OK, matching Wikipedia with my index, here's what I have:
(I really hope that it's an English word!)
Those are the ones I will not consider
Albatross: just 1 maker, no models.
Bluebird: Nissan, Willys, Overland or Campbell's
Condor: about 13 models with that name (Aguzzoli, Altona, ARH, ...)
Crow: Chrysler, Imperia, Toyota...
Curlew: that was a British one-off..
Dove: Harrington's GTR4
Eagle: dozens of models
Falcon: dozens of models
Harrier: beside Zagato's concept there were a military vehicle and the Hustler.
Hawk: dozens of models
Heron: at least 6 makers with that name...
Hummingbird: Baker-Bell and EPC (plus 3 makers)
Jackdaw : there were 2 British vans, built by Imperial and by Minion.
Jay: there was just the Jay-Eye-See...
Kestrel: beside Riley's model there ws just the Scorpion/Dovetail/Protoflight
Kite: beside Fioravanti's concept, there was an obscure maker and a 3-wheeler
Lark: Lexington, Studebaker, Willys
Martin: at least 17 makers with that name plus 4 similar
Monarch: Mercury, but also Auto Parts and few more...no kits.
Pelican: Pashley's 3-wheelers and a French electric triporteur.
Robin: Reliant and few others but no kit cars.
Shrike: Halibrand Indy cars plus 3 kit-cars (Norton, Naf and Phoenix)
Snipe: Humber's model
Sunbird: at least 2 models (Pontiac, Holden)
Sparrow: the Corbin is not a kit car.
Swallow: Alternative Cars, Bishoprick, Brookland, Kit Cars, Zwaluw and few others...
Swift: Suzuki and a couple more
Tyrant: built in Netherland by Cock, was not a kit-car
I have doubts about the following:
Kingfisher: no kits that I now of.
Ibis: there was a kit with this name, but it was from NZ (unless it's the Berkley Bandit revival...)
Flamingo is the closest I found but you wrote " there is another model with the same name, so I figured they were made by the same outfit", and it was not a kit car (or American).
Vulture: there was a British kit car and an American 3-wheeler
Osprey: a British kit car built by 2 companies.
So, my final guess would be
Sandpiper:there was a Buggy with this name, VW-powered and built by Lincoln Industries and Kellison (plus a limited version of the Holden Gemini.)