Dawson and Bulls original 5MBC paper
The 5MBC method, developed in the early 1970s by Dawson and Bull is still regarded as the standard. Before starting a project you should read their original paper:
An observer stands at a count station, usually in forest. Stations are usually 200m apart.
- The observer records the number and species of all birds seen and heard.
- The original method recommended a 200m cut-off but many observers have found it difficult to estimate 200m. As a consequence many studies have stipulated there is no cut-off but recommend observers do not record birds that are clearly a long way away e.g. bellbirds calling from across a valley.
- The observer records:
- their own name
- the number of birds seen and heard of each species
- the location of the station (i.e. station or id number)
- the date
- the start time
- the weather variables; temperature, wind, other noise, sun, precipitation type and precipitation value
- Use the units recommended by Dawson and Bull.
- No bird is knowingly counted twice within a five-minute interval.
- If a bird is heard at two separate stations but the observer believes it is the same bird, it should still be recorded at both locations.
- No birds should be assumed to be present unless they are seen or heard e.g. observers should record the number of silvereyes heard calling, not the size of the flock they think this amount of calling represents.
When to use this method
It is important to remember that, like other index counts, this method does not result in an accurate count of all the birds present. The numbers recorded are used to indicate the number of birds present but many factors introduce variability into the results including:
- Range of observer skill levels for bird identification and bird-call recognition.
- Range of hearing abilities among observers.
- Range of habits and different levels of conspicuousness between species.
- Range of environmental and behavioural factors that change how visible birds are during the course of a day and from day to day.
The relationship between the number of birds seen and the real number of birds out there is unknown and will almost certainly vary from species to species. It may be better to use other, more accurate methods such as mark-resight or distance sampling depending on the objectives of your study.