marie83 wrote:Surely the gap between the grate/pan and actual base of the cage is minimal though?
You don't understand. The bottom goes like this. Grate, pan, nothing. The pan is the last thing closing the cage. There is no other base. So if some jokester pulls those two out, the bird can be extracted out the bottom. Likewise, the food doors are definitely big enough to remove any small parrot (Senegal for sure) or even stick a slender arm in. This is why a padlock wouldn't stop anyone intent on getting the bird out.
The size of the small cage is fine for you but I wouldn't recommend it. There is no grate and the bottom is the only thing between the parrot and outside world. The bottom is removable and not well secured. Under the right circumstances the bottom could be pushed into the cage and fall out entirely.
Honestly, for a gcc (and my Senegal included) a modified plastic cat carrier or wire budgie cage are good enough to travel around in for up to a few days. The medium kings travel cage is good but it's still darned heavy. I wouldn't bother lugging that around for the Senegal. Even though there's more room in it, it's still only two perches (ok as opposed to one in the carrier, not a huge deal). The only reason I keep it is because Truman is too crammed in the carrier for longer periods. He's more playful and needs me to fit more toys there for him. And it's so he doesn't step in his poop and can turn around freely. I got it all because of his clumsiness and size. I wouldn't use it for a smaller parrot unless we needed to travel for longer periods of time together like 3-10 days.
Finally, I would put more effort into seeking a lockable room to leave the bird cage/carrier in than padlocking just the cage shut. If you're in a situation where people might have access to the cage without your permission, even if they don't open it they could taunt the bird or feed it something it shouldn't have. If you're in a place with family or few enough people just explaining not to interact/handle the bird in your absence. If it's a big home with people coming and going it may be best not to bring the bird or to find a lockable room to give it total privacy when you're not around.