More info for the terms: basal area, cover, density, fire severity, frequency, mixed-severity fire, prescribed fire, presence, relative frequency, selection, severity, snag, stand-replacing fire, surface fire, tree, wildfire
Black-backed woodpeckers commonly occur in burned areas in many parts of their distribution, using areas burned by both prescribed fire [22,29] and wildfire [2,5,8,14,22,25,26,28,36,41]. Fire may attract black-backed woodpeckers to areas where they were not previously documented [22,26,90] or found breeding [3,22,29]. Burned areas are considered a critical black-backed woodpecker habitat in some areas like the Interior Rocky Mountains, where significantly more (96% of detections from 13,337 sampling points) black-backed woodpecker detections were from recently burned (postfire years 1-4) forest compared to unburned vegetation types (P<0.001) [40].
Black-backed woodpecker response to fire will be discussed in relation to the following topics:
Use of burned areas for life history activities: Fire may indirectly impact black-backed woodpeckers by modifying habitat structure and/or food supply and reducing predation risk (reviewed by [11,79,80]), making burned areas attractive for black-backed woodpecker nesting and foraging.
Nesting in burned areas: Female black-backed woodpecker and nestling at a nest in a burned area in California. Photo courtesy of Martin Meyers.
Fire generates snags suitable for black-backed woodpecker nesting. Black-backed woodpeckers commonly nest in burned areas, including areas burned by wildfire [5,19,32,63,78,93,106,107] and prescribed fire [22,29]. Black-backed woodpeckers nest in forests burned by fires of varying severity, including mixed [19,78,93,106], moderate [5], and high [5,32,107] severity. They may nest in areas salvage-logged after fire [19,25,32,78]. The following table summarizes literature that documents black-backed woodpeckers nesting in burned areas.
Summary information of black-backed woodpecker nesting in burned areas Location,
forest type Time since fire (years, unless specified) Fire size, severity Habitat comparisons Number of nests Nesting comments
California,
white fir
1,2 years 370 acres,
mixed severity prescribed fire, unburned 1 Colonized the burned area 1 year after fire. A nest was found the 2nd year after fire. Nests were not found in unburned reference stands at any time [22].
California,
red fir
no information no information not studied 3 Two nests within a burned red fir forest, 1 on the edge of a burned pine (Pinus)-red fir forest [71].
Idaho,
mixed conifer
2 fires;
sampling encompassed 1-12 years unknown size,
mixed severity unlogged burned, salvage logged burned 51 Nest-site selection detailed below [78].
Montana and Idaho,
mixed conifer
Montana: 3,4 years
Idaho: 1,2 years
unknown size,
stand-replacing logged and unlogged 44
Nested in logged and unlogged areas, but more nests were in unlogged areas [32].
Oregon,
mixed conifer 1-4 years 85,000 acres,
mixed severity salvage logged and unlogged 297 Nest-site selection detailed below [19]. South Dakota,
ponderosa pine 1-4 years 83,500 acres,
mixed severity not studied 20 No nests were found the first year; 20 nests were found in years 2-4. Nest-site selection detailed below [106]. Washington,
lodgepole pine and mixed conifer 1 year 50 acres,
stand-replacing lodgepole pine and subalpine fir forest, lodgepole pine "thicket" [100] 1 One year after the fire, 1 pair bred in the burned area. None bred in nearby, unburned forest either before or after fire [29]. Washington,
Douglas-fir, ponderosa pine 4,5 years unknown size,
stand-replacing salvage logged and left with high, medium, and low snag densities 2 Black-backed woodpeckers did not nest in the low-density snag areas. There was 1 nest each in the medium- and high-density snag areas over the 2 years [25].
Wyoming,
mixed conifer
1 year 3,492 acres,
mixed severity severe, moderate, and unburned unknown Nested in both moderately and severely burned areas in postfire year 1 [5]. Alberta,
deciduous-dominated mixedwood forest 1,2,3,5 years 35,000 acres, mixed severity burned and unlogged, burned and salvage logged, and unburned and unlogged 1 One nest was found the first year after fire in burned, unlogged forest [93].
Alberta,
mostly quaking aspen, some white and black spruce
2 weeks >270,000 acres,
severe not studied 1 A nest was found within 2 weeks of a fire. The nest tree was located within 100 m of a patch of lightly burned and unburned forest [107].
Quebec,
black spruce
1-3 years 11,120 acres,
mostly severe not studied 92 Nest-site selection detailed below [63].
