3.3.1 Call Playback Surveys

The call playback technique attempts to solicit woodpecker responses to broadcasted recordings of their calls and/or drummings. Playback surveys are suitable for species that respond readily to recordings, occupy relatively large home ranges and/or are otherwise difficult to detect. The response to a call/drumming can be visual and/or vocal. Only 3% of the total responses were visual for a Pileated Woodpecker study that was conducted on south-eastern Vancouver Island. As well, 92% of the responses were solicited as opposed to spontaneous calls (Hartwig 1999). The call playback technique has been successfully used for a variety of species including Pileated (Bull and Holthausen 1993; Hartwig 1999), White-headed (Frederick and Moore 1991), Three-toed and Black-backed Woodpeckers (Goggans et al. 1987), and Yellow-bellied Sapsuckers (Rushmore 1973).

For determining presence/not detected (possible), it is possible to census a group of woodpeckers at the same time. However, it should be noted that drumming imitations are only useful if the responding birds approach close enough for accurate identification. Woodpecker identification based solely on drumming may be inaccurate because differences in resonance between drumming substrates can be greater than differences among certain species (Robbins and Stallcup 1981). Additionally, this inventory technique is still in the experimental stages and it is not known how well various species respond to call playback nor at which stage during the breeding season each species will respond most predictably. Therefore, observers should note if more than one species responds to a call.

In general, call surveys are conducted by walking or driving along a transect line and stopping every 100 - 600 m to broadcast a call or imitate drumming, depending on the density of the forest, the quality of broadcasting equipment and the woodpecker species being inventoried (Johnson et al. 1981; Aubry and Raley 1994). Appropriate distances for spacing call stations have not been determined for each woodpecker species. A distance of 300 metres between call stations and 800 metres between transects was used by Aubry and Raley (1994) while surveying for Pileated Woodpeckers in Oregon forests. As a general rule, surveys for larger species have greater distances between call stations than small species inventories.

Playback/imitation techniques appear to generate very good results in presence/not detected (possible) surveys for woodpeckers. Although these techniques are most effective during the early parts of the breeding season, they may also prove useful during other seasons, especially for species that defend feeding territories in the winter. Possible disadvantages of playback surveys include (i) the greater effort and expense required relative to silent transect walks or point-counts, (ii) annual variations in ecological conditions which affect the timing of breeding and, in turn, the timing of (peak) responsiveness, (iii) dominance interactions between species which might confound the detectability of particular species when attempting to survey for multiple species; and iv) statistical limitations (discussed above).

Office Procedures

• Review the introductory manual No. 1 Species Inventory Fundamentals.
• Compile a list of all potential woodpecker species in the Study Area.
• Obtain relevant maps for Study Area (e.g., 1:5,000 air photo maps, 1:20,000 forest cover maps, 1:20,000 TRIM maps, 1:50,000 NTS topographic maps) and identify regions to inventory on the map.
• Obtain cruise data, wildlife/danger tree assessment reports (Wildlife Tree Committee of B.C. 1993).
• Determine the best distance between call stations based on the density of the survey habitat, the species being surveyed and the quality of the call playback equipment.
• Establish transect routes with calling stations on maps and/or air photos. These may follow roads, trails, predetermined straight lines, contours or drainages. Systematically select random locations within each stratum for initiating transects (Refer to Section 2.3 - Sampling Design in the RIC Species Inventory Fundamentals manual).
• Determine Biogeoclimatic zones and subzones, Ecoregion, Ecosection, and Broad Ecosystem Units for stations.
• Obtain background information on target species (behaviour, habitat requirements, site-specific nesting chronology, activity schedules, characteristic calls or drummings, etc.)
• Obtain information on terrain structure/features of sampling area (slopes, aspects, gullies, cliffs, creeks, etc.) and select transect lines and sampling stations (plots) from maps.

Equipment

• A portable megaphone attached via a mono cord to a walkman is particularly useful for call surveys on foot. The machine should be able to broadcast sounds over a distance of 400 metres; one technical description of a recommended player has a frequency of about 40 Hz to 12 kHz and power output of 1.2 watts at 1 kHz.
• Tape cassettes / CD of calls of woodpecker species of interest.
• Equipment for imitating woodpecker drumming sounds such as two 1-inch hardwood dowels (18 and 7 inches long) used by Rushmore (1973) to imitate the characteristic two-beat drumming and feeding sounds of Yellow-bellied Sapsuckers. Taped recordings of these drumming sounds would make surveys more consistent and would help project the drumming sounds at equal distances between stations.
• Datasheets
• Field identification guides
• Binoculars
• Maps
• Compass
• Hip chain
• Altimeter

