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

Chapter 5: Bird Inventory
Brian F. Powell
Previous Research
There has been considerable bird research at the
Rincon Mountain District, but no comprehensive
and well-documented inventory has been
completed. Monson and Smith (1985) compiled
a checklist for both districts of the park, but there
is no documentation of the data used to create
that list. The list includes abundance categories
for each major vegetation community and this
information was likely based on Gale Monson’s
extensive knowledge of the distribution and
relative abundance of birds in similar vegetation
communities in the region.
A few studies have investigated
songbird community composition in the Sonoran
desertscrub on the west side of the district near
the Cactus Forest Loop Drive (Johnson and
Haight 1991, see also Mannan and Bibles 1989)
and in the Rincon Valley (Boal and Mannan 1996,
Freiderici 1998, Powell 1999, 2004). Only two
multi-species, non-raptor studies have taken place
in the higher elevations of the district (Marshall
1956, Short 2002) and no research has taken
place in the mid-elevation areas of the district or
on the east slope of the Rincon Mountains. In the
1980s the park was concerned about the impact of
non-native cavity-nesting birds on native species
and they commissioned studies to investigate
this (Mannan and Bibles 1989, Kerpez and Smith
1990). Because of the active fire management
program, park personnel have been interested
in the effects of fire on the Mexican spotted owl
(Willey 1998) and songbirds (Short 2002) in the
high elevation areas of the district. The park
contracted for periodic raptor surveys (Felley and
Corman 1993, Berner and Mannan 1992, Bailey
1994, Griscom 2000). Park personnel surveyed
three Breeding Bird Atlas blocks within the
district (Short 1996) and those results are reported
in Corman and Wise Gervais (2005). The Tucson
Bird Count includes three low-elevation sites in
the park, including Rincon Creek (TBC 2005).
Single species studies have included the elf owl
(Goad and Mannan 1987, Steidl 2003), Mexican
spotted owl (Willey 1997, 1998b, Anderson
45
and Schon 1999, Steidl and Knipps 1999), buffbreasted
flycatcher (Conway and Kirkpatrick
2001; they also noted other species; Kirkpatrick
et al. 2006), and purple martin (Stutchbury 1991).
Park personnel survey periodically for the cactus
ferruginous pygmy-owl and Mexican spotted
owl and park staff file annual reports to the U.S.
Fish and Wildlife Service (Saguaro NP, unpubl.
reports) on monitoring and relevant management
activities related to these species.
Methods
We surveyed for birds at the Rincon Mountain
District from 2001 to 2003, though most of our
surveys took place in the springs of 2001 and
2002. We used four field methods: (1) variable
circular-plot (VCP) counts for diurnal breeding
and spring migrant birds, (2) nocturnal surveys
for owls and nightjars (breeding season), (3) line
transects for diurnal birds in the non-breeding
season, and (4) incidental observations for all
birds in all seasons. Although line-transect
surveys were not included in the original study
proposal (Davis and Halvorson 2000), we felt
they were important in our effort to inventory
birds at the district because many species that
use the area during the fall and winter may not
be present during breeding-season surveys.
Nevertheless, we concentrated our primary
survey effort on the breeding season because bird
distribution is relatively uniform in that season
due to territoriality (Bibby et al. 2002). Our
survey period included peak spring migration
times for most species, which added many
migratory birds to our list.
We sampled vegetation around most
VCP stations. Vegetation structure and plant
species composition are important predictors of
bird species richness or the presence of particular
species (MacArthur and MacArthur 1961, Rice et
al. 1984, Strong and Bock 1990). In this report
we use these data to categorize and describe bird
communities. These data will also be useful for
habitat association studies (e.g., Strong and Bock
1990; see Appendix H for results).