Pranz, I just googled "a number were" and got over 8,000 hits. I think maahey hit the nail on the head by pointing out the definite and indefinite articles in the example I pasted from MW. Those articles serve as markers for the choice of either the singular or plural verb. [And, pfranz, you didn't mean to write that nouns "modify" verbs, did you?]
Here are some of the examples from the first page of Google hits:
"A number were sold to producers for personal storage and others were re-adapted by the grain companies to store bulk fertilizers..."
" Among the latter, a number were to be stable constituents of a later codified repertory, whereas other tropes quickly became obsolete...."
"The Shire produced volumes of material and submissions which were put to the Commonwealth Grants Commission and a number were commented on and adopted by the..."
"Anstruther Captains were famed for their seafaring skills and later in the 19th Century a number were actively involved in trade across the oceans, several in..."
Now I ain't sayin' that everything that's listed in Google is grammatical by a long shot. But I think the examples above are ok. I'll now list one that I think might have a problem:
"A number were due to invalid HTML which, unfortunately, had not been spotten when the issue was released."
But since I don't know very much computer language, perhaps this 'spotten' is just a term of trade I haven't seen before.
And so that we won't just talk in circles, are you saying, pfranz, that the word number categorically cannot take a plural verb? If so, I think you're way off.
And, maahey, taking into consideration what you pointed out about the definite and indefinite articles, I suppose Faldage's original sentence would have to remain as it is--but I think it could have been written more clearly.
Edit: Here's something from an Audubon report, but I wonder why the word numbers wasn't used. Perhaps there was a typo--note the lack of 's' on 'specie':
December 21, 1996, the Capital Area Audubon Society hosted its Fifty-first CBC. Cold weather hit the mid-Michigan area early this year and most of the waterbirds had departed by Thanksgiving. By count day, not only were the lakes frozen but large distances on the Grand and Red Cedar Rivers were ice-covered. Count day there was snow on the ground and temperatures ranged from 7 to 34 degrees with a south wind at 15 (gusts to 25). The day's high occurred after most counting was finished and the wind seemed to have many of the birds hunkered down.
When the number were in, they were about what many of us would have predicted but there were some surprises. 56 species and 16,475 individuals were tallied. This was one more specie but 18% fewer individuals than 1995. The average number of species seen 1981-95 is 58 and the average number of individuals is 15,900. The below average number of species was not for lack of trying. Fifty-three birders logged 118.25 party hours (57.5 on foot and 60.75 by car) and traveled 653.25 party miles (53.05 on foot and 600.2 by car) in the field. Almost all of these are higher than last year. Additionally, 8 individuals logged 15 hours watching their feeders. Seven parties traveled 61.1 miles during 8.25 hours seeking owls.
