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The Red-shouldered Hawk call-broadcast survey conducted in Central Minnesota, USA, was analyzed by using maximum-likelihood models to estimate their occupancy and detection probability. Estimates were found similar with different sampling strategies such as double and discontinued sampling and varied in number of sample locations.

A breeding Cooper's hawk population in the urban Milwaukee area, Wisconsin, U.S., is studied over a 12-year period and their reproductive success, age structure, nest-site occupancy and natal dispersal are documented. The study has shown that these nesting areas were not marginal or inferior habitats and that urban Cooper's hawks were not a sink population.

Cooper's hawks in Tucson, AZ, and in exurban areas in the southeastern part of the state were studied from 1994 to 1996 to compare their breeding ecology and productivity, with the end in view of assessing the quality of an urban environment as habitat for a species. Nesting was earlier for urban pairs and their clutches larger than exurban pairs. Urban nests were also found to have higher nesting mortality, with trichomoniasis as the primary cause of death. Urban nests also had a greater overall failure rate than exurban nests.

Recent research has assessed whether red-shouldered hawks and Cooper's hawks living in mainly wooded areas respond equally well to pre-recorded vocalisations of great horned owls as to vocalisations of each conspecific calls. It was found that response patterns do not vary between each type of vocalisation. This result has a number of implications for wildlife management, indicating that using pre-recorded vocalisations of great horned owls can increase detection of woodland hawks during breeding season surveys.

The diminishing numbers of grassland bird species in Western Canada warranted a study of the underlying processes of their decline but this was particularly difficult in the case of Swainson's hawks (Buteo swainsoni) due to insufficient data on survival rates of adults and nestlings. Mark-recaptured data from 1972 to 2003 was used to determine the demography of the Swainson's hawks and though it was determined that their limited numbers were influenced by the level of prey available to nestlings the situation was not considered critical.

The relationship between nesting ferruginous hawks and colonies of Gunnison's prairie dogs in grasslands of New Mexico are described. The effect of prairie dogs on nest-site selection is highlighted.

It has been possible to develop an aerial sightability model to estimate ferruginous hawk population size in two study areas in Wyoming. It was established that presence or absence of ferruginous hawks at the nest site did not seem to affect nest-detection rates. For active nests, the detection rate was 41.4%, while for inactive, natural nests the detection rate was 41.5%. Nest status was not an important predictor in the multiple regression model. Sightability modelling needs detailed planning and data collection, but has considerable advantages over single and stratified correction factors, double-count estimators and line transect.