The Canadian Field-Naturalist (E-Journal)
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Diet and reproductive success of Great Horned Owl (Bubo virginianus) at its northern breeding limit
Get PDFWe studied the diet and reproductive success of Great Horned Owl (Bubo virginianus) at its northern range limit during an apparent high in the Snowshoe Hare (Lepus americanus) population. We performed diet analyses using images from fixed motion sensor cameras and pellet and prey remains collected at active nests, and gathered data on breeding success through camera and visual observations. Pellet data at 14 nests produced 1277 prey records consisting of 65–95% Snowshoe Hare biomass. Great Horned Owls ate 18 different prey types, with overall biomass consisting of 93% mammal, 7% bird, and less than 1% insects, frogs, and fish. The mean prey mass of 714 g (± 34 SE) was 2–25 times the mean prey mass of studies of this species at more southerly latitudes. Camera observations showed that Great Horned Owls delivered an average of 459 g/chick/d (± 75) throughout nesting. This was significantly (P = 0.005) higher than observations from Alberta, at 328–411 g/chick/d. Pellet/prey remains data showed that Great Horned Owls delivering a higher proportion of hares to their nestlings successfully raised more chicks (χ21 = 6.3, P = 0.012), highlighting the importance of this prey in the population dynamics of Great Horned Owl. In addition, we observed Snowshoe Hare removing pellets beneath nest sites, revealing an apparently undocumented bias to the use of pellet analysis
Parasitism and brood mortality in Alfalfa Leafcutting Bee (Megachile rotundata (Fabricius)), nesting in vacated comb cells of European Paper Wasp (Polistes dominula (Christ))
Get PDFSocial paper wasps (Hymenoptera: Vespidae) construct comb nests of tens to hundreds of brood cells that are abandoned each year before winter. The nests are positioned where they are protected from inclement weather and may remain intact for several years. Here, I detail observations of nests provisioned by the non-native, solitary Alfalfa Leafcutting Bee (Megachile rotundata (Fabricius, 1787); Hymenoptera: Megachilidae) in individual brood cells in vacated combs of the invasive, social European Paper Wasp (Polistes dominula (Christ, 1791)) on a green roof in Toronto, Ontario. A total of 12 paper wasp combs were dissected and 280 M. rotundata nests (one per wasp comb cell) were recovered; 22 nests were provisioned in 2013 consisting of 32 individual M. rotundata brood cells. Parasitism by Melittobia and Monodontomerus wasps accounted for 46.9% of M. rotundata mortality in the cells in 2013; mortality from all causes, including parasitism, was 78.1%. In contrast, total mortality of M. rotundata in brood cells provisioned in a human-made bee nest box on the same roof in 2013 was 4.2% and there was no parasitism. Mortality by parasitism and total brood mortality in 391 brood cells provisioned in 41 nests in the bee nest box in 2011–2013 were 2.0% and 21.2%, respectively. Therefore, the use of vacated paper wasp comb cells resulted in an overall >20-fold increase in parasitism and >3-fold increase in brood mortality over that observed in the bee nest box when all years are combined
"Lyme Disease, Ticks and You: a Guide to Navigating Tick Bites, Lyme Disease and Other Tick-Borne Infections" by Shelley Ball, 2021. [book review]
Get PDF"We Are All Whalers: the Plight of Whales and our Responsibility" by Michael J. Moore, 2021 [book review]
No full textDraft Minutes of the 143rd Annual Business Meeting (ABM) of the Ottawa Field-Naturalists’ Club, 11 January 2022
Get PDFDo turtle roadkill hotspots shift from year to year?
Get PDFFreshwater turtles face many threats but roadkill is one of the most serious for many species. Roadkill of turtles is not uniformly distributed across roads but aggregated in certain areas, termed hotspots. A key question in identifying hotspots is whether they are fixed locations or if they shift from year to year because of changes in movement patterns. We compared how one, two, and three years of road survey data compared with the pooled data from four years of surveys. We found 254 turtles during 73 surveys during four years along a 15.5 km road section in Ottawa, Ontario, Canada. The four years of pooled data produced four hotspots (“pooled hotspots”) while each year or combination of years produced from three to five hotspots, four of which approximately corresponded to the pooled hotspots. The average percentage overlap of hotspots between one, two, or three years of survey data and the pooled hotspots ranged from 58.7% to 88.9%. Just one year of surveys sometimes missed one of the pooled hotspots, underestimated the spatial extent of the pooled hotspots, and also sometimes produced an additional “temporary” hotspot. Two years of surveys generally produced better approximations of the pooled hotspots and better identified the spatial extent of those hotspots
Foraging patterns vary with the degree of sociality among Common Loon (Gavia immer) overwintering on a freshwater lake
Get PDFLittle is known about the behaviour of Common Loon (Gavia immer) during the critical overwintering period, let alone the behaviour of the small, but increasing number of loons that overwinter on freshwater lakes in North America. We examined the diurnal time-activity budgets of Common Loon overwintering on a large reservoir in northwest South Carolina between 2018 and 2020. Similar to previous studies of breeding individuals and individuals that overwinter in marine waters, loons (n = 132) overwintering on this reservoir spent most of their time (52%) foraging. However, we found distinct differences in the activity budgets of individuals associated with their degree of sociality. Solitary birds (individuals spending 0–20% of time within 20 m of conspecifics) spent significantly more time foraging than did those that were either loosely-social (>20–<70% of time within 20 m of conspecifics) or strongly-social (70–100% of time). Although solitary loons made as many foraging dives as social birds, their dives were much longer, likely reflecting dives for larger predatory fish. In contrast, social individuals made much shorter, shallower dives, often foraging on shallower baitfish that they appear to pursue to the water surface and consume collectively. Such findings add to our understanding of loon winter behaviour and raise interesting questions regarding social behaviour and the short- and long-term trade-offs associated with social foraging in this species
