The Canadian Field-Naturalist

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2022-01-22T10:40:42-08:00

Eighteenth census of seabirds breeding in the sanctuaries of the North Shore of the Gulf of St. Lawrence, 2015

2021-02-13T03:11:59-08:00

In 1925, ten migratory bird sanctuaries were created on the North Shore of the Gulf of St. Lawrence, and their breeding seabird populations have been censused every five years since. Between 2010 and 2015, only three alcid species exhibited positive population trends (Razorbill [Alca torda], Common Murre [Uria aalge], and Atlantic Puffin [Fratercula arctica]), while the remaining 13 species showed declining trends. Leach’s Storm-Petrel (Hydrobates leucorhous) and Caspian Tern (Hydroprogne caspia) are on the verge of disappearing from the sanctuaries, and the prolonged and rapid decline in Black-legged Kittiwake (Rissa tridactyla) is worrisome. Based on historical records since 1925, it appears that seabird communities are faring well in some sanctuaries (e.g., Baie de Brador, Îles aux Perroquets, and Îles Sainte-Marie), while numbers are at low levels in others (e.g., Île à la Brume, Baie des Loups, and Saint-Augustin). Human disturbance, harvest of seabirds (eggs and birds), and predation are among the issues potentially most affecting seabird populations on the North Shore of the Gulf of St. Lawrence.

Introduced earthworms (Lumbricidae) in restored and remnant tallgrass prairies of southern Ontario

2021-02-10T10:34:25-08:00

Introduced earthworms alter the trajectory and composition of plant communities, for example, through their feeding, burrowing behaviour, and interactions with seeds. High densities of several earthworm species may decrease native biodiversity and disrupt restoration efforts in tallgrass prairies. This affects efforts to conserve and restore such habitat, which is of high conservation and restoration priority in eastern North America and typically restored through seeding events. To date, Lumbricus terrestris (Lumbricidae) and other species have remained largely undocumented in tallgrass prairies. We surveyed 22 tallgrass prairie sites in southern Ontario, Canada, to document earthworm density and species. Lumbricus terrestris was found at all sites. The average density was 66 ± 91 (SD) earthworms/m² across our sampling plots, mostly juveniles (~94%). The number of all earthworms per plot significantly increased with the number of earthworm middens in each plot (χ²₁ = 4.50, P = 0.034). Prairies with a large number of middens had high earthworm density, but middens alone appear to explain little variation in our data (linear mixed-effects model, marginal R² = 0.12) meaning there are other biologically important factors that affect their density. However, we found no effects of soil pH, organic matter content, or texture on the number earthworms per plot suggesting that earthworms can invade a range of tallgrass prairie soils with pH values between 5.27 and 7.67.

Rare species of dodder (Cuscuta L.; Convolvulaceae) in Quebec and a plea for their search in the wild

2021-02-19T07:45:57-08:00

We report three rare dodders (Cuscuta L.) from Quebec: Buttonbush Dodder (Cuscuta cephalanthi Engelmann), Hazel Dodder (Cuscuta coryli Engelmann), and Smartweed Dodder (Cuscuta polygonorum Engelmann). Detailed descriptions of their morphological characteristics, ecology, and host range are discussed. The genus Cuscuta is severely under-collected in Quebec and elsewhere, and targetted fieldwork is needed to better assess the distribution and conservation status of the three rare (or overlooked) species reported here. An identification key to all Cuscuta species from Quebec is provided to aid botanists in accurately identifying these challenging species.

Relative abundance and range extensions of bird species in central Labrador

2020-04-24T13:17:24-07:00

Bird communities in Labrador remain poorly described, including in the lower Churchill River valley, which lies within an offshoot of the boreal shield ecozone and features vegetation communities typically found more than 100 km to the south. Between 2006 and 2016, we conducted 1139 point counts in June and early July at 617 sites along 63 routes within and adjacent to the lower Churchill River valley. We documented 80 species during the surveys and a further nine species incidentally. The most numerous species were Swainson’s Thrush (Catharus ustulatus), Ruby-crowned Kinglet (Corthylio calendula), and Dark-eyed Junco (Junco hyemalis). Relative bird abundance was highest in hardwood and mixedwood forests and lowest in areas dominated by Black Spruce (Picea mariana). Among the species we observed were 19 that we considered to be regionally rare, based on existing documentation. The most abundant of these were Least Flycatcher (Empidonax minimus), Cedar Waxwing (Bombycilla cedrorum), and Magnolia Warbler (Setophaga magnolia), each with more than 80 observations over multiple years, spanning 10 or more areas within the lower Churchill River valley. Almost all of the regionally rare species were strongly associated with either hardwood forests, large conifers, or dense riparian vegetation. These features are relatively widespread within the lower Churchill River valley, but scarce elsewhere in Labrador. It is unclear whether the results observed represent recent range expansions or our surveys were simply the first to document long-standing regional populations; regardless, we recommend that our records be considered in future revisions to range maps for these species.

