2022 Earthwatch Arizona Trip Part 1 - Owls at the Southwestern Research Station

With summer finally here after a very long school year, I decided it would be the perfect time to head down to the Southwestern Research Station in Arizona to do an Earthwatch program focused on researching the local owl species and their nesting habits. This research project is headed by Dr. Dave Oleyar, who has been working with these Arizona owls since 2016 and a population of Utah owls for over two decades.

Most research takes the form of doing cavity plots through which we measure basal area and canopy cover. However, the two most important pieces of data that are collected are cavity maps and information gathered from the capturing of owls. Part of the process of completing a cavity plot involves going around from tree to tree looking for possible cavities. Once one is found, we take data from it, like bearing, height, width, quality, etc. Most of the time, the “cavity” that we find is really just a ledge that has no depth. Even if it is a cavity, sometimes it’s only 1-3 stars in terms of quality. 4-5 star cavities are relatively rare and usually are already occupied by something. These good cavities are essential for owls to continue living in this area as they can only nest in very specific kinds of cavities.

The capturing of owls is even more difficult. It involves a long and complicated night survey that first utilizes playback of their vocalizations and then a mist nest should an owl respond. Once we set up a mist net (an extremely thin type of net that is used to catch birds and bats), capturing an owl usually took between 15 and 30 minutes. However, sometimes it took us as long as 45 minutes, and we barely caught more than 50% of the owls we tried for. The capture difficulty also varies by species. The only one we captured was Whiskered Screech-Owl (Megascops trichopsis), which was relatively easy, but we tried for both Elf (Micrathene whitneyi) and Western Screech-Owl (Megascops kennicottii). On multiple occasions, they eluded us, much to our disappointment and frustration. This particular post will concern specifically the owls and their habitat in the Chiricahua Mountains.

The mountains surrounding the Southwestern Research Station were spectacular in the early morning light. I had to get up at 4:30am to see this sight, and the previous night, or well, that morning, I went to bed at around 1am. My lack of sleep was worth the view though, and I did manage to get a couple of hours here and there throughout the day, and by the time evening rolled around, I was ready to do it all again.

The Chiricahua Mountains are a part of the Sierra Madre Occidental Mountain Range, which runs North-to-South through most of western Mexico and whose northernmost extent just barely reaches into Southern Arizona and New Mexico. A lot of bird species that are endemic to the Sierra Madre Occidental have the edge of their range extend into this region of the Southwestern US. One of the owls we were attempting to find, the Whiskered Screech-Owl (Megascops trichopsis), is a good example of one such species. Most of the habitats in the Chiricahuas that we surveyed were of one of the following three: oak woodlands, semi-riparian woodlands consisting mainly of Arizona Sycamores, and high-elevation pine forests. Each habitat has different species of birds, and with that, unique owls. In the spring, the rivers and streams have a lot more water, but at the time of year I was there, most of it had dried up.

Kassandra Townsend holding a Whiskered Screech-Owl (Megascops trichopsis). She is one of the researchers working with the owls at the Southwestern Research Station. Her research on owls concerns the microclimates within tree cavities and how owls take this into consideration when selecting a nest site.

Here we have an owl being bagged by Kassandra prior to being weighed. Asides from that, we also kept them in bags if we were trying to catch another owl at the same time. This way, we wouldn’t catch the same owl that had already been netted previously. Often while still in the bag or sometimes even when in hand, being more concerned about the fictional trespasser than its own predicament, the captured owl would hoot in response to the recordings we were using to bring in its mate.

At some point after capturing every owl, Dave would tell everyone to turn off their headlamps. Then, he would turn on a black light and shine it on the wings of the owl, illuminating the scene with hues of dark blue and purple. Some owls would look relatively normal under close inspection, but others, like this one, would have feather regions take on a pinkish tone. This denotes where new feathers have recently grown in and indicated to us that this bird was in the process of or had just molted.

Another owl, this time in the hands of Dr. Dave Oleyar. The owl seems to be giving off an expression of bewilderment and confusion over its present situation. Interestingly enough though, the owls were relatively calm and sometimes it took some coaxing to get them to fly off.

Yet another Whiskered Screech-Owl, this time being held by researcher Day Scott, a wildlife photographer, conservationist, educator, and feature writer who has written articles for the blog of the National Audubon Society and for the WREN magazine. You can find her at @thewildernessgoddess on Instagram!

Here is another Whiskered Screech-Owl being held by Day.

Although we never caught this species of owl, we did find a nesting site with a female Western Screech-Owl (Megascops trichopsis) guarding nestlings. This part of the research is tricky and needs delicate care in order to not disturb the owls more than is needed to collect the data.  Not surprisingly she was unhappy we had discovered her nest and struck at the camera several times while we attempted to photograph the nestlings and obtain data about the cavity. Eventually, she stood by and watched while hooting to voice her displeasure at our intrusion. Not wanting to disturb the owl too long, we very quickly recorded the necessary data and then left.

We found this owl via a method called cavity plotting. Plotting is a rather lengthy procedure. The first step is to lay out the 50-meter measuring tapes. We had to do this relatively accurately in order for the plot to work, and thus it involved all nine of us all doing our jobs correctly in perfect cohesion. Usually, we were a couple of meters off when we joined up the tapes. In the best cases, we were a meter or less off, which was pretty good considering we had to bushwhack through all kinds of shrubbery to get to the endpoints. At the 25m points, we extended additional 50m tapes to get a center point at a distance of 25m from each of the other tapes. Then, a pair of two people would go around to each of the points (including the center) and record the canopy cover percentage using a spherical densiometer. That kind of densiometer looks like a small portable handheld mirror with squares carved into it. Using this device, we counted the number of points that are covered by the canopy and how many weren’t (there are four points to a square). While they were doing that, the rest of us would go out and hug trees. That is, calculate DBH, which is the diameter of the tree at chest height. However, it varies from person to person and some people have to measure it at different points. I measured my DBH at my own chest level but most of the other people had to measure it at the bottom of their noses, or in some cases the tops of their heads. However, we had an order to this DBH madness. There was a person at the center point with a keyhole prism to see how many and which trees fit within the BAF, or basal area factor. The trees that fit the appropriate BAF were measured for DBH and had their species determined.

Finally, after that, we divided up into two teams of four, each with a gaffer (cameraperson), a screen person, a scribe, and another person with other tools, such as a DBH tape. Each team then covered two quadrants and examined each tree for cavities. Upon finding one, we checked it to see if it qualified for a cavity and, with the camera, if there was anything inside of it. Then the scribe recorded data. Usually, the cavity searching process was the longest. Depending on how annoying the terrain was to traverse, it could take anywhere from around an hour to sometimes 3 or 4. We only once found an owl among all the plots we conducted, but every plot still had tons of useful data, and we made sure to record all of it.

This concludes part one of a three-part series of my 2022 Earthwatch Arizona Trip. Come back later to see parts 2 and 3!