A total of 5412 birds were documented during this
year’s survey. The 2007 total abundance was greater than the
1985-2007 average of 4991 birds (Figure 2). No BBS surveys were
conducted on the INL in 1992 or 1993. There were a total of 69
unique species (i.e., species richness) recorded during this year’s
survey. This year is above the average species richness of 59 for
all BBS routes combined. Of the remote routes, only Kyle Canyon is
slightly below the average of 25 species with 22 recorded this year,
and all other remote routes were above the average richness.
The Tractor Flats remote route had the greatest bird
abundance with 853 individuals observed (Table 1). Since 1985 the
Tractor Flats route has the greatest average abundance of all BBS
routes with mean bird abundance of 711 individuals. This year the
Tractor Flats route also contained the greatest species richness
with 30 different species recorded.
Horned lark (Eremophila alpestris) was the most abundant species
observed during the 2007 survey with 1416 individuals counted
representing 26 percent of all observations (Table 2). Horned Lark is
continually the most abundant species recorded during the INL BBS.
This species was observed on 83 percent (408) of the total stops made
during the entire survey.
The five most abundant birds are horned lark (n = 1416), western
meadowlark (Sturnella neglecta; n = 987), Brewer’s sparrow (Spizella
breweri; n = 528), sage sparrow (Amphispiza belli; n = 459), and
sage thrasher (Oreoscoptes montanus; n = 410). These five species
comprise over 72 percent of all observations made in 2007. These five
species were also the most abundant in the 2006 BBS survey, and were
observed on every remote and facility route surveyed. In the 21
years of INL breeding bird surveys, these five species have been the
most abundant 16 times, and are among the six most abundant species
recorded in all years. Horned larks, western meadowlarks, Brewer’s
sparrow, and Sage sparrows have all experienced significant
population declines in Breeding Bird Surveys across their range (Peterjohn
and Sauer 1999). Given the fact that many additional sagebrush
obligates are exhibiting population declines due to suspected
habitat loss and disturbance, it is encouraging to see consistently
high abundance among these species.
Rare Observations and Species of Special Concern
New species to the INL BBS have been found
throughout the duration of these surveys, and additional species
were added to the list this year. This survey yielded four new
species observations never recorded in prior surveys on the INL. A
single greater scaup (Aythya marila), bald eagle (Haliaeetus
leucocephalus), osprey (Pandion haliaetus), and turkey
vulture (Cathartes aura) were observed during the 2007 BBS.
The sagebrush steppe habitat on the INL is relatively pristine and
undisturbed and continually supports a high abundance of species
that are showing signs of decline in comparable areas in the western
U.S. There were six species observed during the 2007 BBS that have
been assigned an Idaho state ranking of critically imperiled or
imperiled (Idaho Conservation Data Center 2008) including greater
sage-grouse (Centrocercus urophasianus; n=4), ferruginous
hawk (Buteo regalis; n=8), long-billed curlew (Numenius
americanus; n=7), Franklin’s gull (Larus pipixcan;
n=178), Brewer’s sparrow (n=528), and the grasshopper sparrow (Ammodramus
savannarum; n=102).
Observed bird assemblage proportions can be
considered in the context of the habitat composition within a region
to provide useful insight about general ecological health. For
example, if a study area contains large shrubland and grassland
habitat patches and the corresponding bird assemblage observations
are low, this may be an indication the local population is
threatened or experiencing population declines.
The most abundant species assemblage was the shrub-steppe and
grassland category representing 59 percent of all BBS observations (Figure 3). The shrub-steppe and grassland bird assemblage always dominates
the observed bird abundance as the majority of the INL is composed
of shrub-steppe and grassland habitats. The second most abundant
species assemblage is sagebrush obligates representing 26 percent of all
observations. Given the regional concern for sagebrush obligate
species, it is encouraging to see that obligates are doing well on
the INL.
