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Unfortunately we can only make very gross
comparisons between our two studies because we
did not use the same survey methods and exactly
the same area. Yet a number of species and
communities were quite different between the two
studies. We found 14 species that Russell and
Johnson did not find and they found 62 species that
we did not find (Appendix C). We found blackthroated
sparrow to be among the most common
species in the oak-juniper woodland, but Russell
and Johnson did not find them to be very abundant
(Appendix G). Conversely, in Siphon Canyon, they
found black-chinned hummingbird to be the most
common species, whereas it was among the least
common species in 2003 and was not found at all
in 2004 (Table 4.3). There is little indication of a
regional population decline in this species (Sauer et
al. 2004), though banding data from Hummingbird
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Monitoring Network sites is showing some decline
for 2005 (Larry Norris, pers. comm.). Nevertheless,
the decline that we saw may have been an artifact
of different field methods; species such as
hummingbirds may be more conspicuous while
walking a transect line.
During the non-breeding season the
mesquite-grassland vegetation community had the
most bird species that did not rank as abundant for
the other study (Appendix G). This may have been
an artifact of small sample size from both studies.
It could also reflect the variability of non-breeding
season birds. For example, species such as whitecrowned,
black-throated, Brewer’s, and chipping
sparrows can form large, sometimes mixed-species
flocks which, if encountered, can radically affect
the relative abundance estimates for a transect.