We measured habitat selection, productivity, and nest density of Red-shouldered Hawks (Buteo lineatus) breeding in a largely contiguous forest in northern Wisconsin. We located and followed the reproductive success of 71 breeding attempts within an estimated 26 territories between 2002 and 2006. Mean reproductive rates were 0.7 young per breeding attempt and 2.0 young per successful nest, and nest success averaged 35% per year. Annual nest density ranged from 0.10–0.16 nests per km². Micro- and macrohabitat variables were measured at 400-m² circular plots centered on nest trees and at random plots located in similar forest types. When compared to random plots, nesting areas were significantly shorter distances from the nearest lake or treeless wetland (P < 0.001). The logistic regression model that provided the best fit for our data included the distance to nearest trail or road and the distance to nearest lake or treeless wetland. At the microhabitat scale, nesting areas had greater basal areas and fewer sapling-sized trees (i.e., trees 3–13 cm in diameter at breast height) than found at random plots. The low reproductive success in combination with the observed nest density suggests that immigration of Red-shouldered Hawks from outside the study area may be critical to maintaining this breeding population.

Western Burrowing Owls (Athene cunicularia hypugaea) often live in close proximity to humans, yet their behavioral responses to anthropogenic land use are largely unknown. We compared the diurnal foraging and activity budgets of adult male Burrowing Owls during the breeding seasons of 2004 and 2005 at three urban and three rural sites in northwestern Texas. The owls (N  =  17 urban, 10 rural) spent most of their time being vigilant, resting, preening, perching, and in the burrow; less time was spent hunting, eating, provisioning the mate or young, flying, or engaging in other behaviors. Activity budgets did not differ significantly with land use. There were significant differences in activity budgets among study sites and with respect to times of day, weather variables, and numbers of owlets. Although hunting success and provisioning rates did not vary between urban and rural sites, aerial insects were taken as prey more often at urban than at rural sites. More foraging attempts occurred in habitats dominated by forbs, grasses, and bare ground than in areas with woody vegetation or impervious surfaces. Urban sites generally had more human forms of disturbance, but more mammalian and avian predators of Burrowing Owls were observed at rural sites. Our understanding of the behavioral effects of urbanization is still in its infancy, but the study of urban behavioral ecology will likely increase in importance as urban development continues.

Although the breeding density of Bald Eagles (Haliaeetus leucocephalus) in the lower Chesapeake Bay is known to vary with salinity, the ecological factors that contribute to this distribution have not been explored. In an effort to examine whether variation in prey use is associated with nest density patterns, we investigated the influence of salinity (tidal-fresh vs. mesohaline zones) on Bald Eagle diet composition by using video-monitoring to observe food delivered to nests during the 2002–2003 breeding seasons. Delivered prey items were identified to the lowest taxonomic level possible and sizes were estimated relative to eagle bill length. We used species-specific length-weight relationships for prey to estimate biomass delivery. Overall, the diet included at least 12 species of fishes, three species of birds, four species of mammals, and four species of reptiles. Salinity had no significant influence on diet composition; Ictaluridae and Clupeidae species were the most frequent prey items in both salinity zones. We suggest that pairs nesting in both tidal-fresh and mesohaline zones have access to similar fish species. However, the length and biomass of fish prey varied with salinity such that larger prey on average were delivered to nests in the mesohaline reaches compared to tidal-fresh zones. Thus, we suggest that foraging eagles may be exploiting more energetically-favorable conditions in higher salinity waters. Temporally, diet composition varied between study years, potentially reflecting annual changes in the availability of prey species. We consider differences in weather patterns between study years as the most likely factor contributing to this interannual variation in diet.

We studied the feeding behavior of Black Kites (Milvus migrans) in a rubbish dump in Rome, Italy, from April–September 2005. The earliest kites reached the rubbish dump at dawn and the last left just after dusk. The number of individuals foraging in the dump increased during the course of the day and also from April to August. The number of kites in the rubbish area of the dump was usually small and tended to show rapid increases and equally quick declines. Kites searched for food while directly standing on the rubbish or, more often, while flying low over the ground. The first strategy, which was never observed in April but was more common during the following months, was used when there were few foraging gulls or trucks in the dump. Cleptoparasitism was the technique most frequently used to acquire food (76% of all foraging events). It was directed toward conspecifics in 35% of the observed cases, toward Yellow-legged Gulls (Larus cachinnans) in 57% and toward Carrion Crows (Corvus corone) in 8%. The success rate of cleptoparasitic attempts was 32% against conspecifics, 73% against Yellow-legged Gulls and 66% against crows. The higher frequency of cleptoparasitic attempts against gulls may thus be explained by its higher success rate, although its efficiency declined with increasing gull numbers. The frequency of intraspecific cleptoparasitism paralleled variations in kite density and its effectiveness increased progressively from April–August.

A reintroduced population of Ospreys (Pandion haliaetus) in eight counties surrounding Minneapolis/St. Paul, MN was monitored from 1984–2005. We recorded the behavior of marked birds at 306 occupied nests. Two-yr-old Ospreys were involved in nest attempts more often than previously reported. Twelve were observed; eight of these (five males and three females) occupied nests, and the remaining four were floaters. Readily available nest sites and abundant food resources may have been factors in breeding attempts by these young Ospreys. Age at first known occupied nest averaged 4.13 yr for males (N  =  38) and 3.36 yr for females (N  =  11). Age at first known successful nest averaged 4.39 yr for males (N  =  38) and 3.64 yr for females (N  =  11). In 2003, two 2-yr-old males fledged chicks. We also observed Ospreys copulating with more than one partner in the same breeding season on 14 occasions (10.52% of nests where eggs were laid). All but one extra-pair visit was observed between 2003 and 2005, when the nesting population of the study area exceeded 33 pairs. Fertility insurance, genetic quality, sperm competition, and parental care may have been factors favoring extra-pair-copulation behavior in this population. Because multiple individuals were observed copulating outside the pair bond, the paternity of chicks in these clutches of Ospreys cannot positively be attributed to the social mate.

We collected prey remains and pellets at 16 Peregrine Falcon (Falco peregrinus) nest territories (975 prey items from 152 collections) and one Australian Hobby (F. longipennis) territory (181 prey items from 39 collections) during four breeding seasons in two time periods: 1991–1992 and 2002–2003, a total of 60 peregrine nest-years and three hobby nest-years. By number, European Starlings (Sturnus vulgaris) were the main prey taken by both falcons in 1991–1992 and 2002–2003, but starlings made up a smaller percentage of the diet by number in the latter period, apparently because their numbers had declined in the wild. Although the geometric mean of prey weights and geometric mean species weights were similar in the two time periods, both falcons compensated for the decline in European Starlings in the latter period by taking a greater variety of bird species, particularly small numbers of mostly native birds, rather than taking more of one or two other major prey species. Peregrines took 37 bird species in the latter period not found among their prey remains in the earlier period, and more individuals of some large species such as Gang-gang Cockatoos (Callocephalon fimbriatum), Galahs (Cacatua roseicapilla), and Rock Pigeons (Columba livia). Prolonged drought and competition from increasing numbers of Common Mynas (Acridotheres tristis) may have caused European Starlings to decline, but neither falcon species compensated by catching Common Mynas, even though they are of optimal prey size. Though both falcons, especially peregrines, took the more common bird species found in surveys in the Australian Capital Territory, both tended to avoid large or dangerous species, or agile species that foraged close to cover, such as Common Mynas.