3.3.2 Wildlife Tree/Sign Surveys

Wildlife trees are living or dead trees in various stages of decay. These trees are essential to woodpeckers for nesting, roosting, foraging and communication (i.e., drumming). Therefore, the presence/not detected (possible) of this group in an area may be determined directly through sightings of woodpeckers on wildlife trees and indirectly, using evidence such as nesting or foraging excavations on wildlife trees. Recent excavations can be distinguished from old ones for approximately one year based on the presence, abundance and colouration of wood chips on the ground and on the colouration of wood at the cavity entrance (Bull 1981). Cavities of some woodpeckers can be identified to species based on their size and shape. Sapsucker cavities are difficult to identify to species and should therefore be combined as one group. Table 3 includes descriptions of characteristic woodpecker sign. It is important to recognize that many woodpecker cavities are not completed or used (Bull 1981). For example, in studies conducted by Bull (1981), between 40 and 60% of Pileated Woodpecker nests excavated in north-eastern Oregon were incomplete. Consequently, results obtained from sign surveys should be interpreted cautiously due to the variability associated with sign survey data.

To conduct an intensive wildlife tree/sign survey a simple encounter transect is recommended.

Table 3. Descriptions of feeding and nesting excavations made by selected woodpecker species.

Species	Foraging (F) / Nesting (N)	Description
Pileated Woodpecker (B-PIWO)	N	relatively large oval-shaped holes
Pileated Woodpecker (B-PIWO)	F	relatively large, rectangular holes into the heartwood of standing live/dead trees and stumps and logs
Northern Flicker (B-NOFL)	N	relatively large oval-shaped holes
Three-toed Woodpecker (B-TTWO)	N	round-shaped holes with bark often peeled-off around entrance
Three-toed Woodpecker (B-TTWO)	F	bark flakes removed or bark stripped from the lower bole
Black-backed Woodpecker (B-BBWO)	N	round-shaped holes with bark often peeled-off around entrance
Black-backed Woodpecker (B-BBWO)	F	bark flakes removed or bark stripped from the lower bole
Sapsucker spp.	F	rows of small, squarish holes in a vertical series in the bark of live trees

Using Encounter Transects for Wildlife Tree/Sign Surveys

A generalized method for conducting wildlife tree/sign surveys involves using simple encounter transects and distance sampling methods. Surveyors walk at a relatively slow pace along transects, recording information about woodpecker sign and species encountered en route.

Office Procedures

• Review Section 2 - Survey Design, of the RIC Species Inventory Fundamentals manual.
• Obtain maps, aerial photographs and other existing inventory material. Depending on availability, obtain the following:
• topographic maps (typically 1:50,000 are used, but a larger scale such as 1:20,000 TRIM maps are ideal for identifying and then overlaying transects on to the map sheets)
• forest cover maps (1:20,000)
• aerial photographs (1:20,000 or 1:5,000)
• cruise data, wildlife/danger tree assessment reports (Wildlife Tree Committee of British Columbia 1993)
• Compile a list of all potential woodpecker species in the study area
• Obtain background information on target species (behaviour, habitat requirements, site-specific nesting chronology, activity schedules, characteristic calls or drummings, etc.).
• Obtain information on terrain structure/features of sampling area (slopes, aspects, gullies, cliffs, creeks, etc.) and select transect lines from maps.
• Determine Biogeoclimatic zones and subzones, Ecoregion, Ecosection, and Broad Ecosystem Units for transects.
• Determine the distance between transect lines based on the intensity of the survey and on the density of the habitat.

Equipment

• Maps
• Datasheets
• Compass
• Flagging tape
• Binoculars
• Woodpecker sign identification guide
• Digital timer
• Altimeter
• Thermometer
• Hip chain

Field procedures

• Rotate observers among transects and sites to distribute observer bias evenly.
• Each transect should be of a size that can be surveyed in one morning.
• Record the transect description. This should include: observer(s); date; time start/end; distance travelled; weather; and a unique label which identifies the transect.
• As the transect is walked at a relatively slow pace (0.5 km/hr to 2 km/hr), scan for woodpeckers and for wildlife trees with woodpecker sign. Check around the base of trees for excavated cavity chips.
• For each wildlife tree that has a woodpecker on it or contains woodpecker excavations:
• Record the distance from the centre of the transect to the center of the tree (measured with hip chain). Measures of distance from the transect to the observation will allow for simple measures of abundance (or density).
• Record woodpecker species present on the tree (where the woodpecker was first observed).
• Record the woodpecker species associated with the sign (refer to Table 3) and sign type (active/old nest cavity, roost cavity, new/old foraging excavation).
• Record tree species.
• Record Wildlife tree classification code (refer to Inventory Technical Committee 1995: see Figures 1 and 2).
• Measure tree DBH (to the nearest ± 0.1 cm at 1.3 m height on the high side of the trees) and height.

Data Entry

The Design Component type for this survey is transects. They are the sample unit. When digitally entering your survey data into the provincial database, choose `Transect' from the `Design Component Type' picklist.

	LIVE		DEAD
Decay Class	1	2	3	4	5	6	7	8	9

Figure 2. Wildlife tree classification system of evergreen trees (Figure from Inventory Technical Committee 1995).

	LIVE	DEAD				DEAD FALLEN
Decay Class	1	2	3	4	5	6

Description

Live/healthy: no decay.

Live with defects: dead or broken top, dead limbs, fungal conks. Dying tree.

Dead: most limbs intact, some internal rot, top usually broken.

Dead: most limbs gone, top broken, extensive heartrot.

Dead: top 1/3 or more broken off, no branches, extensive heartrot.

Dead, fallen: downed trees, coarse woody debris.

Figure 3. Wildlife tree classification system of deciduous trees (Figure from Inventory Technical Committee 1995).