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Atlasing After Dark: an overview of nocturnal surveys

By Ashley Peele February 9, 2018
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Fledgling Eastern Screech Owl (Dick Rowe)

As we enter the earliest phase of the 2019 breeding season, more and more reports of Great-Horned Owl breeding activity are coming int to the Atlas.  While it is still early for detecting breeding activity of the other VA-breeding owl species, this is a good time to review key tips for nocturnal surveying.  Keep reading for an overview of nocturnal survey tips and species information…

Nighttime surveys are often the last step needed to ‘complete’ or finish an Atlas block.  This aspect of atlasing can seem a little challenging, so this article provides guidance for volunteers who are ready to start working on nighttime atlasing or for anyone interested in nocturnal species surveys.  If you take nothing else away, remember that your safety is the most important part of any Atlas effort.  Please pay attention to suggestions for safe practices below.

Survey strategy

Observers can use a couple different approaches for night-time surveying.

The first focuses on covering as much ground as possible.

Lay out a driving or walking transect with periodic pauses, e.g. every 0.5 miles, to listen for the territorial calls of males or courtship vocalizations between males and females. 

Here, the goal is to cover as much ground within your block as possible.  Note: If you opt to walk a route at night, remember to play it safe.  Choose a location that you have scouted previously, carry a cell phone and flashlight, drag a buddy along and ALWAYS prioritize your own safety.

The second strategy requires a little more scouting in advance of your trip.  Instead of trying to cover as much ground as possible, the focus is on visiting likely habitats for nocturnal species within your block.

In this approach, observers select several locations within suitable breeding habitats around a block and visit each of these on a given evening of nocturnal surveying.

Early in the breeding season, males are often vocalizing to communicate territorial boundaries and to attract females.  At these times, observers may detect owls with no assistance other than their own ears!  However, playback can also be very effective for eliciting call responses from some species of owl, if used in the right season.

Use of playback

The use of playback recordings should increase the likelihood of detecting owl species, particularly if observers select areas with suitable habitat for a given focal species (see below for focal species info).  Typically, an observer will choose a series of locations along a roadside or trail, which are at least 500m apart.  At each point, they will allow ~5 min of silent listening, followed by a series of call playbacks.

Playback should be used sparingly to avoid excessive disturbance of these animals at a sensitive time in their annual cycle.  Please limit playback use to two 60 second bouts of playback at each location.  Allow 3-5 minutes between each playback for an owl to respond.  Individual owls may take their time responding to you, so allow 5-10 minutes for a response before leaving a given location.

Eastern Whip-poor-will (Dick Rowe)

Weather conditions
Common sense is the guiding principle here.  Birds dislike nasty weather just like people do!  Avoid nights with consistent precipitation and steady winds of 10+ mph.  These conditions will reduce bird activity levels, as well as an observer’s ability to detect sounds or movement.  Some species are more vocal on moonlit nights, e.g. Northern Saw-whet Owls and Eastern Whip-poor-wills.  Since human visibility is also improved by such conditions, volunteers should pay attention to moon phases, as well as weather conditions to increase your odds of detecting nocturnal species.

Reporting your nocturnal observations

A couple quirks of eBird to be aware of.  The eBird system automatically separates diurnal and nocturnal effort based on your start time.  If your checklist starts 40 minutes before sunrise or 20 minutes after sunset, it will be classified as nocturnal.  It is important to always start a new checklist for your nighttime surveys!  Otherwise, it will not be correctly classified within eBird.

Note! It is likely you may detect zero birds on a nighttime count, but please enter the nocturnal checklist anyway.  Stationary or short travelling counts are preferred.  As with all Atlas surveys, try not to go over one or two miles in distance.

Habitat

General guidelines for habitat are difficult, because each species has its own unique preferences.  For specific guidance on nocturnal species, see below.  One important factor to keep in mind is that owls can both hear playback broadcasts and be heard by an observer over large distances.  This means that even if you’re not able to get into an area of good habitat, conducting a survey and playback nearby may still be effective.

Species Profiles

Here we describe the specifics of habitat, timing, and likely breeding codes for focal nocturnal species in Virginia.  Most of these details were gleaned from Birds of North America (birdsna.org) and the ‘gold’ book (Virginia’s Birdlife: An Annotated Checklist).  Each are excellent resources for background information on bird species and Atlas volunteers can purchase a BNA membership at a discounted rate.

Medium-Large Owl species

For some additional details on Great-Horned Owl detections, see The Early Bird: Great-Horned Owls.

 Small Owl species

Nightjar species

American Woodcock – see in-depth article on this species (American Woodcock, the forest species few have seen).

*If you have your own examples of other breeding behaviors that you have documented for any of these species, please write in and share with the project at vabba@vt.edu or on our Facebook Group at http://www.facebook.com/vabba2.

If you still have unanswered questions, please feel free to contact your regional coordinator, the State Coordinator, or put your question to the Atlas community via our Facebook Group (https://www.facebook.com/groups/VABBA2/) or email list.  If you’re not on the mailing list, shoot us a request email at vabba@vt.edu.

~ Dr. Ashley Peele, State Coordinator, VABBA2

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