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The escape responses exhibited by pea aphids were examined at three different temperatures, 15, 20, and 25 °C, using two different predators: syrphid larvae and coccinellid beetles. Coccinellid beetles foraged more vigorously at higher temperatures resulting in greater vibrations on the host plant as they searched for aphids. Foraging rates for syrphids were slower by comparison and did not vary with temperature. We found that most aphids dropped off the host plant when confronted by coccinellid beetles, especially at higher temperatures, and backed up when confronted by syrphid larvae regardless of temperature. We conclude that individual aphids do not have characteristic escape responses, but rather the response adopted depends in part on the foraging rate and species of predator.

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BRODSKY, L. M., and P. J. WEATHERHEAD. 1984. Behavioural thermoregulation in wintering black ducks: roosting and resting. Can. J. Zool. 62: 1223-1226.Black ducks (Anas rubripes) wintering near Ottawa. Canada, used a variety of behaviours to reduce their energy costs. The roost site that they occupied provided greater protection from wind than the feeding site. with the consequent reduction in forced convective heat loss. Time spent at the feeding site (i.e., away from the roost) varied with temperature such that ducks maximized their time at the roost on the coldest days. This relationship was facilitated by the ducks' food supply (cracked corn replenished daily), which precluded extending foraging time to increase food intake in cold weather. At the roost ducks huddled in colder weather and adopted postures that reduced both the nonfeathered area exposed to the air and also the surface to volume ratio. The ducks preferentially faced toward the sun and into the wind, but when these were in opposite directions they faced the sun only when wind speed was low. BRODSKY, L. M., et P. J. WEATHERHEAD. 1984. Behavioural thermoregulation in wintering black ducks: roosting and restingCan. J. Zool. 62: 1223-1226. Des canards noirs (Anas rubripes) qui passent I'hiver prks d'ottawa, Canada, utilisent une skrie de stratkgies de comportement destinkes a rkduire leur dkpense knergktique. Le site de repos (perchoir) qu'ils utilisent leur procure une meilleure protection contre le vent que leur site d'alimentation, ce qui rCduit les pertes de chaleur par convection. Le temps passk au site d'alimentation (loin du perchoir) varie en fonction de la tempkrature de manikre a maximiser le temps passk au perchoir les jours les plus froids. Au cours de cette Ctude, cet arrangement a Ctk facilitk par la prksence d'une rkserve de nourriture (ma'is concassk renouvelk chaque jour) qui rendait inutile le prolongement des pkriodes de recherche de nourriture dans le but d'augmenter la quantitk de nourriture ingkrke par temps froid. Au perchoir, les canards se pressent les uns contre les autres par temps froid et adoptent des postures propres a rkduire l'exposition a I'air des surfaces sans plumes et a diminuer le rapport surface: volume. Les canards prkfkrent s'orienter face au soleil et face au vent, mais lorsque les deux sont opposks les oiseaux s'installent face au soleil seulement lorsque le vent est faible.[Traduit par le journal]

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