SPECIES

White-headed Woodpecker Dryobates albolarvatus

Jeffrey M. Kozma, Teresa J. Lorenz, Martin G. Raphael, Kimball L. Garrett, and Rita D. Dixon
Version: 2.0 — Published July 9, 2020

Diet and Foraging

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Feeding

Main Foods Taken

Invertebrates (primarily adult and larval insects, especially ants [Hymenoptera], beetles [Coleoptera], scale insects [Homoptera]) and conifer seeds (89). Relative importance of these 2 categories varies regionally and seasonally, as indicated by specific studies: A mixture of invertebrates and Coulter pine seeds in southern California gravirostris (21); sugar pine seeds in northern California (90; this study found that 559 of 1,656 healthy cones [34%] were destroyed by White-headed Woodpeckers in Amador County, California, during late August and September, including 85% of 358 original cones on a single tree); a mixture of insects, seeds of ponderosa and sugar pines, and pine sap in Oregon (RDD). In Washington, a formal study of foraging behavior found seed cones were rarely used for foraging by adults (6% of the time) from May through November, and Douglas-fir and ponderosa pine cones were used with approximately equal frequency (91). Common foods in this study included wood-boring beetles in the order Cerambycidae, western spruce budworm, and pine white butterfly larvae (Neophasia menapia). In a separate study in Washington, adult woodpeckers fed nestlings larvae of wood-boring beetles (Buprestidae and Cerambycidae), ants, and caterpillars (e.g., western spruce budworm) most frequently (92); in this study area, adults were observed eating a variety of insects, ponderosa pine seed, and ponderosa pine sap (JMK).

Microhabitat for Foraging

Great majority of foraging activity takes place on trunks, branches, needle clusters, and cones of live coniferous trees (88, 93, 94, 81, 95, 91, KLG, RDD); nonconifers, e.g., oaks (Quercus), quaking aspen (Populus tremuloides), and black cottonwood (Populus trichocarpa), are used less often. Cones of ponderosa pine (88), Jeffrey pine (KLG), sugar pine (90), and Coulter pine (93) are seasonally or locally important. Raphael and White (81) found 26% of 110 foraging observations in the Sierra Nevada, California, were within foliage, 22% on branches, and 53% on trunks, primarily on live pines. Morrison et al. (96), also working in the Sierra Nevada, found a similar pattern, but observed less use of smaller branches and twigs and more use of trunks. In central Oregon, 42% of 2,133 foraging observations were on branches, 23% on upper trunk, 22% on midtrunk, and 13% on lower trunk; foraging height averaged 19.1 m (72); foraged predominantly on large-diameter live ponderosa pine trees. In south-central Oregon, foraged 37% of time on upper trunk, 25% on midtrunk, 7% on lower trunk, 22% on branches, and 9% on foliage; mean foraging height was 20 m (72); foraged primarily on large-diameter live ponderosa and sugar pine trees, but also on snags (13%), on logs (< 1%), on the ground (1%), and in the air (< 1%). Along the east-slope Cascades of Washington, dead wood (cut stumps from recent timber harvests) and live foliage were the most commonly used foraging substrates during the breeding season (91). Douglas-fir and ponderosa pine accounted for 89% of foliage foraging. White-headed Woodpeckers switched from foraging on dead wood and foliage during the incubation, nestling and fledgling periods to primarily live stem foraging (99% of observations on ponderosa pine trunks) during the post-fledgling period. Seven percent of all foraging observations were on cones, with 4% on ponderosa pine and 3% on Douglas-fir (91). Ground foraging noted in southern California (93, KLG) and rarely in Washington where it involves quick and opportunistic capture of insects (JMK). Annual plants, especially stalks of common mullein (Verbascum thapsus; 66, 91), are locally utilized. Flying insects are occasionally captured (97, 92). Also observed foraging for insects within pouch fungus (Cryptoporus volvatus) on dead trees (98, JMK; see ). Trees used for sap feeding in Washington were significantly shorter (13.5 m ± 0.8 SE, n = 32; range 3.6–22.1 m) and had significantly smaller dbh (22.4 cm ± 0.8 SE, n = 74; range 6.1–37.2 m) than trees not used for sap feeding (99). Will visit backyard feeders for suet and sunflower seeds (JMK) and rarely hummingbird feeders (A. Woodrow, personal communication).

