The Canadian Field-Naturalist (E-Journal)
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Nest site characteristics of cavity-nesting birds on a small island, in Haida Gwaii, British Columbia, Canada
Get PDFMany studies of cavity-nesting birds in North America are conducted in large continental forests and much less is known about them in island ecosystems. We describe a 29-year study of tree species, nest site characteristics, and fledge dates of cavity-nesting birds on a small island in Haida Gwaii, British Columbia (BC). Seven cavity-nesting bird species were documented on East Limestone Island and 463 nests were found in 173 different trees. Nest trees were significantly taller and had a greater diameter than a random sample of snags. Tree height did not differ among bird species but diameter at breast height was larger for trees used by Brown Creeper (Certhia americana) than for other species. Cavity-nesters selected tree decay classes 2–7 (all dead/near dead [snags]), with 85% in decay class 4 (35%) or 5 (50%), similar to the random snag sample (class 4, 32%; class 5, 42%). Cavity height ranged from 2.6 to 44.9 m and for all species, except Brown Creeper, the mean nest height was >60% of the mean tree height. Nest heights were generally greater than observed elsewhere in BC. Nest cavity orientation was random except for Red-breasted Sapsuckers (Sphyrapicus ruber), for which only 13% of the cavity entrances faced southeast. Median fledging dates ranged from 7 June (Chestnut-backed Chickadee [Poecile rufescens]) to 28 June (Northern Flicker [Colaptes auratus]). Estimated median dates of clutch completion were similar for all species. Our results show that large snags provide habitat for a high diversity of cavity-nesting birds on Haida Gwaii
Rooting depth and below ground biomass in a freshwater coastal marsh invaded by European Reed (Phragmites australis) compared with remnant uninvaded sites at Long Point, Ontario
Get PDFInvasive European Reed (Phragmites australis subsp. australis) outcompetes native vegetation, reducing floristic diversity and habitat value for wildlife. Research in coastal salt marshes has indicated that P. australis invasion may be facilitated by its relatively deep rooting depth, but in freshwater marshes the growth pattern of below ground tissues in relation to water depth is uncertain. To determine if P. australis is rooting more deeply than resident wetland plant species in a freshwater coastal marsh on Lake Erie, Ontario, we measured the vertical distribution of below ground biomass in P. australis invaded marsh sites and compared it to the below ground biomass distribution in nearby sites not yet invaded by P. australis. These invaded and uninvaded sites were paired by water depth, which is known to influence resource allocation and rooting depth. Below ground biomass in invaded sites was greater than in uninvaded sites (t28 = 3.528, P = 0.001), but rooting depth (i.e., the depth at which 90% of total below ground biomass is accounted for) was comparable (t28 = 0.992, P = 0.330). Using water depth and site type, general linear models could predict below ground biomass (F2,55 = 9.115, P < 0.001) but not rooting depth (F2,55 = 1.175, P = 0.316). Rooting depth is likely affected by other factors such as substrate type and the depth of the organic soil horizon
"Re-Bisoning the West: Restoring an American Icon to the Landscape" by Kurt Repanshek, 2019. [book review]
Get PDF"A Sand County Almanac and Sketches Here and There" by Aldo Leopold. Introduction by Barbara Kingsolver, 2020. [book review]
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Batch spawning in five species of minnows (Cyprinidae) from Ontario, Canada
Get PDFBatch spawning, the act of spawning more than once within a spawning season, is assessed in six species of minnows (Cyprinidae) from Ontario, Canada. The bimodal frequency distribution of egg size in mature specimens suggests that the following species are batch spawners: Blacknose Dace (Rhinichthys atratulus), Brassy Minnow (Hybognathus hankinsoni), Common Shiner (Luxilus cornutus), Creek Chub (Semotilus atromaculatus), and Hornyhead Chub (Nocomis biguttatus). However, there is no evidence that Northern Pearl Dace (Margariscus nachtriebi) is a batch spawner. Thus, we now have evidence that 11 of 39 cyprinid species in Ontario are batch spawners. Knowledge about the reproductive habits of these species should be integrated into the comprehensive standards for the protection of fish habitat in Ontario to ensure the survival of populations
A successfully breeding, partially leucistic American Robin (Turdus migratorius)
Get PDFAmerican Robin (Turdus migratorius) is the most abundant and broadly distributed thrush in North America. Both sexes likely engage in mate choice, and there is some evidence of assortative mating based on breast colour in this species. Over two breeding seasons, we documented a case of partial leucism, primarily of the breast feathers, in a male American Robin in London, Ontario, Canada. We report evidence that the leucistic robin was capable of successful breeding. How the fitness of leucistic versus normal robins compares and how leucism influences mate choice in this and other species remain to be explored
Occurrence of anthropogenic litter in nestling Tree Swallows (Tachycineta bicolor)
Get PDFWhile undertaking a study of the effects of strontium-90 on Tree Swallow (Tachycineta bicolor) near Chalk River, Ontario, we noticed the presence of anthropogenic litter (pieces of metal, glass, and plastic, and paper, plastic, and foil wrappers, >1 mm in size) in the nestlings. Although combustible litter (pieces of plastic and wrappers) were not quantified before the nestlings were incinerated in 2014 and 2015, gizzards were dissected in 2016. Litter (>1 mm diameter) was found in 30% of the 74 nestlings examined. This material is most likely provided to nestlings, along with food (insects) and natural grit (sand, stones, and mollusc shells), which we also found, by parent birds; however, it could lead to internal injuries and/or harmful substances being absorbed by the young birds