4 letters:
bird, burd, byrd, curd, ferd, gerd, gird, herd, hird, hurd, kurd, nerd, word

5 letters:
-ward, berde, bered, birde, derde, dmard, dword, ebird, ferde, heard, herde, jerde, jered, kurde, leard, lered, peard, pferd, sherd, smurd, spred, swerd, tbird, third, tyred, werde, wurde, xword

6 letters:
absurd, alward, begird, birred, braird, burred, byword, engird, furred, gjerde, hybird, jerred, oxbird, purred, reword, t-bird, thered, ungird, unherd, zubird

7 letters:
abiword, absurde, antbird, averred, blurred, catbird, chirred, churred, cowbird, cowherd, dunbird, elsword, gosherd, gunbird, haybird, humbird, icebird, jaybird, keyword, maybird, nayword, oilbird, peabird, poebird, proword, redbird, reheard, sauwerd, seabird, shagird, shirred, slurred, spurred, stirred, sunbird, uncured, unheard, vaxherd, warbird, waxbird, wetbird, whirred

8 letters:
babybird, beambird, beancurd, bearherd, bellbird, bluebird, borujerd, cagebird, codeword, cussword, deferred, demurred, deterred, egg-bird, fig-bird, firebird, foreword, gaolbird, hairbird, hangbird, headword, incurred, inferred, interred, jailbird, ladybird, leafbird, liskeard, lovebird, lyrebird, mailbird, misheard, moorbird, occurred, ovenbird, overgird, overword, password, pre-bird, prefered, puffbird, qua-bird, railbird, rainbird, recurred, reedbird, referred, ricebird, ringbird, safeword, shadbird, shoebird, snowbird, songbird, starbird, surfbird, swanherd, wallbird, westword, yardbird

9 letters:
1password, afterword, backsword, bestirred, bloodbird, bluebird', bowerbird, catchword, cedarbird, concurred, conferred, crankbird, crossword, deathbird, dickybird, doughbird, flamebird, friarbird, frostbird, gooseherd, greenbird, guideword, honeybird, lady-bird, ling-bird, longsword, lyre-bird, moor-bird, moosebird, moundbird, mousebird, nightbird, oceanbird, one-third, overheard, phoneword, preferred, riflebird, scrubbird, shorebird, skatebird, snakebird, snow-bird, song-bird, speedbird, stiltbird, stinkbird, stonebird, sugarbird, swearword, swineherd, thornbird, thumbbird, troopbird, troutbird, undergird, unstirred, watchword, waterbird, weet-bird, wheatbird, wheelbird

10 letters:
beschwerde, bower-bird, butterbird, cushewbird, dickeybird, dicky-bird, dollarbird, doubleword, early-bird, greatsword, half-heard, hotspurred, mound-bird, netherbird, nettlebird, night-bird, nightbirde, pseudoword, reinterred, reoccurred, scrub-bird, smallsword, tailorbird, tonguebird, transfered, tropicbird, undeterred, wattlebird, weaverbird, whirlybird, yellowbird

11 letters:
apostlebird, bristlebird, butcherbird, chauffeured, counterword, dickey-bird, disinterred, forty-third, frankenword, frigatebird, galley-bird, hummingbird, mockingbird, mutton-bird, thunderbird, transferred, unpreferred

12 letters:
butcher-bird, humming-bird, long-spurred, mocking-bird, tax-deferred, thirty-third, twenty-third, umbrellabird

13 letters:
coarse-furred, glossy-furred, secretarybird, short-spurred

7 letters:
inboard

8 letters:
timbered, fingered

10 letters:
splintered, unhindered

11 letters:
springboard

14 letters:
light-fingered