One thing I noticed was how birds simply refuse to gorge themselves. Just the other day as I was sitting out on the patio and I noticed we have one of those huge Tent caterpillar nests on one of the pines. Living around here, you know what I am talking about.
Sprinkled throughout this mess....always cobwebby in design.....are insects who have found themselves permanently fastened 'by death no less' to this cobweb design. I can't tell you when they entered and lost the ability to escape, but I can tell you that many #'s of them were there.
Along came a finch....... This little guy would cherry pick his way thru the nest, pecking away at insects that looked tasty. Now, either some were not to his culinary standards or the bird just became full and not wanting to gorge, it left.
Do birds do that? Chances are that bird flew over to another tree or branch and an insect came their way and 'gulp'....down it went. So if that surely (can't be sure) OR might (a better word as not as definitive) be the case, why not just sit in the nest that was pocked full of insects and nibble away? If you are hungry, you are hungry....take the easy meals.
Or....does a bird's appetite naturally stop at a certain point and no more gorging needed. But does a cat gorge if food is around? Does a cow ever quit eating green grass on the other side of the fence?.... Is 'stopping' and knowing not to gorge just a 'bird thing'? Not sure...I am just guessing that birds just know when to stop. Otherwise a caged canary (a bird) would be a lot larger than needed as food is available to them 24 hours a day. So that natural inclination to 'stop'...is evident in birds.
In my case...was the bird pecking away until full? Probably.... Did the bird then take off and fly to another tree and by hap-chance eat an insect or two along the way? Perhaps.... perhaps not.