Nest-site selection: While many studies document black-backed woodpecker nesting in burned areas, only a few studies (e.g., [19,63,78,106]) examine nest-site selection. Variables positively related to nest-site selection include snag density [19,63,78,106], distance from edge, fire severity [106], prefire crown closure [78], and prefire stand age [63]. Selection for large snags may be positive [78] or negative [19].
Black-backed woodpecker nest searches were conducted for 4 years following a mixed-severity fire in the Black Hills of South Dakota. Twenty nests were found 2 to 4 years after fire. Compared to random locations, nesting areas were farther from unburned edges of forest (1,988.02 feet (605.95 m) vs. 553.48 feet (168.7 m)), had less of the landscape burned at low severity (20.8% vs. 24.9%), and had a higher snag density within 37.1 feet (11.3 m) of the nest sites (26.8 vs. 13.3 snags) [106]. Black-backed woodpecker nests were located following 2 mixed-severity wildfires in Idaho, during postfire years 1 to 12. Based on information from 51 nest sites, black-backed woodpeckers nested in larger snags (mean nest snag DBH approximately 16 inches (41 cm) DBH) and nested in areas with higher snag densities (mean snag density approximately 325 snags >9 inches (23 cm) DBH/ha) than what was randomly available (P<0.05). Nest sites were best predicted by nest snag DBH, snag density, and prefire crown closure (40%-70%) (all positive; P<0.05) [78]. One to 3 years after fire in black spruce forests of southern Quebec, black-backed woodpeckers concentrated nesting in areas that were mature forest prior to fire. Nest sites contained higher proportions of burned forest than random sites (P=0.07). Snag densities were higher in nest tree plots than in random plots (P<0.05), with density of snags >6 inches (15 cm) DBH 3 times higher in nest sites than random sites [63].
One study examined nest-site selection at multiple scales 1 to 4 years after wildfire in mixed-conifer forests in south-central Oregon. Some portions of the study area were salvage-logged, but prescriptions did not significantly reduce snag numbers or diameters within treatment units, and variables relating salvage logging to nest-site selection were not significant. Variables related to snag density were the strongest predictor of nest locations when vegetation was assessed within 165 feet (50 m) and 1,640 feet (500 m) of a nest. Within 165 feet (50 m) of a nest, nest site was positively related to snag density, average snag diameter, and logged stump density and negatively related to nest tree DBH and prefire crown closure. Within 1,640 feet (500 m) of a nest, the odds of nest occurrence nearly doubled for every 50 additional snags >9 inches (23 cm) DBH. Among trees large enough to support a nest cavity (≥6 inches (15 cm) DBH), black-backed woodpeckers chose smaller snags, with every 2-inch (5-cm) increase in DBH decreasing the odds of nesting by 15% [19].
Foraging in burned areas: Fire creates habitat for the bark and wood-boring beetles that are a preferred food item for black-backed woodpeckers (see Diet). Black-backed woodpeckers commonly forage in burned forests following prescribed fire [29] and wildfire [60,63,70]. Burned areas are used for foraging in the breeding [32,35,57,63,64,70] and nonbreeding [7,46,109] seasons. Selection of foraging sites may occur at the tree or the stand level.
Foraging tree selection: In burned forests, black-backed woodpeckers generally forage on relatively large, dead trees. Tree species and the amount of charring may also influence foraging tree selection. Few studies (e.g., [64]) investigated the presence of prey items in relation to foraging tree selection.
Black-backed woodpeckers often forage on dead trees in burned areas. After a stand-replacing prescribed fire in mixed-conifer forests in central Washington, black-backed woodpeckers foraged extensively on dead but foliated trees, though large areas of dead, defoliated trees were available [29]. One year after a wildfire in jack pine forests in Quebec, black-backed woodpeckers foraged on large, deteriorated snags that had high densities of insect entrance holes and larval exit holes [64]. Black-backed woodpeckers foraged primarily on dead trees in burned areas in California [28], Minnesota [3], and Washington [46].
Relatively large trees are often chosen for black-backed woodpecker foraging, though this pattern is not universal. Black-backed woodpeckers foraged on relatively large trees in California [28], Idaho, Montana [70], and Quebec [63,64], and on relatively small trees (average 7 inches (18 cm) DBH)) in South Dakota and Wyoming [57].
