We investigated habitat selection using single‐ and mixed‐scale modeling at 2 spatial scales, stand and home range, by the only known population of American martens (Martes americana) remaining in the historical range of the Humboldt subspecies (M. a. humboldtensis) in California, USA. During 2000 and 2001, we sampled a 12 times 14 grid with 2‐km spacing, using 2 sooted track plates at each grid point. We detected martens at 26 of the 159 grid points. We used resource selection probability functions and an information‐theoretic method to model habitat at detection locations. At the stand scale, martens selected conifer‐dominated stands with dense, spatially extensive shrub cover (x̄ = 74% cover, SE = 4) in the oldest developmental stage. At the home‐range scale, martens selected the largest available patches (x̄ = 181 ha, SE = 14) of old‐growth, old‐growth and late‐mature, or serpentine habitat. Mixed‐scale models revealed that habitat characteristics from both scales best explained marten occurrence compared to one scale alone. Dense, spatially extensive shrub cover is a key habitat element for martens in coastal forests. Dense shrubs provide refuge from predators, cover for prey, and may also deter larger‐bodied competitors. Managers can increase the likelihood of marten population persistence and encourage expansion in coastal forests by maintaining and restoring late‐mature and old‐growth, conifer‐dominated forests with dense shrub cover in large, contiguous patches.

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Season affects many characteristics of populations and, as a result, the interpretations of surveys conducted at different seasons. We explored seasonal variation in occupancy using data from four studies on the Pacific marten Martes caurina. Detection surveys were conducted during winter and summer using either cameras or track stations. We conducted a 'multiple location, paired season' analysis using data from all four study areas and a 'multiple season' analysis using seasonally replicated occupancy data collected at one of the areas. In the former analysis, summer occupancy estimates were significantly lower than winter and per visit probabilities of detection were indistinguishable between seasons. he probabilities of detection for the complete survey protocol were high (0.83 summer, 0.95 winter). Where summer and winter surveys were replicated, probability of occupancy was 5 times higher in winter (0.52) than summer (0.09). We considered the effect of seasonal variation in occupancy on the habitat models developed using summer and winter survey data. Using the same habitat suitability threshold (0.5), the weighted average of winter models predicted significantly more suitable habitat than summer models. he habitat predicted by the summer model was at higher elevation, and was distributed among more, and smaller, patches of habitat than the model developed using winter data. We expect a similar magnitude of differences if summer or winter data were used to monitor occupancy. he higher occupancy in winter is probably due to the abundance of young animals detected during dispersal. Summer survey results reflect the distribution of territory-holding adults, thus these surveys may reliably detect breeding individuals and represent reproductive habitat. he implications of season on the interpretation of survey results, and corresponding habitat models and monitoring programs, provide a challenge to managers that make decisions about habitat management for martens, and other species with disparate occupancy among seasons.