Welcome!
I'm a huge proponent of using a daily Probiotic, both for myself and for all of my birds, and all of my birds have been getting a daily Avian Probiotic for years now, and not once have they developed any type of GI Infections or become "ill" in-general. You do need to give a Probiotic supplement to your bird, your dog, cat, reptile, or yourself once every single day (my Bearded Dragon also has a Probiotic mixed into her dust for her live insects every day too, lol)...I don't know why anyone would write that you "shouldn't give a Probiotic every single day", as that's a necessary component of them working continually and being beneficial to begin with, but that just goes to show that you can't go by information on the internet, even mine I guess

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"Probiotics" is a general-term for many different strains of bacteria that are normally found throughout the GI Tracts of most mammals, birds, reptiles, etc. (living creatures with a "typical" GI/Intestinal Tract), and that are responsible for many actions that happen throughout the GI Tract, but the big ones are #1) Keeping all Fungi from growing inside of the warm, dark, moist environment of the GI Tract (specifically the Intestines, both small and large), and then #2) Aiding in the digestion of most food that is eaten, specifically in the Small Intestine. All mammals, birds, reptiles, etc. have billions of normal, healthy strains of bacteria living throughout our GI Tracts performing these two functions 24/7, along with a bunch of other functions as well.
There are several things that can occur throughout the GI Tract that will either render these healthy bacteria inoperable, or simply kill them all off quickly, the big ones being #1)Taking any types of Antibiotics, and #2) Having a condition/illness or simply an ideopathic change that causes a pH change somewhere throughout the GI Tract. I'm not going into detail here, but basically the GI Tract of most living creatures has all kinds of beneficial bacteria inside of it, from start to finish, and if that beneficial bacteria stops functioning, is killed, or in some living creatures their bodies don't have the correct GI pH level for them to grow/live in the first place, then the GI Tract can be taken-over by Fungi (including Yeast), stop properly digesting food, stop processing waste materials properly (resulting in abnormal stools/feces, such as diarrhea or constipation), or have an improper pH level which can cause many different issues/illnesses/conditions...
So, taking a daily Probiotic supplement when you're not sick or suffering from some type of GI problem will ensure that your GI Tract has plenty of normal, healthy, beneficial bacteria growing throughout it, keep your GI Tract healthy, within the correct pH range, free of Fungi/Yeast, and moving waste through correctly and continually. And if you happen to have to take an Antibiotic for any reason, if you are already taking a daily Probiotic supplement then you're not going to have to worry about a secondary Fungal/Yeast infection anywhere in the body, not only the GI Tract, but also in the Sinuses/Eyes/Ears/Throat (Thrush) or the Vagina in females. And the reason you need to take it daily is simply to keep that healthy bacteria growing, as it does die-off naturally for any number of reasons.
Probiotics are not "medications" or "drugs" in any way, and some times people confuse them for such, and feel that you're going to "overdose" on them, so that could be one reason someone would think they are not good to take every day. However, the only real negative to taking a daily Probiotic only occurs if you take more than the recommended dosage, and you really do have to take quite a bit, which can cause an upset-stomach/GI Tract. That's it. But if you simply take the recommended dose once a day, you're good to go. And most people notice that their GI Tracts are running much more efficiently and regularly after taking a daily Probiotic supplement for only a couple of weeks straight...just ask Jamie Lee Curtis about her "Activia" yogurt
That's the other thing; We take-in Probiotics in certain foods all the time, specifically fermented dairy products, such as yogurt. All milk-based yogurt contains millions/billions of Probiotics (as well as Prebiotics, but that's another thing entirely, however also very beneficial, and I take a daily supplement that contains both Prebiotics and Probiotics, as well as Digestive Enzymes)...
As far as our birds go, they even have an added organ that benefits from a daily Probiotic supplement, the Crop. I'm sure you've heard of birds developing Fungal/Yeast infections in their Crop before, as the Crop is a part of the GI Tract in birds, and is a very warm, dark, moist storage-bin for Fungi/Yeast to grow and live happily if allowed to, and actually most birds who have their Crops flushed and cultured will test positive for at least some levels of different Fungi, most commonly Yeast. So when you give your birds a daily Probiotic supplement, you're keeping their GI Tracts healthy from their Crops down to their Vents/Cloacas.
