Abundance -
A total of 6,726 individual birds were recorded along the 14
survey routes (Figure 2). This is above the annual mean of 4,917
birds (no surveys were conducted in 1992 or 1993).
Horned larks (Eremophila alpestris) were
the most abundant species recorded on the INL during 2005.
Horned larks comprised of more than 30 percent of all birds
counted, occurred on all routes, and on 87 percent of stops
(Table1a,1b, 1c).
Other common species were western meadowlark (Sturnella
neglecta), Brewer’s sparrow (Spizella breweri), and
sage thrashers (Oreoscoptes montanus), each of which
occurred at more than 300 stops along all 14 routes (Table1a,1b, 1c).
These four species account for approximately 65 percent of all
birds counted. Mourning doves (Zenaida macroura) and
brown-headed cowbirds (Molothrus ater) also occurred
along each of the 14 routes but in smaller numbers than the
preceding species. Although sage sparrows (Amphispiza belli)
were the fifth most abundant bird recorded during 2005, it only
occurred on 13 of the 14 routes.
The high numbers of birds counted in 2005,
however, does not necessarily reflect large numbers of birds
counted among all taxa. Many species observed were neither
widespread nor abundant. Of the 71 species recorded in 2005, 20
species (28 percent) occurred along only one of the 14 routes,
and 37 species (52 percent) were represented by fewer than ten
individuals (Table1a,1b, 1c).
Additionally, many species were at or below long-term averages
and a few species observed in six or more previous years were
absent in 2005 including: bank swallow (Riparia riparia),
northern shoveler (Anas clypeata), and American avocet (Recurvirostra
americana). Instead, the total count was inflated by high
counts of horned lark and western meadowlark. Several species
recorded during 2005 do not actively nest on the INL. These
include American white pelican (Pelecanus erythrorhynchos),
Franklin’s gull (Larus pipixcan), ring-billed gull (Larus
delawarensis), mountain bluebird (Sialia currucoides),
and rough-legged hawk (Buteo lagopus).
Overall, 14 routes were surveyed on the INL with
approximately 180 km2 total area surveyed (Table 2).
This represents about 8 percent of the INL. Each remote route
surveyed an area of approximately 25 km2 with an
average of 27.9 birds observed per km2. The Tractor
Flat route continues to have the highest density of birds with
33.3 birds observed per km2. The area surveyed on the
nine facility complex routes ranged from 3 km2 at WTF
to more than 12 km2 at TAN. This is a total of
approximately 55 km2 surveyed at the facilities. The
highest density of birds observed on a facility route was at MFC
which averaged 101 birds observed per km2. This
number was inflated due to the large number of Franklin’s gulls
observed during the survey using the man-made ponds at MFC. The
area surveyed at each stop on remote routes is greater than the
area surveyed at each stop on the facility routes, so
comparisons between facility and remote routes are not
analogous. Appendix A contains a
list of species observed and their relative abundance along the
14 survey routes.
Overall, the five most numerous species in order
of abundance were horned larks, western meadowlarks, Brewer's
sparrows, sage thrasher, and sage sparrows. More than 70 percent
of all birds detected in 2005 are the above five species, which
are typically the most frequently counted species on the INL.
Species Richness - In 2005, 71 species were detected
during the surveys. This is the greatest number of species
recorded during a breeding bird survey at the INL (Figure 3) and
is well above the average of 57
± 4
recorded from 1985-2004. In 2005, there were 24
± 3
species per route, with many similar species recorded along
remote routes (25
± 7)
and facility routes (24
±
4). The fewest number of species (N=16) was observed along the
Circular Butte route while TRA had the greatest number of
species (N=36).
Species assemblages - In addition to the
density of individuals and the number of species recorded on the
INL, the composition of species in relation to habitat is an
important indicator to ecological health.
Waterfowl - Nine species of waterfowl
(order Anseriformes, family Anatidae) were observed during the
2005 survey which contributed <1 percent (Figure 4) to the total
individuals observed. Gadwall (Anas Strepera) was the
most abundant species and occurred along five of nine facility
routes. Waterfowl have limited distribution on the INL and occur
either in natural areas along the Big Lost River or in man-made
ponds near facilities. Waterfowl counts at the INL were slightly
below the long term average and only observed at the facility
wastewater treatment ponds. Natural waterways located on the INL
(The Big Lost River, Sinks and Spreading Areas) have not
contained water since summer of 1999, thus reducing the number
of birds that would otherwise use these areas.
Shorebirds, Grebes, Gulls, Pelicans and Waders – Eight
species of shorebirds/gulls and terns/grebes/pelicans and wading
birds were observed (Table1a,1b, 1c). Of these, only three were
observed on remote routes, three were only observed on facility
routes, and the other two occurred along both types of routes.
