarding population size for individual subspecies is lacking.

Nutrition

A study conducted in Hawaii found non-native rodents present in 99.7% of pellets, birds in 15%, and insects in 1.3% (Snetsinger et al., 1994). Throughout the native range, the diet is highly variable and flexible and T. alba is not known to dramatically impact populations of threatened or endangered species (with one exception in the Seychelles -- see 'Impact: environmental' section). Voles are the predominant prey in North America and partially nocturnal small rodents are the primary prey worldwide. Small numbers of lagomorphs, mustelids, social-roosting and open-roosting passerines, seabirds, bats, and insects are taken as locally available (Long, 1981; Bruce, 1999; Bontzorlos et al., 2005; Marti et al., 2005; López-Ricardo and Borroto-Páez, 2012).

Note that the Natural Food Sources table refers only to species that have been recorded as prey items in the introduced range. A complete list for the whole range would include hundreds of species.

Environmental Requirements

T. alba is a cosmopolitan species limited by cold winters, with only vagrants reaching high northern and southern latitudes due to an inability to store sufficient fat stores for overwintering (Konig et al., 1999; Marti et al., 2005). The species generally occurs below 4000 m elevation (Bruce, 1999).

Natural Food Sources

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Food SourceLife StageContribution to Total Food Intake (%)Details
Adult
Adult
Adult
Adult
Adult
Adult
Adult
Adult
Adult
Adult
Adult
Adult
Adult

Climate

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ClimateStatusDescriptionRemark
A - Tropical/Megathermal climate Preferred Average temp. of coolest month > 18°C, > 1500mm precipitation annually
Am - Tropical monsoon climate Tolerated Tropical monsoon climate ( < 60mm precipitation driest month but > (100 - [total annual precipitation(mm}/25]))
As - Tropical savanna climate with dry summer Tolerated < 60mm precipitation driest month (in summer) and < (100 - [total annual precipitation{mm}/25])
Aw - Tropical wet and dry savanna climate Preferred < 60mm precipitation driest month (in winter) and < (100 - [total annual precipitation{mm}/25])
BS - Steppe climate Preferred > 430mm and < 860mm annual precipitation
BW - Desert climate Preferred < 430mm annual precipitation
C - Temperate/Mesothermal climate Preferred Average temp. of coldest month > 0°C and < 18°C, mean warmest month > 10°C
Cf - Warm temperate climate, wet all year Preferred Warm average temp. > 10°C, Cold average temp. > 0°C, wet all year
Cs - Warm temperate climate with dry summer Preferred Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers
Cw - Warm temperate climate with dry winter Preferred Warm temperate climate with dry winter (Warm average temp. > 10°C, Cold average temp. > 0°C, dry winters)
D - Continental/Microthermal climate Preferred Continental/Microthermal climate (Average temp. of coldest month < 0°C, mean warmest month > 10°C)
Df - Continental climate, wet all year Tolerated Continental climate, wet all year (Warm average temp. > 10°C, coldest month < 0°C, wet all year)
Ds - Continental climate with dry summer Preferred Continental climate with dry summer (Warm average temp. > 10°C, coldest month < 0°C, dry summers)
Dw - Continental climate with dry winter Preferred Continental climate with dry winter (Warm average temp. > 10°C, coldest month < 0°C, dry winters)

Latitude/Altitude Ranges

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Latitude North (°N)Latitude South (°S)Altitude Lower (m)Altitude Upper (m)
58 55

Air Temperature

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Parameter Lower limit Upper limit
Mean annual temperature (ºC) 2 16
Mean maximum temperature of hottest month (ºC) 22 30
Mean minimum temperature of coldest month (ºC) -24 23

Natural enemies

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Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Bubo virginianus Predator Adults/Juveniles not specific

Notes on Natural Enemies

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Natural enemies do not appear to impact T. alba populations. Great Horned Owls (Bubo virginianus) have been reported to predate upon captive released T. alba in Iowa, USA, but there few reports of such predation in the wild (Ehresman, 1984; Marti et al., 2005). Adults are taken occasionally by a variety of large raptor species and nestlings are predated upon by snakes and stoats in North America (Marti et al., 2005). There is no reported predation by introduced or invasive species.

