A Comparison of Bird Detection Rates Derived from On-Road versus Off-Road Point Counts in Northern Montana

We conducted a series of 275 paired (on- and off-road) point counts within 4 distinct vegetation cover types in northwestern Montana. Roadside counts generated a bird list that was essentially the same as the list generated from off-road counts within the same vegetation cover type. Species that were restricted to either on- or off-road counts were rare, suggesting that restricted occurrences were a consequence of small sample sizes and not a product of habitat differences surrounding on-versus off-road points. Nevertheless, there were significant differences in the mean number of individuals detected between on- and off-road points for a number of species. Some of these differences appear to be a product of habitat changes associated with the presence of roads, and those differences appear to be less pronounced on narrower roads. Therefore, we recommend that, if one wishes to extrapolate results from on- to off-road areas, care should be taken to select smaller, secondary or tertiary roads as transect routes