Firstly, I don't have any experience with Amazons, so if I'm talking rubbish, someone please correct me. I believe that some species do need a little more fat in their regular diet than others. I remember Michael mentioning this before, but I cannot remember what species he was referring to. I appreciate that attempting to trim weight requires a more specialised diet, away from the norm.
Is it necessary to have the pellet with dried fruit & veg in it? AS30 will have some of that, plus you're also providing fresh F&V, which Echo is taking? Roudybush also produce a low fat pellet. Again, I do not know if that is suitable for Amazons, alongside fresh F&V, but potentially worth considering once Echo's weight is where it needs to be.
It seems that a lot of vets encourage us to feed pellet. I discussed it with ours and it seems that they do it because a lot of keepers feed poor diets to their birds. Good pellet has the essential vits & mins that are missing if seed/parrot mix is the only thing provided. Most people on this forum are far better informed than those that have been (poorly) advised by shops or previous owners. A lot of the members here have also put far more effort into diet research and provision for their birds, and are able to offer expert, species specific advice. Our vet is satisfied that we are providing a well balanced diet and he has backed off on the pellet recommendation.
Let's face it, pellet alone would be seriously boring! Okay, it may be possible to provide a more accurate amount using only pellet. Assume X percent discarded/ejected/ignored and you may get a more reliable figure for what is actually being consumed.
As for weight monitoring, I try to do it before the birds have had anything to eat as it produces more consistent results. I use a kitchen scale than can be zeroed (TARE) when anything is placed on it. I use a homemade T-stand, zero the reading then pop the bird on the stand. Jardine Jessie is very accommodating, but Eclectus Frankie is a bit of a fidget (plus he is more interested in trying to bite me), so a stable reading can be a little harder to get Budgies? No chance of weighing them, but they are all eating well and remain constantly hyperactive, so they all seem to be fighting fit!
I weigh them less often now as they both seem to be in roughly the right place for their species. I basically do it to check for significant changes which would need investigating.
To get a parrot to lose weight it is necessary to reduce their overall consumption, rough amount per day is roughly 10% of their body weight. If Echo likes pellets and is still eating too much, ie too much going in and not enough being used up he will still be overweight. With Plum who would clear his dish this is what I had to do. I used to weigh him before breakfast and he would step onto a flat scale, praise or treats as reward. Not necessary every day, just about once per week. Please don't put the pellet before the fresh foods, but watch what carbs are being added. I have managed to get Rubes' weight down with plenty of fresh foods, very little carbs/treats, a small amount of Harrisons pellets, high potency then onto adult lifetime (wouldn't eat my preferred, TOPs) but she also got a very small amount of seed, at night. This went against my AV but her heart murmur disappeared and her levels were down to normal range regardless in just over a year. Rubes won't eat pellets everyday which is fine because she is good with her fresh foods. A lot of achieving a lesser parrot is in our head tbh, we have such strong affection for these birds and want to nurture them too much.
She's really taken to the pellet diet and I like it because I can tell what she's eating.. With the seed she super selectively eats and because she leaves all the shells in the bowl I can't tell whats been eaten..
The next step in this pellet diet though is to put the seed into foraging toys so she can have something to keep her busy.. But that will come a bit later on
I'm really proud of her
I like the pellet because it's no waste, what she doesn't eat goes back into the bag and mixed to