Here's my list of owls that I have seen. I have adopted a loose taxonomy in anticipation of future splits.
Tasmanian masked-owl
Sulawesi masked-owl
Minahassa masked-owl
Australasian grass-owl
Ashy-faced owl
Common barn-owl
Javan barn owl (Mikkola suggested split)
Australian barn owl
Indian barn owl
Andaman Masked owl
North American barn-owl
South American barn owl
White-winged barn owl (Clement's group, Jamaica)
Colombian barn owl
Galapagos barn owl
African barn-owl
Red owl
Sri Lanka Bay owl
Mountain scops-owl
Vandewater's scops owl Sibley and Monroe suggested split from Mountain scops owl (Sumatran)
Indian scops-owl
Sunda scops-owl
Singapore scops owl
Wallace's sops-owl
Palawan scop's owl
Lowland Luzon scops-owl
Everette's scops-owl
Negros scops-owl
Luzon scops-owl
Javan scops-owl
Flores scops
Rajah scops owl (Sumatra) Clement's group
Mindanao scops-owl
Oriental scops owl
Walden's scops owl
Andaman scops owl
Elegant (Calayan) scops-owl
Common scops-owl
Cyprus scops-owl
Pallid scops-owl
Arabian scops
Flammulated owl
Moluccan scops-owl
Rinjani scops owl
Simeulue scops owl
Mantanani scops-owl
Sulawesi scops-owl
Sangihe scops owl
Peleng scops owl
Sokoke scops owl
Malagasy scops-owl
Torotoroka scops-owl
Mayotte scops owl
Anjouan scops owl
Grand Comoro scops owl
Moheli scops owl
Seychelles scops owl
Western screech-owl
Vinaceous screech owl (xanthusi race-per HBW)
Sutton's screech owl (Clement's group from Western screech)
McCall's screech owl (Clement's group from Eastern Screech)
Balsas screech owl
Santa Marta screech-owl
Whiskered screech-owl
Eastern screech-owl
Pacific screech-owl
Oaxacan screech-owl
Tropical screech-owl
Long-tufted screech-owl
Koepcke's screech-owl
Apurimac screech-owl
Peruvian screech-owl
Tumbesian screech-owl
Colombian screech-owl
Rufescent screech-owl
Cloud-forest screech-owl
Bare-shanked screech-owl
Bearded screech-owl
Hoy's screech-owl
Cinnamon screech-owl
Vermiculated screech-owl (Choco)
Guatemalan screech-owl (West Mexican)
Mesoamerican screech-owl (West Mexican)
Rio Napo screech-owl
(Southern) tawny-bellied screech-owl
(Northern) tawny-bellied screech-owl
(Belem) tawny-bellied screech owl
Black-capped screech-owl
White-throated screech-owl
Northern white-faced owl
Giant scops-owl
Great-horned owl
Magellan owl
Eurasian eagle-owl
Rock eagle-owl
Dusky Eagle owl
Pharaoh eagle owl
Desert pharaoh eagle owl (Clement's group)
Vermiculated eagle-owl
Arabian eagle-owl (Spotted)
Mackinder's Eagle-owl
Forest eagle-owl
Barred eagle-owl
Verreaux's eagle-owl
Snowy owl
Philippine eagle-owl
Buffy fish-owl
Brown fish owl
Turkish fish-owl
spotted wood-owl
Mottled wood-owl
Mexican spotted-owl
Northern spotted-owl
California spotted owl
Brown wood-owl
Bornean wood owl
Nias wood owl
Mountain wood-owl
tawny owl
Maghreb owl
Hume's owl
Omani owl
Mottled owl
Atlantic mottled owl
Mexican wood owl
Rufous legged owl
Chaco owl
Rufous-banded owl
Rusty-barred owl
Black and white owl
Black-banded owl
San Isidro owl
Fulvous owl
Northern barred owl
Mexican barred owl
Ural owl
Great gray-owl
African wood-owl
Crested owl (Choco)
Crested owl (Amazon)
Spectacled owl
Short-browed owl
Tawny-browed owl
Band-bellied owl
Northern hawk-owl
Collared owlet
Sumatra owlet (or Sunda proposed split from Collared by Eaton)
Pearl-spotted owlet
Eurasian pygmy-owl
Northern (Pacific) pygmy-owl
Northern (Rocky Mountain) pygmy-owl
Mountain pygmy-owl
Guatemalan Pygmy owl
