The Canadian Field-Naturalist

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2022-04-29T08:31:24-07:00

News and Comment

2022-04-28T21:08:01-07:00

Index to Volume 135

2022-04-28T21:02:43-07:00

Another mention of Meadow Vole (Microtus pennsylvanicus) found in pellets of Snowy Owl (Bubo scandiacus) in northern Ungava Peninsula, Canada

2021-03-01T21:19:35-08:00

The examination of raptor pellets can be used to evaluate Arctic biodiversity. We found the remains of Meadow Vole (Microtus pennsylvanicus) and Ungava Collared Lemming (Dicrostonyx hudsonius) in pellets from Snowy Owl (Bubo scandiacus) nesting in the northern part of the Ungava Peninsula. We differentiated the two species by visual identification and geometric morphometric analysis of molar shape. The results of our study combined with historical data suggest that most commonly used range maps of Meadow Vole should be revised.

Paedomorphic Blotched Tiger Salamander (Ambystoma mavortium melanostictum) in ovo counts, British Columbia, Canada

2019-01-23T15:22:00-08:00

Reproductively mature larval morphs, known as paedogens, are a rare occurrence in Blotched Tiger Salamander (Ambystoma mavortium melanostictum). The Southern Mountain population of this subspecies, confined to the southern interior of British Columbia, is listed federally as Endangered and has been facing increasing pressures from anthropogenic stressors in both their aquatic and terrestrial landscapes. In 2017, we examined a subset of 36 frozen Blotched Tiger Salamander paedogens collected in September 1985 after rotenone treatment in preparation for a recreational fishery near Oliver, British Columbia. We estimated total in ovo numbers in nine gravid individuals to gain insight into paedogen reproductive condition. The number of eggs per individual averaged 227 ± 109 [SD]; range 28–421), with larger dark eggs accounting for 133 ± 69 and smaller pale eggs (possibly follicles or colour may be an artifact of storage) accounting for 94 ± 49. Salamanders were collected in September after the expected egg-laying period for the terrestrial form (early spring); thus, the reproductive stage of the eggs is unclear, but is assumed to be post-breeding and representative of developing eggs and follicles. Canadian data on in ovo counts within the body cavity have not been reported for Blotched Tiger Salamander paedogens and our study provides valuable information on the reproductive condition of paedogens. Although terrestrial forms have been observed, the presence of paedogens in the treated wetland has yet to be detected.

Parasitism and brood mortality in Alfalfa Leafcutting Bee (Megachile rotundata (Fabricius)), nesting in vacated comb cells of European Paper Wasp (Polistes dominula (Christ))

2021-02-03T09:16:02-08:00

Social 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.

Apparent winterkill of Painted Turtle (Chrysemys picta)

2021-02-19T20:52:16-08:00

Around the margin of an artificial pond in Ottawa, Ontario, we found 25 Painted Turtles (Chrysemys picta) that appeared to have died over the course of two winters (17 during the first winter and eight during the second). We examined meteorological data to try to determine the cause of the mortality. Summer and fall rains were only slightly below normal in both years, suggesting water levels should have been close to normal. The winter air temperature was warmer than normal and winter snowfall was slightly above normal in both years. Unseasonable weather does not appear to be responsible for the winter mortality and the pond’s maximum depth of 1.7 m should prevent freezing to the bottom. It is possible that the artificial nature of the pond creates suboptimal overwintering habitat, rendering the site an ecological trap; however, there is no direct evidence to support this theory. It is also possible that winter mortality of turtles is widespread at temperate wetlands, but that dead turtles were more detectable at this site because of the bare shoreline around the pond. Winter mass mortality events, if common, may represent an additional threat to turtle populations, which are declining from various anthropogenic threats.

Gimme shelter: anthropogenic structures as resting sites for American Marten (Martes americana)

2021-12-09T14:54:31-08:00

Several species of martens (Martes spp.) are reported to use buildings as resting or den sites. However, such behaviour has not been attributed to American Marten (Martes americana). We report American Marten using occupied buildings and evidence of suspected use of an abandoned cabin, as resting sites in southern Yukon, Canada. These observations further highlight the behavioural flexibility of North American species of Martes with regard to using novel structures as resting sites.

Diet and reproductive success of Great Horned Owl (Bubo virginianus) at its northern breeding limit

2020-12-07T14:13:06-08:00

We 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.