Black-backed woodpeckers may forage preferentially on certain tree species, though the preferred species varies by location. In the spring and summer 3 years after a stand-replacing fire in a boreal forest of east-central Alberta, both male and female black-backed woodpeckers selected jack pine more and white and black spruce less than expected by chance (P=0.015), though all 3 tree species were used [35]. Tree species preferred for foraging also differed between 2 sites burned by stand-replacing wildfire (postfire years 1 and 2) in Idaho and Montana [70]. Following stand-replacing fire at 3 mixed-conifer sites in Montana and 1 in Idaho, black-backed woodpeckers foraging in the breeding season used Douglas-fir more than expected based on its availability (P<0.001) [32]. Winter foraging patterns were observed 1 to 4 winters after a mixed-severity wildfire in mixed-conifer forests in northeastern Washington. Black-backed woodpeckers foraged exclusively on western larch and Douglas-fir, the 2 most abundant tree species. This pattern differed from the available distribution of tree species (P<0.001) [46].
The severity of tree charring sometimes influences foraging tree choice, though this selection pattern may change over time. Two years after a severe wildfire in black spruce forests in southern Quebec, breeding black-backed woodpeckers preferred moderately charred trees to severely charred trees (P<0.01). The authors noted that the moderately burned trees used for foraging often occurred at the edges between burned and unburned areas [63]. The breeding season after fire in jack pine forest in Minnesota, black-backed woodpecker pairs were observed feeding almost exclusively on severely burned jack pine, most of which appeared to be dead [3]. Male black-backed woodpeckers shifted from foraging on severely burned to moderately burned trees between the 1st and 2nd year after a human-caused fire in a white spruce forest in interior Alaska [60]. In the spring and summer 3 years after a stand-replacing fire in a boreal forest of east-central Alberta, burn severity was not significantly related to forage tree selection. Both sexes selected moderately burned, large-diameter (>6 inches (15 cm)) jack pines more and moderately burned, medium-diameter (3-5.9 inches (76-150 mm) DBH) spruce trees less than expected by chance (P<0.10) [35].
Foraging stand selection: As of this writing (2011), studies examining foraging habitat selection at the stand level within burned areas were limited. The available studies suggest that foraging habitat selection may vary with fire severity and/or salvage logging. One to 5 years after 2 fires in west-central California, black-backed woodpeckers were only found foraging in severely burned, unlogged forests and not in severely burned logged forests, moderately burned unlogged forests, or unburned forests. At least 5 to 15 large snags/ha were retained in salvage-logging treatments [28]. The results of one study suggest that factors other than prey availability may influence habitat selection in the breeding season. Breeding-season foraging selection was studied at 2 locations that varied in canopy tree species and time since stand-replacing wildfire (1 vs. 2 years after fire). Patches where foraging occurred did not have higher prey densities than random patches, and foraging did not occur in relatively prey-rich areas at one site. The author suggested that foraging habitat selection relies on a variety of factors that likely vary by site, including but not limited to tree species and insect density [70].
Unburned forest near burned forest may provide important foraging habitat. A study in ponderosa pine forests in southwestern South Dakota and northeastern Wyoming examined foraging patterns in burned and adjacent unburned forest and found that most foraging occurred in unburned areas. Black-backed woodpeckers were observed in burned areas within a year of a 321,000 acre (130,000 ha) wildfire. Over 2 years of observations, most (76%) foraging bouts occurred in unburned areas. Foraging locations had less understory structure and more canopy cover (P<0.05) than random sites. Black-backed woodpeckers foraged in areas with higher snag basal area (P=0.002), greater snag density (P=0.021), and lower snag height (P=0.013) than what was available throughout the study area [57].
Relative use of burned and unburned areas: Black-backed woodpeckers are more abundant [26,46,57,58,65,71] and more likely to nest [2,8,22,29,34,96] in burned areas compared to nearby unburned areas.
Abundance or occurrence of black-backed woodpeckers in burned areas compared to adjacent unburned areas Location Forest type Time since fire (years) Abundance or occurrence details California pine-red fir 6-8 Black-backed woodpecker territory density was 0.7 territory/plot/year in burned areas and 0.1 territory/plot/year in unburned areas approximately 1,300 feet (400 m) from the fire perimeter [71]. Minnesota jack pine and black spruce 1,3,7 Black-backed woodpeckers occurred (but were not territorial) in burned areas and were not detected in 80- and 98-year-old unburned forest [26]. South Dakota and Wyoming ponderosa pine 1 Black-backed woodpecker detection was higher in burned forest (1 woodpecker/2.5 sampling transects) than unburned forest (1 woodpecker/10 sampling transects) [57]. Washington mixed conifer 1-4 Overwintering black-backed woodpeckers were significantly more abundant in burned than unburned areas in all years (P=0.001); abundance was 0.406 individual/sampling point in burned areas and 0.019 individual/sampling point in unburned areas [46]. Newfoundland black spruce 5 Black-backed woodpeckers were detected but uncommon in burned areas in the breeding season. They were not found in unburned, clearcut sites that were 5, 14, and 27 years old [87]. Quebec jack pine and black spruce <2 Black-backed woodpeckers were detected at 80% of sampling areas that were recently burned; 39.1% of sampling areas that were in mature coniferous forest <1.2 miles (2 km) from a recently burned area; and 30.8% of sampling areas that were in mature coniferous forest >1.2 miles (2 km) from a recently burned area [42]. Saskatchewan mixedwood (quaking aspen, white spruce) and jack pine 3 Black-backed woodpeckers were only detected in burned areas, but at an abundance too low to analyze. They were not found in unburned forests of any vegetation type [58].
