Flammulated Owl habitat

The Flammulated Owl (Otus flammeolus) is a small insect-eating owl that breeds in western North America.  It is similar in appearance to the screech owls, but is smaller and has dark eyes.  It also has a different voice, and is more migratory. 

These habitat photographs were taken in July 2005, in western Montana, in the Bitterroot National Forest.  All images Copyright (c) 2005 by Scott Haywood.  Click on an image to enlarge it. 

A Flammulated Owl was calling from the ridge in the foreground in early July, 2005.  This view looks east toward the ridge.  Most of the trees are Douglas-fir (Pseudotsuga menziesii), including the one in the foreground right. There are some large ponderosa pines (Pinus ponderosa), and some large snags on the ridge.  This is in the Bertie Lord Creek watershed, in the Sula Ranger District.

A Flammulated Owl was found here in early June, 2005.  It called from a Douglas-fir near the right side of the picture.  Notice the large ponderosa pines (the tallest trees in this picture), and the snag at the far left.  This is a south-facing slope.  The south-facing slopes tend to be relatively dry, and seemed to be more likely to support Flammulated Owls.  (Sheep Creek watershed, West Fork Ranger District.)

Two Flammulated Owls were calling within 50 meters of this location, in mid-July, 2005.  The trees are Douglas-fir and ponderosa pine.  There were many decaying fallen trees.  The photo on the right shows a nearby ponderosa pine snag, with a diameter at chest height of about 45cm.  A Pileated Woodpecker called from this snag during daylight hours.  The large tree on the right side of that photo is also a ponderosa pine.  (Woods Creek watershed, West Fork Ranger District.)

I surveyed for Flammulated Owls ("flams") in the Bitterroot National Forest, in western Montana, from mid-May to mid-July, 2005, and found them in forests with large ponderosa pines, Douglas-fir, large old snags, and forest openings.  My remarks here refer to those surveys. 

Large ponderosa pines seemed to be a requirement, but not sufficient: most areas with large ponderosa pines did not have the owls.  "Large" here means roughly 40cm diameter or more at chest height, although I did not take measurements.

The most numerous tree in flam habitat was Douglas-fir, which was usually shorter than the ponderosa pine, with denser foliage. 

When located to a particular tree, the owls were calling within the canopy of a ponderosa pine or Douglas-fir. 

I did not find the owls in dense contiguous forests that lacked openings.  Some mountain slopes of the Bitterroot are covered entirely with dense Douglas-fir, for example.  Flams might use these areas if near more open forest.  Nor did I find them in very open forest, with less than, say, 15% canopy over a large area.  A possible exception was one survey transect that had widespread areas of standing burned trees. 

The presence of other conifers, that tend to grow on moister sites, or higher elevations, such as Engelmann spruce (Picea engelmannii), lodgepole pine (Pinus contorta), or subalpine fir (Abies lasiocarpa) seemed to be a negative indicator: flams were not calling in areas dominated by these species. 

Snags (dead standing trees) are particularly valuable as a component of flam habitat when they are old, perhaps several decades after the death of the tree, with most or all of the bark gone, and decayed enough to make it easy for woodpeckers to dig cavities in them.  Flams use old woodpecker holes as nest sites.  By searching during daylight hours, I could usually find large old snags near where the owls had been calling.  Most of these were ponderosa pines.  The snags were not always visible from the forest roads.  Woodpeckers also create cavities, which might be used by flams, in lightning scars of the larger ponderosa pines. 

The presence of certain species of woodpeckers might help to indicate good habitat.  Flams are known to use cavities created by Pileated Woodpeckers (Dryocopus pileatus) and Northern Flickers (Colaptes auratus).  Both of these are larger than Flammulated Owls.  Williamson's Sapsuckers (Sphyrapicus thyroideus) are smaller, but are often found in Flammulated Owl habitat. 

Burned trees did not necessarily prevent the owls from using an area.  The two survey transects where I counted the highest numbers of calling flams had large areas of burnt forest. 

The other owls I found were Northern Saw-whet (Aegolius acadicus, calling in May), Great Horned (Bubo virginianus), Barred (Strix varia), and Western Screech (Megascops kennicottii).  One might assume that flams would be hard to find if potential predators, such as the Great Horned or Barred Owl, were present, but I did not find this to be true. 

More about Flammulated Owl habitat in western Montana can be found in "Conservation Implications of a Multi-scale Study of Flammulated Owl (Otus flammeolus) Habitat Use in the Northern Rocky Mountains, USA", by Vita Wright, Sallie J. Hejl, and Richard L. Hutto, presented at the Second International Symposium on the Biology and Conservation of Owls of the Northern Hemisphere (February 5-9, 1997 Winnipeg, Manitoba, Canada), and available on the web as General Technical Report NC-190 from the U.S. Forest Service.  Flammulated owls are known to nest in other forest types, at least in other parts of their range.  See for instance, "Flammulated Owls (Otus flammeolus) Breeding in Deciduous Forests", by Carl D. Marti, in the same Technical Report.