3.2.3 Weather

Table 5. Acceptable weather conditions for surveying for waterfowl and their allies.

Weather	Ground & Boat	Aerial
Wind	<10 km/h ( <3 Beaufort scale)	Not >25 km/h ( <5 Beaufort scale)
Precipitation	No rain or fog	No rain or fog
Visibility	>10 km	Overcast sky preferred
Seas	<1.5 m in height, no whitecaps ( <3 Beaufort scale)	Smooth ocean surface preferred ( <3 Beaufort scale)

3.2.4 Transportation

Ground Surveys

Advantages:

• Easier to detect birds and to distinguish species, age and sex classes on the ground than from the air; therefore, counts are more accurate especially for breeding birds, which are more difficult to detect (because they occur at relatively low densities on wetlands partly covered in emergent vegetation); and
• A quiet approach on foot causes less disturbance to birds than an aerial survey.

Disadvantages:

• Study area must be accessible by road if vehicles are used;
• Slower method, therefore it is not possible to cover as large an area as covered by air; and
• Birds flushed between basins or observations stations may be double counted.

Aerial Surveys: Fixed-wing

Advantages:

• Most efficient way to obtain extensive coverage of open habitat; and
• The only way to survey inaccessible regions.

Disadvantages:

• Difficult to detect birds from the air (depending on plumage colour and glare) (Stott and Olsen 1972);
• Difficult to obtain accurate estimates of large flock sizes;
• Repeated surveys are highly variable (not precise) (Briggs et al. 1985);
• Species, age and sex classes can be difficult to distinguish from the air; and birds may respond to aircraft by flying, diving or hiding, e.g., adult Trumpeter Swans seek cover in tall emergent vegetation and cygnets clump into a tight group which can make it difficult to count individuals (Shandruk and McCormick 1989); Goldeneye and Red-breasted Mergansers consistently flushed when they were approached by low-flying aircraft (Stott and Olsen 1972); loons, grebes, goldeneye and scoters often dive when approached by an aircraft over the ocean (Summers, pers. comm.).

Aerial Survey estimates are very sensitive to transect width, altitude, glare and flight speed; therefore, it is important to conduct surveys consistently (Caughley 1974; Briggs et al. 1985).

Aerial Surveys: Helicopter

Helicopters can be used (1) as an alternative survey method to ground searches, boat searches, or multiple observation stations, or (2) as an alternative aircraft to fixed-wing for aerial transect surveys.

As a survey method, helicopters are recommended to survey breeding pairs and broods in locations inaccessible by road (e.g., Boreal Forest, northwest BC). Complete counts by helicopters or from the ground over smaller portions of the study area can be used to derive correction factors for transect surveys made from fixed-wing aircraft.

When used as an aircraft for transect surveys, helicopters enable more accurate counts than fixed-wing aircraft (Shandruk and McCormick 1989). Compared to fixed-wing, the improved visibility, lower flight speed, greater manoeuverability, and variable flight heights of helicopters improve the ability of observers to detect birds (Ross 1985) when used for presence/not detected surveys. For relative or absolute abundance surveys, flight speed and height would be standardized. Unfortunately, the limited range and greater operating costs (at least double the cost of fixed-wing) limit their use in surveys. More information is provided later as to the circumstances under which helicopters are preferred to fixed-wing aircraft for conducting transect surveys.

Boat Surveys

Advantages:

• More area is covered in a shorter period of time from a motor boat or airboat than from the ground;
• On open water, a boat survey allows a more prolonged or closer view of birds than air or ground surveys, respectively; therefore, it is easier to distinguish species, age and sex classes than from the air or ground;
• In wetlands surrounded by thick emergent vegetation, a canoe or kayak allows better access to birds; and
• It is possible to collect data on habitat characteristics (e.g., sample water quality, invertebrates, temperature) while surveying birds.

Disadvantages:

• Birds flushing ahead may be double counted, exaggerating apparent densities (Tasker et al. 1984); chance of double counting birds that flush ahead is higher in slow moving boats;
• Birds (e.g., loons) may respond to close approach by flying or diving (boats may disturb birds);
• More time consuming and covers less ground than aerial surveys;
• Can not use high powered scopes because of vibrations and movement; and
• Limited view from low perspective in smaller boats.

3.2.5 Survey Design Hierarchy

Waterfowl surveys follow a sample design hierarchy which is structured similarly to all RIC standards for species inventory. Figure 1 clarifies certain terminology used within this manual (also found in the glossary), and illustrates the appropriate conceptual framework for a survey for grebes and coots using observation stations. A survey set up following this design will lend itself well to standard methods and RIC data forms.

Figure 1. RIC species inventory survey design hierarchy with examples.