Boreal songbirds and variable retention management: a 15-year perspective on avian conservation and forestry

Partial retention harvest (PRH) has received attention as an alternative to clear-cutting, yet most studies of its effects on boreal songbirds have been conducted shortly after harvest. We assessed responses of songbird assemblages to PRH over a 15-year post-harvest period at the EMEND experiment in the mixedwood forest of Alberta, Canada. Four partial retention levels (10%, 20%, 50%, and 75% of stems) were applied in a series of 10 ha “compartments” during winter 1998–1999 with matching clearcuts and unharvested control compartments in each of three replicates in four common mixedwood cover-types. Songbirds were surveyed using the point count method in 1998 (pre-harvest) and after harvest in 1999, 2000, 2005, 2006, 2012, and 2013. Partial retention harvests that left ≥20% of merchantable stems mitigated changes to songbird assemblages away from, and accelerated recovery toward, the unharvested benchmark. However, assemblages of 14- to 15-year-old controls differed from those observed prior to harvest, no...