Birds & Insects

Birds and Insects

An important rationale for evaluating the response of birds, ants, and butterflies to treatment is to gain confidence about the patterns of whole system effects. In particular, we hope to understand to what extent other components of the system, not directly related to vegetation management, track the response of the vegetation over time. Understanding these effects will provide managers with much more confidence on how their treatments influence the whole system. If wildlife and invertebrate response is consistently related to vegetation response over time, then managers can argue that the changes they observe in the managed landscape are reflected within.

Demography and Habitat Use of Song Birds

Song birds are of keen interest because sage-obligate species are considered to be especially at risk of habitat loss and subsequent population declines given the rapid habitat changes now occurring in sagebrush steppe ecosystems. Species richness and diversity, and productivity of song birds are being evaluated across a suit of species that breed in habitats along a woodland invasion gradient. Primary questions being addressed are:

• What are the dominant habitat characteristics that determine response in the bird community?
• What spatial and temporal scales are the primary drivers of change in bird assemblages?
• What are the primary mechanisms by which the bird community responds to changes in quantity, composition, and configuration of their habitat? Does productivity at the individual and/or population level change relative to habitat treatments?

Point counts are being conducted twice a year during the breeding season across the SageSTEP woodland network to study species richness and density in relation to the various ecosystems. Response of sagebrush-obligate species (Sage Thrasher, Brewer’s Sparrow, Sage Sparrow, Vesper Sparrow, Black-throated Sparrow, Green-tailed Towhee, and Gray Flycatcher) to management treatments is being studied intensively at the Onaqui, Seven Mile, South Ruby, and Five Creeks woodland study sites. Data collection for intensive study includes delineating territories, mist-netting and color-banding individuals, and assessing nesting success.

Taking measurements on a color-banded Brewer’s Sparrow in the field.

A field technician conducts a point count.

Species Richness and Colony Dynamics of Ants

Ants are ecologically dominant arthropods in sagebrush steppe ecosystems. Ants serve as scavengers, predators, symbiotic partners of other invertebrates, predators and dispersers of seeds, and as prey for a wide array of vertebrates, including many sage-obligate birds. We are evaluating species composition and relative abundance of ants, harvester ant colony density, and spatial dynamics of ant foraging systems. Since ant species differ markedly in the ecological roles they play, and these roles are generally well known for sagebrush species, we will be able to understand how management treatments alter the balance between roles over time. Primary questions to be addressed include:

• Does the ratio of seed harvester versus seed disperser change as a result of treatment, and how might this influence the distribution and abundance of plants?
• Do ant communities follow plants in terms of recovery after treatment, or do they precede plant communities?
• Do ants hinder or facilitate recovery of the plant community after treatment?

Ants are being collected throughout the SageSTEP network using pitfall traps, one trap deployed in the center of each of the 1150 sub-plots.  Ant community data can then be compared directly to all vegetation, soils, and fuel information collected within each sub-plot.

Species Richness and Foraging Habitats of Butterflies