Bird Response to Wildlife Enhancement Silvicultural Treatments Daniel Twedt U. S. Geological Survey Patuxent Wildlife Research Center
Forest Management Desired Forest Conditions for Wildlife
Desired Stand Conditions Reduced basal area Patchy canopy cover (reduced and with gaps) Understory developed Emergent trees Cavity & den trees Stressed/dead/dying trees Vines & cane present
Stand Conditions (Primary Management Factors) Forest measurement Desired Stand Condition Conditions that may warrant management Canopy cover 60 70 % >80% Mid-story cover 25 40 % <20% or >50% Basal area 60 70 ft 2 /acre >90 ft 2 /acre with > 25% older age class Tree stocking 60 70 % <50% or >90%
Stand Conditions (Secondary Management Factors) Forest measurement Desired Stand Condition Conditions that may warrant management Dominant trees >0.5 / acre <0.25 / acre Under-story cover 25 40% <20% or >60% Regeneration (advanced intolerant) 30-40% of area <20% of area Coarse woody debris >200 ft³ / acre <100ft³ / acre Small cavities (< 10 diameter) Den trees (> 10 diameter) Standing dead / stressed trees >4 visible holes / acre <2 visible holes / acre >1 visible hole / acre <1 visible holes / acre >6 stems / acre >10 dbh <4 stems / acre >10 dbh >2 stems/ac >20 dbh <1 stem/ac >20 dbh
Desired Landscape Condition (>10,000 acres) Habitat Type Proportion of area Forest Cover 70 100 % - Managed forest 70 95 % - Regenerating forest <10 % Passively managed forest 5 30 % Shrub/scrub <5 % At any point in time 35 50% of area would meet DSC
Forest Management Options Even-aged Clear cuts Shelterwood Seed tree Results Little overstory Even canopy Bird species change Mostly shrub species Uneven-aged Thinning Group selection Patch cuts Single tree selection Results Overstory remains Uneven canopy Bird species stable Priority species increase
Forest Management Options
Desired Stand Conditions Conditions achieved though: Clustered or Variable-Retention thinning That result in: Retained and protected dominant trees Open canopies that promote understory proliferation Patch-cuts wherein shade-intolerant tree species (e.g. oaks) regenerate
Uncut Thinned Thinned with patches
Stand Conditions Parameter Control Treated Canopy Cover (%) 94 80 Basal Area (ft 2 /acre) 140 96 Understory Cover (%) 59 78 Advanced Regeneration 42 585 Dead Trees (stems/acre) 10 4 Crown Projection Area (ft 2 ) 322 366 Stem Diameter (QMD inch) 13 13 6 years post-harvest
Stand Conditions Parameter Control Treated Canopy Cover (%) 94 80 Basal Area (ft 2 /acre) 140 96 Understory Cover (%) 59 78 Advanced Regeneration 42 585 Dead Trees (stems/acre) 10 4 Crown Projection Area (ft 2 ) 322 366 Stem Diameter (QMD inch) 13 13
Treatments intended to benefits bears, migratory songbirds, and resident game species. Are treatments effective? How do breeding and wintering birds respond to silviculture treatments
Silviculture & Bird Densities THINNED Thinned 1 13 years post-treatment (most <6 years) Thinned with patches UNCUT THINNED Uncut WITH PATCHES
Breeding Bird Densities 23 stands: 25m 50m 100m 9 thinned, 9 uncut, 5 patch-cut 6 point-counts / stand 3 visits / year for 2 years
Breeding Bird Densities (Similar Densities Treated and Control) Blue-gray Gnatcatcher Carolina Wren 3.5 birds / ha Yellow-throated Vireo Northern Cardinal Hooded Warbler Blue Jay Downy Woodpecker Great-crested Flycatcher Northern Parula Red-bellied Woodpecker Wood Thrush <0.1 birds / ha
Breeding Bird Densities (Similar Densities (Neutral response Treated and?) Control) Prothonotary Warbler 0.88 birds / ha 0.05 birds / ha Swainson s Warbler
Breeding Bird Densities (Negative response: birds / ha) Species Treated Control Acadian Flycatcher 3.4 4.6 Tufted Titmouse 2.3 3.1 Carolina Chickadee 1.0 1.3 Summer Tanager 0.6 1.0 Red-eyed Vireo 0.4 0.7
Breeding Bird Densities (Positive response: birds / ha) Species Treated Control Orchard Oriole 0.22 0.04 Red-headed Woodpecker 0.11 0.06 Kentucky Warbler 0.19 0.06 Eastern Towhee 0.66 0.12 Yellow-breasted Chat 1.06 0.01 Eastern Wood-pewee 0.24 0.16
Breeding Bird Densities (Positive response: birds / ha) Species Treated Control Indigo Bunting 1.91 0.92 White-eyed Vireo 1.83 1.03 Brown-headed Cowbird 1.48 1.20
Temporal Response
Detections Years post-treatment
Detections Years post-treatment
Detections Years post-treatment
Breeding Bird Densities Temporal Effects Species Apex Duration Red-headed Woodpecker 1 8 Eastern Wood-pewee 3 10 Orchard Oriole 5 11 Brown-headed Cowbird 7 12 White-eyed Vireo 8 16* Swainson s Warbler 16* 28* * Exceeds span of years evaluated
Winter birds -250 m line transects -2 transects per stand Thin Patch Uncut Species 16 16 14 Abundance 105 172 70 Thin: Rusty Blackbird & Red-headed Woodpecker Patch: Swamp and White-throated Sparrows, Common Grackle, & American Goldfinch Uncut: Golden-crowned Kinglet & American Robin
Constant Effort Netting
Constant Effort Netting 50 Treated Contol Daily Captures 40 30 20 10 0 May June July August
100 90 80 70 60 50 40 30 20 10 0 Winter Captures Year 1 Year 2 Year 3 Thin Patch Uncut Captures / 100 net hours
Captures / 600 net-hours 60 50 40 30 20 10 0 INBU YBCH 0 2 4 6 8 10 12 14 Years Post Treatment
Captures / 600 net-hours 60 50 40 30 20 10 0 NOCA WEVI 0 2 4 6 8 10 12 14 Years Post Treatment
Captures / 600 net-hours 30 25 20 15 10 5 0 HOWA SWWA 0 2 4 6 8 10 12 14 Years Post Treatment
Recommendations Treatment severity >50% canopy retained Embedded in matrix of treatment ages (0 13 yrs) Patch-cuts up to 3 acres Treatment extent DFC recommendation of 30% area non-treated Treatment Intervals 12 16 years for most species >20 years for some species
Priority Birds Methods West Coast Option! Ecologically Appropriate Landscape Context Thinning = > Understory Multiple Tree Species Retention of Forest Structure How Much and Where Snags and Downed Wood Bird Response
Questions?