Cape pygmy owl
Yungas pygmy-owl
Austral pygmy owl
Costa Rican pygmy-owl
Andean pygmy-owl
Tucamen pygmy-owl
Colima pygmy-owl
Tamaulipas pygmy owl
Central American pygmy-owl
Amazonian pygmy-owl
Least pygmy owl
Subtropical-pygmy-owl
Cloud forest pygmy-owl
Ferruginous pygmy-owl
Colombian pygmy-owl
“ucayalae" pygmy owl
Ridgeway's pygmy-owl
Peruvian pygmy-owl
Apurimac pygmy-owl
Asian barred owlet
Malabar barred owlet (Konig suggested split)
Javan owlet
Jungle owlet
Whitney's Elf owl
Texas Elf owl
Sanford's Elf owl
Long-whiskered owlet
(Northern) Burrowing owl
(Hispaniola) Burrowing owl
Venezuelan burrowing owl
(Ecuadorian) burrowing owl
(Andean) Burrowing owl
(Littoral) Burrowing owl
(Grallaria) Burrowing owl
(Southern) Burrowing owl
Spotted owlet
Little owl
Cucumai
Lillith owl
Forest owlet
Boreal owl
Northern saw-whet owl
Unspotted saw-whet owl
Buff-fronted owl
Brazilian buff-fronted owl
Barking owl
Sumba boobook
Southern boobook
Tasmanian boobook
Timor boobook
Rote boobook
Little Sumba hawk-owl
Brown hawk-owl
Hume's hawk owl
Andaman hawk owl
Chocolate boobook
White-browed owl
Luzon hawk-owl
Mindanao boobook
Sulu boobook
Mindoro hawk-owl
Romblon hawk-owl
Cebu hawk-owl
Camiguin hawk-owl
Ochre-bellied boobook
Speckled boobook
Cinnabar boobook (& "white-spotted boobook")
Togian boobook
Jamaican owl
Stygian owl
Long-eared owl
Wilson's owl
Madagascan long-eared owl
Short-eared owl
Galapagos short-eared owl
Field owl
Antillean owl
Hawaiian Owl
Marsh owl
Striped owl (#234)
And here is a list of owls I still need to see:
Madeira barn owl Robb split from Eastern barn owl
Slender-billed barn owl Robb split from Eastern barn owl
Curacao barn owl
Lesser Antilles barn owl
Dominican barn owl (poss split from Lesser Antilles barn owl)
Cape Verde barn owl
Sao Tome barn owl
Bioko barn owl Clement's group from Eastern barn owl
Boang barn owl
Santa Cruz Barn Owl (from Australian)
Golden masked owl
Taliabu masked owl
African grass owl
Buru (lesser) masked owl Clements group from lesser masked owl
Tanimbar (lesser) masked owl Clements group from lesser masked owl
Seram masked owl
Manus masked owl
Australian masked owl
New Guinea masked owl Sibley and Monroe suggested split from Australian Masked owl
Lesser sooty owl
Greater sooty owl
New Guinea sooty owl Konig suggested split
Itombwe owl
Oriental bay owl
Sri Lanka bay owl Mikkola suggested split from south Indian birds
Serendib scops owl
Reddish sandy scops Clement's group from Sandy scops
Sandy scops owl Clement's group from Sandy scops
White-fronted scops owl
Stressmann's scops owl (possibly not a species)
Mindoro scops owl
Sao Tome scops owl
Principe scops owl
Socotra scops owl
African scops owl
Snowy scops owl Clement's group from African scops
Annabon scops owl Konig suggested split and Clement's group from African scops
Somali scops owl undescribed form, possible split from African scops owl
Formosan scops owl Sibley and Monroe suggested split from Mountain scops owl
Bornean scops owl Sibley and Monroe suggested split from Mountain scops owl
Sulu scops owl Sibley and Monroe suggested split from Mantanani scops owl
Northern Oriental scops owl taxonomy unclear, possible split from Southern birds
Lanyu scops owl possible split from Elegant scops owl
Rykuyu scops owl possible split from Elegant scops owl
Daito Scops-Owl possible split from Elegant scops owl
Wetar scops owl
Sula scops owl
Siau scops owl (possibly extinct)
