Equipment

• hands-free light source, such as a headlamp
• and compass
• battery-powered portable tape player
• endless loop cassette with the appropriate call recorded on it
• hand-held microcassette recorder (for taking notes during the census period - written notes are difficult to make in the dark)
• and pencil (for taking notes when a light source can be used)
• countdown timer with an audible alarm
• flashlight or Cyalume light stick
• batteries for headlamp and recorders

Field Procedures

• arrival at each point on the survey, the observer should extinguish all light sources for a period of one minute before beginning the count.
• this time, the observers should use a compass to orient themselves. If the compass lacks a luminescent dial, a small flashlight or Cyalume light stick may be used to provide just enough light to make the compass face visible.
• this time, start the countdown timer and begin call playbacks.
• playbacks should be given in series of five or six calls, followed by approximately 30 seconds of silence during which the observer listens for a response.
• a response is heard, estimate and record a rough distance to the bird, and note its direction.
• is more difficult for nighthawks who may be flying high in the air. In this case, try to note the distance and direction to the point on the ground directly below the bird.
• nighthawks will respond to call playbacks by diving and "booming" and, in this fashion, they can be distinguished from females.
• a bird is seen, be careful to keep it in sight so that if it moves to a new location, it will not be counted twice. This sounds obvious, but at night this is not an easy task.
• the observation period when the timer indicates that five minutes has passed.
• recorded on microcassette recorders should always be transcribed to data sheets immediately following each night of censusing before unrecorded information is forgotten.

Data Analysis

• Detected: Positive detection of a species in a sampling area provides evidence of presence. If a bird is not detected during an inventory, this does not necessarily mean that the species is not present within the sampled area. The probability of accurately determining which species are present and absent from a sample area is directly related to sampling effort. It is recommended that information about presence/not detected inventory be presented along with information about how much sampling effort was used during the investigation.
• Abundance: Estimates are obtained by using the minimum number of detected males as follows:
• the total number of detected birds within the census area to obtain the minimum number of males.
• the number of males by two to obtain the minimum population size for the area censused (assuming that all males and females have mates).

3.4 Absolute Abundance

Recommended method(s): No standard methods recommended at this time.

Unlike many diurnal birds, it is virtually impossible to visually detect roosting goatsuckers, especially at night. Nighthawks especially, are easily spotted when they are feeding, as they often forage high in the air over a large area (up to 12 km from nest site; Brigham 1988). Most often, nighthawks can be detected only by listening for their calls. Thus, it is very difficult to make distance estimates to observed birds. Because distance measures are difficult to make, estimates of absolute abundance are not possible using point counts.

Although mark-recapture studies may be able to yield estimates of abundance, mist-netting is ordinarily not suitable for determining abundance estimates for goatsuckers. Nighthawks and poorwills are territorial during the breeding season, and therefore, are widely dispersed in space. Generally, mist-netting efforts yield very low numbers of captured birds. An exception to this would be in situations where nighthawks (and rarely poorwills) flock together or aggregate at a common foraging site. One example occurs at Okanagan Falls Park near Okanagan Falls, British Columbia, where a large number of nighthawks aggregate to forage for emerging insects over the Okanagan River (see Brigham 1990; Firman et al. 1993). In such a situation it may be possible to conduct a mark-recapture study to estimate the size of the local population. However, the habitat and area over which the population resided would not be known unless radio-telemetry data about the range of individuals were available.

Nest searches are a valuable method that provide direct measurement of nest success for a given habitat. However, frequent nest visitation is necessary if nests are to be monitored to assess success or productivity. Nest searches have the advantage of yielding habitat specific information, something mist-netting can not do. However, nest-searching requires considerable time and people-power, and the area covered by this method is usually small.