Breeding and Behavior Codes provide a way for birders to document the breeding activities of birds around the world, providing crucial information for research and conservation globally. Our goal is to collect information about the timing and locations of bird breeding behavior on a year-round and worldwide basis.
Piping Plover by Kyle Tansley/Macaulay Library the Cornell Lab (ML162730121)
Quick Links
Entering Breeding and Behavior Codes
Breeding and Behavior Code Definitions
Breeding and Behavior Code FAQ
Breeding and Behavior Code Data Quality
Entering Breeding and Behavior Codes
To enter these codes on eBird Mobile, tap a species name to pull up the Observation Details menu, tap "Add breeding code" to access the menu, and then choose the highest-ranking code from the list (lower down and darker purple = higher-ranking).
You can also add these codes from the eBird website as you enter data or by clicking the “Edit Species” button on a submitted checklist. Once you’ve found the species you want to enter a code for, click the "Add Details" button next to the species, select "Breeding Code" from the tabs that appear, and then choose the highest-ranking code that you observed for that species on this checklist.
Note: you can access your collected breeding code information from each checklist's observation report and through "download my data.” Using the download option allows you to see all breeding records that you have submitted to date.
Breeding and Behavior Code Definitions
These are the definitions for our breeding codes and how they should be used. These codes generally describe behaviors that signify breeding. Specific projects (e.g., eBird Atlases) may suggest using codes only during certain times of year or situations. Please refer to specific project guidelines if you are participating in that project. If you are unsure which code to use, do not record a code but put notes in your species comments.
- NY Nest with Young (Confirmed) -- Nest with young seen or heard.
- NE Nest with Eggs (Confirmed) -- Nest with eggs.
- FS Carrying Fecal Sac (Confirmed) -- Adult carrying fecal sac.
- FY Feeding Young (Confirmed) -- Adult feeding young that have left the nest, but are not yet flying and independent (for some projects should not be used with raptors, terns, and other species that may move many miles from the nest site; often supersedes FL).
- CF Carrying Food (Confirmed) -- Adult carrying food for young (for some projects should not be used for corvids, raptors, terns, and certain other species that regularly carry food for courtship or other purposes).
- FL Recently Fledged Young (Confirmed) -- Recently fledged or downy young observed while still dependent upon adults.
- ON Occupied Nest (Confirmed) -- Occupied nest presumed by parent entering and remaining, exchanging incubation duties, etc.
- UN Used Nest (enter 0 if no birds seen) (Confirmed) -- Nest is present, but not active. Use only if you are certain of the species that built the nest.
- DD Distraction Display (Confirmed) -- Distraction display, including feigning injury.
- NB Nest Building (Confirmed/Probable) -- Nest building at apparent nest site (should not be used for certain wrens, and other species that build dummy nests; see code "B" below for these species).
- CN Carrying Nesting Material (Confirmed/Probable) -- Adult carrying nesting material; nest site not seen.
- PE Physiological Evidence (Probable) -- Physiological evidence of nesting, usually a brood patch. This will be used only very rarely.
- B Wren/Woodpecker Nest Building (Probable) -- Some species, including certain wrens (e.g., Marsh Wren), woodpeckers, and certain other cavity nesters (e.g., barbets) may build dummy nests and thus nest building activity cannot be considered confirmation. Use this category in those cases.
- A Agitated Behavior (Probable) -- Agitated behavior or anxiety calls from an adult. This excludes responses elicited by "pishing", playing recordings, or mobbing behavior that species engage in year-round (for instance, mobbing an owl).
- N Visiting Probable Nest Site (Probable) -- Visiting repeatedly probable nest site (primarily hole nesters).
- C Courtship, Display or Copulation (Probable) -- Courtship or copulation observed, including displays and courtship feeding.
- T Territorial Defense (Probable) -- Permanent territory presumed through defense of breeding territory by fighting or chasing individuals of same species.
- P Pair in Suitable Habitat (Probable) -- Pair observed in suitable breeding habitat (for some projects only during breeding season).
- M Multiple (7+) Singing Birds (Probable) -- At least 7 singing birds present in suitable nesting habitat (for some projects only during breeding season).
- S7 Singing Bird Present 7+ Days (Probable) -- Use only if you have observed a singing bird at the same spot (not elsewhere) one week or more earlier in the season.
- S Singing Bird (Possible) -- Singing bird present in suitable nesting habitat (for some projects only during breeding season).
- H In Appropriate Habitat (Possible) -- Adult in suitable nesting habitat during its breeding season.
