3.5 Boat transects

Recommended use(s): Relative abundance and absolute abundance of wintering and breeding grebes. See Table 2 for species-specific recommendations

Relative abundance

Recommended for estimating relative abundance of wintering grebes in protected coastal waters. It is best used in conjunction with surveys of other waterbirds.

Absolute abundance

Recommended for surveys of concentrations of Western Grebes and Eared Grebes on breeding lakes where counts cannot be made effectively from land, where total nest counts cannot be made, and in marine habitats for nonbreeding grebe populations where land-based counts are not feasible.

Boat transects involve identifying all birds encountered along a transect line (straight or contours with shorelines), or by counting all birds in areas of concentrations from a boat. This technique is especially useful for waterbirds that are relatively small, and difficult to identify at a distance, or waterbirds that can occur at low densities and be easily missed from aircraft (wintering B-RNGR, B-EAGR). It is not useful for surveys of Great Blue Herons.

Surveys of waterbirds by boat have been used extensively in coastal marine areas in British Columbia and have been found to be a good technique for censusing grebes (e.g., Vermeer 1983, 1989; Morgan 1989; Rodway 1989; Vermeer and Morgan 1992; Vermeer et al. 1994). Observers sit or stand, depending on size of boat and roughness of water, and count birds as they are encountered. Most surveys are done from small, fast boats, rather than large ships, and one observer spots from each side of the boat. Transects can be as wide as observers can see and accurately identify waterbirds. Maximum distances depends on sea and weather conditions. In calm waters, binoculars can be used to extend the width of the transect up to about 200 m. In rougher waters, it is difficult to use binoculars and small birds like grebes can disappear behind waves or swells. Under less than calm conditions, transect widths should be about 75 m. This method can also be used on large interior lakes to census grebes.

Boats can be used to survey areas not accessible from land-based viewpoints (remote marine coasts, large lakes, large rivers), and considerable distances can be quickly covered. The slow speeds of watercraft, compared to aircraft, allow observers sufficient time for accurate species identification and inventory, and boats can stop to allow observers to count concentrations. Surveys of known localized concentration areas may be cost-effective compared to aerial surveys.

Factors to consider in the use of surveys by watercraft

• Strong winds, rain, and tidal action can cause biases in counts, pose danger to personnel, or preclude surveys altogether. Extra gear such as survival suits and HF radios are recommended. Personnel must have a high tolerance to motion sickness.
• Grebes may dive if approached too closely, making accurate counting difficult. However, observers can easily determine if they are approaching too closely and should scan ahead to count birds that may dive.
• Large geographic areas cannot be covered quickly, as with aerial surveys (100s of km²), but smaller areas (10s of km²) can be efficiently covered.

Office Procedures

• Review the section, Conducting a Wildlife Inventory, in the introductory manual Species Inventory Fundamentals (No. 1).
• Select study areas from 1:20 000 or 1:50 000 maps, marine charts based on personal experience with the study area, and existing data.
• Determine Biogeoclimatic zones and subzones, Ecoregion, Ecosection, and Broad Ecosystem Units for census areas from maps.
• Select survey route and draw transect lines on maps.

Sampling Design

Stratified random sampling.

• Stratify habitat based on expected densities (low, medium, high) for the species under study and select survey routes.
• For large-scale studies, randomly select sample blocks from the three strata. For intensive studies, all areas will be traversed.
• When surveying "shoreline" transects, follow a contour 100-300 m from shore (distance to be determined onsite and depends on distance at which birds can be identified and counted).
• When surveying sample blocks in open waters navigate along straight lines within the sample block, ensuring that the entire sample block is covered but that transects do not overlap. Note that tidal currents can confound efforts to navigate.
• When surveying areas within discrete geographic boundaries, survey all available habitat.

Sampling Effort

• 50 to 100 kilometers of transects can usually be surveyed per day in small, fast boats.
• Repeat surveys several times during the season.
• Western Grebes - Annual monitoring is recommended for wintering and breeding population.
• Red-necked/Eared Grebes - Monitor colonies every 3-5 years. Monitor wintering populations annually?

Sampling Standards

Weather

• Surveys should not be conducted if the wind speed is over 25 km/hr, or during periods of rain, fog or snow.

Tides

• In estuaries, conduct surveys at mid to high tide, not at low tide.

Personnel

• An experienced boat operator is needed with knowledge of local waters and navigation techniques. Preferably they may also be able to act as navigator and backup observer.
• The survey crew (2-4 people) should be led by a biologist with excellent skills in identifying waterbirds. Other personnel must be experienced in identifying waterbirds. All personnel must have high tolerance for motion-sickness.

Equipment

• A suitable boat for local conditions (inflatables or small hard-hulled craft for surveys on lakes or nearshore marine waters; larger vessels for surveys in remote marine areas), with GPS or other positioning equipment on board (for surveys along marine coasts).
• Each observer must have 7-10x binoculars.
• Waterproof notebooks, data forms, mechanical pencils.
• Appropriate safety equipment (life-jackets or survival suits, flares, HF radio, spare fuel, emergency rations, etc.)

Field Procedures

• Survey routes should be traversed at speeds that allow complete identification and counting of birds within the transect width. Appropriate speeds will vary between 5-50 km/hr depending on numbers of birds present and water conditions. Choose a speed and navigate at that speed throughout the survey, but stop to count concentrations if necessary.
• One observer should count on each side of the boat out to a range of
  50-300 m, depending on the survey design and visibility. Transect widths of 100 m is suggested for grebes, but concentrations of Western Grebes should be counted and recorded if they are beyond 100 m.
• Record observations on data forms or in notebooks or on tape recorder (to be transcribed onto data forms after the survey).
• Monitor observer fatigue and take breaks as necessary to maintain sharpness.
• Map areas of concentrations (>10 birds for wintering B-RNGR, >20 birds for B-GBHE, >100 birds for wintering B-WEGR).

Data Analysis

• Enter all data into the Species Inventory datasystem.
• Densities can be calculated as outlined in Aerial Surveys.
• Relative and absolute abundance estimates can be made by determining total counts for specific locations, by calculating numbers of birds per unit area (density), or numbers of birds per km of transect (see Aerial Surveys).
• Data can be displayed as:
• mapped locations with relative abundance (i.e., different sized circles for various group sizes);
• tables comparing presence/not detected in different surveys, temporally or in geographic distribution; and
• for relative abundance, a table can show indices in birds/km.