Quote:
Originally Posted by witham  Thanks very much, (I think) still a bit  who gives you the required number to start with |
OK witham, since you asked
- here's an extract from "Expedition Field Techniques - Bird Surveys" by Colin Bibby, Martin Jones and Stuart Marsden which explains the technique in detail -
5.3.3 Mackinnon lists
Mackinnon Lists (Mackinnon and Phillips, 1993) provide another means of
calculating a species discovery curve and an index of relative abundance.
Mackinnon Lists differ from the other techniques in that the unit of effort is
the time taken for an observer to record a pre-determined number of species.
The advantage of this is that it makes the method relatively less susceptible to differences in ability and concentration of the observer. If an inexperienced
observer takes a long time to identify each species detected this does not
greatly affect the results providing he/she does eventually identify all species
detected. Similarly recording during a period of low activity such as over
midday will not greatly affect the results – it will just take longer to detect a
given number of species.
The observer makes a list by recording each new species until a predetermined number of species is reached. A species can only be recorded
once in each list but may be recorded in subsequent lists. The appropriate
length of list can vary between 8 and 20 species; the larger the likely total
number of species at the site the longer the length of list chosen. Comparisons can only be made between surveys where the same length of list was chosen.
Surveys are repeated until a minimum of ten and preferably more than fifteen
lists have been produced for each site. When recording data the observer is
free to search for birds in as efficient a manner as possible, using whatever
search techniques from section 5.2 are appropriate for the site. However, the
observer should endeavour to cover different ground at least from one list to
the next to avoid recording the same individuals on repeated lists. A species
discovery curve, as described above, can then be drawn by replacing the unit
of survey effort with the number of lists and plotting this against the
cumulative total number of species. As above the position of the plateau of
the curve reflects species richness and the shape indicates how many more
species are still likely to be found in that locality (see Section 5.4.1 for
analysis of Species Discovery Curves).
Got that? I'll be testing you later
Jeff
Linear Mode
