Densité et succès reproducteur de la grive des bois (Hylocichla mustelina) dans les parcs nationaux d’Oka et du Mont-Saint-Bruno

Densité et succès reproducteur de la grive des bois (Hylocichla mustelina) dans les parcs nationaux d’Oka et du Mont-Saint-Bruno

Marc-André Villard, Thierry Grandmont, Mathieu Lemay and René Charest - Le Naturaliste canadien - Volume 148, Number 1, Spring 2024

La grive des bois (Hylocichla mustelina) a été désignée espèce menacée au Canada en 2012. De 1970 à 2021, ses effectifs auraient chuté de 75 % au Canada et de 84 % au Québec. La présente étude visait à déterminer le statut de l’espèce dans 2 parcs nationaux de la région de Montréal. En 2021 et en 2022, 88 nids ont été trouvés dans le parc national d’Oka, contre 10 au parc national du Mont-Saint-Bruno (2022). La densité de nids était nettement inférieure à Mont-Saint-Bruno (0,03/ha versus 0,10/ha), possiblement en raison du surbroutement de la végétation par le cerf de Virginie (Odocoileus virginianus). Les taux de survie des nids variaient d’un parc à l’autre et d’une année à l’autre (Oka : 68,2 % en 2021 et 27,6 % en 2022 ; Mont-Saint-Bruno : 68,9 %). La cause principale d’échec des nids était la prédation. Le taux de parasitisme par le vacher à tête brune (Molothrus ater) était plus élevé à Mont-Saint-Bruno (25 % versus 1,9 %). À Oka, la prédation des nids était plus forte chaque année le long du sentier le plus fréquenté, ce qui suggère un effet négatif du taux de passage des visiteurs sur le succès des nids.

The Wood Thrush (Hylocichla mustelina) was listed as Threatened in Canada in

2012. Between 1970 and 2021, its numbers are estimated to have declined by

75% nationally, and by 84% in the province of Québec. The aim of the present

study was to document the status of this species in two national parks in the

Montréal region. Eighty-eight nests were found in Oka National Park (parc

national d’Oka, 2021 and 2022 combined), and 10 in Mont-Saint-Bruno National

Park (parc national du Mont-Saint-Bruno, 2022). Nest density was substantially

lower at the Mont-Saint-Bruno site (0.03/ha versus 0.10/ha), possibly due to

overbrowsing by white-tailed deer (Odocoileus virginianus). Nest survival rate

varied as a function of location and year: Oka: 68.2% in 2021 and 27.6% in

2022; Mont-Saint-Bruno: 68.9%. The main cause of nest failure was predation.

The rate of brood parasitism by brown-headed cowbird (Molothrus ater) was

higher at Mont-Saint-Bruno (25% versus 1.9%). In Oka, nest predation was

higher along the most heavily used trail in both study years, suggesting a

negative impact of trail use by visitors on nest success.

Losing the edge: How wood thrush population trends differ in different parts of their range

Losing the edge: How wood thrush population trends differ in different parts of their range

Dr. Rémi Torrenta - Birds Canada/Oiseaux Canada - 18 August 2022

Focusing mostly on breeding populations in Ontario and Québec, we found important differences between populations of the St. Lawrence Lowlands, located at the inner core of the species’ Canadian breeding range, and populations of the Canadian Shield, located at the edge of its Canadian breeding range. The population in the core was surprisingly stable despite high rates of forest loss and fragmentation. At the edge of its range, Wood Thrush populations may be more at risk of local extinction due to a combination of factors: lower habitat quality and prey availability, but also fewer new birds moving into these areas (i.e., lower immigration) ... the first important thing to mention is that those forest fragments have a dense understory layer, which has been very favorable to the Wood Thrush, especially following regeneration after the 1998 ice storm. The other thing we found is that young birds moving into these fragments from larger forests (i.e., natal dispersal) may compensate for the low number of young produced within these fragments, thus “subsidizing” this fragile population.

Links/Liens: Research paper/Article de recherche, 

Echoes of the Forest: Tracking the Journey of the Wood Thrush

Echoes of the Forest: Tracking the Journey of the Wood Thrush: A two-year study aimed at the conservation of one of Vermont’s treasured songbirds
Pete Patrick - Audubon Vermont - September 02, 2025

During breeding season, Wood Thrush prefer mature deciduous or mixed forests with tall trees and a dense understory for foraging and nesting. Unfortunately, both of these habitats are experiencing fragmentation which leads to limited access to quality food and shelter ... Declines in Wood Thrush populations have been especially prevalent in the northeastern regions of their range, with an overall population loss of 59% since 1970. ... As such, scientists have noticed a decades-long trend of population decline. In response to this decline the U.S. Fish and Wildlife Service recruited bird banders and organizations, like Audubon Vermont, for the Wood Thrush Nanotagging Program, colloquially named WOTH Party. WOTH Party is a two-year study that tracks the movements and behavior of Wood Thrush in their breeding and wintering grounds using nanotags.