Woodpeckers are near passerine birds of the order Piciformes. They are one subfamily in the family Picidae, which also includes the piculets and wrynecks. They are found worldwide and include about 180 species.
Woodpeckers gained their English name because of the habit of some species of tapping and pecking noisily on tree trunks with their beaks and heads. This is both a means of communication to signal possession of territory to their rivals, and a method of locating and accessing insect larvae found under the bark or in long winding tunnels in the tree or upright log.
Physiology and behaviour
Some woodpeckers and wrynecks in the order Piciformes have zygodactyl feet, with two toes pointing forward, and two backward. These feet, though adapted for clinging to a vertical surface, can be used for grasping or perching. Several species have only three toes. The woodpecker's long tongue, in many cases as long as the woodpecker itself, can be darted forward to capture insects. The tongue is not attached to the woodpecker's head in the same way as it is in most birds, but instead it curls back up around its skull, which allows it to be so long.
The woodpecker first locates a tunnel by tapping on the trunk with its head. Once a tunnel is found, the woodpecker chisels out wood until it makes an opening into the tunnel. Then it worms its tongue into the tunnel to try to locate the grub. The tongue of the woodpecker is long and ends in a barb. With its tongue the woodpecker skewers the grub and draws it out of the trunk.
Woodpeckers also use their beaks to create larger holes for their nests which are 15–45 cm (6–18 inches) below the opening. These nests are lined only with wood chips and hold 2–8 white eggs. Because the nests are out of sight, they are not visible to predators and eggs do not need to be camouflaged. Cavities created by woodpeckers are also reused as nests by other birds, such as grackles, starlings, some ducks and owls, and mammals, such as tree squirrels.
Several adaptations combine to protect the woodpecker's brain from the substantial pounding that the pecking behaviour causes: it has a relatively thick skull with relatively spongy bone to cushion the brain; there is very little cerebrospinal fluid in its small subarachnoid space; the bird contracts mandibular muscles just before impact, thus transmitting the impact past the brain and allowing its whole body to help absorb the shock; its relatively small brain is less prone to concussion than other animals'.
Some species have modified joints between bones in the skull and upper jaw, as well as muscles which contract to absorb the shock of the hammering. Strong neck and tail-feather muscles, and a chisel-like bill are other hammering adaptations which are seen in most species. Other species of woodpecker, such as the Flicker, uses its long tongue primarily to grab prey from the ground or from under loose bark. It has few shock-absorbing adaptations, and prefers to feed on the ground or to chip away at rotting wood and bark, habits observed in birds outside of the woodpecker family. A "continuum" in skull structures, from little- to highly specialized for pounding is seen in different genera (groups of related species) of woodpeckers alive today. In his classic "Birds of America," John James Audubon describes the slight gradations in hyoid horn length found in different species of living woodpeckers. The slack of tongue is kept under the loose skin behind its neck. The tiny bones divide into essentially two tongues, coming back together before entering the beak.
The systematics of woodpeckers is quite convoluted. Based on an assumption of unrealistically low convergence in details of plumage and behavior, 5 subfamilies were distinguished. However, it has turned out that similar plumage patterns and modes of life are not reliable to determine higher phylogenetic relationships in woodpeckers, and thus only 3 subfamilies should be accepted.
For example, the genera Dryocopus (Eurasia and Americas) and Campephilus (Americas) of large woodpeckers were believed to form a distinct group. However, they are quite unrelated and instead close to a Southeast Asian genus, Mulleripicus and Chrysocolaptes, respectively. In addition, the genus allocation of many species, e.g. the rufous woodpecker, has turned out to be in error, and some taxa with unclear relationships could be placed into the phylogeny.
Genus Palaeonerpes (Ogalalla Early Pliocene of Hitchcock County, USA) - possibly dendropicine
Genus Pliopicus (Early Pliocene of Kansas, USA) - possibly dendropicine
cf. Colaptes DMNH 1262 (Early Pliocene of Ainsworth, USA) - possibly malarpicine
This is a list of woodpecker species, presented in taxonomic order.
