Population dynamics of the Ferruginous Hawk during a prey decline

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} A nesting population of Ferruginous Hawks ( Buteo regalis ) at the eastern edge of the Great Basin in west - central Utah was studied for three nesting seasons, 1972 – 1974, during which time a significant decline in jackrabbit numbers occurred. The total number of hawks and nesting pairs varied throughout the study. In 1972, 16 pairs occupied territories and only 1 pair failed to nest. By 1974, however, only 5 pairs and 2 single birds occupied territories. The number of young fledged ranged from 31 in 1972 to 3 in 1974. The nesting phenology of the Ferruginous Hawk and the reproductive period of black - tailed jackrabbits are clearly correlated. Of the jackrabbit remains collected from hawk nests, 90 percent were from rabbits younger than 13 weeks. The decline in hawk numbers is thought to be directly correlated with a drop in the jackrabbit population.        

Notes on the Swainson's Hawk in central Utah: insectivory, premigratory aggregations, and kleptoparasitism

A premigratory flock of Swainson's Hawks numbering at least 213 individuals was observed during July and August of 1984. Aerial feeding on grasshoppers was noted and kleptoparasitism was recorded between the Swainson's Hawk and the American Kestrel.     

Ground nesting and aggressive behavior by the Swainson's Hawk ( Buteo swainsoni )

A successful ground nesting by Swainson’s Hawks, Buteo swainsoni, is reported for central Utah. Unusual aggressive nest defense behavior is described for this ground nesting pair.     

History of the naming of the Ferruginous Hawk

The Ferruginous Hawk, a breeding bird endemic to North America, was named Falco ferrugineus in 1838 by H. Lichtenstein, curator of the Berlin Zoological Museum. The type was collected by F. Deppe near present day Monterey, California. In 1844 G.R. Gray of the British Museum assigned the Buteo regalis to a Ferruginous Hawk specimen of unknown origin, but perhaps donated to the museum by John Phillips, a renowned British geologist. The species was known as Falco (Buteo) ferrugineus until the 1920s when it was discovered that this epithet was occupied. The next name in priority was Gray's Buteo regalis , which then became valid. The species has been known by a number of common names. Even though any reference to the rusty brown markings on the otherwise white plumage is no longer part of the species specific name, the Ferruginous Hawk continues to be the most frequently used common name.