As many of our readers may already be aware, this year marks the 100th anniversary of the Migratory Bird Treaty Act. This landmark leglislation paved the way for legislative regulation of bird hunting/harvest, ultimately helping to prevent the loss of many species of wading birds, waterfowl, and brighthly-colored songbirds.
Many conservation organizations are marking this milestone by focusing on birds for 2018. Since the VABBA2 project is already all about birds(!), we’ve decided to mark this year by turning our attention to the often overlooked nocturnal species. Owls and nightjars can be some of the most difficult species to survey for, so we have asked volunteers and agency personnel with specific expertise, to write a series of articles for you, the Atlas volunteers. These articles will each highlight one or two nocturnal species of interest.
For our first Night Bird Series article, we have asked Dr. John Spahr to share his knowledge and experience with studying screech owls in western VA. Dr. Spahr is one of the coordinators for region 3 of the Atlas, a long-time member of the VSO, and a prolific birder. The following article provides recommendations for screech-owl searching, but keep in mind that these methods are far more involved than what is required for ‘completing’ an Atlas block.
Prowling for Screech Owls
By John Spahr
I’ve been researching Eastern Screech Owls (EASO) in Highland County, VA for the past 4 years, doing three or more nocturnal surveys every month (regular 10-stop routes using a defined protocol), as well as monitoring 25 nest boxes. These projects have yielded hundreds of encounters with this attractive little owl and have given me some insights into the how, what, when and where of searching for this species and potential breeding documentation.
These are my survey suggestions to optimize observation/documentation of Eastern Screech Owls.
- Time of Year: The warm months are generally better than winter. My own data indicates that the spontaneous calling frequency and response to playback is highest from July to September in the western mountain regions of VA. This is when the adults are attending to fledglings and when young birds begin to disperse, presumably necessitating contact communication. Cornell’s Birds of North America section on EASO mention a similar seasonal frequency. Note: peak calling and response time may be 2-4 weeks earlier in the warmer, eastern regions of Virginia.
- Time of Day: At night, obviously. Any time after sunset and before dawn. Most of my surveys begin shortly after sunset, dictated in part by weather. There are reports that periods of gibbous and full moon yield increased spontaneous calling. I’ve personally not been able to confirm or refute this.
- Weather: Avoid windy and rainy nights, and severe cold. Wind makes it difficult for you to hear calls, and if playback is used, for the owls to hear you. Avoid nights when the wind is greater than Beaufort scale 3 (ie. more than a gentle breeze defined as leaves and small twigs in constant motion). A light mist or slight drizzle is OK, but anything more than that should be avoided. As mentioned above the warm summer and early fall months are best. If you do go out in the winter select a relatively warm night, as much for your own comfort and for the greater likelihood of encountering owls.
- Habitat & site selection: Forest edges and wooded areas are ideal. Screech owls avoid dense, uninterrupted forests. Residential areas are OK as long as there is a combination of trees and open fields or grassy areas. Nearby streams, marshes and ponds are very good as these afford an increased array of prey items. These birds do not wander far to hunt, especially when nesting. I would suggest scouting out potential sites during the day. Select locations where the habitat seems right and where you can safely pull off the road if surveying by car.
- Listening: Listen first, even if using playback. A listening period of at least 2 minutes at each stop is advised. If you are averse to using playback, stay and listen longer, e.g. 10 minutes. Study the two basic vocalizations of the EASO in advance.
- Using Sound Recordings (playback): Nocturnal and cryptic species like the EASO can be difficult to detect using passive listening alone. Limited and judicious playing of recorded calls of this species often entices birds to respond by calling back and/or flying in close. If you use playback, then I recommend using a speaker that can project the sound a reasonable distance. Most recommended protocols begin with at least a 2-minute silent listening period. If you get a spontaneous call there is no need to use the playback. The protocol that I use consist of a 30-second period of playback followed by a 30-second period of listening. This should be repeated no more than 3-4 times or until an owl responds. I follow this up with a 2-minute silent listening period.
- Spotlighting Owls: A bright flashlight or headlamp is essential. These owls often come quite close if playback is used. Since we are searching for breeding evidence, visual observation can be very revealing (see below).
- How Much Time to Allot: At least one, but up to three hours, should yield a decent survey for this species. Survey several sites in a given Atlas block, situated at least one-half mile apart. (You can survey for several owl species at the same time. However, if using playback play the larger owl first.)
Documenting Breeding Evidence and use of Atlas Codes for EASO
- H In Appropriate Habitat: This will be the code most frequently used as single bird responses are most common.
- P Pair in Suitable Habitat: I use this cautiously in two circumstances.
- When I hear two nearby owls calling in two distinct voices. Males have a lower pitch call than females and when this distinction is obvious, I use this code.
- When I see two owls sitting close by and one is obviously physically larger than the other. Owls exhibit sexual size dimorphism, with females being noticeably larger than males. (On one occasion after spotting two of different size the smaller one mounted the larger for an obvious, brief copulation, validating my “P” assessment!)
- FL Recently Fledged Young: This is where a bright headlamp and careful observation is needed. At first glance a fledgling capable of flight can look like an adult. However, if you get a good look at it you might see residual natal down about the head of the bird (see image).
- I have also used the FL code judiciously when I hear or see more than two birds in close proximity during the late spring, summer and early fall, suggestive of a family group. This may seem like a bold assumption, but these birds at this time of year do not stray far and overlapping of breeding territories is highly unlikely. I’ve encountered as many as 4 individuals together and, on a few occasions, was able to see that at least one had the head plumage of a fledgling.
- NE / NY Nest with eggs / young: I’ve encountered a few of these situations in monitoring my nest boxes. If one knows of a potential nest cavity one can observe the site and look for adults carrying food CF into the cavity or maybe even an owlet poking its head out of the hole.
NOTE: When you see two screech owls together it’s not uncommon for one to be red (rufous) and one gray. These color patterns (morphs) have nothing to do with sex or age and alone cannot be used to infer the presence of a pair.