3.4 Absolute Abundance

The following protocol for conducting nest counts is included under the heading "Absolute Abundance" as it provides an estimate of nesting density. This technique is by no means "absolute" as it will not account for the presence of juveniles, other non-breeders, failed breeders, or the occurrence of polygyny (noted among American Bitterns, Gibbs et al. 1992). In addition, this technique is relatively experimental and will have potentially greater impacts on marsh birds and their habitat then will call playback surveys. For these reasons, biologists are encouraged to limit the use of this technique to those sites where nest information is specifically required, and to continually re-assess the benefits of each survey against its impacts, and cease if appropriate.

3.4.1 Fixed-width Transect (Nest Count)

It has been suggested that surveys of breeding rails (especially those using call playback) suffer from lack of an independent measure of actual breeding numbers (Eddleman et al. 1988). Using Pointing dogs may provide a measure of nesting numbers which is independent of call playback.

Pointing dogs have been used to locate male and female Yellow Rails that did not respond to call playback (Bookhout and Stenzel 1987). Pointing dogs would be useful for determining Absolute Abundance of bitterns and rails in marsh habitats. This method should not be attempted without expertly trained dogs, a proper permit to use them to locate wildlife, and assurances that the habitat will not be adversely affected (e.g., severely trampled vegetation as a result of repeated transects). Dogs have been used extensively in surveys for upland game birds such as spruce and ruffed grouse. Persons conducting this research should be contacted for information and as a potential source of trained dogs and handlers. Using dogs in wildlife surveys are further described in Zwickel (1980).

It is expected that foot surveys within fixed-width transects will be limited to only areas of wetland and accessible property that will allow surveyors to walk through them. Due to the possibility of permanently damaging emergent vegetation (Oelke 1981), repetition of the transects should be limited to only two or three visits per season.

Advantages

• Using trained dogs to find nest and birds is more productive than unassisted foot surveys;
• It is probably the only method that will allow you to find enough nests to estimate the breeding population of rails and bitterns in any size wetland;
• Call playback surveys with a follow-up to locate nests will provide surveyors with two indices of actual breeding populations.

Disadvantages

• Properly trained dogs and handlers may be difficult to find;
• There is potential to damage the vegetation in the wetland with repeated surveys;
• It may be difficult for dogs to locate waterbirds by scent (relative to terrestrial nesting birds);
• Surveys may be biased by the abilities of the dog and their handlers;
• This type of survey can be very time intensive, perhaps to the point that this method might best be used for research-level questions at a small scale.
• Surveys are restricted to shallow marsh areas and areas with permission granted for this type of activity;
• Some studies (e.g., forest birds, waterfowl) have shown that human visitation to nests can be correlated with increased predation risks and incidence of desertion by the laying/brooding bird.

Office Procedures

• To conduct this sort of survey, it will be necessary to obtain permission from the Canadian Wildlife Service office in Delta, B.C. This will hopefully eliminate any confusion which may result if a Conservation Officer encounters you looking for birds with a trained dog. Requests should be made in writing.
• Review the section, Conducting a Wildlife Inventory, in the introductory manual Species Inventory Fundamentals No. 1 manual. For further discussion on statistical power in waterbird surveys refer to Gibbs and Melvin (1997).
• Obtain relevant maps of the Project Area (e.g., 1:50 000 air photo maps, 1:20 000 forest cover maps, 1:20 000 TRIM maps, 1:50 000 NTS topographic maps).
• Outline the Project Area on a map and determine Biogeoclimatic zones and subzones, Ecoregion, Ecosection, and Broad Ecosystem Units for the Project Area from maps.
• Delineate one to many Study Areas within this Project Area. Study Areas should be representative of the Project Area if conclusions are to be made about the Project Area. For example, this means if a system of stratification is used in the Sampling Design then strata within the Study Areas should represent relevant strata in the larger Project Area.
• One Study Area may consist of one or more marsh habitats. Recent colour aerial photographs of the marsh habitats that will be surveyed will be especially useful (see Sampling Standards above).
• Determine Biogeoclimatic zones and subzones, Ecoregion, Ecosection, and Broad Ecosystem Units for areas surrounding the wetland. Determine wetland class using the Riparian Management Area Guidebook (B.C. Min. Environ. and For. Serv. 1995) as a general reference.
• Determine the size of the marsh habitat by estimating the area covered by non-woody, emergent vegetation (see Habitat Data Standards above).
• Identify access points for surveys from the small scale colour aerial photographs.
• Review the life histories of the marsh birds that may potentially be in your Study Areas. Since marsh birds have generally not been studied in B.C., use the known range only as a general guideline, and rely more on general habitat descriptions for each species as an indication of potential presence.
• Complete the following Data Forms that are included in the Species Inventory Fundamentals No. 1 [Forms] (previously referred to as the Dataform Appendix).
• Wildlife Inventory Project Description Form
• Wildlife Inventory Survey Description Form - General
• Locate Field Personnel and TRAINED dogs and dog handlers.

