C. Stuart Houston

Demography of Ferruginous Hawks Breeding in Western Canada

Abstract We assessed age-dependent survival, site-fidelity, and, together with data on prey and reproduction, trends in the population of ferruginous hawks (Buteo regalis) breeding in western Canada. Our analysis included 7,129 ferruginous hawks banded near Hanna, Alberta, and Kindersley-Alsask, Saskatchewan, from 1972 to 2003. We estimated annual adult survival rate to be 0.708 (SE = 0.024) and first year survival for nestlings was 0.545 (SE = 0.147). Resighting probability was modeled as a constant for nestlings (0.009, SE = 0.010), but it varied among years for adults consistent with our sampling efforts. Band reporting rate was at 0.022 (SE = 0.007) for both nestlings and adults. Fidelity to the study site was 1.00 (SE = 0.000) for adults and 0.035 (SE = 0.014) for nestlings. Nesting density ranged from 3.1 to 14.0 pairs/100 km2 and averaged 9.8 pairs/100 km2. We observed an average clutch size of 3.2 (SE = 0.06) and brood sizes of 2.71 (SE = 0.07) near Hanna and 2.79 (SE = 0.99) at Kindersley-Alsask. Richardsons ground squirrels (Spermophilus richardsonii) made up 95% of ferruginous hawk prey. Prey availability was positively correlated with number of offspring near Hanna and Kindersley-Alsask. We believe the lower than expected adult survival did not result in population decrease; rather, declines in reproduction resulting from declines in the abundance of ground squirrels better explain an observed 4.5-fold decline in nesting densities during the study. The results suggest that ferruginous hawk management should address prey in addition to habitat management, and that management needs are regional in scope with particular emphasis on the breeding range within the northern Great Plains.

Demography of Swainson's Hawks Breeding in Western Canada

Abstract Our objective was to estimate demographic parameters and population trends for Swainsons hawks (Buteo swainsoni) breeding in southeast Alberta and southwest Saskatchewan, Canada, from 1972 to 2003. We assembled mark–resighting–recovery histories of 6,606 banded Swainsons hawks for a joint analysis of survival and resighting probability, including band-reporting rate and fidelity of animals, following Burnhams joint resighting–recovery model provided in program MARK. Our best-fitting survival model specified age-related variation in survival, resighting probability, and fidelity, and it specified age-by-temporal variation in nestling survival and adult resighting probability. From estimated survival rates and previously published data on reproduction, for the period 1973–1996 we estimated the populations finite rate of increase, λ, to be 0.996 (95% CI: 0.945–1.057). We believe that population limitation of Swainsons hawks is primarily related to the influence of prey availability on brood size and nestling survival. Despite indications of recent population declines, we conclude that Swainsons hawks breeding in western Canada are not currently in need of special management action.

Winter Ranges of Migratory Turkey Vultures in Venezuela

Abstract We used four Global Positioning System (GPS) satellite transmitters to calculate the wintering ranges of migratory Turkey Vultures (Cathartes aura) that breed in Saskatchewan, Canada, and winter in Venezuela. Between 2007 and 2011, 95% fixed-kernel estimators of range size varied from 54 to 76 731 km2 with an average of 16 814 ± 28 606 km2 (SD), while those calculated with 95% Minimum Convex Polygons ranged from 22 to 46 778 km2 and averaged 9545 ± 17 356 km2. The smallest wintering range was comparable to previously reported range sizes, but our largest wintering range greatly exceeded anything yet recorded. Variation in winter range sizes may be attributed to resource availability, migration costs, and the absence of obligations associated with breeding. Each vulture had a “primary nocturnal roost” to which it returned frequently; each spent more hours (evenings, nights, and mornings) at and within 1 km of such roosts, than it did foraging during midday. Our results increased our understanding ...

Caffey's disease

Sir, The paper by Saatci, Brown and McAlister [1] demonstrates the value of MR in showing the marrow and soft tissue changes in an atypical case of monostotic cortical hyperostosis. No mention is made of the diminishing prevalence of the polyostotic, non-familial Caffeys disease, much more common when I was a radiology resident in the early 1960s. In Saskatchewan, we saw our last example of this polyostotic sporadic form in 1976 [2]. Now we see only about one case a year of the polyostotic familial presentation in a French-Canadian family from one rural area [3]. J.-C. Hoeffel

Probable Identity of Purported Rough-Legged Hawk Nests in the Western U.S. and Canada

of Scotts Oriole from Colorado. West. Birds 8:157158. ROGERS, T. H. 1969. Northern Rocky Mountain-Intermountain region. Audubon Field Notes 23:501. SMITH, M. 1959. Redlands Christmas bird count. Audubon Field Notes 13:252. WEBSTER, F. 1981. South Texas region. Am. Birds 35: 203. WILLIAMS, F. 1970. Southern Great Plains region. Am. Birds 24:65. WILLIAMS, F. 1977. Southern Great Plains region. Am. Birds 31:196. WILLIAMS, F. 1981. Southern Great Plains region. Am. Birds 35:200. WILLIAMS, F. 1983. Southern Great Plains region. Am. Birds 37:198. WITZEMAN, J. 1982. Southwest region. Am. Birds 36: 319.