The typical senior pattern at the food dish
Most aging budgies do not stop eating dramatically; they edit. A senior may visit the dish as often as ever but consume a little less at each visit, leave foods he once attacked first, and take longer over husking seed as his beak and jaw muscles tire. Favourite soft foods and millet may hold their appeal while everyday seed loses ground, which can quietly narrow an already simple diet.
Appetite also follows activity and comfort. A budgie with stiff feet who must climb awkwardly to reach his dish may eat less because getting there costs more, not because the food has changed. Moving food and water to a lower, easily reached position sometimes restores his intake within days, which is a useful clue that access, rather than illness, was part of the story, though it never rules illness out on its own.
Weight drift in both directions
The classic senior change is slow weight loss driven by muscle loss. Feathers hide it well: his silhouette stays round while the keel bone along his chest becomes easier to feel and the muscle either side of it thins. Because budgies are so small, a loss of a few grams is a significant proportion of him, and it usually happens too gradually to see, which is why the scale, not the eye, is the senior owner's main tool.
The opposite pattern is just as common. A budgie who flies less and naps more while eating the same energy-dense seed diet can gain steadily, and extra weight carried on a small frame strains joints, breathing, and organs. Neither drift is a diagnosis; both are information. What matters is knowing his personal normal, because a stable budgie at either end of the typical range is less concerning than one who is clearly travelling away from his own baseline.
Watching him like a keeper, not a worrier
Weigh him weekly on a small digital scale, at the same time of day and ideally before his first big feed, and write the number down with a word or two about appetite and energy. Learn the gentle feel of his keel during normal handling so you can notice muscle change between weigh-ins. Also watch the practical evidence: how much seed is actually husked rather than scattered, whether droppings shrink in number or change, and whether he still hurries to a favourite treat.
Offer food in ways that suit an older bird: dishes at easy heights, a little soft food or soaked or sprouted seed if his vet agrees it suits him, and fresh items presented where he rests rather than only where he used to climb. Avoid sudden diet overhauls, which a picky senior may simply refuse; change one element at a time and let the scale tell you whether it is working.
Changes that are not normal ageing
Treat appetite loss as urgent when it is sudden or paired with other signs. A budgie who stops eating, sits fluffed with half-closed eyes, breathes with a bobbing tail, produces markedly fewer or changed droppings, vomits, or loses weight quickly over days rather than months needs an avian vet promptly, because a bird of his size has very little reserve to draw on. Gradual pickiness with stable weight is a topic for his next checkup; a bird going quiet and light is not.
Keeping the weekly figures, food notes, and any vet advice together in his KinsLe Pet Passport turns those small numbers into a clear senior record his vet can act on at a glance.