The Canadian Field-Naturalist (E-Journal)
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Comparative reproductive parameters of sympatric Lesser Scaup (Aythya affinis) and Ring-necked Duck (Aythya collaris) in parkland Manitoba
Get PDFWaterfowl 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
Abundance and arboreal tendencies of slugs in forested wetlands of southwestern Nova Scotia, Canada
Get PDFNon-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
Relative abundance and range extensions of bird species in central Labrador
Get PDFBird 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
Rare species of dodder (Cuscuta L.; Convolvulaceae) in Quebec and a plea for their search in the wild
Get PDFWe 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
Raven (Corvus corax) as a novel food item for lynx (Lynx canadensis)
Get PDFCanada Lynx (Lynx canadensis) is a specialist predator of Snowshoe Hare (Lepus americanus), which dominates its diet. However, hare populations cycle over 9–11 years, and many lynx disperse or starve during cyclic lows of their prey. Here, I report observations of Canada Lynx scavenging and attempting to prey on Common Raven (Corvus corax). In addition, I provide a brief review of birds as a food item of lynx. These are the first observations of ravens as a food source for lynx and may be a response to lynx being malnourished. The value of these observations is that they highlight the adaptability of some lynx to opportunistically use novel prey species during the decline phase of cyclic Snowshoe Hare