Tribe Dendropicini
Genus Melanerpes
White woodpecker, Melanerpes candidus
Lewis' woodpecker, Melanerpes lewis
Guadeloupe woodpecker, Melanerpes herminieri
Puerto Rican woodpecker, Melanerpes portoricensis
Red-headed woodpecker, Melanerpes erythrocephalus
Acorn woodpecker, Melanerpes formicivorus
Yellow-tufted woodpecker, Melanerpes cruentatus
Yellow-fronted woodpecker, Melanerpes flavifrons
Golden-naped woodpecker, Melanerpes chrysauchen
Beautiful woodpecker, Melanerpes pulcher
Black-cheeked woodpecker, Melanerpes pucherani
White-fronted woodpecker, Melanerpes cactorum
Hispaniolan woodpecker, Melanerpes striatus
Jamaican woodpecker, Melanerpes radiolatus
Golden-cheeked woodpecker, Melanerpes chrysogenys
Gray-breasted woodpecker, Melanerpes hypopolius
Yucatan woodpecker, Melanerpes pygmaeus
Red-crowned woodpecker, Melanerpes rubricapillus
Gila woodpecker, Melanerpes uropygialis
Hoffmann's woodpecker, Melanerpes hoffmannii
Golden-fronted woodpecker, Melanerpes aurifrons
Velasquez's woodpecker, Melanerpes santacruzi
Red-bellied woodpecker, Melanerpes carolinus
West Indian woodpecker, Melanerpes superciliaris
Genus Sphyrapicus
Williamson's sapsucker, Sphyrapicus thyroideus
Yellow-bellied sapsucker, Sphyrapicus varius
Red-naped sapsucker, Sphyrapicus nuchalis
Red-breasted sapsucker, Sphyrapicus ruber
Genus Xiphidiopicus
Cuban woodpecker, Xiphidiopicus percussus (Placement in Dendropicini tentative)
Genus Dendropicos
Little grey woodpecker, Dendropicos elachus
Speckle-breasted woodpecker, Dendropicos poecilolaemus
Abyssinian woodpecker, Dendropicos abyssinicus
Cardinal woodpecker, Dendropicos fuscescens
Gabon woodpecker, Dendropicos gabonensis
Melancholy woodpecker, Dendropicos lugubris
Stierling's woodpecker, Dendropicos stierlingi
Bearded woodpecker, Dendropicos namaquus
Fire-bellied woodpecker, Dendropicos pyrrhogaster
Golden-crowned woodpecker, Dendropicos xantholophus
Elliot's woodpecker, Dendropicos elliotii
Grey woodpecker, Dendropicos goertae
African grey-headed woodpecker, Dendropicos spodocephalus
Olive woodpecker, Dendropicos griseocephalus
Brown-backed woodpecker, Dendropicos obsoletus
Genus Dendrocopos
Sulawesi woodpecker, Dendrocopos temminckii
Philippine woodpecker, Dendrocopos maculatus
Brown-capped pygmy woodpecker, Dendrocopos nanus
Sunda woodpecker, Dendrocopos moluccensis
Grey-capped pygmy woodpecker, Dendrocopos canicapillus
Japanese pygmy woodpecker, Dendrocopos kizuki
Brown-fronted woodpecker, Dendrocopos auriceps
Fulvous-breasted woodpecker, Dendrocopos macei
Stripe-breasted woodpecker, Dendrocopos atratus
Yellow-crowned woodpecker, Dendrocopos mahrattensis
Arabian woodpecker, Dendrocopos dorae
Rufous-bellied woodpecker, Dendrocopos hyperythrus
Darjeeling woodpecker, Dendrocopos darjellensis
Crimson-breasted woodpecker, Dendrocopos cathpharius
Middle spotted woodpecker, Dendrocopos medius
White-backed woodpecker, Dendrocopos leucotos
Great spotted woodpecker, Dendrocopos major
Syrian woodpecker, Dendrocopos syriacus
White-winged woodpecker, Dendrocopos leucopterus
Sind woodpecker, Dendrocopos assimilis
Himalayan woodpecker, Dendrocopos himalayensis
Genus Picoides - this genus is in need of revision (Moore et al., 2006). See the genus article for more.