Means of Movement and Dispersal

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Natural Dispersal

T. alba historically colonized Bermuda, Australia, and Tasmania through flight and occurs as a vagrant to its latitudinal range limits (Long, 1981; Marti et al., 2005). Individuals are thought to have reached New Zealand in this way, although it is not certain that the recent records of nesting in New Zealand are a result of natural colonization (Hyde et al., 2013).

Accidental introduction

Some individuals are known or suspected to have reached New Zealand as stowaways on aircraft or ships (Hyde et al., 2013).

Intentional Introduction

T. alba was introduced as a biocontrol agent for invasive rodents on several islands of the Seychelles, throughout the Hawaiian Islands, on St. Helena, on Lord Howe Island (Australia), and in New Zealand (Long, 1981). It failed to establish on Lord Howe Island and New Zealand.

Pathway Causes

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CauseNotesLong DistanceLocalReferences
Biological controlTo reduce invasive rodent populations. Fewer than 100 individuals released on each occasion. Yes Bruce, 1999; Klavitter, 2009; Kowalsky et al., 2002; Long, 1981
HitchhikerOn ships and aircraft Yes Hyde et al., 2013
Self-propelledTo Bermuda, Australia and New Zealand Yes Hyde et al., 2009; Long, 1981; Marti et al., 2005

Impact Summary

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CategoryImpact
Cultural/amenity Positive
Economic/livelihood Positive
Environment (generally) Positive and negative

Environmental Impact

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Impact on Biodiversity

A local race of White Tern (Gygis alba candida) was nearly eliminated on Mahé Island, Seychelles, after introduction of T. alba as a biocontrol agent for invasive rodents. However, a successful reduction of the T. alba population has prevented further negative impacts (Lever, 2010). The species is known to take Magpie Robins (Copsychus sechellarum) (Long, 1981), and itcompetes with two native raptor species, the critically endangered Seychelles Scops owl (Otus insularis) and the vulnerable Seychelles Kestrel (Falco araea) (Lever, 2010).

Based on limited study, it appears that T. alba in Hawaii feeds primarily on rats and mice, but a small proportion of its diet may consist of native birds, with the proportion of birds in the diet greater than in Europe (Byrd and Telfer, 1980; Snetsinger et al., 1994; Kowalsky et al. 2002; Klavitter, 2009). There has been one reported incident of seabird take. The species is not known to consume the endangered Hawaiian Hoary bat, Lasiurus cinereus semotus (F. Bonnaccorso, Pacific Island Ecosystems Research Center, U.S. Geological Survey, Kilauea Field Station, Hawaii National Park, HI, USA, personal communication, 2012). The native Short-eared Owl or Pueo (Asio flammeus sandwichensis) is primarily diurnal and crepuscular; the extent to which T. alba competes with it for food and habitat is unknown (Riper and Scott, 2001; Pitt and Witmer, 2007).

Threatened Species

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Threatened SpeciesConservation StatusWhere ThreatenedMechanismReferencesNotes
Gygis alba candidaNo details No detailsSeychellesPredationLever, 2010; Long, 1981
Myadestes obscurusVU (IUCN red list: Vulnerable) VU (IUCN red list: Vulnerable)HawaiiPredationSnetsinger et al., 1994
Palmeria dolei (crested honeycreeper)CR (IUCN red list: Critically endangered) CR (IUCN red list: Critically endangered); USA ESA listing as endangered species USA ESA listing as endangered speciesHawaiiPredationBerlin and Vangelder, 1999

