# Bag of Wonder: The Robin > Sky-blue eggs, a baby growing inside, hatching day, and first hops on the lawn. Cheep! A free interactive 3D exhibit for children aged 2 to 6, from Curiosity's Child in Troy, Michigan. - Interactive exhibit: https://bagofwonder.com/look-inside/robin/ - Ages: 2 to 6. The story is pitched at the youngest; the tap cards give older children more to chew on. - Cost: free, with no sign-in, no ads and no tracking. - Works on: phones, tablets and computers, in a web browser. Sound on for the narration. ## What it is Interactive 3D model of an American robin's nest and egg. A time slider follows the mother robin building her nest of grass, mud and soft lining, laying four blue eggs and sitting on them; a candling view looks inside one egg as the baby grows from a tiny spot to a curled chick that fills the egg; then the hatching, the pink hatchlings, the parents bringing worms, and the spotty fledglings leaving the nest. A second slider pulls the egg apart (shell, membranes, air pocket, white, yolk and baby) and the nest apart (twigs, mud cup, lining), with labels; tapping a part shows a child-friendly fact. How to play: press play to hear the story (read aloud in Kelly's voice, with the words on screen). Slide the time slider back and forth to see any part again. Slide "Pull apart" to see what is hidden inside. Tap any glowing button for a fact. ## The story 1. In spring, a mother robin builds a nest in the fork of a branch. She weaves grass and twigs into a cup, plasters the inside with mud, and lines it with soft, fine grass. 2. She lays four eggs, one each morning. They are sky blue! People call this color robin's egg blue. 3. She sits on the eggs to keep them warm. She will sit for about two weeks. 4. Let's look inside! Shine a light through an egg and the baby shows as a shadow. On the yellow yolk, a tiny spot starts to grow. 5. A tiny heart starts to beat. Red lines carry food from the yolk to the baby. It curls up, with one big eye. 6. It grows and grows until it fills the whole egg. The yolk and the white are nearly used up, and the air pocket at the round end gets bigger. 7. Hatching day! The baby pecks a little hole with a tiny bump on its beak, the egg tooth. Then it pushes its way out. 8. Hello, little robins! They are pink, with hardly any feathers, and their eyes are shut. When a parent comes near, their big yellow mouths open wide for food. 9. Mum and Dad bring worms and bugs all day long. After about five days the eyes open, and soft gray feathers start to grow. 10. After about two weeks, the young robins hop out of the nest. They are fluffy, with spotty chests and short tails. Dad keeps feeding them while they learn to fly. 11. Here is a grown-up robin on the lawn, looking and listening for worms. Birds are the dinosaurs that are still with us! ## The parts, and what we tell children These are the tap cards, word for word. - **Twigs and grass**: The outside of the nest is grass and little twigs, woven round and round into a cup. The mother robin does the building, and it takes her about a week. - **Mud cup**: Inside the grass is a cup of mud. The mother brings beakfuls of wet mud, then presses it smooth with her chest, turning round and round. - **Soft lining**: The very inside is lined with soft, fine, dry grass, so the eggs have a cozy bed. - **Robin's eggs**: A robin's egg is sky blue, with no spots, and about as long as your thumb. Most mothers lay four, one each morning. - **Mother robin**: She has a grayish head and an orange chest. She keeps the eggs warm with a bare, warm patch of skin under her tummy feathers. - **Father robin**: He has a darker, blacker head and a brighter orange chest. He helps feed the babies, and he sings from the treetops before the sun is up. - **The tree**: Robins build their nest in the fork of a branch, in a tree or a bush, and sometimes on a ledge of a house. - **Shell**: The shell is hard, like chalk, with thousands of tiny holes too small to see, so air can get in for the baby to breathe. - **Skin inside the shell**: Two thin, papery skins lie just inside the shell. You can see them when you peel a boiled egg. - **Air pocket**: At the round end there is a little pocket of air. It grows bigger every day. Just before hatching, the baby pokes its beak in and takes its very first breath. - **Yolk**: The yellow yolk is the baby's food, not the baby. The baby grows on top of it and slowly eats it all up. - **Egg white**: The white is mostly water. It is a soft water-bed that keeps the baby safe, and the baby drinks it up as it grows. - **Baby robin**: It starts as a tiny spot and grows in about two weeks. Its heart starts