Abundance - A total of 5,974 individual birds
were recorded along the 13 survey routes. This is above the annual
mean of 4,970 birds (no surveys were conducted in 1992 or 1993.
Approximately 68 mi2 (177 km2) total area was
surveyed (Table
1) during the BBS, representing approximately 8 percent of the INL.
Total bird abundance on the INL varied significantly among years
(p=1.2-07) with the greatest number of birds observed in 1998 (n=6805)
and the lowest in 1988 (n=2119).
During the 2006 BBS approximately 10 mi2
(25 km2) was surveyed and an average of 27 birds was seen
per 0.4 mi2 (1 km2) on each remote route. The
Tractor Flats route continues to have the highest density of birds
with 31 birds detected per 0.4 mi2 (1 km2) (Table
1). Bird abundance on remote routes varied significantly from 1985
to 2006 (p=3.7-07). The highest number of birds recorded on remote
routes was counted during the 1998 BBS with 3,638 (Figure
2). The fewest number of birds recorded on the remote routes was
in 1988 with only 1,092 (Figure
2).
A significant difference in bird abundances (p=0.0005)
is also detected between the five remote routes. The Tractor Flats
route has on average the greatest number of individuals (n=704) seen
per year as well as the greatest fluctuations over time (Figure
3).
The area surveyed on the eight facility complex routes
range from approximately 1.5 mi2 (4 km2) at MFC,
NRF, and RWMC to more than 4.6 mi2 (12 km2) at
TAN. This is a total of roughly 20 mi2 (52 km2)
surveyed at the facilities. Total bird abundance on facility routes
varied significantly from 1985 to 2006 (p=4.92-04). In 1998 bird
numbers peaked on facility routes with 3,167 birds counted. Only 1,027
birds were detected in 1988, the fewest numbers of birds recorded on
the facility routes. The highest density of birds observed per 0.4 mi2
(km2) on a facility route during the 2006 BBS was at NRF
which averaged 66 birds. The area surveyed on each facility routes
differs, so comparisons between facility routes are not analogous.
Horned larks (scientific names of all species are
provided in
Table 2) were the most abundant species recorded on the INL during
2006. Horned larks totaled 27 percent of all birds counted, occurred
on all routes, and on more than 85 percent of stops (Table
2). Other common species include western meadowlark, Brewer’s
sparrow, sage thrasher, and sage sparrow, each of which occurred at
more than 200 stops along all 13 routes (Table
2). These five species account for approximately 71 percent of all
birds counted. The common raven and brown-headed cowbird also occurred
along each of the 13 routes but with lower abundances. Mourning dove
and vesper sparrow occurred in high numbers but were only recorded on
12 of the 13 routes.
The high numbers of birds counted in 2006 does not
necessarily reflect large numbers of birds counted among all taxa.
Many species observed were neither widespread nor abundant. Of the 66
species recorded in 2006, 18 species (27 percent) occurred along only
one of the 13 routes, and 34 species (51 percent) were represented by
fewer than ten individuals (Table
2).
Additionally, many species were at or below long-term
averages and a few species observed frequently in previous years were
absent in 2006 including: bank swallow, eastern kingbird, and mountain
bluebird as well as many waterfowl and wading species. Instead, the
total count was inflated by high counts of horned lark and western
meadowlark. Several species recorded during 2006 do not actively nest
on the INL, including Canada goose, and Franklin’s gull. The six most
numerous species in order of abundance were horned larks, western
meadowlarks, Brewer's sparrows, sage thrasher, and sage sparrows and
mourning dove. More than 76 percent of all birds detected in 2006 are
the above six species. Appendix B
contains a list of species observed and their relative abundance along
the 13 survey routes.
Species Richness - In 2006, 66 species were
detected during the surveys. Although there were slightly fewer
species observed than in 2005 (Figure 3) it is above the average of 58
(SE=1.8) recorded from 1985 to 2005. In 2006, the mean number of
species per route was 25 (SE=0.9), with many similar species recorded
along remote routes (mean=25 SE=1.8) and facility routes (mean=24
SE=0.9). The fewest number of species (19) was observed along the PBF
route while the Tractor Flat route had the greatest number of species
(31).
Species richness varied significantly from 1985 to
2006 (p=1.9-14). On average, more species (mean=25) were observed per
route during the 2006 survey than in previous years (Figure
4). The fewest number of species per route (mean=15) was observed
during the 1987 BBS. Data analysis also showed a significant
difference in the number of species between all routes (p=1.2-15),
remote routes (p=1.8-08), and facility routes (p=2.3-08). The greatest
average annual number of species occurred on the Kyle Canyon route
(mean=25.4) while the PBF route (mean=15.3) had the least number of
species detected.
