Author: Melanie Steinkamp, Wetlands International, 4401 North Fairfax Drive, Room 730, Arlington, Virginia 22203, melanie_steinkamp@fws.gov, 703-358-1953

Population: a measure of the total population. For the purposes of this manual, population is defined as the total number of birds within the entire area of interest.
Population Index: an index of the total population useful for establishing population trends.
Survey: a general term for any type of inventory and monitoring procedure.
Inventory: a term applied to methods determining presence, relative abundance, and/or distribution of species.
Monitoring: a term applied to methods determining population trends or measuring health of populations over space and time.
Accuracy: a measure of the nearness of the data you collect to the actual value of the variable being measured.
Precision: a measure of the variability within your data or the closeness to each other of repeated measurements of the same quantity. Variability results from many factors, including observer differences, collecting data during different nesting stages, collecting data during different times of day, changes in weather conditions from year to year or site to site, etc…
Bias: a systematic error associated with the methodology which results in consistently over or under-counting the variable of interest, in our case, number of breeding pairs or number of nests. For example, one might end up including nonbreeders in a count of nesting pairs, including non-targeted pair members, or end up missing targeted pairs; all would lead to consistently over- or under-counting.
Parameter: describes or characterizes a population.
Detectability: a measure of the ability of an observer to detect the individuals within a sample. Detectability will vary by observer and by site or sample.