Chest heights, foot loading, and behavior of moose (Alces alces), caribou (Rangifer tarandus), wapiti (Cervus canadensis), white—tailed deer (Odocoileus virginianus), Dall sheep (Ovis dalli), bighorn sheep (Ovis canadensis), pronghorn antelope (Antilocapra americana), and bis (Bison bison) were used to calculate indices of snow—coping ability for each species. When species were grouped into regional faunas, those with higher indices occurred in more snowy regions. Within a local area, a variety of species can survive in winter by living and feeding in different habitats defined on the basis of snow conditions. Bison, deer, and wapiti have considerable sexual dimorphism in chest height and foot loading. These differences between the sexes have potential value for individual survival in snow by permitting use of food resources over a greater proportion of the species' home range. Wolves (Canis lupus), coyotes (C. latrans), and a wolverine (Gulo luscus) showed similar levels of morphological adapation to snow, higher than all but two of the ungulates studied (caribou and moose); predation appears to have been a factor influencing evolution of ungulate behavior in snow.

We deal with possible morphological adaption to varied snow conditions by four North American ungulate species. Chest heights and weight loads on track are key parameters in estimating capabilities of species, and of age and sex classes within species, to cope with snow. Methods believed suitable for measuring those parameters in replicable fashion are discussed. Comparative studies of bison (Bison bison), moose (Alces alces), wapiti (Cervus elaphus), and white-tailed deer (Odocoileus virginianus) are described. There are pronounced differences in both parameters between species and between some age and sex classes within species. Chest heights of the three cervids differed by a fixed interval suggesting that differential ability to use varied snow depths may play a role in resource partitioning. Differential winter mortality may be related to sex and age class differences in ability to cope with snow. Morphological differences relate to regional distributions by determining species suitability for survival in varying snow regimes.

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1987. Correlates and consequences of coloniality in great blue herons. Can. J. ZOO^. 65: 572-577. Sixty percent of the breeding great blue herons (Ardea herodias) in a colony at Pender Harbour, British Columbia, were individually marked to test three hypotheses concerning the benefits of colonial breeding. ( i ) Most herons fed near the site of the colony, but neighbours or members of a pair did not tend to choose adjacent feeding sites, as predicted by the information center hypothesis. Food supply was predictably distributed in time and space, and birds that did most of their feeding outside Pender Harbour bred less successfully than locally feeding birds. (ii) Nests that failed because of predation were nearer to the edge of the colony in 1978 but not in 1979. The colony was abandoned in 1980 after 2 years of high predation. Predation may, therefore, select for colonial breeding in herons, but heavy predation may force colony abandonment. (iii) Most herons chose new nest sites and new mates each year. The colony site may therefore serve as an assembly site for mate finding. Mate finding and avoidance of predation are therefore more likely to explain coloniality in great blue herons than are advantages associated with finding food. SIMPSON, K. J., J. N. M. SMITH et J. P. KELSALL. 1987. Correlates and consequences of coloniality in great blue herons. Can. J .Zool. 65 : 572-577. Soixante pourcent des Grands Herons (Ardea herodias) d'une colonie de Pender Harbour, Colombie-Britannique, ont ete marques dans le but de verifier trois hypotheses sur les avantages de la reproduction en colonies. ( i ) La plupart des herons se nourrissaient prks du territoire de la colonie. mais des oiseaux voisins ou les partenaires d'un couple n'avaient pas tendance a se choisir des sites d'alimentation adjacents, comme prevu selon I'hypothese du ((centre d'information >>. Les sources de nourriture etaient reparties dans le temps et dans l'espace selon les modeles, et les oiseaux qui se nourrissaient surtout hors de Pender Harbour avaient un succes reproducteur moins elevi que les oiseaux qui se nourrissaient localement. ( i i ) Les nids victimes de predation etaient plus prks de l'exterieur de la colonie en 1978, mais pas en 1979. La colonie a eti abandonnee en 1980 aprks 2 ans de predation intense. La predation peut donc favoriser la reproduction en colonies chez les herons, mais une predation trop intense peut entrainer I'abandon de la colonie. (iii) Chaque annee, la plupart des herons choisissaient de nouveaux emplacements pour construire leur nid et de nouveaux partenaires. Le territoire de la colonie peut donc servir de territoire de rassemblement pour le choix d'un partenaire. Le choix d'un partenaire et la protection contre les predateurs semblent donc des facteurs plus susceptibles d'expliquer la vie en colonies que ne le sont les avantages relies B l'acces plus facile a la nourriture chez le Grand Heron.[Traduit par la revue]