Comparative reproductive parameters of sympatric Lesser Scaup (Aythya affinis) and Ring-necked Duck (Aythya collaris) in parkland Manitoba

2020-10-21T10:52:35-07:00

Waterfowl managers are concerned that Lesser Scaup (Aythya affinis) breeding populations remain below conservation goals. Contrasting population growth trajectories for sympatric, phylogenetically similar Lesser Scaup and Ring-necked Duck (Aythya collaris) at Erickson, Manitoba, Canada, prompted investigations that might help explain these trends and provide insight for population management of both species. We collected data (2008–2018) on productivity (broods/pair), water levels, hatching dates, age class-specific brood sizes, duckling daily survival rate, and brood female response to disturbance and compared results between species over time. Ring-necked Duck productivity was greater (0.42 versus 0.28, P < 0.01), hatching dates were earlier (19 July versus 27 July, P < 0.001), and females attempted to hide their broods more often than did Lesser Scaup (16% versus 3%, P < 0.001), but Ring-necked Duck age class-specific brood sizes were smaller than for Lesser Scaup (Ia broods: 6.1 versus 6.8, P = 0.02; IIa broods: 5.6 versus 6.2, P = 0.02). Duckling daily survival rates were similar. Productivity of both species was positively related to annual change in pond water level and both demonstrated similar rates of response to change. There was no support for an association between productivity and one- or two-year lagged pond water levels. Consistent with previous findings, our results suggest that greater Ring-necked Duck productivity is a likely proximate cause for the differing population growth trajectories between the species. We suggest that better Ring-necked Duck nest placement may be a contributing factor to the greater nest success observed.

Distribution, status, and habitat characteristics of Columbia Quillwort (Isoetes minima, Isoetaceae) in Canada

2020-10-30T09:28:57-07:00

In Canada, the globally rare lycophyte, Columbia Quillwort (Isoetes minima), is currently known from four subpopulations, all within a 25-km radius of Castlegar in the Selkirk and Monashee Mountain ranges of southern British Columbia. These constitute just over a quarter of all known subpopulations in Canada and the United States. The species is found in Canada in sloping pocket meadows that are naturally fragmented within a larger forested matrix. The plants grow in spring seepage areas in thin soils that discourage the establishment of larger, more vigorous vascular plant competitors. Long combined within Isoetes howellii (sensu lato), I. minima has only recently been confirmed to be a distinct species, and, in 2019, it was assessed as Endangered by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). We build on information in the COSEWIC status report by describing the species’ morphology and ecology in greater detail and provide a comparison of critical identification features of closely related species as well as a dichotomous key for Isoetes species in British Columbia.

Abundance and arboreal tendencies of slugs in forested wetlands of southwestern Nova Scotia, Canada

2020-12-10T11:08:08-08:00

Non-native slugs, such as Arion, are becoming a concern for land managers in Nova Scotia, Canada, particularly in forested wetlands. They appear to have a highly diverse diet and may pose a particular risk to native slug species and to rare or at-risk lichens. We provide novel information on the distribution, abundance, arboreal tendencies, and seasonality of slugs in forested wetlands across southwestern Nova Scotia. We collected a total of 402 slugs representing seven species including two native species, Pale Mantleslug (Pallifera dorsalis) and Meadow Slug (Deroceras laeve), and five non-native Arion taxa. The three most abundantly caught taxa were Northern Dusky Arion (Arion fuscus), D. laeve, and Western Dusky Slug (Arion subfuscus). Arion fuscus and D. laeve were collected on the forest floor and on lichen-bearing trees, while A. subfuscus was collected only on the ground. All three taxa showed differences in collectability between July and September and low arboreal tendencies. We highlight that further studies are needed to better understand the biology and ecology of this largely neglected invertebrate group that seems to be dominated by non-native Arion species in the study region. Such information is crucial for conservationists and forest managers untangling the question of how non-native slugs affect native slug taxa and other groups including at-risk lichens.

First evidence of White-footed Deer Mouse (Peromyscus leucopus) on mainland New Brunswick, Canada

2020-09-25T20:25:59-07:00

White-footed Deer Mouse (Peromyscus leucopus) and the closely related, and more northerly ranging, Deer Mouse (Peromyscus maniculatus) broadly overlap in distribution and are often difficult to distinguish from each other. Based on molecular genetic data (cytochrome b gene), we report two new distribution records for P. leucopus for New Brunswick, Canada, the first mainland localities for this species in the province. Previous sampling of Peromyscus in New Brunswick may have overlooked the presence of P. leucopus, possibly because the specimens collected were all assumed to be P. maniculatus. However, current detection in New Brunswick may be part of a broader recent northward range expansion documented to be underway in P. leucopus. Although our use of a single mitochondrial gene to identify P. leucopus does not eliminate the possibility that the New Brunswick specimens are of hybrid origin, our results support the presence of P. leucopus in New Brunswick and suggest more detailed analyses will be required to determine the nature of any genetic interaction between P. leucopus and P. maniculatus in the province. Recognition of morphologically cryptic Peromyscus in southern New Brunswick also emphasizes the need to incorporate comprehensive methods to ensure the correct identification of specimens of this genus in Maritime Canada. We also note the potential implications of this discovery with respect to the incidence of Lyme disease in New Brunswick.

News and Comment

2022-01-21T20:12:18-08:00

"In Defense of Plants: an Exploration into the Wonder of Plants" by Matt Candeias, 2021. [book review]

2021-09-27T09:23:48-07:00

"Lyme Disease, Ticks and You: a Guide to Navigating Tick Bites, Lyme Disease and Other Tick-Borne Infections" by Shelley Ball, 2021. [book review]

2022-01-21T19:58:57-08:00

"A World on the Wing: the Global Odyssey of Migratory Birds" by Scott Weidensaul, 2021. [book review]

2021-12-07T20:19:07-08:00

"Bears: the Mighty Grizzlies of the West" by Julie Argyle, 2021. [book review]

2021-09-21T10:28:11-07:00

"The Redemption of Wolf 302: from Renegade to Yellowstone Alpha Male" by Rick McIntyre, 2021. [book review]

2021-08-20T13:26:24-07:00

New Titles

2022-01-21T20:08:24-08:00

Cover

2022-01-21T20:15:03-08:00