Absence of evidence is not evidence of absence

Imperfect detection of a species is often a problem when attempting to establish its presence or absence at a set of locations. Failing to find the required evidence that a species is present at a location does not imply that the species is absent, merely that it has not been found. Some of the consequences of imperfect detection is that assessments of factors influencing species presence/absence can be misleading, and how certain can one be that the species is really absent given it has not detected at a location. In this talk I shall briefly review some of the consequences of imperfect detection, methodological advances that enable the detection process to be explicitly accounted for, and practical ways in which the required additional information can be collected.