Shrub-steppe and Grassland
This species assemblage has always yielded the greatest number of
observations in past BBS and continues to dominate the observations
in 2007 with 3231 individuals representing 59 percent of the total
observations. Common shrub-steppe and grassland species include
horned lark, western meadowlark, brown-headed cowbird (Molothrus
ater), and vesper sparrows (Pooecetes gramineus). Horned lark (n =
1416) and western meadowlark (n = 987) were the most abundant
species within this assemblage, and were also the top two abundant
species for the entire survey. Horned lark abundance has steadily
risen across the INL as wildfire continues to impact and alter the
plant communities across the site converting shrub dominated
communities into more grassland dominated vegetation communities.
Sagebrush Obligates
The sagebrush obligate assemblage had the second
largest species abundance with 1401 individuals representing 26
percent of all observations. This assemblage contains four species
including Brewer’s sparrow, sage sparrow, sage thrasher, and greater
sage-grouse. Brewer’s sparrow was the most abundant sagebrush
obligate with 528 individuals counted. These data suggest that the
sagebrush obligates are thriving on the INL which contains fairly
undisturbed sagebrush-steppe habitat in the Intermountain west. In
many other western states, sagebrush obligates are facing
significant habitat loss and conversion, and consequently sagebrush
obligate species are showing population declines. The population
trend across the INL shows a consistent high abundance of sagebrush
obligates (Vilord 2007).
Raptors and Corvids
The raptor and corvid assemblage contained 193
observations representing 4 percent of the total observations.
Twelve species of raptors (eagles, hawks, falcons, and owls) were
recorded. Red-tailed hawk (Buteo jamaicensis) was the most
abundant raptor species detected with 39 individuals, and marks the
highest abundance ever recorded for this species during the INL BBS.
Other notable observations include the first INL BBS records for
bald eagle, osprey, and turkey vulture.
The Corivdae family includes ravens and crows, magpies, and jays.
The common raven (Corvus corax) was the most abundant species
within this assemblage with 89 individuals. The raven population on
the INL has shown a steady increase and the 2007 raven abundance
ties 2005 for the highest numbers ever recorded. Recent research has
shown that ravens negatively impact sage-grouse nest success (Coates
2007), and the continued increase in raven abundance may become a
concern as sage-grouse populations exhibit declines across the
western U.S.
Urbanized and Exotics
This species assemblage represents birds associated
with urban or human-altered environments, and are most commonly
found around facilities. Example species include European starling (Sturnus
vulgaris), rock pigeon (Columba livia), and American
robin (Turdus migratorius). This assemblage constitutes 4
percent of the total observations in 2007 with 210 total
individuals. Barn swallows (Hirundo rustica) were the most
abundant species in this assemblage with 75 individuals followed
closely by European starlings with 57 individuals.
Waterfowl
Waterfowl are commonly reported on the BBS despite
the fact the INL contains very little standing water. With the
exception of the ephemeral and sporadic presence of the Big Lost
River and Sinks wetland, the only standing water bodies on the INL
consist of wastewater treatment ponds found near facilities. These
man-made ponds serve as stopover locations for migrating birds and a
number of different species have been observed using these sites
since 1985.
There were nine waterfowl species documented with an abundance of
149 individuals representing about 3 percent of the total
observations. The number of waterfowl observations was primarily
driven by a single large flock of Canada geese (n = 95) from the
Test Area North (TAN) survey route. Many species within this
assemblage included only a few individuals and contributed the
lowest assemblage proportion of total bird observations.
Shorebirds
The shorebird
assemblage including grebes, gulls, and waders had low combined
abundance with eight species detected this year. There were a total
of 228 individuals representing 4 percent of the total BBS
observations. Due to the lack of standing water across the INL, most
observations within the shorebird assemblage occurred in proximity
to waste ponds at facilities. The total number of observations was
influenced by two large flocks of Franklin’s gulls (60 and 81 birds)
counted along the Tractor Flats route representing 62 percent of all
shorebird observations. The close proximity of the Tractor Flats
route to Mud Lake agricultural areas can explain why so many gulls
were observed. Without the inclusion of Franklin’s gull, this
assemblage would only contribute about 1 percent of all
observations.