The results of 2 studies suggest that higher abundance in burned areas may vary by season or change over time. Six years after mixed-severity wildfire in black spruce and jack pine forests in northwestern Quebec, black-backed woodpeckers were detected at 74% of 80 sampling points and were significantly more abundant in burned areas versus unburned areas (P<0.05). Eight years after fire, black-backed woodpeckers occurred at 27% of 55 sampling points, and there was no significant difference between burned and unburned forest [65]. One year after a mixed-severity surface fire in Yosemite National Park, California, black-backed woodpecker relative frequency was higher in the breeding season (late May to mid-July) in unburned forest than burned forest (P<0.05), but the reverse was true in the late breeding season (mid-July to mid-August) (P<0.05). Two years after fire, black-backed woodpeckers were detected in both burned and unburned forest, but their frequency was higher in burned forest in both the breeding and late breeding seasons (P<0.05). The author suggested that black-backed woodpeckers were initially limited by nest sites in the burned forests because the fire may have consumed existing snags and did not kill enough trees to provide new nesting snags. The author also noted that the burned and unburned study areas were located close to each other, so it was likely that individuals moved between both habitat types while foraging [22].
Several studies also document black-backed woodpeckers nesting in burned forest but not in adjacent or nearby unburned forest, including 1 and 2 years after a mixed-severity wildfire in Wyoming [96], 2 years after a mixed-severity prescribed fire in California [22], 1 to 3 years after a mixed-severity wildfire on the Upper Peninsula of Michigan [2], and 1 year after a stand-replacing prescribed fire in Washington [29]. A few studies found black-backed woodpeckers nesting in both burned and nearby unburned forest, though nest density was higher in the burned forest. Six, 7, and 8 years after a 39,000 acre (16,000 ha), high-severity wildfire in north-central California, black-backed woodpeckers bred in both burned and unburned forest, though more breeding took place in burned areas. Surveys suggested that black-backed woodpecker density over the 3-year study period was 3.2 pairs/100 acres in burned forest and 0.5 pair/100 acres in unburned forest [8]. Over 2 years of sampling in lodgepole pine forests in the Great Yellowstone Ecosystem of Idaho and Wyoming, black-backed woodpeckers did not nest in recently clearcut forest. Over both years, 1 nest was found in undisturbed, late-seral forest. In areas burned by a mixed-severity wildfire, 1 nest was found 1 year after fire, and 13 were found 2 years after fire [34].
Spatial use of a burned landscape: A burned landscape contains many features that may be more or less suitable as habitat for black-backed woodpeckers. Black-backed woodpeckers have been documented using both the interior and perimeter of burned areas, though few studies have examined their relative use or importance. For example, black-backed woodpeckers used both the interior and edge of an area severely burned by wildfire in South Dakota and Wyoming [57].
Some observations suggest that fire edges are well-used by black-backed woodpeckers. In year-round surveys 1 to 3 years after an 8,700-acre (3,500-ha) wildfire near Fairbanks, Alaska, black-backed woodpeckers were not observed in the fire interior and primarily used the edge of the burned area [60]. Two years after a mostly severe fire in black spruce forests in southern Quebec, the foraging locations of 10 black-backed woodpeckers were concentrated on moderately-charred trees, which occurred at the edges between burned and unburned areas [63].
While edge habitat may provide foraging opportunities, 2 studies suggest that black-backed woodpeckers may nest farther from fire edges to reduce predation risk. In models of nest survival of 46 nests 1 to 12 years after 2 mixed-severity wildfires in Idaho, nest survival probability increased with distance to unburned forest. The authors suggested that this pattern may be the result of reduced predation risk in burned forest, with unburned forest acting as a source for nest predators such as tree squirrels [79]. Two to 4 years after a mixed-severity wildfire in South Dakota, black-backed woodpeckers nested farther from unburned forest edges compared to random locations (1,988 feet (606 m) vs. 553 feet (169 m)), which the authors also linked to reduced predation risk [106].