Food Capture and Consumption

In addition to direct pecking, this species flakes and chips bark of conifers with angled strokes (100, 88); represents “chisel” maneuver of Remsen and Robinson (101). Foraging involves much peering into crevices and cracks in bark (see ); probes into crevices in ponderosa pine bark with tongue (88; see ). Ligon (88) twice observed males scratching bark loose with feet. Hammering or boring directly into deeper sub-bark layers is generally less common; as a result, foraging is quiet relative to foraging of Hairy Woodpecker (Dryobates villosus), which often uses harder foraging blows and more frequently feeds on more resonant dead wood. However, White-headed Woodpeckers have been observed excavating wood-boring beetle (Buprestidae and Cerambycidae) larvae from stumps and fire-killed trees (JMK, 92, 91). When foraging for wood-boring beetle larvae, appears to locate larva via sound or by frass accumulation at boring holes; bird then pecks into dead wood or at a frass hole to widen it, and then rapidly moves bill in and out of larvae tunnel with a sewing machine motion, using the barbed tongue to maneuver the larva toward the bill for extraction (JMK, TJL). Gleans caterpillars (e.g., western spruce budworm) by moving through foliage and probes terminal need clusters of ponderosa pine and dwarf mistletoe (Arceuthobium spp.) clumps for insects (JMK). In Washington in late spring, both sexes observed to systematically peck open male pollen cones of ponderosa pine, presumably to feed on sawfly (Xyelidae) larvae (JMK). When foraging at cones, often clings to sides and bottoms of cones; such foraging acrobatics minimize direct body contact with cones, which are often heavily laden with sap (Figure 2 ). Chips cones open to expose seeds, usually with a series of lengthwise furrows (90, 88; see ; Figure 3 ) and slides bill between partially open scales of cones to remove seeds (JMK; see ). May remove pine seeds whole or nearly whole from cones and takes them to anvil (seed-cracking) sites (usually on same tree or another tree within about 20 m), where wedges the seeds into bark crevices, breaks them apart with bill, and consumes them (KLG). Sap consumption noted in Oregon, Washington and in the Sierra Nevada, California; in Oregon and Washington, drills own sap wells in horizontal rings equally spaced along tree trunk, usually on smaller trees (72, 99). Sap wells excavated almost exclusively in conifers, mainly pines, though has been observed making sap wells in aspen (S. Shunk, personal communication). In Washington, orientation of sap wells significantly favor a southwest aspect and sap-well trees often used over multiple years (99). In British Columbia and Washington, observed clinging to stalks of common mullein to extract seeds (91). Sally-strike maneuvers (101) are used occasionally to capture flying insects, especially female carpenter ants (Camponotus spp.; JMK). Quantitative studies of foraging in central Oregon (72) showed the following division of techniques: gleaning (35%), cone-feeding (31%), pecking (24%), and sap-sucking (7%) (n = 2,133 observations). In south-central Oregon (87), foraged by gleaning (52%), pecking (40%), flaking (2%), sallying (< 1%), seed-harvesting (5%), and other methods (< 1%; n = 1,053). In the Sierra Nevada, California (81), 85% of observations in summer were gleaning, 12% drilling, 4% sap-sucking (n = 110). Overall, this species exhibits a high degree of year-round plasticity in its foraging behaviors and food consumption.

Sexual Differences in Foraging

Appears to vary by region and even among study sites in a given region. No sexual differences in foraging sites or techniques in western Idaho (88). However, males were more likely to initiate foraging on cones, with females mainly using cones already partly excavated by males. In central Oregon, only slight sexual differences in foraging site and technique were noted (72): Mean foraging height was slightly but significantly higher in males; males spent relatively more time feeding at cones. In Washington, no overall differences in foraging substrate by sex (91). In one study of gravirostris in a Coulter pine-dominated habitat (21), males concentrated on upper third of tree and on cones, whereas females foraged mainly on trunks and proximal portions of lower lateral branches. Females also foraged more slowly and deliberately than males. Hilkevitch (93) found no sexual differences in repertoire of foraging techniques in 2 populations of gravirostris, apart from again demonstrating a bias toward males among birds foraging on Coulter pine cones; he did find slight differences in tree preferences (males used larger variety of trees and emphasized foraging on Coulter pine, whereas females strongly preferred ponderosa pine and incense cedar). Amount of overlap between sexes in foraging sites on given tree varied with species of tree (considerable overlap on ponderosa pine, but little overlap on Coulter pine; 93). Males in western Sierra Nevada Mountains, California, tended to forage higher in trees than females, especially in winter (102, 103). Healthy trees were used more frequently by males than by females. In summer, males used incense cedar more frequently than females; reverse was true in winter. Males used ponderosa pine more frequently than females in summer, and Douglas-fir more frequently than females in winter. In general, males and females used more similar substrates in summer than in winter (102, 103).

