Vascular Plant and Vertebrate Inventory of Saguaro ... - USGS

Figure 5.2. Location of section breaks for non-breeding season (winter) bird transects and nocturnal
survey stations, Saguaro National Park, Rincon Mountain District, 2001 and 2002.
one-minute intervals beginning at the start of
the active period), and the sex and/or age class
(adult or juvenile), if known. We did not measure
distances to birds that were flying overhead
nor did we use techniques to attract birds (e.g.,
“pishing”). We made an effort to avoid doublecounting
individuals. If we observed a species
during the “passive” count period (between
the eight-minute counts), which had not been
recorded previously at a station on that visit, we
recorded its distance to the nearest station.
Effort
In 2001, we spent more effort surveying at
focal-point stations (n = 272) than at non-
48
random stations (n = 160; Table 5.2). In 2002
we surveyed exclusively at non-random stations,
both repeat-visit (n = 130) and reconnaissance (n
= 107). In both years the number of stations and
visits varied among transects except for random
transects, which had four stations that we visited
four times in 2001 (Table 5.2).
Analysis
Relative Abundance. We calculated relative
abundance of each species along each transect as
the number of detections at all stations and visits
(including zero values) and divided by effort
(total number of visits multiplied by total number
of stations). We reduced our full collection of