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Nest Visit and Outcome Codes Explained

See code sheets for a full list of available codes:

Visit Status Codes

Adults building the nest

Use these codes if you find a nest under construction that does not yet contain eggs.

Eggs in the nest

  • Eggs cold or warm. Warm eggs indicate an adult was recently incubating; cold eggs may be a clue that incubation has not started yet. Many birds, especially songbirds, lay all of their eggs before starting to incubate. This allows all eggs from the same clutch to hatch at about the same time.
  • Eggs covered. Some species, such as ducks and geese, leave eggs covered with nest material (e.g., vegetation, down) while away from the nest. Use this code if the eggs are covered.
  • Pipping/calling from egg. An egg is considered "pipped" when the chick has just started to break the shell. Cracks at one end are visible or a little hole in the shell enables the observer to see the beak. Some chicks call from within the egg for one to two days before hatching.
  • Hatching egg. An egg is hatching when its shell is cracked but the young is not yet out of it. This process usually lasts only a few hours.

Young in the nest

  • Naked young vs. downy. Most songbirds hatch without any feathers then gradually grow a down layer. Precocial young, those that leave the nest almost right after hatching (e.g. ducks, Killdeer), emerge from the egg with full down cover.
  • Blind vs. eyes open. Young birds of nidicolous species (those with young that hatch naked, blind, and helpless), including all songbirds, need a few days before they can open their eyes.
  • Ready to fledge indicates the nestlings are well feathered and look ready to leave the nest (whether they can fly or not).
  • Left naturally before fledging indicates that young left the nest on their own before being able to fly. Record this information but please do not disturb them.
  • Audible young in nest. Use this code when food-begging or hunger calls of the young are heard in the nest, but you are unable to see into the nest.

Adult activity

Use the codes that best describe the activity of the adults. The status In vicinity should only be used if an adult is visibly anxious (e.g., giving alarm calls) or carrying food in the vicinity of the nest before the young have fledged.

Outcome Codes


A nest is considered successful if at least one young successfully left the nest. For nidicolous species (e.g., songbirds) this usually means the young can fly, although not necessarily very well. The young of nidifigous species (e.g. ducks, shorebirds), hatch covered with down and are able to leave the nest quickly. For this group, you may use the code NN (Fledged young seen near nest) if the young are observed near the nest, even if they cannot yet fly.

  • All of these codes indicate (or suggest) that the young successfully left the nest: Young capable of leaving nest on previous visit, Young seen leaving (fledging) naturally, Fledged young seen near nest, Adult carrying food near nest, Adult visibly agitated or giving alarm calls near nest.
  • Some young fledged, other live young still in nest. The count of young should include only young still in the nest.
  • Nest empty, undisturbed and containing feather scales and/or droppings. The brood has left the nest. You can also use this code in cases of partial success, e.g., when a dead chick or egg is found trampled at the bottom of a nest but you know the rest of the brood fledged.
  • Young "exploded" from nest when inspected. Older nestlings may "explode" from their nest (i.e., they leave in all directions) in direct response to being approached by a nest recorder. If this happens, leave the area immediately so the parent can come back quickly.
  • Hatched shell fragments in empty nest. This code only applies to nidifigous species (e.g. ducks, shorebirds) because for nidicolous species (e.g. songbirds), adults carry eggshells away from the nest or eat them; shells found at the bottom of their nest would indicate predated eggs.


Multiple codes can be used, if necessary, to indicate the fate of various eggs or young, or the apparent cause of failure. If more than two codes are possible, select the most appropriate. Additional codes can be added under the Comments section.

  • The fate of eggs or young can be identified with one of these codes: Eggs not hatched, Injured/broken, Killed/thrown out by Brown-headed Cowbird, Deserted/starved/dead, Empty undamaged nest.
  • Possible causes of failure include: Flooded nest, Human causes - intentional or unintentional, Empty damaged nest, Livestock, Other/unknown, Predation, Thrown/fallen out, Usurped from nest by other bird species, Wind damage.


Use this code if you were unable to follow the nest to fledging, or if your last visit was so long after the expected fledging date that you can no longer tell what happened. Even if you are not sure of the outcome, your data are still valuable to us, especially if you visited the nest more than once!

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