Ten foot long want to spray some kind of wood filler

Does it have to be spray foam? How about using a length of wood with a balled up rag soaked in fiberglass resin or similar on the end that you could position into the hole and let it set up? Could maybe try the procedure with just a wet rag first, to figure it out, see that it looks possible. This would have the advantage that if you can't get it right, you may be able to bail on it. Foam, IDK, if aesthetics matter, seems more unpredictable to me and that's if you can figure out some way to do it. I guess if you have a true applicator for that intended purpose, it would be controllable, but I doubt you will find anything that long.

Lots are available from a simple google search - here's just one example :

"...that the birds *keep* making"?

That seems to imply that you have managed to seal it up, at least temporarily, on multiple occasions. What have you tried that keeps failing?

And is it "holes" or "a hole". Just curious, since you've used both terms.

If the hole(s) go through the wall such that the birds can enter, how will you provide a backing for any type of sealant? Won't the e.g. spray foam just go into the hole(s) and behind the wood?

How about rigging up a way to hang this from the overhang in front of the hole(s)? Form and function. ;-)

Epoxy, long poles, flat boards, wax paper, etc. Could be tricky.

Did you miss the whole "forty foot ladder" issue? Should he use a hammer with a 10' handle? ;-)

Good job, so they do exist.

Actually, the "forty foot ladder" makes me wonder what type of four+ story (storey in canada?) building John is working on, and whether it is feasible work from above rather than below.

You don't own a 40' ladder and don't want to buy one that you'll probably only ever use this one time. I'm with you so far.

So what about renting the equipment you need to do the job right? One and done is usually the best way to go. Rent a ladder, scaffolding, or a cherry picker bucket truck and get up there to replace the failed wood board. Your foam approach isn't likely to last long, if at all.

Sure, and I have a 10' pair of pliers to hold it in place to start it. I'll lend them to him.

Not required...

Which I noted in my first response.

Or is it lids? He said "hole" but he also said "holes". Still waiting on an answer to that question. "Holes" may mean "lids" which may mean a house looking like it has a case of the shiny measles. ;-)