Gregory J. Robertson

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Due to limited interaction of migratory birds between Eurasia and America, two independent avian influenza virus (AIV) gene pools have evolved. There is evidence of low frequency reassortment between these regions, which has major implications in global AIV dynamics. Indeed, all currently circulating lineages of the PB1 and PA segments in North America are(More)
The primary hosts for influenza A viruses are waterfowl, although gulls and shorebirds are also important in global avian influenza dynamics. Avian influenza virus genes are separated phylogenetically into two geographic clades, American and Eurasian, which is caused by the geographic separation of the host species between these two regions. We surveyed a(More)
Corticosterone (CORT) levels in seabirds fluctuate across breeding stages and in different foraging conditions. Here we use a ten-year data set to examine whether CORT levels in Atlantic puffins differ in years with high or low availability of capelin, the preferred forage species. Female puffins had higher CORT levels than males, possibly related to(More)
A new chromogenic plate medium, CHROMagar Orientation, was evaluated for use in the differentiation and presumptive identification of gram-negative bacilli and Enterococcus species by a multipoint inoculation (replicator) technique. In this study, 1,404 gram-negative bacilli and 74 enterococcal isolates were tested on CHROMagar Orientation. Six control(More)
On 21 November 2004, about 1000 barrels of crude oil were accidentally released from the Terra Nova FPSO (floating production, storage and offloading) onto the Grand Banks, approximately 340 km east-southeast of St. John's, Newfoundland. We estimated the number of vulnerable seabirds (murres (Uria spp.) and dovekies (Alle alle)) at risk from this incident(More)
Hypotheses regarding the evolution and maintenance of intraspecific nest parasitism were tested with data collected during a 3-year study of common eiders (Somateria mollissima) breeding near Churchill, Manitoba. The nest parasitism rate was highest (42.4% of nests) during the year with the highest nest density and the best environmental conditions, and(More)
Lipovitellin-salt-mannitol (LSM) plate medium was examined for its ability to directly isolate, recover, and presumptively identify Staphylococcus aureus from 418 clinical specimens. The criteria for medium evaluation included colony morphology reactions, selectivity, and ease of isolation. For 298 specimens used for screening, LSM agar medium was compared(More)
Adult seabirds experience predation by many species. At sea, they are taken by predatory fish such as white sharks Carcharodon carcharias (Johnson et al. 2006), and by marine mammals including killer whales Orca orcinus (Dahleim & White 2010), true seals (Penny & Lowry 1967, Cobley & Bell 1998), fur-seals and sealions (McHugh 1952, Long & Gilbert 1997,(More)
We determined the time of day at which eggs were laid and the laying interval (time between laying of successive ggs in a clutch) in the Hudson Bay race of the Common Eider (Somateria mollissima sedentaria), at La P6rouse Bay, Churchill, Manitoba (58?24'N, 94?24'W). Nests were found at the one-egg stage and were subsequently visited three times daily.(More)