Site selection for terrestrial habitats
A total of 450 sites representing forests, grasslands, and wetlands (150 of each: 30 sites per habitat per year) were randomly selected from across the state on both public and private land using the Illinois Land Cover Map and Illinois Wetland Inventory. Habitat areas vary in size, but to be sampled for birds, plants, and insects, forest sites must have a minimum area of 20 acres of suitable habitat and grasslands/wetlands a minimum area of 500 m2. Beginning with forests, then wetlands, and finally grasslands, sites are visited during the growing season from mid-May to the end of August (or the end of July for birds).

Plant Sampling
At each site biologists collect data on herbaceous and woody vegetation. In forests they establish three 50 m transects and set ten 1/4 m2 quadrats along each to estimate ground cover using a modified Daubenmire method. Also, along each transect they establish a 4 m x 50 m shrub plot and a 10 m x 50 m tree plot. In wetlands and grasslands the INHS scientists use a single 41 m transect. Along this transect they place twenty 1/4 m2 quadrats to estimate ground cover and establish a 4 m x 41 m shrub plot and 41 m x 50 m tree plot. The locations of the center point and transects at each site are geo-referenced to facilitate relocation.

For each site, biologists measure several ecological indicators including species richness, diversity, dominance of native vs. non-native species, and threatened and endangered (T&E) species.

Bird Sampling
INHS ornithologists conduct from one to 15 point counts (PC) per site, 150 m apart in forests and 300 m apart in grasslands/wetlands. One of these PCs overlaps with the center point of plant sampling. Ten-minute point counts are carried out at each point. In each count, they note the 3, 5, 6, 8, and 10 minute marks to facilitate data comparisons with other data sets. During each counting ornithologists list all bird species that they hear or see. In the case of wetlands the ornithologists also play a tape with the calls of 14 wetland dependent species after the PC for 30 minutes and record any species that respond.
Bird species are classified as area sensitive species (ASSp), habitat dependent species (HDSp), and threatened and endangered (T&E) species. Highly, moderately, and low ASSp refers to the tolerance of bird species to habitat fragmentation. For example, if a species is highly area sensitive then it will require large tracts of habitat for nesting. Habitat dependent species are those that can only be found in a particular habitat. For example, forest dependent species are those found primarily in forests. For each species, the detection rate (total number of times a given species is detected divided by total number of visited sites) was determined per habitat for each year and for all years combined.

Terrestrial Insect Sampling
Quantitative sampling of insects consists of two 50-m linear sweeps (100 sweeps each) conducted 3 meters out on both sides of a plant transect. Each sweep sample is transferred to PTUIE for at least 30 minutes. The PTUIEs are used to separate insects from duff (leaves, seeds, sticks, etc.) in the field while the insects are still alive. After 30 minutes, insects are stored in vials of 70% ethanol and maintained for sorting and future study in the INHS insect collection.

Stream Monitoring of Aquatic Insects
CTAP aquatic entomologist uses three orders of aquatic insects as indicators of stream condition: the Ephemeroptera (mayflies), Plecoptera (stoneflies), and Trichoptera (caddisflies) (collectively, EPT taxa). Sampling of EPT taxa takes place April 1 through 15 May each year since this season provides the greatest richness of larval EPT species in Illinois. Progression from southern to northern Illinois helps maintain comparability of data statewide. A standardized, semi-quantitative, multi-habitat approach is used in two habitats (bank and riffle/wood debris are the preferred habitats). This approach yields a large proportion of the EPT species richness found in streams, while also weighing time and resources necessary for processing of samples. All EPT are sorted from sample debris alive and identified to lowest taxonomy possible in the laboratory. All samples are field picked alive and specimens preserved in 80% EtOH. All specimens are deposited in the INHS insect collection and included in a web-based EPT database (http://www.inhs.uiuc.edu/cbd/EPT/index.html).

In addition to EPT species richness, the Hilsenhoff Biotic Index, a weighted average of the pollution/disturbance tolerance of stream dwelling aquatic insects provides another measure of stream condition. Measurements of habitat quality help to estimate the potential for in-stream and streamside habitat to support healthy aquatic communities. Snapshot values of several water chemistry and physical attributes including water temperature, dissolved oxygen, pH, and conductivity are collected at each site.