Also, something I forgot to talk about is what the issue with your Budgie was in the first-place, the issue that lead you to go out and mistakenly buy a second Budgie because you thought he "needed a friend"...
***The very first thing that you need to know about owning ANY birds of any kind as pets or at least being responsible for them, whether they are parrots, doves/pigeons, poultry birds, or any other species or type of bird, is that all birds possess a natural, innate survival instinct that forces them to hide ANY AND ALL outward signs/symptoms of illness and pain for as long as they possibly can. This applies to all birds of any level of tameness, from a completely hand-tame, loving, cuddly bird to a completely wild, parent-raised bird. They do this because they are Flock-Animals, they all live in Flocks naturally in the wild, as well as when they are tame and live with people, as their people are their Flocks...Any bird in a Flock that visibly appears to be weak, sick, or injured instantly becomes a target for predators such as cats, foxes, wolves, coyotes, larger predatory birds like Vultures, Hawks, Eagles, Ravens, Crows, etc. So this not only puts the outwardly sick/injured bird at-risk for being killed by a predator, but it puts the entire Flock at-risk. This is why all birds end-up hiding all outward signs/symptoms of illness and/or pain for as long as they possibly can, sometimes for months and months to even over a year.
***By the time we as people see outward signs of illness or pain in our birds, they have usually been sick or injured for quite some time already. Usually at the point that we notice something is wrong with our birds they actually been sick for months and months, and are often very close to death, sometimes being too far gone to save, even with Veterinary care. So if you see a bird displaying any common signs of illness or pain that means that you need to get them to either a Certified Avian Vet or an Avian Specialist Vet (no "Exotics" Vets, I'll talk about this later) right away...And I'm talking about ANY of the common signs and symptoms of illness and/or pain in birds, including Lethargy and not playing or moving as much as they normally do, sleeping more than normal, having their feathers "fluffed-up" for long periods of time (indicates they may be feverish and having chills), if they are spending time down on the bottom of their cages (this is because they are having issues balancing on perches or climbing on the cage bars), vomiting, loose or runny feces, feces with any blood in them (appears either bright red, dark red, or black; also can appear to look like coffee-grounds), feces that have undigested food/seeds visible in them, ANY change in their appetites such as suddenly not eating as much as they normally do or not eating anything at all during a day (this is a HUGE sign that they are not feeling well and are in critical need of an Avian Vet), sudden weight loss, any Feather-Destructive Behavior or Self-Mutilation, any respiratory issues such as sneezing, coughing, wheezing when they breath, any open-mouth breathing or heavy breathing, any discharge coming from their nostrils, eyes, or ears (any color, doesn't matter), etc....If you notice ANY of these signs/symptoms being suddenly displayed by your bird, or if your bird gradually or progressively develops signs/symptoms of illness that you can actually see getting worse and worse; the best example of this is a bird who starts having issues flying, such as not being able to control their landings or having crash landings, then it progresses to them crashing into walls and not being able to turn or land at all, then finally they can't even gain altitude at all...This is a very common progression for Neurological symptoms, which can be due to an Avian Viral Disease, a Bacterial Disease, or an infection that is severe and spreading like an inner or middle ear infection or sinus infection that is causing them disorientation and vestibular issues, such as Vertigo...
***With your Budgie you mentioned that he suddenly started acting "differently" than he had been acting since you had brought him home...Now I'm not sure exactly what you mean by "acting differently", but it's extremely difficult to tell whether or not a bird is sick after only being in a new home/environment and with new people for only a week, especially a parent-raised, non-handtame bird that is not used to human interaction at all...It could simply be that the bird is stressed about the change in environment, and with a non-handtame bird that went from being with a bunch of other Budgies to suddenly in a cage by itself in a new place with new people...
HOWEVER, any time you bring home a new bird, whether from a breeder or pet shop, and whether young or old, you always need to take the bird to a Certified Avian Vet or Avian Specialist Vet for a complete "Wellness Exam", and then you need to take them at least once a year for these Wellness-Exams for the rest of the bird's life...This is the best way to ensure that your bird is not suffering from any illness and catching any illnesses that they are suffering from as early as possible, instead of waiting for your bird to become critically ill and in the late/end stages when they finally start showing outward signs and symptoms...The first Wellness-Exam should be done within the first month of bringing a new bird home, and the sooner the better. The reason that you must find either a CAV or Avian Specialist Vet to take your bird to for their Wellness-Exam is because Exotics Vets or General Vets have absolutely no extra education or training in Avian medicine at all (in the US anyway), and Exotics Vets are simply General dog/cat Vets who decide that they are willing to see/treat animals other than dog and cats. That's it. You do not have to have any extra education, training, licenses or certifications in the US to call yourself an "Exotics" Vet, and typically they see birds, reptiles/amphibians, rodents, marsupials, primates, livestock, etc. So you definitely want to find the closest Board-Certified Avian Vet or Avian Specialist Vet (these ONLY see birds) to you, which we can help you with. There's a great search-tool here in the forum for finding Avian Specialist Vets all over the world...
***The first and the future yearly Wellness-Exams of your bird need to include a full visual and physical exam of your bird, followed by a Fecal Culture being sent-out to the laboratory that the Vet uses, as well as having them do basic Microscopy and Gram-Staining of the Fecal-sample right there in the office to test for any Bacterial, Fungal/Yeast, Protozoan, and/or Parasitic infections throughout the GI Tract (in birds this includes their entire GI Tract from their Crops all the way through their Stomachs, through their Intestinal Tracts, and through their Cloacas)....You should always collect fresh droppings from either the night before of the morning of the day of your bird's appointment, and simply put them in a baggie or a container and keep them in the fridge until it's time to go to the appointment....In addition to the Fecal tests, a Wellness-Exam should also include standard baseline/routine Blood-Work to check for Infections, Anemia, Nutritional Deficiencies/Metabolic issues, and most-importantly in birds is checking their Liver and Kidney functions/health. So it's imperative that you request that your Avian Vet always do standard Blood-Work at each yearly Wellness-Exam, and especially at your bird's first Wellness Exam within the first month of you bringing him home, because it's extremely common for all birds, whether coming from a pet shop, bird shop, private-breeder, or from a Rescue to be exposed to all kinds of Bacterial, Fungal, and Parasitic infections, as well as to certain Avian Viral Diseases, some of which are fatal without treatment.{/B]
****So you need to find the closest Avian Vet to you and make an appointment for your bird's first Wellness-Exam anyway, but since he started "acting differently" it makes this first Wellness-Exam all the more important...Usually the only signs that we as their owners get that our birds are sick or in pain are very subtle changes in their personalities, so it's extremely important that we take-note of these very subtle personality changes and we get our birds to our Avian Vets as soon as possible after noticing them, so that we catch conditions like infections, diseases, etc. before they become extremely advanced and harder or impossible to treat.
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