Assessing migration strategies and cause specific mortality of adult female White-tailed Deer (Odocoileus virginianus) in North Dakota, USA

2020-10-07T14:00:00-07:00

Life-history characteristics of White-tailed Deer (Odocoileus virginianus) have been documented in areas of the Northern Great Plains, but limited information is available in grassland dominated regions. We documented migration strategy, home range use, and survival of adult female White-tailed Deer in central North Dakota. We monitored 62 radio-collared adult (>1.5 year-old) female White-tailed Deer from February 2010 to December 2012. We documented 86 summer home ranges and classified deer as resident, migratory, or exhibiting a late season movement. Mean migration distance between non-overlapping summer and winter home ranges was 11.76 km (SE 0.86, n = 21). Mean late season movements were 20.69 km (SE 2.94, n = 7) and were likely the result of deer exhausting food resources throughout winter. We also developed five competing models that represented variation in survival among time periods (e.g., pre-hunt, hunt, and post-hunt in 2010 and 2011). Our top model indicated that survival (S) was similar between hunt 2010 and post-hunt 2011 periods but was lower (S = 0.82; SE 0.04, 95% CI 0.73–0.89) than the remaining time periods (S = 0.97; SE 0.01, 95% CI 0.93–0.99). Our results suggest that deer migration strategies and survival are likely influenced by a combination of winter severity and food availability. Mortalities attributed to hunter harvest were low during our study, which may indicate that increased recreational opportunities could be made available, even after severe winters.

Hiding in plain sight: combining field-naturalist observations and herbarium records to reveal phenological change

2020-11-27T10:23:40-08:00

As the climate warms, northern ecosystems are experiencing warmer winters and seasonal climatic shifts. Vascular plants are expected to respond to climate change by adjusting flowering or seeding periods. To determine how a native mixed-wood boreal floral assemblage has responded to warming temperatures over the 20th century, we collated historical observations made by field-naturalists as well as voucher data from the Thunder Bay region of Ontario, Canada. Combining these datasets, we performed regression analyses on 11 species of spring-flowering vascular plants to evaluate temporal trends and used spring cumulative growing degree day (sGDD0) to determine the influence of climate on flowering times. Four species showed consistent positive temporal trends (i.e., flowered later with time), while four species (three of which also demonstrated temporal trends) showed negative trends with sGDD0 (i.e., flowered earlier with an increased number of degree days above 0°C). The unexpected observation of later flowering times but predicted observation of earlier blooming with increased sGDD0 indicates that the inclusion of climate metrics may be necessary to determine the response of native vascular plants to the onset of changes in their environment. These observations were not statistically significant when field-naturalist or herbarium voucher data were analyzed separately, possibly due to low statistical power. Combining data from both sources, however, revealed common responses to climate warming among species within an ecoregion.

Status and declining trend of Sparrow’s-egg Lady’s-slipper (Cypripedium passerinum) orchids in Pukaskwa National Park, Ontario, Canada

2021-03-09T12:49:59-08:00

Pukaskwa National Park hosts part of a disjunct population of the perennial orchid species Sparrow’s-egg Lady’s-slipper (Cypripedium passerinum) on the north shore of Lake Superior, Ontario, Canada. Monitoring of C. passerinum within Pukaskwa National Park occurred between 1979 and 2019. During that period, the total number of stalks and the number of C. passerinum colonies within the park have declined, while the proportion of flowering stalks at colonies has increased. Although the number of stalks at extant colonies is stable, this population may be suffering from lack of recruitment and is at risk of extirpation. We hypothesize that the decline and lack of recruitment are a result of changing habitat conditions due to natural and anthropogenic influence.

Continuing expansion of Narrow-leaved Cattail (Typha angustifolia) and decline of a provincially rare fen in the Holland Marsh, Ontario

2021-05-06T16:34:49-07:00

At the time of European settlement, an extensive graminoid wetland existed at the confluence of the East and West Holland Rivers at the southern end of Lake Simcoe, Ontario. However, by 1925, clearing and draining of the marsh for specialty agriculture (i.e., market gardens) had begun and, by the 1940s, ~46% of the wetland had been cleared and another 13% was lost before 2016. Concurrent with marsh conversion has been an increase in Narrow-leaved Cattail (Typha angustifolia) in the remnant wetland. This study documents the change in the Holland Marsh wetland by delineating boundaries between marsh, fen, and shrub communities on aerial photographs taken at ~10-year intervals between 1946 and 2015 and documenting vegetation change along transects running perpendicular to tributaries bisecting the wetland. The extent of fen habitat within the Holland Marsh has been decreasing since 1946 at an average rate of 0.24 ha/year because of increases in both shrub and marsh (i.e., T. angustifolia) communities. Typha angustifolia expansion has been predominantly from along the margins of the Holland River where soil phosphorus concentration is significantly higher than in the core of the fen. Beyond 30 m from the river, vegetation dominance shifts from T. angustifolia to sedges (Cyperaceae). Managing phosphorus loading from upstream land uses will be of critical importance in protecting this habitat, which is rare in southern Ontario.

New Titles

2022-04-28T21:05:25-07:00

The Canadian Field-Naturalist welcomes our new Book Review Editor

2022-04-28T20:48:07-07:00

"We Are All Whalers: the Plight of Whales and our Responsibility" by Michael J. Moore, 2021 [book review]

2022-04-28T20:51:00-07:00

"Wolves: Western Warriors" by Julie Argyle, 2022 [book review]

2022-01-27T12:02:18-08:00

Cover

2022-04-28T21:00:27-07:00