Cat attack!

Is Willow spayed? If she is in heat, males will wait outside for her to come out so they can mate. If she is spayed, then you have a couple of options for the stray:

Call the warden, but the chances are that the cat will be euthanized (I don't advise that).

Put signs out in your neighborhood and try to find the owner of the stray. Ask them to put their cat inside and get him fixed if he is not.

Contact a TNR group in your area to come and trap the stray and get him neutered.

Keep Willow inside for a while. The stray may disappear and you can let her out again in the future.

If Willow doesn't want to go outside, consider yourself lucky and keep her in, where she's safe! Heaven only knows what sorts of diseases she's been exposed to already from fighting with this tom. Are her shots up to date?

It sounds like this poor tom desperately needs to be cleaned up, looked at by a vet, and neutered -- so even if he does have an owner, it's not a responsible one. I wouldn't hesitate to call a no-kill shelter or rescue group and see if they can trap him, give him the help he needs, and eventually find him a home...

"She loves being out with the birds"? There are statistics that show regular songbirds (and others) that normally live in towns with people have been absolutely decimated (to the point where some are almost extinct) by cats allowed to roam outdoors. They're killing machines and much as we love them, we also love birds (who doesn't?!) and it's unfair to allow the cats to be out there. And it's been proven by studies that collar bells do NOT work at all as the birds don't seem to 'get' it. Your cat doesn't really like being out apparently, and could already have infections/abscesses from the scratches so I'd get her checked out and just let her live peacefully indoors.

Not to turn this into a debate, but the statistics on the bird population being "decimated" by free roaming cats are largely overstated based on a theory and flawed studies used by anti-cat groups to further their agenda.

http://straypetadvocacy.org/html/pre..._reviewed.html
http://straypetadvocacy.org/html/wisconsin_study.html

Back to the original topic, though, I have to agree with MomofMany and Carol_Petunia. And really, if Willow is being injured by another cat, wouldn't it be for her own safety to keep her inside at least until the threatening cat leaves the area? If any of those wounds becomes abcessed it could mean very high vet bills for you...

I guess to me even one bird dying unnecessarily adds up to decimation - we all know for sure that cats will kill birds (and anything else they can catch) if allowed, so nitpicking about which study is perfectly accurate doesn't seem like much help. I guess I just got turned off statistics when I asked about the possibility of some protection for birds who liked to nest on flat rooftops surrounding a busy parking lot - only to be told that the species was not endangered. Somehow that didn't make me feel a whole lot better - and cats weren't even the issue, but people and cars (the babies would routinely fall down, and while managing to survive the fall, had a hard time with the rest of us).

If you don't already have a litter tray indoors, I would get one asap, and ensure Willow knows how to use it.

If she has to go outside to use the toilet, and is scared and comes back covered in scratches, it must really be stressing her out! At least an indoor litter tray will give her the choice to stay indoors where it is safe, until you find a solution to the problem of the agressive stray.