***There are a lot of different manufacturers of Avian Probiotic supplements, which contain the specific bacterial strains that will benefit birds the most, and in the correct quantities for birds (obviously they require a smaller amount than a person would). The two most commonly-found Avian Probiotic supplements are #1) Benebac, and #2) Qwiko Avian Probiotics. Benebac isn't made specifically for birds per se, it's labeled for dogs, cats, birds, rodents, etc. But it's an all-inclusive Probiotic supplement that works very well, and it comes in both a powder and a "paste"...Qwiko Avian Probiotics are made specifically for birds, and is in powder-form, and it comes with a pre-measured "scoop" inside the bottle (not really a "scoop" at all, it's a very small amount of powder that you simply sprinkle on top of whatever their "staple" food is, either pellets or seed-mix)...I've been giving all of my birds Qwiko Avian Probiotics once daily for almost 2 years now (prior to that I always used a human probiotic supplement and crushed the tablets)...My birds eat pellets as their dietary "staple", but they also each get 1/4 cup of a healthy, low-fat seed-mix each day too, in-addition to their pellets. So I always mix one "scoop" of the Qwiko Avian Probiotic powder into their daily seed-mix, as it's a much easier way to give it to them and to ensure they get the entire dose; if you sprinkle one "scoop" of the Qwiko powder on top of their seed-mix first thing each morning, and then mix it in very slightly, just enough that they can't see it, they will ingest it bit by bit with every seed they put inside their mouths/beak, as the powder easily dusts/coats the outside of each seed. If you don't feed your birds any seed-mix every day but rather just a pellet every day, then you simply sprinkle the "scoop" of powder all over their pellets, and try to spread it out so it's not very visible to them, as sometimes when they see anything "different" they refuse to eat it...Also, if you give your bird a daily "chop" mix of veggies/fruit, it's very easy to mix the very small amount of Qwiko powder into that as well and they can't see it, you just have to make sure that they eat all of their chop/veggies/fruit each day...My guys always finish all of their daily seed-mix (as they only get a very small amount each day), so that works best for them. They have no idea that it's there, as the Qwiko Avian Probiotic powder really is an extremely small amount of powder that you have to mix in. It's best that you give them their daily Probiotic supplement first thing in the morning on their new food...
If you choose Benebac Probiotics, either the paste or the powder, it works just as well as the Qwiko probiotics, but it's a larger amount of powder than the Qwiko by-far, and I've not ever given the paste formulation of Benebac, but would imagine that it would be much more difficult to give them...That's the main reason I chose to use the Qwiko Avian Probiotic powder, because it's a very small amount of daily powder that is easy to hide in their food/seed-mix. And it's also available at any Petco for $9.99, and one bottle lasts for quite a long time, as it's a large bottle compared to the size of each dose. I would say I buy a new bottle once every 3 months, and that's giving it every day to 4 larger birds and then 8 Budgies...So if you only have 1 bird a bottle of the Qwiko powder should last you over 6 months.
I would highly suggest that everyone consider giving a daily Avian Probiotic to all of their birds, as it can't hurt them, it can only help them, and again, I can only speak from my own experience with myself and my birds, as well as my female Bearded Dragon (who I got when she was a month old and 5" long, and who just turned 2 in October and is now 21" long and healthy as can be, never had any type of bacterial, fungal, or parasitic infection, and more importantly has never once been Impacted, Prolapsed, and who has a regular bowel movement at least twice a week)...
And if you don't want to give your birds and other pets a daily Probiotic supplement, at the very least you should give them one any time they are put on any antibiotic, from day one of them taking the antibiotic through at least one week AFTER they stop taking the antibiotic, as this will keep them from getting a Fungal/Yeast infection secondary to the antibiotics killing-off all of the healthy bacteria throughout their GI Tracts, which is responsible for keeping the growth of all Fungi/Yeast in-check.