One study found that patches of live forest within a burned matrix were used by black-backed woodpeckers. Five years after a mixed-severity wildfire in a boreal forest of northeastern Alberta, black-backed woodpeckers were uncommon and only found in unburned patches within a burned area. They were not detected in burned areas, continuous forest adjacent to a burned area, or forest patches that had been clearcut prior to the fire [95].
Importance of time since fire: Some reviews state that black-backed woodpeckers prefer or are most abundant in recently burned forests [17,80]. Recently burned forest provides both increased foraging opportunities as insect populations increase for a short time after fire [35,60,77] and reduced predation risk, because it may take several years for potential nest predators to recolonize a burned area. As time since fire increases, snags begin to fall naturally, leading to a decline in nesting and foraging opportunities. Habitat conditions for potential predators may also improve as time since fire increases (reviewed by [79,80]).
Few studies follow a particular black-backed woodpecker population for long periods of time or monitor burned areas beyond the first few years. Studies comparing several burned sites of different ages seldom sample the full spectrum of postfire years. Both fire characteristics (e.g., severity) and local conditions (e.g., forest type, management history) also vary by study, making widespread inferences difficult.
Studies monitoring the same burned area over time generally support the assertion that black-backed woodpeckers are most abundant in recently burned forest, though the actual years of population peaks and declines vary by site. One study sampled black-backed woodpecker populations 7 different years, ranging from 1 to 30 years after a stand-replacing fire in northeastern Minnesota. Black-backed woodpeckers occurred 1, 3, and 7 years after fire and were not detected 19, 22, 23, or 30 years after fire [26]. Black-backed woodpecker territories were studied at 3 time intervals following a stand-replacing wildfire in north-central California: postfire years 6 to 8, postfire years 15 to 19, and postfire year 25. Territories were found in burned forest 6 to 8 years postfire but were not found in the later sampling periods [71]. Black-backed woodpecker population trends were followed year-round after wildfire in Alaska. Black-backed woodpeckers were common 1 year after the fire, most abundant the fall 1.5 years after the fire, and continued to be abundant through the fall 2.5 years after the fire. By postfire year 3, they were considered rare. They were no longer detected by the 4th winter after the fire [60]. One study observed nest density 1 to 12 years after 2 mixed-severity fire wildfires in western Idaho. Black-backed woodpecker nest density peaked in postfire years 4 and 5 [77]. After a severe wildfire in mature and young forest in central Quebec, black-backed woodpecker nest density was highest the 1st year after fire and declined significantly the 2nd and 3rd years (P<0.001); the 2nd year after fire, nest density was about half of what it was the 1st year [62]. Black-backed woodpecker abundance declined between 6 and 8 years after a mixed-severity wildfire in black spruce and jack pine forests in northwestern Quebec [65].
Several studies compare black-backed woodpecker populations in different forests at different times since fire. The results of these studies suggest that in burned areas, black-backed woodpeckers are most common in recently burned forest. One study examined black-backed woodpecker presence or absence in burned areas of various ages in Alberta: 3, 4, 8, 8, 16, and 17 years after fire. Black-backed woodpeckers were detected in areas burned 3,4 and 8 years previously, and their occurrence was not significantly different between these different stand ages. They were not detected in area burned 16 or 17 years previously; their numbers were significantly lower 16 years after fire compared to 8 years after fire (P<0.1) [35,36]. A review of available literature on the presence of black-backed woodpeckers after fire in northern Rocky Mountain coniferous forests reports that black-backed woodpeckers were most likely to be detected <10 years after fire. They were detected in 78% of the studies conducted in areas burned <10 years previously (23 sites), and they were not detected in areas burned 10 to 40 years previously (5 sites) [38]. In a study examining the abundance of black-backed woodpecker pairs in areas of varying age since fire (range: 1-304 years after fire ) in coniferous forests in Yellowstone and Grand Teton National Parks, black-backed woodpecker pairs were found in areas 1 to 3 years after fire, but they were absent from areas >5 years after fire [97]. In north-central Alberta during the breeding season, black-backed woodpeckers were only found in areas burned 1 year previously, and not in areas burned 14 or 28 years previously [33]. Data from 13,337 sample points in northern Idaho and Montana showed that black-backed woodpeckers occurred most (96% of detections) in recently burned (postfire years 1-4) areas compared to unburned vegetation types (P<0.001) [40].