A pipped egg is an egg where the developing chick has broken through the shell for the first time, creating a small crack or hole. This is the visible sign that hatching has begun, and it typically appears as a tiny raised bump or star-shaped crack on the wider end of the egg. Pipping is a normal, critical stage that can last anywhere from a few hours to over a day before the chick fully emerges.
How Pipping Works
In the final stage of development, a chick uses a small, hardened calcium structure on the tip of its beak called an egg tooth to punch through the shell from inside. This temporary tool, first described by ornithologist William Yarrell in 1826, works like a tiny chisel. The chick repeatedly strikes the shell while pressing its shoulders and legs outward, eventually creating that first visible crack.
Pipping actually happens in two distinct stages. Internal pipping comes first: the chick pierces the inner membrane to reach the air cell at the wide end of the egg. This is when the chick takes its first breath of air, and you may hear faint peeping from inside the shell even though you can’t see any crack yet. External pipping follows when the egg tooth breaks through the outer shell itself, producing the visible hole or crack most people recognize as a “pip.”
What Happens After the First Pip
Once the chick makes that initial hole, it rests. This pause can last several hours or even a full day, and it’s completely normal. The chick is adjusting to breathing with its lungs for the first time. Before pipping, it gets oxygen through a network of blood vessels in the membrane lining the shell. After breaking into the air cell, lung breathing kicks in gradually, starting with irregular breaths roughly once every five seconds before settling into a steadier rhythm.
During this rest period, the chick also absorbs the remaining yolk sac through its abdomen. This yolk provides nutrients that sustain the chick for up to 72 hours after hatching, which is why newly hatched chicks don’t need food immediately. If you see a chick making yawning or swallowing motions through the pip hole, it’s still absorbing the yolk and shouldn’t be disturbed.
From Pipping to Zipping
After resting, the chick enters the “zipping” phase. Starting from the original pip hole, it rotates counterclockwise inside the egg (viewed from the wide end), chipping a line of connected cracks around the circumference. This looks like a zipper slowly opening around the shell. Once the line extends far enough, the top cap of the egg pops off and the chick pushes free.
Zipping usually finishes within about an hour once it starts. The entire process from external pip to full hatch takes roughly 12 to 24 hours for chickens, though ducks and geese can take significantly longer.
Why Humidity Matters During Pipping
The three days before hatching, often called “lockdown,” require humidity levels of 65 to 70% inside the incubator. This is higher than the rest of incubation for a specific reason: the inner membrane needs to stay moist and flexible so the chick can push through it. If humidity drops too low, the membrane dries and tightens around the chick like shrink wrap, trapping it inside even after it pips the shell. This “shrink-wrapping” is one of the most common causes of chicks dying after pipping.
During lockdown, the incubator should stay closed. Every time you open it, humidity drops rapidly. Egg turning also stops on day 18 (for chickens) so the chick can settle into the correct hatching position: head tucked under the right wing, beak pointing toward the air cell at the wide end.
When a Pipped Egg Needs Help
Most pipped eggs hatch without any intervention, and patience is the single best thing you can do. But there are specific timelines that signal trouble.
- After internal pip with no external pip: If 18 to 24 hours pass after you hear peeping or see the membrane bulging but no crack appears in the shell, a small safety hole chipped into the shell can give the chick fresh air while it continues working.
- After external pip with no zipping: If 18 to 24 hours pass after the visible pip with no further progress, the chick may need assistance. For ducklings and goslings, allow 24 to 36 hours before considering help, since they naturally take longer.
- Zipping stops partway: Once a chick starts zipping, it generally finishes within an hour. A chick that begins zipping and then stops is stuck and needs the zip completed for it.
The most common reason chicks get stuck is malposition. Nearly half of all malpositioned embryos have their beak above the right wing instead of tucked under it, which means the egg tooth can’t reach the shell properly. Another 20% have their feet positioned over their head. These chicks often pip in the wrong spot (the narrow end, for example) or fail to pip at all.
If you do assist, the key concern is active blood vessels in the membrane. Bright red veins visible through the membrane mean the chick is still connected to its circulatory support system, and tearing through those vessels can cause fatal bleeding. If you see active veins after removing a bit of shell, put the egg back and wait several more hours. A chick that’s truly ready to come out will be actively pushing against the membrane, striking with its beak, and often vocalizing loudly.
Pipping in Other Species
Pipping isn’t unique to chickens. All birds pip their way out, and the egg tooth appears across reptiles and even egg-laying mammals like the platypus and echidna. Some bird species have egg teeth on both the upper and lower beak, including avocets, stilts, and woodcock. In most birds, the egg tooth falls off within a few days of hatching. Songbirds like finches and sparrows are an exception: their egg tooth is gradually reabsorbed back into the growing beak.