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Bird Habitat Conservation Toolkit

Image of Bird
A striking bird with a striking song. Listen for “see-see-see-see-see-SooZIE” in pure or mixed white spruce stands.

Black-throated Green Warbler

(Setophaga virens)
Overview
status
AlbertaSensitive
British ColumbiaBlue
Primary Habitat
Old coniferous/mixedwood
Nest Type
Canopy (conifer)
Territory Size
0.12 - 1 ha
Nest Reuse
No
Breeding Window
Jan
Feb
Mar
Apr
May
Jun
Jun
Jul
Aug
Sep
Sep
Oct
Nov
Dec
Peak: mid-June to late August
Stand-Level
High dispersed retention or >0.5 ha patches of large-diameter Sw, Bw
Landscape-Level
Old (100–130 years) riparian Sw or mixedwood, >100 ha if possible

Habitat Ecology

  • Black-throated Green Warblers are found in a wide range of forests containinglarge white spruce (including mixedwoods and deciduous-leading forests), with their highest densities in 100–130 year stands where they often use small-scale canopy gaps.1,2 They are also known to occupy young to mature forests.3,4
  • In BC, mature riparian white spruce or mixedwood forests are considered their most important habitat, while mature or old deciduous forests containing mature spruce may attract them.3
  • These warblers forage and nest on large-diameter (>50 cm dbh) white spruce.1
  • Black-throated Green Warblers usually nest in conifers5 but have shown some preference for paper birch with ~20 cm dbh in Alberta.1

Response to Forest Management

  • This species is most abundant on unlogged landscapes6 with a strong preference for forests exceeding the rotation age.7
  • In deciduous-dominated forests in Alberta, they disappeared from stands with 2–6% retention but were present at low levels in harvests with 40% retention.⁸ They were unlikely to be present in clearcut (i.e. no planned retention) stands up to 33 years postharvest.9
  • They may be sensitive to fragmentation: in New England, they were absent from forests <100 ha,5 and there is evidence that they avoid cutblock edges and crossing openings ≥25–40 m wide.2,10

Stand-level Recommendations

  • High retention (>40%) may be needed to reduce short-term harvest effects on this species, however these recommendations are based on studies from aspen-leading boreal mixedwood forests and may not be applicable to spruce-leading or -dominated forests.11,12
  • Retention patches placed ≤40 m apart may make it easier for these warblers to travel across large harvest areas, however this strategy has not been tested for efficacy.
  • Mixed-species retention patches (0.5 ha) containing large-diameter spruce may provide suitable nesting habitat in 30–60 years within a harvest block.2
  • Riparian buffers >20 m may support pairs, but larger (>60 m) buffers will likely be more effective.13

Landscape-level Recommendations

  • Mixedwood management to maintain coniferous-deciduous mixed stands on the landscape, as is present under NRV scenarios, will benefit this species.
  • Old (100–130 year-old) mixed and spruce-leading stands >100 ha will provide important habitat on intensively-managed landscapes, as retention patches are expected to take several decades to provide suitable breeding habitat.2
  • The role of older-than-rotation stands will likely be most important in BC, where its range is extremely limited and riparian spruce or mixed forests are highly valuable.3

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