Breeding Bird Survey Results 2003

Abundance
The 2003 Breeding Bird survey took place June 1 - June 25. A total of 5,844 individual birds were recorded along the 13 survey routes. This is above the 1985-2002 average of 4,375 birds/year (no surveys were conducted in 1992 or 1993).

Although bird numbers remained relatively unchanged from the 2002 survey, drought conditions continued during 2003 with higher than normal rainfall occurring in April and lower than normal in May and June. Horned Larks and Meadow Larks comprised more than 50% of all birds counted on the 2003 survey. Horned Larks are a dominant component of grassland communities on the INL. The conversion from sagebrush to grassland, due to large fires, has allowed this species to increase in abundance. At the same time sagebrush obligate species (e.g. Brewer’s Sparrow, Sage Sparrow, and Sage Thrasher) have remained relatively stable but slightly decreased

The downward trend in the number of sagebrush obligate species is consistent with the notion that sagebrush habitat is being lost and may be negatively affecting these populations of birds. This trend is very evident on the Big Lost River route where in 2000 a wildfire consumed sagebrush on more than 60% of the route. Before the 2000 fire more than 82% of the vegetation on the route was dominated by sagebrush. After the fire, only 22% of the route remained in sagebrush dominated habitat. The figure below illustrates the dramatic increase in Horned Lark numbers and the general decrease in the sagebrush obligate species such as Brewer’s Sparrow, Sage Sparrow, and Sage Thrasher. Although large expanses of sagebrush habitat remain of the INL and fire is a natural part of the Snake River Plain ecosystem, concern for the preservation of sagebrush habitat is valid given that much of this habitat has been lost by conversion to agriculture or development. At the very least, further sagebrush habitat loss should continue to be monitored.

The high numbers of birds counted in 2003, however, does not necessarily reflect large numbers of birds counted among all taxa. Several species were at or below long-term averages and a few species observed in six or more previous years were absent in 2003, including Burrowing Owl, Bank Swallow, and Blue-gray Gnatcatcher. Waterfowl counts at the INL were also low due to the lack of water in the Big Lost River over the past 4 years. The Big Lost River, Sinks and Spreading Areas have not held water since summer of 1999, thus reducing the number of birds that would normally use these areas. The only waterfowl observed in 2003 were at the facility wastewater treatment ponds.

Several species recorded in six or more previous years were not observed in 2002.

  • Burrowing Owl 
  • Bank Swallow
  • Blue-gray Gnatcatcher

Overall, 13 routes were surveyed on the INL with approximately 446 ± 162 total birds counted per route. On the five remote routes the average number of total birds observed was 595 ± 77 with an average of 12 ± 3 birds per stop. The eight facility complex routes averaged 352 ±126 total number of total birds observed with an average of 12 ± 4 birds per stop (see above). 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 directly comparable.

Overall, the five most numerous species in order of abundance were:

  • Horned Larks (Eremophilia alpestris)
  • Western Meadowlarks (Sturnella neglecta)
  • Sage Sparrows (Amphispiza belli )
  • Brewer's Sparrows (Spizella breweri)
  • Sage Thrashers (Oreoscoptes montanus)

These species were the most frequently counted species each year and usually comprise >70% of all birds detected.


Species Richness

 In 2003, a total of 67 species were detected during the surveys. This is above the average of 56 ± 8 recorded from 1985-2002. One new species for the BBS, the Ring-necked Duck, was observed at the NRF wastewater pond, increasing the total number of species detected along the routes (1985-2003) to 114. In 2003, there were 24 ± 5 species per route, with many similar species recorded along remote routes (23  2) and facility routes (24 ± 6). Facility routes had the fewest (N=15 @ PBF) and the greatest (N=31 @ NRF & CFA) number of species observed. The number of species observed on remote routes was similar with 20-26 species observed on each route.


Habitat and species assemblages

A limited assemblage of breeding bird species that are typical of sagebrush steppe or grassland communities within the Snake River Plain dominated the avifauna of the INL. These species included native species such as Sage Sparrow, Brewer’s Sparrow, Sage Thrasher and Sage Grouse in the sagebrush, Rock Wrens within rocky outcrops, Horned Larks and Vesper Sparrows in the grasslands, and the ubiquitous Western Meadowlark, Mourning Dove, Brown-headed Cowbird, Common Nighthawk, and Raven. Other less common, but widespread species included the Common Poorwill, Loggerhead Shrike, Grasshopper Sparrow, Lark Sparrow, Great-horned Owl, Ferruginous Hawk, Red-tailed Hawk, Swainson’s Hawk, and Prairie Falcon. There were also several other bird species that are not usually found in sagebrush steppe or grasslands and are principally relegated to a variety of other distinct habitat types. For example, there were species of birds that were found on the INL only in junipers in patches near the buttes or along the base of the Lemhi and Lost River Mountains. These species, including Chipping Sparrow, and Gray Flycatcher, were counted at the same sites almost every year and nowhere else. Waterfowl and shorebirds were another group of birds that has limited distribution on the INL, either in natural areas along the Big Lost River (when it contains water) or in man-made ponds near the facilities.

An additional array of bird species that would not normally be observed in sagebrush steppe or grassland habitats were found in altered or man-made habitats of the INL. Permanent water, different food resources, and buildings and planted trees for nest sites make these areas suitable for species that would otherwise not be located in this area. These species included House Finch, Barn Swallow, American Robin, and Bullock’s Oriole. Most of these species are native to well-watered areas within the Snake River Plain and/or surrounding mountains, but the facilities provide habitat for these species as well as non-natives such as the Rock Dove, House Sparrow, and European Starling. Finally, there were birds, such as the Brewer’s Blackbird, Black-billed Magpie, and Say’s Phoebe that were found both near the facilities and in remote areas.

Species of special concern

State and Federal species of special concern observed during the 2003 census included:

  • Long-billed Curlew (N = 1)
  • Ferruginous Hawk (N = 13)
  • Swainson’s Hawk (N = 3
  • Loggerhead Shrike (N = 39)
  • Greater Sage Grouse (N = 19)

The Burrowing Owl has not been observed since 2000. The sagebrush steppe habitat on the INL continues to support species of birds that are low or declining in number throughout the Intermountain West.

Download full 2003 Breeding Bird Survey report

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