Field Procedures

• The time of year for commencing call surveys can be determined from knowledge of when egg laying will occur.
• Studies have shown Three-toed and Black-backed Woodpeckers respond well to playbacks of their drummings during the cavity excavation period (approximately three weeks long) and most responses are obtained one to two hours after sunrise.
• In general, Black-backed Woodpeckers are more responsive throughout the breeding season than Three-toed Woodpeckers (Goggans et al. 1987).
• For sapsuckers, the highest proportion of responses were obtained during the pre-nesting period (87%), followed, in decreasing order, by the nesting (61%), post-nesting (54%), and pre-migration (41%) periods (Rushmore 1973).
• Call surveys for Pileated Woodpeckers in Oregon were conducted from mid-March to mid-April, before birds began to incubate eggs and when birds were most territorial (Aubry and Raley 1994).
• Surveys should be conducted in the morning from one half hour after sunrise until noon.
• Stations along transects can be surveyed by driving along roads and getting out of the vehicle to play calls or by broadcasting calls while on foot.
• Although call surveys are known to be effective, there have been no standard distances determined for inventorying each species. Calling stations should be separated far enough apart in order to maximize distance covered and minimize duplication of called areas. Calling stations used to survey Pileated Woodpeckers in forested areas were separated by approximately 300 m. Distances will vary according to woodpecker species being inventoried (the smaller the woodpecker species, the shorter the distance between stations), density of habitat and survey equipment used (i.e., broadcasting distance). For consistency, stations must be separated by a minimum of 200 m.

At each station:

• Upon arriving at a call/drumming station, surveyors should listen for one minute for calling birds, before broadcasting a call or imitating drumming. Use this time to record location and weather conditions. You may collect habitat data for the station at this time or on your route back after you have completed the call playback surveys on your transect.
• If no birds are heard, broadcast a call for a particular species at 60⁰ from the transect line, turning left or right and continuing in the same direction during subsequent turns; listen and watch for 30 seconds. Turn 120⁰ and repeat the procedure, then turn another 120⁰ and repeat the procedure.
• For consistency, multi-species call playback surveys for woodpeckers should include three series of 20 s of calls/drumming followed by a 30 s break (e.g., 20/30, 20/30, 20/30) for a total of 2.5 min. for each species, with a minimum two-minute pause between each species. Calls should be played in order from smallest to largest species. Once a response has been elicited, discontinue the call playback for that species. Wait one minute, and then continue with other species. If call playback of the additional species results in undue disturbance to other species, discontinue call playback entirely and continue on to the next point. Note at what species call playback was discontinued for each point on the data sheet. This will be important in an evaluation of survey effort (e.g., to evaluate the total number of times or the total number of points at which call playback for particular species was conducted).
• When drumming to supplement call playbacks or as a follow-up to unsuccessful playbacks, follow the above procedures. A drumming sequence should last for approximately 5 seconds, followed by a 10 second pause and should be repeated three times as above (e.g., 5/10, 5/10, 5/10).
• For Yellow-bellied Sapsuckers, Rushmore (1973) developed a method using two 1-inch hardwood dowels to produce a series of hard, short, rapid taps lasting one second, followed by a few slower, louder, spaced taps, illustrated as follows (taps = -; pause = ´):
  柎柎柎柎柎柎柎柎柎柎柎柎礂创礂创礂创礂创礂
• Rushmore (1973) obtained even better results when he varied the drumming imitations with the sapsucker's softer, very rapid bark-feeding taps such as in the following sequence (taps = - ; pause = ´ ):
  柎柎柎柎柎创创创礀创礀创创创创枛枛枛枛创创创创枛枛
• If a woodpecker responds to the call or drumming sequence, stop playing the calls or drumming. Record the necessary information on the data sheet.
• If no response is received, move to the next call station and repeat the above procedures.

Completing a transect:

• Continue the above procedures until the transect is complete, looking and listening for birds between stations. At the last station, the surveyor should wait ten minutes after the calls have been played or drumming has occurred, before ending the survey and leaving the area.
• Following each call survey, woodpecker detections should be plotted on a master map.

Data Entry

The Design Component types for this survey are transects and call playback stations. However, in this case the station is used as the sample unit. Thus, you are only required to enter information about the call playback stations (not about the transects) when digitally entering your survey data into the provincial database. To do this, choose `Station' from the `Design Component Type' picklist.