beating after only a day or two. Curled up, it fills the whole egg. - **Egg tooth**: It is not really a tooth. It is a tiny hard bump on the tip of the beak, just for cracking out of the egg. It falls off a few days later. - **Baby robins**: New robins are pink, with hardly any feathers, and their eyes are shut. When a parent lands, they open their big yellow mouths wide and cheep for food. Their eyes open after about five days. - **Worm**: Robins love earthworms. The parents bring food to the nest about a hundred times a day! - **Spotty chest**: Young robins have a spotty chest and a short tail. The spots fade as they grow up. Their dad keeps feeding them for a couple of weeks while they learn to fly. - **Grown-up robin**: This robin tips its head to look and listen for worms. Birds are the dinosaurs that are still with us, so a robin is a tiny, feathery cousin of T. rex! ## Getting the science right What we checked, and the myths we steer around: - The American robin is Michigan's state bird, and is a thrush, not a relative of the smaller European robin. - The female builds the nest, a cup of grass and twigs plastered inside with mud, then lined with soft grass. - She lays one egg a day, usually 3 to 5 eggs (four is typical), and sits on them for about two weeks. - The baby hatches using a tiny egg tooth on its beak; the newborn is pink, blind and almost bare. - Both parents feed the nestlings; they leave the nest at about two weeks old, still with spotted chests and short tails, and Dad keeps feeding them while they learn to fly. - Robins listen and look for worms on the lawn; they do not hear worms underground in any proven way, so the story says "looking and listening". ## How to use it with children Watch the story once, then slide slowly through the egg days and ask, "What is the baby doing inside?" Count the eggs together, one a day. Ask more than you tell, and let the child drive. Then step away from the screen: look for robins hopping on a lawn after rain. If you find a nest, watch from far away and never touch it: the law protects wild birds' nests and eggs. Make a cup nest from play dough and dry grass. A few minutes together is plenty. The exhibit is a doorway to the real thing, not a replacement for it. ## Credits and licenses The real scans, maps and photographs belong to their makers, under the licenses below. The words, story and code are Curiosity's Child's. - An American robin (Turdus migratorius), the bird on Michigan lawns. The robins, the nest and the nestlings are made from photographs taken at Curiosity's Child by Kelly Smith, turned into 3D on our own computer (the young birds were first redrawn alone on a plain background with Grok, then built with Pixal3D). The baby inside the egg is made from Grok pictures with Pixal3D; an earlier hatchling, still in the files, is a real nestling scan, [baby sparrow 1](https://sketchfab.com/3d-models/dead-animal-series-baby-sparrow-1-b21f469fafd14ccb8eb6d9e7a49f71db) by [bybob](https://sketchfab.com/bybob) (CC BY 4.0). Colors checked against the Naturalis Biodiversity Center robin skins (CC0) and [Roger Culos's photograph of Muséum de Toulouse robin eggs](https://commons.wikimedia.org/wiki/File:Turdus_migratorius_MHNT.ZOO.2010.11.189.14.jpg) (CC BY-SA 4.0). The flowering tree and the summer lawn are watercolor paintings Kelly made with Grok. The eggs, the inside of the egg and the pulled-apart mud cup and lining are built in code after photographs and the Cornell Lab of Ornithology's robin facts - Real sounds from Freesound ([CC0](https://creativecommons.org/publicdomain/zero/1.0/), thank you!): [an American robin singing](https://freesound.org/s/616955/) (TRP), [spring birds](https://freesound.org/s/683566/) (hargissssound), [young birds cheeping](https://freesound.org/s/430063/) (BeeProductive) - Music-box lullaby made for this page - Narrated by Kelly, in her own voice ## More on the Garden & Pond shelf - [The Pumpkin](https://bagofwonder.com/look-inside/pumpkin/index.md): From one little seed to a big orange pumpkin. Open it up! - [The Frog](https://bagofwonder.com/look-inside/frog/index.md): From tiny floating eggs to a wiggly tadpole to a big bullfrog. Jug-o-rum! ## About Bag of Wonder A free library of interactive 3D "look inside" science exhibits, made at Curiosity's Child, a licensed home daycare in Troy, Michigan. Secular and science-based; welcoming to all. - All exhibits and how we make them: https://bagofwonder.com/llms.txt - For grown-ups and AI assistants: https://bagofwonder.com/look-inside/about/ - To cite: "The Robin", Bag of Wonder, Curiosity's Child (Troy, Michigan). https://bagofwonder.com/look-inside/robin/