Kept 'split'? Four of the ten readers we tried this on kept it and three more argued for it afterwards, which makes it the strongest word in the sentence that is not in the answer, and you can see why, because a beak split down the middle is the thing you picture first. It still cannot go in, because the only slot it could take is the one 'with' is holding, and 'kea's split beak rebuilt gel' is a pile of words rather than a line you can read. The split is also only half of what happened, and the five keeps the half where somebody fixed it.
This one really happened. Staff at the Arthur's Pass Cafe, in the Southern Alps of New Zealand's South Island, noticed a kea behaving oddly and called for help, and when he was picked up his beak had split vertically with a chip out of one side and he had not eaten properly for several days. He spent 48 days at Christchurch Wildlife Hospital, where the lead veterinarian Pauline Howard gave him pain relief and antibiotics and rebuilt the beak with fingernail gel hardened under an ultraviolet lamp, the same stuff a salon uses to extend a nail, and he picked most of the material off himself, so careful trimming is what finally restored the beak's function. He gained about 40 grams and shared an enclosure with Pukeki, a younger kea brought down from Aoraki with severe lead poisoning, and Howard said the two of them behaved like siblings, pushing and pecking at each other. When he went back to the mountains the village gathered at the Arthur's Pass community centre with a homemade lemon cake, which the kea did not get, and Howard's own summary of the whole thing was that it takes a village to care for a kea.
Every word, accounted for
TheA little word. It only holds the sentence together.
kea'sWhat he is, and the bird the beak belongs to: the only alpine parrot in the world, and one most readers have never seen. Take it out and this is any bird anywhere.
beakThe thing that was mended, and the reason he could not feed himself. A parrot with a broken beak cannot eat at all.
hadA little word. It only holds the sentence together.
splitWhat was wrong with it. The beak had split vertically with a chip out of one side, and the five keeps the repair rather than the damage.
leavingJoins the damage to what it did to him. The sentence needs it and the five does not.
theA little word. It only holds the sentence together.
alpineWhere kea live, in the mountains of the South Island. A kea is already an alpine bird, so the word says it twice.
parrotWhat a kea is, for anyone meeting one for the first time. 'Kea' is the same word with the country and the mountains already inside it.
unableHow bad it was. He was not refusing food, he could not pick it up.
toA little word. It only holds the sentence together.
eatThe problem that started it. He had gone days without a proper feed, and the five keeps the fix rather than the problem.
andA little word. It only holds the sentence together.
wasA little word. It only holds the sentence together.
rebuiltWhat was done to it. Not treated, not patched: built back up in layers until it worked again.
overA little word. It only holds the sentence together.
48How long he was in care at Christchurch Wildlife Hospital. A real number, and still the length of the stay rather than the thing that happened in it.
daysGoes with 48.
withA small word doing the biggest job in the five. Drop it and you get 'kea's beak rebuilt gel', which is not English and does not say the gel was the stuff the beak was made back out of.
aA little word. It only holds the sentence together.
gelWhat the beak was rebuilt out of: fingernail gel, set hard under an ultraviolet lamp, the same trick a salon uses to extend a nail.
hardenedHow the gel was set. The method behind the method, and the five has room for the material only.
underA little word. It only holds the sentence together.
anA little word. It only holds the sentence together.
ultravioletThe lamp that set it, and the detail that makes people stop. It costs two slots to say, and the gel carries it.
lampGoes with ultraviolet.