The wingspread of a male Flammulated Owl that has been on the study site for five years
Let’s revisit the unsuccessful female-catching story from last week. It’s June 19 and once again I am standing below the four-cavity aspen. I am raising the net attached to a yellow fiberglass pole, the measurements on the side inching higher and higher: 16ft…17ft…18ft…four more inches…stop. I lean the net against the top hole. I can predict what will happen next because I have already visited this nest, in this same position, three times previously. The male will fly in a little after 9 PM and give a few location calls. The female will reply from within the cavity. Anxious of the net sitting ominously over his cavity, the male will abort his prey delivery and fly to the east. Here, one of three things may happen: (A) The female flies out of the cavity, hits the net, but escapes out the side as I lower the pole, (B) the female continues to beg to the male but never leaves the cavity, or (C) I back the pole away to allow the male to make his prey delivery and try catching him instead. Of course, I might also be successful and catch her when she flushes…
Flammulated Owls are intriguing birds, few would disagree. But, as Dr. Linkhart pointed out to me this week, they are part of an ecosystem beautiful in its complexity. Although Flammulated Owls appear to nest primarily in quaking aspen, the ponderosa pine ecosystem as a whole is vital to their survival. They are particularly reliant on the ponderosa pine itself, that vanilla-scented giant with puzzle-like bark. Flammulated Owls often nest in aspen due to its soft bark, which makes the aspen choice pecking ground for many woodpeckers and sapsuckers, whose old holes the owls use. Most other aspects of a Flammulated Owl’s life, however, take place in the boughs of the ponderosa, where the owls roost and forage, gleaning moths off needles and branches. Furthermore, Linkhart has found that Flammulated Owls demonstrate higher long-term reproduction in older forests of ponderosa pine and Douglas-fir. Such forests are periodically thinned out by natural forest fires and become open, with only the oldest, tallest trees standing. Younger forests tend to be thick with undergrowth and less optimal for owl reproduction. This carries strong implications for the conservation of old growth forests and says something about fire ecology. How does human suppression of forest fires hurt or benefit wildlife?
Obviously habitat is a deeply intertwined facet of owl ecology. But what about food source? This year the study also includes sampling moths throughout the season. During the week we set up a backlight on a nearby ridge top. On certain days we turn it off and bag our prize, a carcass parade of Lepidopterans. Linkhart will spread the insects out on a piece of paper and sort through them by family. He explains to us a difference between Geometrids (moths which hold their wings flat, away from their bodies) and Noctuids (which fold their wings over the abdomen). Lepidopterans, particularly the assortment of moths, can be hard to identify to species, so the samples may be sent to an entomologist to be sorted and classified. In general, Linkhart believes the owls prefer medium-sized moths. The sphinx moths may be too large and the smaller moths, some of which are no more than a centimeter in length, simply do not provide enough nutrition. How interesting it would be to compare our observations of what we see the owls’ preying upon in the field to the moths that we collect as the season progresses.
Releasing a male Flammulated Owl
Another exciting event this week concerns the hatching of owlets, which marks a new stage in the Flam Crew’s work. So stay tuned, the next post is sure to be an exciting one! By the way, I did finally catch that female. After holding the net for 45 minutes, she was ensnared in a matter of seconds and released in a matter of minutes.
I highly recommend viewing the following documentary by Dakin Henderson, a fellow Flam Crew member: http://www.sciencefriday.com/videos/watch/10217