Jr. Zelenak et Jj. Rotella, NEST SUCCESS AND PRODUCTIVITY OF FERRUGINOUS-HAWKS IN NORTHERN MONTANA, Canadian journal of zoology, 75(7), 1997, pp. 1035-1041
In 1993 - 1994, we investigated nest success and productivity of Ferru
ginous Hawks (Buteo regalis) in northcentral Montana. The 171-km(2) st
udy area contained a variety of habitats, a high density of breeding r
aptors, and 24 occupied Ferruginous Hawk territories. Only 42% of occu
pied nests produced fledglings. Occupied territories produced an avera
ge of 0.96 fledglings (SE = 0.19). Successful nests produced an averag
e of 2.30 fledglings (SE = 0.21, n = 20). Lagomorphs were scarce on th
e area. Richardson's ground squirrels (Spemrophilus richardsonii) were
more numerous along the edges of cropfields and roads than in grassla
nds. Multiple regression indicated that Ferruginous Hawk nests closer
to cropfields and roads and farther from other breeding raptors produc
ed more young than other nests. Thus, habitats altered by humans, whic
h were not extensive (20% cultivated), apparently had higher densities
of ground squirrels and thereby benefited breeding hawks. However, be
cause our multivariate analysis was exploratory and based on a moderat
e sample size, our results should be interpreted cautiously and furthe
r evaluated in future studies.