Risk and Impact Factors

Top of page Invasiveness
  • Proved invasive outside its native range
  • Has a broad native range
  • Abundant in its native range
  • Highly adaptable to different environments
  • Is a habitat generalist
  • Tolerant of shade
  • Capable of securing and ingesting a wide range of food
  • Highly mobile locally
  • Benefits from human association (i.e. it is a human commensal)
  • Has high reproductive potential
  • Has high genetic variability
Impact outcomes
  • Conflict
  • Reduced native biodiversity
  • Threat to/ loss of native species
Impact mechanisms
  • Interaction with other invasive species
  • Predation

Uses

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Economic Value

The economic value T. alba provides to agriculture through rodent predation is unquantified. Nevertheless, it may be of economic value by reducing rodent populations that cause damage to agricultural crops.

Uses List

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Environmental

  • Biological control

General

  • Sociocultural value

Detection and Inspection

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The distinctive flight pattern and appearance of T. alba allow for sufficient detectability despite its fairly cryptic and nocturnal behaviours. Survey methods used to detect other nocturnal owl species (e.g. voice, pellets) may be used to detect and monitor T. alba.

Similarities to Other Species/Conditions

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The sister species T. glaucops may be confused with T. alba in North America, but is distinguishable by plumage (Marti et al., 2005). There is little overlap in appearance among other Tyto species beyond North America.

Prevention and Control

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Prevention

T. alba is unlikely to be used for biological control in the future due to its failure to reduce invasive rodent populations at places of introduction. Prevention of introduction will require minimum effort, as more effective agents are now available for rodent control.

Control

The most effective treatment to remove T. alba from islands in the Seychelles was a bounty system employed the the Department of Agriculture. Other removal efforts included box traps, playback calls, mist net capture and hunting with air rifles. The species persists on most islands, although the population is considered controlled, and has been eradicated from Aride and Cousin islands (Fanchette, 2012).

Gaps in Knowledge/Research Needs

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There is scope for long-term monitoring of T. alba populations in areas of introduction, although given the localized nature of T. alba as an introduced species and previous successful efforts to reduce the Seychelles Islands population, extensive monitoring may not be warranted. Research may be needed to protect current populations and preserve subspecies diversity due to recent declines of the species across North America and Europe.

References

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Ash J; Atkins J, 2010. Birds of Ethiopia and Eritrea. London, UK: A & C Black, 463 pp.

Avibase, 2012. Avibase - the world bird database. http://avibase.bsc-eoc

Belterman RHR; Boer LEM De, 1984. A karyological study of 55 species of birds, including karyotypes of 39 species new to cytology. Genetica, 65(1):39-82.

Berlin KE; Vangelder EM, 1999. Akohekohe (Palmeria dolei). The Birds of North America Online [ed. by Poole, A.]. Ithaca, New York, USA: Cornell Lab of Ornithology, unpaginated. http://bna.birds.cornell.edu/bna/species/400

BirdLife International, 2012. Tyto alba. In: IUCN Red List of Threatened Species, Version 2012.1. http://www.iucnredlist.org

Bontzorlos VA; Peris SJ; Vlachos CG, 2005. The diet of Barn owl in the agricultural landscapes of central Greece. Folia Zoologica, 54(1-2):99-110.

Bowler J; Betts M; Bullock I; Ramos JA, 2002. Trends in Seabird Numbers on Aride Island Nature Reserve, Seychelles 1988-2000. In: Waterbirds, 25(1). 26-38.

Brooks J, 1991. The enigmatic owl. American Birds, 45(3):382-387.

Bruce MD, 1999. Family Tytonidae (Barn-owls). In: Handbook of the birds of the world. Vol. 5: Barn-owls to Hummingbirds [ed. by Hoyo, J. del \Elliott, A. \Sargatal, J.]. Barcelona, Spain: Lynx Edicions, 34-75.

Bunn DS; Warburton AB; Wilson RDS, 1982. The Barn Owl. Vermillion, South Dakota, USA: Buteo Books, 264 pp.

