3.6 River Shoreline Surveys (Breeding Pairs/Broods for All Species)
Recommendations: Walking alongside the river may be the most practical method to inventory breeding pairs and find nests and broods, for short rivers or sections of rivers. Walking surveys are recommended at the watershed level scale. For larger and longer rivers, surveys from a watercraft (raft, kayak, etc.) are recommended where navigation is not difficult. Walking and watercraft river surveys are recommended for all species during the breeding season to determine presence/not detected (possible) and relative abundance. Driving on roads that are beside rivers, watching for birds, and stopping to scan at convenient lookouts may also be used if roadside visibility is good. This technique can be used to determine presence for all three riverine species, but can only be used to determine relative abundance for harlequins and kingfishers. Roadside surveys along rivers are recommended at the watershed level scale.
Breeding pairs, individuals, or broods of riverine birds can be detected by walking along the shores of rivers. This method has essentially the same assumptions as the line transect method (Emlen 1977). Birds are relatively easily detectable on smaller systems because of the close range of the observer, although they can fly or swim past unnoticed if observers are not constantly watching the river. Riverine birds are constantly moving up and down the river so observers need to note the direction and numbers of birds moving past. Dippers and kingfishers can often be heard before they are seen which increases detection rates. Some rivers are easily walked but many, especially those in rugged terrain, are not. Marked birds can enhance population estimates.
Harlequins are relatively stationary during the pre-laying period and tend to not move very far, or to other rivers (Bengtson 1972). They are still difficult to detect because of their secretive behaviour and Cassirer and Groves (1994) noted that walking surveys under-estimate the number of breeding pairs by 25-35%. Both kingfishers and dippers are territorial, move actively up and down rivers within their territories, and are relatively easily detected.
Walking along rivers is the best method of censusing dippers (Price and Bock 1983). Price and Bock suggest that one person wade if possible, to help locate hiding birds. They also suggest throwing rocks into dense bushes during high waters and pounding ice ledges with poles, as most hiding birds would flush and be detected (Bakus 1959). Note that dippers are polygamous, males may have one or two mates, which confounds estimates of breeding populations.
Kingfishers may nest away from the river if nest sites are limited, so surveyors may miss birds if they are not foraging or resting along the river. During incubation, they are relatively secretive and less detectable. Kingfishers may be most detectable when adults are making frequent trips to the nest to feed nestlings (M.J. Hamas pers. comm.).
Family groups of riverine birds are visible along the river for various lengths of time. Brood counts are feasible for all species but different breeding chronologies mean it will be difficult to time surveys when all three species will have broods. Brood counts for harlequins have been routinely conducted in many areas (Bengtson 1971; Hunt 1993; Cassirer and Groves 1994). Timing of counts is important if only one survey is to be conducted: brood counts should be conducted when most harlequin females are likely to have broods. Broods have been found in British Columbia between 16 June and early September, with most found from 10 July to 13 August (Campbell et al. 1990a).
Local knowledge of rivers and the birds present there is necessary before embarking on labour-intensive walking surveys (R. Ydenberg pers. comm.). Dippers occur in most fast streams with whitewater. Kingfishers prefer slower streams with cutbanks for nesting. Harlequins are patchily distributed in different geographic regions. Helicopter transport to survey areas can greatly increase efficiency when surveying remote locations.
This method is useful for all three riverine species for determining presence, and relative and absolute abundance on short rivers or sections of rivers. If surveys are repeated, then estimates of breeding success and brood survival may be possible.
Virtually the same technique as above but observers are in boats rather than walking. Breeding pairs can be detected relatively easily, but observations in difficult sections of the river can be impaired by attention being concentrated on getting downstream safely, rather than looking for birds. This method is most feasible in medium-sized rivers where navigation is not difficult. Long distances can be covered, much more rapidly than on foot (D. Genter pers. comm.). Rafting with one person rowing, and one person looking for birds is best.
This method involves driving along roads beside rivers, watching for birds, and stopping to scan at convenient lookouts. It is a useful method in situations where sections of river are visible from roads and the route is frequently travelled (i.e., high number of samples). Harlequins, kingfishers, and dippers can all be detected by this method, in that order of efficiency. At normal driving speeds harlequins will stand out more easily than kingfishers, which will be more visible than dippers. Even though all sections of a river may not be visible, an index of relative abundance and/or presence can be determined.
Four potential biases in this method include: 1) river flow rates (which depend on rate of melting and size of snow pack) which may affect distribution of birds on the river, 2) seasonal or temporal effects related to presence and activity of males and females, 3) habitat used for loafing or foraging (i.e., when birds may be most visible) may not occur along sections visible from roads, and 4) timing will affect visibility depending on the extent of deciduous foliage that has emerged. For example, harlequin males may move to mouths of rivers during the incubation period, and may be joined by females in early evening (I. Goudie pers. comm.). Dippers and kingfishers, however, tend to stay within their territories until young fledge.
Assuming that the quality of habitat does not change, then changes in numbers detected can be assumed to indicate changes in population sizes, rather than movements of birds to areas of the river that are not observed. This method is currently being used, in Jasper National Park, for monitoring the number of harlequin breeding pairs along streams that have roads beside them (B. Hunt pers. comm.).