Sampling Design

• Survey lines should run systematically in fixed-width transects throughout a marsh habitat. The intention of this survey is to gain a measure of Absolute Abundance of target species' nests within a marsh habitat, on a marsh-by-marsh basis. Therefore, any design which ensures full coverage of the marsh habitat is encouraged.

Sampling Effort

• A maximum of three visits should be made to marshes and wetlands to avoid extensive damage to emergent vegetation.
• The time that it will take to cover a marsh habitat depends on the expertise of the dogs and the handlers. One observer can cover a 1.6 km long and 0.4 km wide fixed-width transect in one hour in Michigan wetlands when surveys are conducted at night between approximately 2300 to 0430 (Bart et al. 1984).

Personnel

• This survey method requires an extremely well-trained dog. A general discussion of breeds, training, and care of dogs can be found in Zwickel (1980). To avoid excessive damage to the marsh vegetation, and disturbing the breeding cycle of marsh birds, this survey should only be attempted by experienced dog handlers using well-trained dogs. Contact local hunting clubs and inquire about persons with this experience.
• A professional biologist familiar with marsh birds and their habitats must accompany all surveys that use dogs. If it is apparent that the dog or the survey itself is posing a threat to the study species, then the survey should be stopped immediately.
• At least one person should be familiar with the collection of habitat data.

Equipment

• Equipment required for the dogs (probably at least a bell; this will be the responsibility of the handler)
• Animal Observation Form - Marsh Bird Transects
• Nest Site Description Form (see RIC guidelines in the Species Inventory Fundamentals No. 1 [Forms])
• 8-10x wide angle binoculars
• 35 mm camera for photodocumentation of habitat and nest site. For confirmation of identification you may need very clear colour photographs of the eggs in the nest
• Maps, air photos or GPS units (NAD83) to record locations of transects and nests.

Field Procedures

• It is generally helpful to divide the marsh up into sections and flag these out when you begin. This will help ensure that you are getting complete coverage of the marsh habitat. Two people, one a dog handler and the other a biologist, should then walk fixed-width transects, approximately 50-75 m wide. Ideally, the two people should walk down the middle of the transect while the dog searches a wider area under the direction of the handler.
• Essentially, do whatever it takes to cover the marsh habitat thoroughly without damaging the habitat, or creating excessive disturbance to the birds. The actual methods used will vary in different situations.
• Conduct this survey in the late morning to late afternoon (i.e., outside of the peak calling periods) during the same time of year recommended for call playback surveys (between 20 May and 5 July throughout B.C.).
• It is important to be especially alert so that you may catch sight of the bird flushing off the nest. This will provide positive identification of species and confirmation that the nest is active.
• When a nest site is found, ensure that the dog poses no threat and then describe the nest and map its location. A Nest Site Description form is available in Species Inventory Fundamentals [Forms].

Data Analysis

• Calculate Absolute Abundance by summarizing the number of nests found by the total area covered by fixed-width transects in a marsh habitat (see Glossary for definition).
• Refer to the Data Analysis and Report Preparation section for Call Playback Analysis.