Byrd GV; Telfer TC, 1980. Barn owls prey on birds in Hawaii. 'Elepaio, 41(1):35-36.

Campbell RW; Dawe NK; McTaggart-Cowan I, 1997. Birds of British Columbia Volume 2: nonpasserines: diurnal birds of prey through woodpeckers. Vancouver, BC, Canada: UBC Press, 635 pp.

Dickinson E, 2003. The Howard and Moore complete checklist of the birds of the world, 3rd edn. London, UK: Christopher Helm, 1039 pp.

Eaton MA; Brown AF; Noble DG; Musgrove AJ; Hearn RD; Aebischer NJ; Gibbons DW; Evans A; Gregory RD, 2009. The population status of birds in the United Kingdom, Channel Islands, and Isle of Man. British Birds, 102(6):296-341.

Ehresman BL, 1984. Common barn-owl restoration in Iowa. Wildlife Rehabilitation [Proceedings of the National Rehabilitation Symposium], 3:10-19.

Ehrlich PR; Dobkin DS; Wheye D, 1988. The birder's handbook: a field guide to the natural history of North American birds. New York, USA: Simon & Schuster Inc, 785 pp.

Fanchette R, 2012. Invasive alien species: threat to biodiversity and human well-being. Seychelles strategy. Paris, France: IUCN France, unpaginated. http://www.especes-envahissantes-outremer.fr/pdf/atelier_ocean_Indien_2012/Seychelles.pdf

Foster JT, 2009. The history and impact of introduced birds. In: Conservation biology of Hawaiian forest birds: Implications for island avifauna [ed. by Pratt, T. K. \Atkinson, C. T. \Banko, P. C. \Jacobi, J. D. \Woodworth, B. L.]. New Haven, Connecticut, USA: Yale University Press, 312-330.

Golemanski V; Stoev P; Dobrev D; Beron; P; Zhivkov M; Popov A; Popov V; Beschkov V; Deltshev C; Michev T; Spassov N, 2011. Red Data Book of the Republic of Bulgaria (digital edition): Volume 2 - Animals. Red Data Book of the Republic of Bulgaria (digital edition): Volume 2 - Animals. Sofia, Bulgaria: Bulgarian Academy of Sciences and Ministry of Environment and Water. http://e-ecodb.bas.bg/rdb/en/vol2/

Hyde NHS; Matthews K; Seaton R, 2013. Barn Owl. In: New Zealand Birds Online: the digital encyclopaedia of New Zealand birds [ed. by Miskelly, C. M.]. http://www.nzbirdsonline.org.nz/species/barn-owl

Hyde NHS; Matthews K; Thompson M; Gale R, 2009. First record of Barn owls (Tyto alba) breeding in the wild in New Zealand. Notornis, 56(4):169-175.

IUCN, 2012. IUCN Red List of Threatened Species. Version 2012.2. www.iucnredlist.org/

Kirwan G, 2010. Birds of Turkey. London, UK: A & C Black, 512 pp.

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Links to Websites

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WebsiteURLComment
Birds of North America Onlinehttp://bna.birds.cornell.edu/bna
British Trust for Ornithologyhttp://www.bto.org/
IUCN Red Listhttp://www.redlist.org
New Zealand Birds Onlinehttp://nzbirdsonline.org.nz/
The Owl Pageshttp://www.owlpages.com

Organizations

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Switzerland: International Union for Conservation of Nature (IUCN), IUCN Conservation Centre Rue Mauverney 28, 1196, Gland, www.iucn.org

UK: BirdLife International, Wellbrook Court Girton Road, Cambridge CB3 0NA, http://www.birdlife.org

UK: BTO (British Trust for Ornithology), The Nunnery, Thetford, Norfolk, IP24 2PU, http://www.bto.org/

Contributors

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18/09/2012: Original text by:

Christina Leopold, Hawaii Cooperative Studies Unit, PO Box 10029 Hilo, HI 96721, USA.

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