Flammulated Owl Distribution and Habitat Associations During the Breeding Season in the Western United States

The flammulated owl is a small insectivorous owl that occupies forests in western North America during the spring and summer breeding season. The species has not been extensively studied across its range but is considered sensitive or at risk by many states, provinces, and forest management agencies. We implemented the largest survey ever performed for this species across multiple western states to assess its distribution and habitat associations. We completed one to three survey visits at 3137 points from 2009 – 2021 and detected flammulated owls at 309 (9.8%) survey points. We used machine-learning occurrence modeling to estimate habitat associations. We found flammulated owl presence to be most strongly associated with a specific climate envelope, potentially putting them at increasing risk from climate change. Flammulated owls in our study had a positive association with aspen, Douglas-fir, and to a lesser degree, ponderosa pine forests, and a negative association with lodgepole pine. They occupied sites (100-ha areas centered on the survey point) with higher canopy cover, moderate slope and roughness, located closer to ridgetops, and with higher probability of wildfire. Forests at over 15% of our sampled points have burned in the time since they were surveyed. In addition, our finding of a weak association with ponderosa pine forest may reflect changes due to fire suppression that in many areas may have degraded habitat quality of those forests for flammulated owls. We suggest that maps of the range and distribution for the species be updated to reflect our findings, specifically in western Wyoming, south-central Idaho, and southern California, which may impact planning for forest management in some areas. Furthermore, forest management actions to promote aspen restoration and regeneration, and to restore ponderosa pine stands to their historical structure and condition, may help this sensitive species adapt to impacts of climate change. Lastly, while this study covered a broad portion of the western United States, it did not cover several areas where flammulated owls are known to exist – Montana, Oregon, southern Utah, Nevada, Arizona, and New Mexico; we encourage further research in these areas.