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Breeding Codes & Behavior Codes

Breeding Codes, perhaps most appropriately called behavior codes, provide the ability to enter the highest-level breeding codes that you made for each species into your checklist to reflect behaviors you observe for any species while birding. Aside from the FLYOVER code, the purpose of these codes is to document the breeding range and breeding phenology of a species within their breeding range.

To add these codes to species on your checklists, 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 possible code. See the image to the right. Details about what the codes mean and when to use them can be found below in this same article.

Our goal is to collect information about the timing and locations of bird nesting. This is the first continuous, year-round, worldwide, breeding bird atlas effort. Breeding Bird Atlases have been conducted in many countries, states, and provinces around the world and have taught us much about where and when birds are breeding. This eBird effort differs in a few fundamental ways.

First, there are no "safe dates". Many atlases make assumptions about the breeding status of a species based on where and when it occurs. At eBird, you provide these specifics with your complete bird checklists and in the future we hope to be able to use these data to automatically identify periods of breeding or probable breeding. That said, every effort should be used to use these codes only 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 it is outside of the breeding range.

Although our breeding codes are listed as confirmed, probable, or possible, we realize this listing is highly dependent on species, location, and date and in many cases may require a bit more information before being useful for establishing breeding presence of a species. These are meant as a general guide; the more important thing is to record the behaviors observed within the breeding range of a species. Future users of the data can analyze the data in conjunction with local understanding of status to make their own assumptions about breeding based on the location, date, and behaviors observed.

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.

eBird currently does not have any data output (i.e., under 'View and Explore Data') associated with this information (although as the data accumulates, the development of output graphics moves higher on our task list). We can provide the data to interested parties upon request. We do plan to implement ways to view and explore the data within eBird in the future.

Below are the definitions for our breeding codes and where and when they should be used. Please also read the FAQ below for the use of breeding codes.


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 exact spot (same tree or shrub) one week or more earlier in the season. Do not use if you have observed a singing male a week earlier elsewhere on the same transect covered by your checklists.

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 -- This is not necessarily a breeding code, but can be a useful behavioral distinction. Please see this page for more detail.





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 a egg should be counted in your eBird submission.

If I see a nest with eggs, should I count the eggs in my eBird submission?

No! Eggs are not yet birds, so please do not count them. However, you may want to enter a species comment listing how many eggs were observed (as well as other details of where the nest was, how high, what it was made of, etc.). In some cases, the nests of certain tropical species have yet to be described for science, so your observation could be really important.

If I see baby grouse, baby geese, or baby Killdeer that cannot yet fly, what code should I use?

Use "FL". We realize that these birds are not really "fledged" in the sense that they can fly, but they are fledged in the sense that they have left the nest. In fact, birds fall in to two camps in terms of how they leave the nest. Altricial birds grow their feathers in the nest and then leave the nest when they are about ready to fly (pigeons, hummingbirds, hawks, and sparrows are all altricial). Precocial birds have nestlings that leave the nest essentially as soon as they hatch, have downy feathers when they emerge from the egg, and run around behind their parents to stay safe (waterfowl, gulls, shorebirds, grouse, and quail are examples of precocial species.)

Basically, "FL" should be used until the point where 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. For example, S (singing male) will help us to understand the phenology (timing) of when birds gear up for breeding season and P (observation of a pair) will help us to know when pairs are formed. Use these codes, and the H code (appropriate habitat), whenever you judge the bird to be in a possible breeding situation: a Marsh Wren singing from a dry grass field or a Sedge Wren singing on its wintering grounds on the Texas coast both would not qualify, but a Pine Warbler singing from pine trees within its breeding range would. Note that the breeding season begins very early for many species, with species like Great Horned Owl already singing and forming pair bonds in December, or earlier in some places. Even species like Black-capped Chickadees that nest later, may begin singing on territory by January, i.e. months before initiating nesting.

If you are unsure, do not record a code but put notes in your species comments.
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