3.5.3 Transects

See Tables 2 and 3 for species-specific recommendations.

Ground transects - Absolute Abundance for detecting breeding pairs and broods (Sandhill Cranes), and for sampling non-breeding birds in wetlands (some species).

Boat Transects at sea - Boat transects are suitable for determining Absolute Abundance when surveying flocks of moulting and wintering sea birds in defined areas such as bays or inlets, (Savard 1982). If absolute abundance estimates of larger areas are being attempted, transects must sample a known proportion of the study area.

Aerial Transects - Absolute abundance for swans: breeding pairs, incubating birds, or broods in open habitat. Care must be taken to survey transects of a known fixed width so that densities can be calculated.

Protocols

These techniques are also used for relative abundance surveys. Only differences from the relative abundance survey are listed here. For details on how to conduct this type of survey see section 3.4.3.

Sampling Design

• For Absolute Abundance surveys, counts must be done in a known area, and must sample a known proportion of that area. Note that these surveys can only be considered estimates of total abundance if all biases have been eliminated. Biases that can not be eliminated should be measured (usually with more survey effort) and used to correct counts.
• Non-breeding Birds: Use fixed-width, known-length transects in an area of known size.

Data Analysis

• Precision is calculated as the square root of the variance around the mean for replicate transects within each strata.
• Long term annual trends may be analyzed using route-regression analysis (Geissler and Noon 1981, Dickson 1989) although further research may reveal a more appropriate method (Thomas pers. comm.).
• Density estimates may be calculated by dividing the number of birds observed by the area surveyed in transects of fixed length and width. Total abundance can be calculated by multiplying the density estimates by the size of the study area. These densities can be used to calculate total abundance only if all biases have been eliminated or corrected for with a more intensive measure.

Example:
As part of a larger study to determine the distribution of birds in habitats around Boundary Bay and to estimate the amount of land required to support the current populations of birds, Breault and Butler (1992) used direct counting to estimate the absolute abundance of American Wigeons, Mallards and Northern Pintails on farmlands in the Lower Fraser River delta. Telemetry studies had shown that birds of these species found in Boundary Bay, Roberts Bank and Sturgeon Bank spent at least a part of every 24 h period in the fields between early November and late March. They counted the number of birds in roadside farmlands from a vehicle driven along the transect survey route one day each week when the tide was high. The open habitat enabled them to count birds in the entire field from viewpoints along the road. They counted the number of birds along the dykes at high tide once each month to estimate the numbers of ducks on Roberts Bank and Sturgeon Bank. Each duck was counted in flocks with fewer than 400 ducks and larger flocks were counted by summing the number of groupings of 100 birds. They calculated the estimated error of their flock size counts by counting the same birds several times. The area of the sampled habitat was determined from satellite images. The numbers of ducks in farmlands during the day was estimated by assuming that the density of ducks in the areas not sampled was the same as the density in the sampled farmland.

3.5.4 Nest Counts

See Tables 2 and 3 for species-specific recommendations. Absolute abundance can be obtained for almost all breeding waterbirds (except ducks) by conducting nest counts. The proportion of the area searched must be measured on the ground or from maps or airphotos, if less than 100%.

Ground transects - for detecting nests of upland ducks breeding in open habitat in confined areas. Dragging a chain or rope between two tractors or two people on foot over nesting habitat flushes incubating birds and reveals the location of nests (Higgins et al. 1969). Care must be taken to ensure the chain is sufficiently light, or suspended far enough above the ground to prevent damage to nests.

Foot Searches in Wetlands - Searching by wading on foot through the emergent vegetation of the wetland along the shoreline (possibly using chestwaders) is recommended for wet areas.

Boat Searches in Wetlands - used when conducting nest counts for species that nest over water. For deeper wetlands, shorelines may be searched using a canoe for transport.

Helicopter Surveys - In wetlands of known size, do complete searches for incubating birds of conspicuous species which nest in locations visible from the air (e.g., swans). See section 3.5.2 for protocol.

Aerial Transects - Aerial transects by helicopter are conducted for incubating swans or other very conspicuous, widely dispersed birds nesting in open habitat. See section 3.5.3 for protocol.

Advantages

• Improves chances of detecting nests in cover.

Disadvantages

• May disturb incubating birds and cause abandonment of nests or increase predation;
• Time consuming;
• Difficult to cover representative areas; therefore, biased to surveying most accessible areas; and
• Nests of many species are often concealed and easily missed.

Office Procedures

• Review the introductory manual No. 1 Species Inventory Fundamentals.
• Obtain maps for Project and Study Area(s) (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). Any map which is used to record data should be referenced to NAD83.
• 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. Generally, a Study Area will be equivalent to a single wetland.
• For each Study Area:
• Determine Biogeoclimatic zones and subzones, Ecoregion, Ecosection, and Broad Ecosystem Units for areas surrounding the wetland.

Sampling Design

• For Absolute Abundance surveys, both the area of the wetland sampled and the Study Area size must be known. Note that these surveys can only be considered estimates of total abundance if all biases have been eliminated. Biases that can not be eliminated should be measured (usually with more survey effort) and used to correct counts.
• If appropriate, wetlands may first be stratified by habitat type.
• Survey systematically. Conduct total counts of defined areas following a grid pattern or otherwise ensuring complete coverage.
• If sampling along a transect, use a fixed width narrow enough that nests will not be missed.
• For ground/water transects also measure the distance from the transect center line to all nests observed, whether in or out of the transect width.