Thanks Richard - I had not intended any criticism of the system - just that
people I think need to be aware of the limitations of all recording systems.
The approach of filtering "unusual" records is good - but again ultimately
we all must choose whether or not to believe that a bird such as a Grass Owl
could turn up at Werribee!
I guess one of the ways in which a more "representative" approach could be
taken when showing the bird list for a location is to provide an option to
exclude surveys where less than a certain number of birds were recorded -
this would "weed out" the one-off sightings (and those sourced from the
birdline) and enable people to see what may "typically" be seen on a
"normal" survey of the property. Not sure how feasible this would be to do?
On 09/02/07, Richard and Margaret Alcorn <> wrote:
Re: Completeness and reliability of surveys entered into Eremaea Birds.
Anyone registered with Eremaea Birds can enter surveys. The database
checks each survey for unusual records. (An unusual record is defined as one
where the species has not been observed in the one degree block concerned
within 12 months of the survey.) If an unusual record is detected, the
survey is marked for review by a moderator, otherwise the survey is
automatically included in the Eremaea Birds atlas (which forms the basis for
all public reports). The task of the moderator is to accept or query the
unusual records. The main purpose of this whole exercise is to prevent data
entry errors. The general policy is to accept observations where the
observer is confident of what they have seen, although the moderator can
choose to exclude the survey from the atlas if they still have serious
reservations (a rare occurrence).
Surveys are also sourced from the Eremaea Birds Birdline reports. These
are generally accepted without query since they have already been moderated.
With regard to completeness, an Eremaea Birds survey can be anything from
an incidental sighting to a 24 hour survey. (Surveys can be of longer
duration, but only single-day surveys are included in the atlas). Birdline
surveys, of course, only list highlights. As noted by others, the inclusion
of incidental and "birdline" surveys increases the reporting rates for
scarce species and decreases it for common species. In the end, the
reporting rate is the reporting rate, and it is published in order to give
some idea of the liklihood of occurrence of a species, even though it is
heavily distorted by what people actually care to report.
I hope this helps. Suggestions are always welcome.
Richard Alcorn
Eremaea Birds
www.birding-aus.org
birding-aus.blogspot.com
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