There are four levels of evidence:

1. Species observed in breeding season (no indication of breeding).

2. Possible breeding.

3. Probable breeding.

4. Confirmed breeding.

There are various types of evidence required for each of these levels:

OBSERVED

X   Species observed in its breeding season (no evidence of breeding). Presumed migrants should not be recorded.

POSSIBLE BREEDING

H   Species observed in its breeding season in suitable nesting habitat.

S   Singing male present, or breeding calls heard, in its breeding season in suitable nesting habitat.

PROBABLE BREEDING

P   Pair observed in their breeding season in suitable nesting habitat.

T   Permanent territory presumed through registration of territorial song on at least 2 days, a week or more apart, at the same place.

D   Courtship or display between a male and a female or 2 males, including courtship feeding or copulation.

V   Visiting probable nest site.

A   Agitated behaviour or anxiety calls of an adult.

B   Brood patch on adult female or cloacal protuberance on adult male.

N   Nest-building or excavation of nest hole.

CONFIRMED BREEDING

DD   Distraction display or injury feigning.

NU   Used nest or egg shell found (occupied or laid within the period of the study).

FY   Recently fledged young or downy young, including young incapable of sustained flight.

AE   Adults leaving or entering nest site in circumstances indicating occupied nest.

FS   Adult carrying faecal sac.

CF   Adult carrying food for young.

NE   Nest containing eggs.

NY   Nest with young seen or heard.