What is the duty to mitigate in the context of wrongful dismissal claims?

The duty to mitigate in the context of claims for damages arising from wrongful dismissal was summarized by Laskin C.J. in Michaels v. Redeer College, 1975 CanLII 15 (SCC), [1976] 2 S.C.R. 324 at p. 330 as follows: …It is, of course, for a wronged plaintiff to prove his damages, and there is therefore a burden upon him to establish on a balance of probabilities what his loss is. The parameters of loss are governed by legal principle. The primary rule in breach of contract cases, that a wronged plaintiff is entitled to be put in as good a position as he would have been in if there had been proper performance by the defendant, is subject to the qualification that the defendant cannot be called upon to pay for avoidable losses which would result in an increase in the quantum of damages payable to the plaintiff. The reference in the case law to a "duty" to mitigate should be understood in this sense.