Kalidupa scops owl
Pemba scops owl
Nicabor scops owl
Sri lankan scops (from Oriental)
"Bengal scops" (From Oriental)
Enggano scops owl
Mentawai scops owl
Rajah scops owl (Borneo)
Collared scops owl
Chinese collared scops Mikkola suggested split from Collared scops
Pryer's Scops-Owl from Japanese scops
Japanese scops owl
Costa Rican screech owl (from Choco Screech)
Puntarenas screech owl (from Choco Screech)
Puerto Rican screech owl
Alagoas Screech owl Dantus
Xingu screech owl Dantus
Duida screech owl (Konig suggested split from Tropical screech)
Foothill screech Roraima (Clement's group)
Venezuelan screech owl (N Venezuala and Sierra Perija of N Colombia)
Cuban bare-legged owl
Palau scops owl
Southern white-faced owl
Byzantine eagle owl Robb suggested split from Eurasian
Ethiopian Eagle owl (from Mackinder's)
Cape eagle owl (Clements group from Mackinder's)
Akun eagle owl
African spotted eagle owl
Fraser's eagle owl
Usambara eagle owl May be a ssp of Fraser’s
Shelly's eagle owl
Tawny fish owl
Bengal fish owl Robb split from brown fish owl
Blakiston's fish owl Continental birds
Blakiston’s fish owl Japanese birds
Pel's fish owl
Vermiculated fish owl
Rufous fish owl
Bartell's wood owl (Likely same as Bornean birds)
Himalayan wood owl
Taiwan wood owl (poss split from Himalayan wood)
Sichuan wood owl May be lumped with Ural owl
Lapland owl Robb split from great-gray owl
Maned owl
Western red-chested owlet Clement's group from red-chested owlet
Pycraft's red-chested owlet Clement's group from red-chested owlet
Eastern red-chested owlet Clement's group from red-chested owlet
Trinidad pygmy owl (poss split from Ferruginous)
Neblina pygmy owl (undescribed Luis Fabio Silveria) may be ferruginous pygmy owl
Chaco Pygmy Owl (from Ferruginous, different from Tucuman)
Pernambuco pygmy owl possibly extinct
Cuban pygmy owl
chestnut-backed owlet
Sjoeatedt's owlet
Scheffler's owlet Clement's group from African barred
African barred (Ngami) (central)
Cape owlet Clement's group from African barred
Etchecopar's owlet
Chestnut owlet
Albertine owlet
Borneo owlet (Proposed split from Sunda owlet by Eaton)
Taiwan owlet (from collared)
Hutton's little owl Clement's group from little owl
Northern (or Eastern) Little owl Mikkola split from Little owl
Florida burrowing owl (Clements group, separate from Hispaniola birds)
Clarion Burrowing owl
Llanos burrowing owl
Guiana Burrowing owl
Ethiopian little owl
Tengmalm's owl Robb split and Clement's group from Boreal
Queen Charlotte Island saw whet Clement's group
Rufous owl
Powerful owl
Morepork
Alor boobook
Red boobook
Babar boobook
Moa boobook Poss split from Southern boobook
Savu Boobook Poss split from Southern boobook
Northern boobook
Taiwan/Ryukuyu boobook possible split (birds of NE Asia) from Northern boobook (genetic divergence about 1.7%)
West Solomon boobook
Guadalcanal boobook
Malaita boobook
Makira boobook
Christmas hawk-owl
Jungle hawk owl
New Britain hawk-owl
Buru Boobook
Seram boobook
Halmahara boobook
Bacan boobook Mikkola suggested split from Halmahara boobook
Tanimbar boobook Clements group from Moluccan hawk owl
Gede boobook (Mikkola comment that an undescribed boobook lives on Gede Is)
Manus hawk-owl
Bismark hawk-owl
Eurasian Northern hawk-owl Robb split from Northern hawk owl
Papuan hawk owl
Fearful owl
Abyssinian long-eared owl
Pohnpei short-eared owl Clements group from short-eared owl
Tumbes owl 141