Seasonal Differences in Foraging

In California, foraging on seeds from pine cones peaks late summer through winter, but timing varies with species of pine. In species such as sugar pine, in which bracts open and seeds are shed in relatively short period in fall, cone foraging is concentrated in period from August to October (90, KLG). Pine seeds used in Idaho in August and April, but not June (88); here there was strong preference for feeding at terminal needle clusters in June, but not in August or April. Female gravirostris fed at Coulter pine cones mainly from April to September, whereas males utilized these cones throughout year (93). Morrison et al. (102) and Morrison and With (103) compared winter and summer foraging behavior and found little difference in foraging height; target tree species, however, shifted toward increased use of incense cedar in winter. In winter there was also increased use of trunks, especially by females (which showed 74% winter use versus 13% summer use). In Washington, observed feeding on sap only in spring through early summer, ending around the time nesting begins; birds not observed feeding on sap in summer or fall (99, 91). In Washington, spring foraging concentrated on dead wood (cut stumps from past timber harvest) and fir foliage, transitioned to pine foliage by mid-summer, and in autumn woodpeckers mostly foraged on trunks of ponderosa pine trees (91).

Geographical Variation in Foraging

Foraging substrate and food items vary geographically; see above.

Diet

Major Food Items

Arthropod and plant material. Variety of adult insects, including ants (e.g., Camponotus, Formica), beetles, termites, scale insects, etc., as well as insect larvae including those of wood-boring beetles, pine white butterfly, and spruce budworm (89, 104, 92, 91). Scolytid beetles (probably Dendroctonus ponderosae) taken in Idaho (88), and cicadas (Homoptera) taken in Oregon (RDD) and Washington (92). Pine seeds, especially those of ponderosa pine, Jeffrey pine, sugar pine, and Coulter pine, but also known to take seeds of knobcone pine and white fir (4, 105, 106). Foraging also occurs on annual stalks of common mullein (33, 91). Tree sap taken in Oregon (RDD), Washington (99), and California (81). Birds frequently utilize suet provided at feeders, and have been observed (rarely) visiting hummingbird feeders (A. Woodrow, personal communication).

Quantitative Analysis

Observations from Morrison and With (103), Dixon (87), Kozma and Kroll (92), and Lorenz et al. (91) in Oregon and Washington are summarized above. Beal (89) examined stomach contents of 14 individuals and found that about half of diet was composed of pine seeds, and half of the animal food consisted of ants. Otvos and Stark (107) examined stomach contents of 44 individuals from the Sierra Nevada, California, and found ponderosa pine seeds only in fall, when they accounted for 14% of diet in males and 8% in females. Invertebrates of 51 taxa made up 74% of total food volume of males and 85% of females; beetles, scale insects, and ants dominated diet of both sexes. Material from stomachs of 4 birds collected in western Idaho in April contained 70–90% pine seeds (88). Halvorson (106) noted, with respect to inland montane west, that this was the woodpecker species “most interested in cones and able to damage them in quantity”; he noted that its effect (and that of other bird species) on pre-dispersal (within-cone) conifer seed remains to be assessed. In the Sierra Nevada, California, Morrison et al. (102) found significant differences in use of tree species for foraging in winter versus summer and between males and females; females (but not males) shifted to more frequent use of incense cedar in winter, apparently because of abundant scale insect (Xylococculus macrocarpae) that occurs under cedar's loose, flaky bark.

Food Selection and Storage

Storage of food not known, but conifer seeds extracted whole may be removed to anvil sites (KLG, RDD). Tevis (90) found that feeding was concentrated on certain cone-bearing sugar pines, with nearby cone-bearing pines remaining untouched.

Nutrition and Energetics

No information.

Metabolism and Temperature Regulation

No information.

Drinking, Pellet-Casting, and Defecation

Drinking

Drinks frequently from pools, puddles, creeks (see ), and melted snow; also drinks water welled up in hollows in trees (KLG) and at anthropogenic water sources such as cattle troughs and backyard bird baths (JMK). May bathe and drink in close association with mate or with heterospecifics (e.g., Hairy Woodpecker, Evening Grosbeak [Coccothraustes vespertina], White-breasted Nuthatch [Sitta carolinensis], and Yellow-rumped Warbler [Setophaga coronata]) in Oregon (RDD) and Washington (JMK). Frequent drinking thought to correlate with high proportion of dry vegetable matter (pine seeds) in diet (88). In Washington from August–October, White-headed Woodpeckers (n = 90) were caught in mist-nets at 23-liter (6-gallon) tubs filled with water 7.5 times more often than Hairy Woodpeckers (n = 12), even though both species are common breeders in areas where trapping occurred (JMK). This suggests that water intake is greater than that of other woodpeckers.

Pellet-casting

Pellet casting has rarely been observed. In Washington, an adult male was observed repeatedly opening its bill wide and shaking its head vigorously from side to side to expel small black masses that resembled the undigested remains of insects (JMK).

Defecation

Defecates from perch while foraging, or in flight.

Recommended Citation

Kozma, J. M., T. J. Lorenz, M. G. Raphael, K. L. Garrett, and R. D. Dixon (2020). White-headed Woodpecker (Dryobates albolarvatus), version 2.0. In Birds of the World (P. G. Rodewald and B. K. Keeney, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.whhwoo.02