The most abundant was Franklin’s gull which was observed along
one remote and one facility route. This was the first time the
American white pelican was documented on the INL during the
annual BBS. Pelicans typically nest on a low mound of earth and
debris on a marshy island and occasionally on rocky islands in
desert lakes. Therefore these birds were most likely migrating
through the INL. No wading birds were observed during the 2005
survey.
Like waterfowl, many shorebirds and wading birds
are closely tied to water, which is currently only available at
waste-water ponds near facilities or adjacent agricultural
fields. Shorebirds/gulls and terns/grebes/pelicans and wading
birds represent 3 percent of all individual birds observed
(Figure 4). This number is inflated due to the large number of
Franklin’s gulls observed migrating through the INL.
Raptors and Corvids - Nine species of
raptors (eagles, falcons, hawks, and owls) were observed along
the survey routes. One percent of all birds counted were raptors
(Figure 4). Red-tailed hawk (Buteo Jamaicensis) and
ferruginous hawk (Buteo regalis) were the most abundant
species on both facility (N=6 and 5) and remote routes (N=13 and
10). Although common during the winter, rough-legged hawks were
observed for the first time during the 2005 BBS. We presume that
these individuals were just passing through to the breeding
grounds farther north.
Corvidae is a family of birds which contains the ravens and
crows (Genus Corvus), magpies (Genus Pica), and
jays (Genus Perisoreus, Gymnorhinus, and
Nucifraga).
Common ravens (Corvus corax) were the most abundant
corvid (N=89) and were observed on all routes. More ravens were
observed on remote routes and raven populations continue to
increase across the INL (Figure 5). Raptors and corvids
constituted 2 percent of the total individuals observed
(Figure 4).
Urbanized and Exotic Species - Species
associated with human activities (introduced species, or species
associated with human-altered landscapes) typically occur on
facility routes rather than remote routes. House sparrow (Passer
domesticus), house wren (Troglodytes aedon), American
robin (Turdus migratorius), and rock pigeon (Columba
livia) were only observed on facility routes. Although barn
swallow (Hirundo rustica), house finch (Carpodacus
mexicanus), and European starlings (Sturnus vulgaris)
were observed on both facility and remote routes they occurred
in much smaller numbers on the remote routes. Urbanized and
exotic species made up 2 percent of all individual birds
observed during the 2005 survey (Figure 4).
Sagebrush Obligates - Even though
sagebrush obligate numbers continue to be below the long term
average, the trend in population abundance remains stable for
both facility and remote routes (Figure 6).
On remote routes, sagebrush obligates were most often observed
(per km²) on the Tractor Flat route during the 2005 survey. Over
the long term, sagebrush obligates occurred most often on the
Big Lost River route, but since the 2000 Tin Cup fire their
populations have dramatically declined. Brewer’s sparrow was the
most abundant sagebrush-obligate species on both remote and
facility routes (Table 3a,
3b). Twenty-four percent of the total
number of birds observed during the 2005 Breeding Bird Survey
were sagebrush obligates (Figure 4).
Other Common Shrub-steppe/Grassland Species
- Common shrub-steppe/grassland species that occur on the INL
include horned lark, western meadowlark, Brewer’s blackbird (Euphagus
cyanocelphalus), brown-headed cowbird, common nighthawk (Chordeiles
minor), mourning dove and vesper sparrow (Pooecetes
gramineus). Of all individual birds observed during the
2005, more than 54 percent are shrub-steppe/grassland species (Figure 4).
Although more shrub-steppe/grassland species were observed on
remote routes, the number per km² was much greater on facility
routes with the most species observed per km² at MFC. Horned
lark and western meadowlark were the most common species
recorded and occurred on all routes. Although horned lark
populations appear to be stabilizing they continue to increase
across the INL and have reached record numbers on both facility
and remote routes (Figure 7). This increase is likely the result
of a land cover change from shrub-steppe to grasslands caused by
wildfires.
Species of special concern - The
sagebrush steppe habitat on the INL continues to support species
of birds that are low or declining in number throughout the
Intermountain West. Species of special concern are more often
observed on remote routes than facility routes. Nine species
with a state rank of rare or uncommon, imperiled, or critically
imperiled recorded in 2005 including American white pelican
(N=6), ferruginous hawk (N=15), long-billed curlew (Numenius
americanus) (N=9), Franklin’s gull (N=123), ring-billed gull
(N=2), western burrowing owl (Athene cunicularia) (N=4),
loggerhead shrike (Lanius ludovicianus) (N=40), northern
mockingbird (Mimus polyglottos) (N=1), and lark bunting (Calamospiza
melanocorys) (N=4). This is the first year that the American
white pelican was observed during the annual BBS. Although
Franklin’s gull was the most abundant species of special concern
during the 2005 survey, they are closely tied to cicada hatches
on the INL and agricultural fields where they spend time
foraging. The most common and routinely observed sensitive
species are loggerhead shrike, ferruginous hawk and long-billed
curlew whose populations have remained stable or slightly
decreased since the BBS began in 1985 (Figure 8).