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 - Seven species of waterfowl (order
Anseriformes, family Anatidae) were observed during the 2006 survey
which contributed approximately 1 percent (Figure
5) to the total individuals observed. Even though Canada goose
was the most abundant species only a single flock was observed
flying over TAN. 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 observed at the facility
wastewater treatment ponds or in transit to nearby areas where water
is more abundant. Although water was present in the river channel of
the Big Lost River during the 2006 BBS, it was not abundant enough
to reach the Big Lost River Sinks or the Spreading Area near RWMC.
Shorebirds, Grebes, Gulls, Pelicans and Waders – Five species
of shorebirds/gulls, terns/grebes/pelicans and wading birds were
observed (Table
2). Of these, Franklin’s gull and long-billed curlew were only
observed on the Tractor Flat route. American coot, killdeer,
Wilson’s phalarope, and willet were observed only on facility
routes.
Like waterfowl, many shorebirds and wading birds are
closely tied to water, which is available at waste-water ponds near
facilities, natural waterways (The Big Lost River, Sinks, and
Spreading Areas), and adjacent agricultural fields. Shorebirds/gulls
and terns/grebes/pelicans and wading birds represent 1 percent of
all individual birds observed (Figure
5).
Raptors and Corvids - Ten species of raptors
(eagles, falcons, hawks, and owls) were observed along the survey
routes. Red-tailed hawk was the most abundant species on both
facility (n=10) and remote routes (n=24) and in the greatest numbers
since 1986 when 35 red-tails were recorded. The second observation
of a Merlin seen during a BBS route was recorded in 2006. Both were
spotted on the Kyle Canyon route.
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=77) and were observed on all routes. More ravens
were observed on remote (n=43) than facility (n=34) routes. Raptors
and corvids constituted 3 percent of the total individuals observed
(Figure
5).
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. European starlings, Say’s
phoebes, house sparrows, and rock pigeons were only observed on
facility routes. Although barn swallows, American robins, and house
finches were observed on both facility and remote routes they
occurred in much smaller numbers on the remote routes. Urbanized and
exotic species made up 4 percent of all individual birds observed
during the 2006 survey (Figure
5).
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 Kyle Canyon route during the 2006 survey
(Table 3). Over the long term, sagebrush obligates occurred most
often on the Big Lost River route, but since the 2000 Tin Cup fire
their numbers have dramatically declined. Brewer’s sparrow was the
most abundant sagebrush-obligate species on both remote and facility
routes (Table
3). Twenty-eight percent of the total number of birds observed
during the 2006 Breeding Bird Survey was sagebrush obligates (Figure
5).
Other Common Shrub-steppe/Grassland Species -
Common shrub-steppe/grassland species that occur on the INL include
horned lark, western meadowlark, Brewer’s blackbird, brown-headed
cowbird, common nighthawk, mourning dove and vesper sparrow. Of all
individual birds observed, more than 60 percent are
shrub-steppe/grassland species (Figure
5). 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 NRF. Horned lark
and western meadowlark were the most common species recorded and
occurred on all routes. Although, horned lark populations dropped
from record numbers recorded in 2005 horned larks are still greater
than in years preceding wildfires that occurred across the INL
landscape during the mid 1990’s and early 2000’s (Figure
7).
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. In
February of 2006 the U.S. Fish and Wildlife Service accepted the
Idaho Comprehensive Wildlife Conservation Strategy (CWCS) submitted
by Idaho Department of Fish and Game (2005). The aim of the CWCS is
to provide a long-term approach for the benefit of Species of
Greatest Conservation Need (SGCN). The CWCS evaluated all animals
thought by experts to be a candidate for SGCN. Even though species
identified in their list contained many previously considered
species of concern, several species were not listed such as
loggerhead shrike, lark bunting, and northern mockingbird. Species
that are new to this list include Brewer’s sparrow, short-eared owl,
and Wilson’s phalarope. Nine species indicated as SGCN were recorded
during the 2006 BBS. These species include Brewer’s sparrow (794),
sage grouse (46), Franklin’s gull (41), ferruginous hawk (10),
western burrowing owl (5), long-billed curlew (5), short-eared owl
(4), Wilson’s phalarope (4), and Merlin (1). This is only the second
year that a Merlin was observed during the annual BBS.
