Breeding Codes used in the Second Pennsylvania Breeding Bird Atlas
Breeding behaviors were summarized into a set of codes to record evidence of nesting, ranging from the simplest detection by sight or sound through confirmation of active nests and fledged young. Birds observed in breeding habitat and within their particular breeding season were placed in one of four categories based on the level of breeding evidence: Observed outside breeding habitat, or Possible, Probable, or Confirmed breeding evidence. Species distribution maps reflect these breeding categories. Specific behaviors were identified by field observers in 16 categories, listed below. These codes closely follow standards set out by the North American Bird Atlas Committee (Laughlin et al. 1990).
Observed (These non-breeding codes were not mapped or counted toward block coverage.)
- "O" Individual of a species simply observed (seen or heard) within safe dates but not in suitable habitat
- "X" Individual of a species seen or heard in suitable nesting habitat within safe dates, but not exhibiting any of the breeding behaviors described in the following 15 categories.
- "P" Pair (male and female) of a species seen in close proximity to and/or interacting non-aggressively with one another; in sexually monomorphic species, like Song Sparrow, two birds seen feeding or perched close together without displaying aggression.
- "T" Territorial behavior observed, including counter-singing, drumming in woodpeckers (drumming bird must be seen for species I.D.), aggressive interaction between same sex individuals, or a singing male in the same location on visits separated by 5 days or more.
- "C" Ritualized courtship behavior (e.g., aerial displays, courtship feeding) or copulation between two birds observed.
- "U" Used nest of species found (cannot be used in first year of Atlas, 2004); only species with highly distinctive nests may be assigned this code (see Handbook for list). Because of the difficulty in identifying the old nests of many species, and because used nests, especially in protected settings, can persist for years, "U" is taken only as evidence of probable breeding during the Atlas.
- "A" Agitated behavior or anxiety calls given by adults due to observer or predator presence (does not include agitated reaction to "pishing")
- "CN" Adult bird seen carrying nest material (note: use of this code for larger species, like crows or herons, which may collect nesting material well outside the block in which they nest, or for species like wrens that build "dummy" nests, will equate to probable breeding; for these species, attempt to upgrade to one of the next nine confirmed breeding codes).
- "PE" Physical evidence of breeding condition observed for birds in hand, specifically a highly vascularized (edematous) brood patch and/or visibly gravid condition (supported by appropriately increased body mass); this code limited to use by experienced bird banders.
- "NB" Nest building observed at nest site (note: this code will equate to probable breeding in the case of wrens and excavating species like woodpeckers, kingfishers, and tits, which build so-called "dummy nests" or excavate cavities that may not end up using for nesting; for these species, attempt to upgrade to one of the following seven confirmed breeding codes).
- "DD" Distraction display (especially injury feigning), or apparent direct defense of unobserved nest/young.
- "FL" Recently fledged young observed (downy young of precocial birds, like Ruffed Grouse, or stub-tailed juveniles of altricial species, like American Robin). Use this code very sparingly, because birds truly at this stage should, in fact, be attended/defended by adults--wait for adult to appear as a stronger confirmation, e.g., DD or CF, if possible).
- "CF" Adult seen carrying either food or fecal sac.
- "FY" Adult seen feeding fledged young.
- "NE" Nest of species found containing eggs (nest containing cowbird eggs should count as "NE" both for host species and cowbird).
- "ON" Occupied nest of species found, but contents unknown because adult is on nest or nest placement prevents examination of contents (also includes observations of hole-nesting species, like woodpeckers, kingfishers, swifts, and tits, seen entering and remaining in cavities).
- "NY" Nest of species found containing young (nest containing cowbird nestlings count as "NY" both for host species and cowbird).
North American Atlas Committee Source
Laughlin, S. B., J. R. Carroll, and S. M. Sutcliffe. 1990. Standardized breeding criteria codes: recommendations for North American Breeding Bird Atlas projects. in Handbook for Atlasing North American Breeding Birds (C. R. Smith, Ed.). Vermont Institute of Natural Science, Quechee, VT. http://www.bsc-eoc.org/norac/atlascodes.htm