Geology topics
A. D. Afton
Publications and source records attributed to A. D. Afton.
Nest morphology and body size of Ross' Geese and Lesser Snow Geese
Arctic-nesting geese build large, insulated nests to protect developing embryos from cold ambient temperatures. Ross' Geese ( Chen rossii ) are about two-thirds the mass of Lesser Snow Geese ( C. caerulescens caerulescens ), have higher mass-specific metabolic rate, and maintain lower nest attentiveness, yet they hatch goslings with more functionally mature gizzards and more protein for their size than do Lesser Snow Geese. We compared nest size (a reflection of nest insulation) in four distinct habitats in a mixed breeding colony of Ross' Geese and Lesser Snow Geese at Karrak Lake, Northwest Territories, Canada. After adjusting measurements for nest-specific egg size and clutch size, we found that overall nest morphology differed between species and among habitats. Nest size increased progressively among heath, rock, mixed, and moss habitats. When nesting materials were not limiting, nests were smaller in habitats that provided cover from wind and precipitation than in habitats that did not provide cover. Ross' Geese constructed relatively larger, more insulated nests than did Lesser Snow Geese, which may hasten embryonic development, minimize energy expenditure during incubation, and minimize embryonic cooling during recesses. We suggest that relative differences in nest morphology reflect greater selection for Ross' Geese to improve nest insulation because of their smaller size (adults and embryos), higher mass-specific metabolic rate, and lower incubation constancy.
Evening flights of female northern pintails from a major roost site
We monitored evening flights of female Northern Pintails (Anas acuta) from Lacassine National Wildlife Refuge (NWR) in southwestern Louisiana during winters of 1991-1992 and 1992-1993. We analyzed the influence of female age, winter, and date within wintering period on three flight parameters: distance, duration, and departure time. Flight distance and duration increased with date within wintering period, and age differences in flight distance and duration were not consistent between winters. Females departed 12 min later, on average, on clear, moonlit evenings than on overcast, moonless evenings, and 4 min later when winds were light rather than heavy. After controlling for variation due to environmental conditions, immature females departed Lacassine NWR 1.3 min earlier, on average, than did adults. Flight parameters of females did not differ between hunting and non-hunting time periods. Estimated daily transit costs ranged from 27-54% of basal metabolic rate, 7-19% of daily energy expenditure, and 8-20% of daily dietary intake of rice (Oryza sativa). Our findings that flight distance and duration increased with date within wintering period were consistent with predictions of refuging theory, but alternative hypotheses also could explain these results. Evening flights of Northern Pintails roosting on Lacassine NWR were greater in distance and duration than those reported for most other species of wintering waterfowl. We recommend that proximity of refuges to feeding sites be considered in conservation and management plans for wintering Northern Pintails and other refuging waterfowl.
Portable platforms for setting rocket nets in open-water areas
Portable platforms for setting rocket nets in open-water habitats were developed and used to capture 1116 waterfowl of seven species during September and October 1991 and 1992 in southwestern Louisiana. Incidence of mortality (1% of captured birds) and escape (3% of captured birds) was low. Rocket-netting from platforms was a reliable and efficient technique for capturing waterfowl, and should be applicable to other avian species using open-water habitats.
Workshop summary: Habitat selection
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Use of small fences to protect ground bird nests from mammalian predators
Abstract has not been submitted