Harpies

Bird people! Bird legs ending in talons, feathered wings/arms similar to archeaopteryx (with thumbs, of course). Plumage color on wings, tail, and body typically reflects their main source of food during molting (1/year, late summer/early fall). Carnivores (preferably fish/bugs, but birds/larger animals... anything!), but eats seeds/nuts/fruit in small amounts (even considered as delicacies). Sharp teeth, no beak. Eyes similar to a bird of prey, internal ears but small feather "tufts" near them, stylized longer feathers on their head that can be trimmed or shaped while minimally affecting flight. Above average senses of smell and hearing. Magnetoreception (can tell direction in relation to the planet's magnetic field). Can survive in high altitude climates. Cannot carry more than 1/4 of own body weight while flying.   ~5'5" tall on average fully grown, but can vary with extremes being just under 5' and just over 6'. Weighs ~2/3 of a similar sized human. Lifespan of ~150 years, matured ~20 years. Hermaphroditic, typically limited to 1 child every 3-4 years. Raise young communally. Cannot reproduce with other races.     Harpy isles! 4 "Islands" scattered around the world, 1 mile above sea level. each one big enough to hold/feed about 5,000 harpies comfortably, initially 500 holds. I'm trying to decide on whether the biomes on the islands should mimic the land underneath, or if they have their own totally unique features? Or a cute idea to me is that each one could be "locked" to a season (maybe with these islands even moving across the globe to stay within those seasons relative to the earth?). I'm looking for some fun flora & fauna to set them apart from the overworld! In general, I'm thinking that things grown/raised on these islands are naturally more filling and nutritious, in order to combat overharvesting of resources. One thing I have are "Plastic Beetles" (name is just a placeholder)- when fully grown, which is ~1.5 years old, these beetles are about a foot long! Their shells are about as hard and lightweight as a modern plastic, and can with heat applied to them the shape can be bent, or "welded" to other shells to make bigger sections.