counts one needs to decide on a settling time once the counting station is
reached, and on the duration of the count itself. For ease of comparison across
studies of terrestrial breeding birds, we recommend the minimum number of
visits to a plot is two and a maximum four. We recommend a 5- or 10-min count
period plus an initial settling time of 1 min. For the longer period, we suggest
that birds recorded in the first and second 5 min are noted separately (allowing
some check on double counting, on whether birds are attracted to the observer,
and allowing comparison with 5-min counts). We recommend a minimum of
two distance bands, 0–30 m and over 30 m, better still would be 3 bands, 0–30,
30–100 and over 100 m. Lastly, we suggest a minimum of 200 m between
counting stations. Ralph et al. (1995) review point count methods and provide
practical recommendations for their use.
The North American Breeding Bird Survey, which is a continent-wide survey,
involves point counts along randomly selected road transects (Sauer et al. 2001;
http://www.mbr-pwrc.usgs.gov/bbs/)..)
2.3.5 Rules for recording birds in the field
The aim is to record all birds identified by sight or sound with an estimate of
distance when first detected. It might be helpful to indicate whether a bird
is detected by sight or sound on a recording form. Birds that are seen flying
over the census area (aerial species) are recorded separately because they cannot
be included in standard density estimation. For such mobile species, it is best to
make an estimate of their numbers along each section of transect, or at each
point. If birds fly away as you are counting, record them from the point you first
saw them. We recommend that birds flushed as you approach a point count
station should be recorded from that point and included in the point count
totals (but you must make this plain in the write-up). Try to avoid double-
counting the same individual birds at a point count or within a transect section
by using careful observation and common sense. It is, however, correct to record
what are likely to be the same individual birds when they are detected from
subsequent point counts or transect sections.
2.3.6 Choosing between line and point transects
There is little to choose between line and point transects because they are so
adaptable to species and habitats, but each is better suited to particular situations
(Table 2.1). The strengths and weaknesses of the methods need to be matched
against your survey objectives.
Both methods require a relatively high level of observer skill and experience
because a large proportion of contacts and identifications will be by song or call.
Field methods| 41