By Wakamiya, Sarah; Roy, Charlotte L.
Endangered Species Update , Vol. 25, No. 3
In Illinois, the peregrine falcon (Falco peregrinus anatum) has not yet recolonized cliff sites historically used for nesting, and remains restricted to urban areas. We conducted an exploratory study in the potential recovery of peregrine falcons by identifying nesting sites and evaluating potential reintroduction sites. We used Geographic Information Systems (GIS) to identify cliffs, identified suitable nesting cliffs using measures of height, elevation, distance to water, and cliff dominance, determined cliff suitability for reintroduction using great homed owl surveys, and ranked reintroduction sites using measures of cliff height, length, slope, elevation, dominance, distance to water, % agriculture, disturbance, and ownership. Most (18 of 23) of the cliffs identified in GIS were consistent with acceptable peregrine falcon nesting sites. Of those 18 sites, 8 were suitable for nesting but were occupied by great horned owls, leaving 10 suitable reintroduction sites in southern Illinois. Monroe County contained the 4 best reintroduction sites. Another site in Jackson County also was highly ranked and may be near historical nesting sites, making it a good alternate area for reintroduction. This study constitutes the first step in assessing peregrine falcon habitat and potential for recovery in southern Illinois. We are not recommending reintroductions without further investigation of the costs and benefits of such an action relative to other management options.
Key words: Illinois, Falco peregrinus anatum, Illinois, peregrine falcon, reintroduction
The North American peregrine falcon (Falco peregrinus anatum) historically nested on cliffs and bluffs throughout the United States before the use of DDT (Dichloro-diphenyl-trichloroethane) led to widespread population declines during 1950-1970 (USFWS 1999). The banning of DDT and intensive reintroduction programs led to the removal of peregrines from the federal list of endangered and threatened wildlife in 1999, yet in Illinois they remain state-threatened (USFWS 1999) and among the "species in greatest need of conservation concern" (IDNR 2005).
Though the pre-DDT peregrine population in Illinois was not adequately surveyed prior to their extirpation, conservative estimates report 60 pairs nested in the Midwest (Hickey 1942). Pairs were documented in northern Illinois nesting on bluffs along Lake Michigan and in the south, along the Mississippi River. Jackson, Jersey, and Union counties of southern Illinois contain many cliffs and bluffs adjacent to open agricultural areas, rivers, and lakes and historically supported nesting peregrines (Ridgeway 1889; Widmann 1907; Bohlen 1978; Enderson et al. 1995).
Because initial peregrine reintroductions in the Midwest were meeting greater success rates in urban areas than rural areas (Redig and Tordoff 1988), Illinois concentrated their reintroduction efforts on buildings in the Chicago metropolitan area. Consequently, all 11 pairs that currently hold territories in Illinois nest on buildings and bridges in Chicago (Redig et al. 2007), while historic nesting cliffs remain unoccupied since the species' extirpation from the state in 1957. High site fidelity may partially explain why they have not returned to historic cliff sites (Newton 1988; Tordoff et al. 1998). Therefore, reintroducing peregrines to cliff sites may be necessary to promote the recolonization of these sites. Reintroductions resulting in a viable cliff-nesting population in southern Illinois could link regional populations of urban falcons (i.e., Chicago, IL, St. Louis, MO, Indianapolis, IN) and decrease overall metapopulation extinction risk.
Reintroduction programs can facilitate recovery, but they are costly and time consuming and often fail unless carefully planned (Seddon et al. 2007). Therefore, the feasibility of reintroduction should first be evaluated by assessing habitat availability, identifying suitable reintroduction sites, and modeling populations with varying reintroduction strategies (IUCN 1998). …