Breeding and Behavior Codes provide a way for birders to document the breeding activities of bird species within their breeding ranges, 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


Entering Breeding and Behavior Codes

To enter these codes on eBird Mobile, tap a species name to pull up the “Observation Details” menu, tap “Breeding Code” to access the menu, and then choose the highest-ranking code from the list (the lower down, the higher-ranking). 


You can also add these codes from the eBird website as you enter data on Step 3 or by clicking the “Edit Species” button. Once you’ve found the species you want to enter a code for, click the "Add Details" button next to the species in the checklist, 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 where and when they should be used. These codes should only be used within the breeding range of a species. We do not intend these codes to be used broadly for any time that behavior was seen. For instance, a Cape May Warbler singing in Cape May on 7 May, should not be labelled as singing because Cape May Warblers do not breed in southern New Jersey and outside of the breeding range there. If you are unsure, 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 (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 (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 within breeding season.

M Multiple (7+) Singing Males (Probable) -- At least 7 singing males present in suitable nesting habitat during breeding season.

S7 Singing Male Present 7+ Days (Probable) -- Use only if you have observed a singing male at the same spot (not elsewhere) one week or more earlier in the season. 

S Singing Male (Possible) -- Singing male present in suitable nesting habitat during its 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, S, 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 singing from a dry grass field would not qualify, nor would a Sedge Wren singing on its wintering grounds on the Texas coast, but a Pine Warbler singing from pine trees within its breeding range would. If you are unsure, do not record a code but put notes in your species comments.