River habitat characterization
Physical variables describing the river and riparian zone at each site
were recorded alongside bird surveys to capture information on river
channel structure, flow character, bank structure, riparian vegetation
and adjacent land use following methods developed by Sinha et al. (2019)
after Raven et al. (1997). Observations were made at two different
scales, respectively: (i) perpendicular transects or ‘spot checks’ at 10
points every 50 m along each 500 m reach specifically recording
progressive lateral changes at each point in flow character and habitat
features from the channel to the riparian zone; (ii) ‘sweep up’
assessments that recorded features over the whole 500 m survey site. The
resulting data blended quantitative and semi-quantitative methods, for
example with features recorded as present (<33% of the survey
reach) or extensive (>33%), or on a six-point scale
(rare:1–20% cover; occasional 21–40%; frequent 41–60%; abundant
61–80%; dominant 81–100%). A more extensive description of the
variables recorded and their ability to detect variations among
locations is provided by Manel et al. (2000).