| The objective of this study was to evaluate the relationship between landscape structure and variables linked to the nesting success of birds (NSB) following timber harvest in the humid boreal balsam fir forest, of the Laurentian massif located in the southern part of the boreal zone. I first examined three variables from landscape structure (forest area, core area of the forest, and length of edges present in the landscape) at two spatial scales (83 and 1610 ha) and I measured their association with four extensive methods linked with NSB, based on parental activity and nest predator activity (visit to bait stations, presence of gray jays Perisoreus canadensis or red squirrels Tamiasciurus hudsonicus). Variability in all indicators was small over the study area and independent from landscape structure variables. Nest predator activity was low in the mature forest and can explain the lack of associations among NSB indicators. Since the current timber harvesting methods are powerful generators of forest edges, I next performed an experiment to evaluate, at a third spatial scale (0–120 m), the existence of a relationship between edges and the activity of nest predators. No increase in the activity of nest predators was associated with the proximity to the edges and depredation events were not associated with the prior detection of the red squirrel. Depredation was higher on the ground than in trees, however. Finally, the distribution of nest predator activity in relation to landscape can provide further insight on the impacts of forest management on NSB. A telemetric assessment of bird locations for eleven groups of gray jays showed that they concentrated their activities near the forest edges, especially at less than 30 m from open areas. Moreover, their movements were slower in landscapes with abundant edges, suggesting that they focused their foraging within those areas. In conclusion, the NSB is not affected by modification of landscape structure variables in the humid boreal balsam fir forest, but a high population density of gray jays could affect NSB at less than 30 m from forest edge. |