- F Flyover (Observed) -- Flying over only -- Use it only when all individuals are seen as flyovers; do not use it if just one bird stops or is located feeding on the ground or in vegetation. Raptors, swallows, and swifts that are flying overhead and not obvious migrants are not flyovers, since these birds are often using the habitat in ways not obvious to observers on the ground. This restriction depends upon the judgment of the observer, so when in doubt, do not use this code.
Breeding and Behavior Code FAQ (Frequently Asked Questions)
If I see a nest of birds, should I include the count of the adults and the young in my eBird submission?
Yes! Any bird that has hatched from an egg should be counted in your eBird submission.
If I see a nest with eggs, should I count the eggs towards the count of the species in my eBird submission?
No! Eggs are not yet birds, so please do not count them. We encourage you to enter a species comment and upload a photo of the nest/eggs, but do not add them to the tally for the species.
If I see baby grouse, baby geese, or baby shorebirds that cannot yet fly, what code should I use?
Use "FL". They are fledged in the sense that they have left the nest, which is typical for the young of “precocial” species. "FL" should be used until young birds become independent of their parents, since it is safe to assume that they are near the nesting site until that point.
How do I know when to use P and H?
These categories should be used whenever one or more birds are observed in appropriate breeding habitat and within breeding range. A Marsh Wren in a dry grass field would not qualify, nor would a Sedge Wren on its wintering grounds on the Texas coast, but a Pine Warbler in pine trees within its breeding range would. If you are unsure, do not record a code but put notes in your species comments.
Breeding and Behavior Code Data Quality
eBird data quality is of utmost importance, and every checklist and observation goes through a multi-layered data quality process. In regions where there is an active eBird Breeding Bird Atlas (BBA), there is also a review process specifically for breeding and behavior codes.
In eBird Atlases, teams led by atlas coordinators will evaluate observations with breeding and behavior codes in ways that include:
Is the reported code something that this species does?
Is the location where the code was reported a location where the bird is breeding?
Is the time of year when the code was reported a time when the bird is breeding?
Is the reported code appropriate for the time of year?
If a breeding and behavior code is identified for review based on questions like the above, BBA reviewers will review the scenario of the reported code (code, date, location, species) and supporting evidence (photos, audio, comments). Based on the scenario and supporting evidence, BBA reviewers decide on one of 3 outcomes for each reviewed code:
The code fully represents both breeding and behavior components of the reported code (the default behavior when an eBirder enters a code)
The code represents the behavior observed, but the breeding meaning is different than the default for the behavior for that location and date for that species
The code appears to be a likely error
Outcome 1 — fully represents both breeding and behavior
No review action is taken on the record: it appears across eBird on maps and tables of breeding codes, and is available in data downloads for researchers with both a “breeding code” and a “behavior code” component. The display of this outcome when viewing the checklist is of a single code titled “Breeding & Behavior Code.”
Outcome 2 — breeding meaning is different
A new code focused on breeding meaning is attached to the observation: the originally reported code is used as the “behavior code” (available in data downloads for researchers), and the post-review code is used as the “breeding code”, appearing on maps and tables of breeding codes, and available as “breeding code” in data downloads for researchers. The display of this outcome when viewing the checklist is:
Outcome 3 — likely error
A new breeding and behavior code is attached to the observation: the new code appears across eBird on maps and tables of breeding codes, and is available as both “breeding code” and “behavior code” in data downloads for researchers. The display of this outcome when viewing the checklist is:
Specific examples of Outcomes 2 and 3
Since Outcome 1 is the majority of records in any given atlas (millions of observations), examples focus on Outcomes 2 & 3 in which review decisions have been made.
Outcome 2 — breeding meaning is different
Example 1: Migratory birds singing in areas where they don’t typically breed
A breeding and behavior code of “S Singing Bird” is given to Cape May Warbler in May, south of the boreal breeding grounds. The behavior of singing is correct, but at that location there is no breeding meaning, so after review the observation would have no breeding code, and the behavior code would be “S Singing Bird.”
Example 2: Waterfowl performing courtship in locations where they don’t breed
A breeding and behavior code of “C Courtship, Display, or Copulation” is given to Northern Shoveler in March, south of the breeding grounds. The behavior of courtship is correct, but at that location there is no breeding meaning, so after review the observation would have no breeding code, and the behavior code would be “C Courtship, Display, or Copulation.”
Outcome 3 — likely error
Example 1: Code reported for a species that doesn’t exhibit that code
A breeding and behavior code of “NB Nest Building” is given to a Brown-headed Cowbird—a brood-parasite species that doesn’t build a nest. The reported code is a likely error, and after review the observation would have the code “H In Appropriate Habitat” used for both the breeding code and behavior code. The original code entered by the atlaser is retained on the checklist view.