Small group
Lesser spotted woodpecker, Picoides minor - previously Dendrocopos
Downy woodpecker, Picoides pubescens
Nuttall's woodpecker, Picoides nuttallii
Ladder-backed woodpecker, Picoides scalaris
Large group
Red-cockaded woodpecker, Picoides borealis
Smoky-brown woodpecker, Picoides fumigatus
Hairy woodpecker, Picoides villosus
White-headed woodpecker, Picoides albolarvatus
Strickland's woodpecker, Picoides stricklandi
Arizona woodpecker, Picoides arizonae
Three-toed group (Picoides sensu stricto)
Eurasian three-toed woodpecker, Picoides tridactylus
American three-toed woodpecker, Picoides dorsalis
Black-backed woodpecker, Picoides arcticus
Genus Veniliornis
Red-rumped woodpecker, Veniliornis kirkii
Golden-collared woodpecker, Veniliornis cassini
Choco woodpecker, Veniliornis chocoensis
Yellow-eared woodpecker, Veniliornis maculifrons
Red-stained woodpecker, Veniliornis affinis
Bar-bellied woodpecker, Veniliornis nigriceps
Scarlet-backed woodpecker, Veniliornis callonotus
Yellow-vented woodpecker, Veniliornis dignus
Little woodpecker, Veniliornis passerinus
Dot-fronted woodpecker, Veniliornis frontalis
Blood-colored woodpecker, Veniliornis sanguineus
White-spotted woodpecker, Veniliornis spilogaster
Striped woodpecker, Veniliornis lignarius
Checkered woodpecker, Veniliornis mixtus
Tribe Malarpicini
Genus Campethera
Fine-spotted woodpecker, Campethera punctuligera
Nubian woodpecker, Campethera nubica
Bennett's woodpecker, Campethera bennettii
Reichenow's woodpecker, Campethera scriptoricauda
Golden-tailed woodpecker, Campethera abingoni
Mombasa woodpecker, Campethera mombassica
Knysna woodpecker, Campethera notata
Little green woodpecker, Campethera maculosa
Green-backed woodpecker, Campethera cailliautii
Tullberg's woodpecker, Campethera tullbergi
Buff-spotted woodpecker, Campethera nivosa
Brown-eared woodpecker, Campethera caroli
Genus Geocolaptes
Ground woodpecker, Geocolaptes olivaceus
Genus Dinopium
Olive-backed woodpecker, Dinopium rafflesii
Himalayan flameback, Dinopium shorii
Common flameback, Dinopium javanense
Black-rumped flameback, Dinopium benghalense
Genus Meiglyptes
Buff-rumped woodpecker, Meiglyptes tristis
Javan buff-rumped woodpecker, Meiglyptes tristis tristis - extinct (c.1920)
Black-and-buff woodpecker, Meiglyptes jugularis
Buff-necked woodpecker, Meiglyptes tukki
Genus Hemicircus (Placement in Malarpicini tentative)
Grey-and-buff woodpecker, Hemicircus concretus
Heart-spotted woodpecker, Hemicircus canente
Genus Micropternus (formerly in Celeus)
Rufous woodpecker, Micropternus brachyurus
Tribe Picini
Genus Picus
Banded woodpecker, Picus mineaceus
Lesser yellownape, Picus chlorolophus
Crimson-winged woodpecker, Picus puniceus
Greater yellownape, Picus flavinucha
Checker-throated woodpecker, Picus mentalis
Streak-breasted woodpecker, Picus viridanus
Laced woodpecker, Picus vittatus
Streak-throated woodpecker, Picus xanthopygaeus
Scaly-bellied woodpecker, Picus squamatus
Japanese green woodpecker, Picus awokera
European green woodpecker, Picus viridis
Iberian green woodpecker, Picus sharpei
Levaillant's woodpecker, Picus vaillantii
Red-collared woodpecker, Picus rabieri
Black-headed woodpecker, Picus erythropygius
Grey-headed woodpecker, Picus canus
Genus Mulleripicus
Ashy woodpecker, Mulleripicus fulvus
Sooty woodpecker, Mulleripicus funebris
Great slaty woodpecker, Mulleripicus pulverulentus
Genus Dryocopus
Helmeted woodpecker, Dryocopus galeatus
Lineated woodpecker, Dryocopus lineatus
Pileated woodpecker, Dryocopus pileatus
Black-bodied woodpecker, Dryocopus schulzi
White-bellied woodpecker, Dryocopus javensis
Andaman woodpecker, Dryocopus hodgei
Black woodpecker, Dryocopus martius
Genus Celeus
Cinnamon woodpecker, Celeus loricatus
Scaly-breasted woodpecker, Celeus grammicus
Waved woodpecker, Celeus undatus
Chestnut-colored woodpecker, Celeus castaneus
Chestnut woodpecker, Celeus elegans
Pale-crested woodpecker, Celeus lugubris
Blond-crested woodpecker, Celeus flavescens
Cream-colored woodpecker, Celeus flavus
Rufous-headed woodpecker, Celeus spectabilis
Caatinga woodpecker, Celeus obrieni
Ringed woodpecker, Celeus torquatus
Genus Piculus
Rufous-winged woodpecker, Piculus simplex
Stripe-cheeked woodpecker, Piculus callopterus
Lita woodpecker, Piculus litae
White-throated woodpecker, Piculus leucolaemus
Yellow-throated woodpecker, Piculus flavigula
Golden-green woodpecker, Piculus chrysochloros
Yellow-browed woodpecker, Piculus aurulentus
Genus Colaptes
Golden-olive woodpecker, Colaptes rubiginosus
Gray-crowned woodpecker, Colaptes auricularis
Crimson-mantled woodpecker, Colaptes rivolii
Black-necked woodpecker, Colaptes atricollis
Spot-breasted woodpecker, Colaptes punctigula
Green-barred woodpecker, Colaptes melanochloros
Golden-breasted woodpecker, Colaptes (melanochloros) melanolaimus
Northern flicker, Colaptes auratus
Yellow-shafted Flicker, Colaptes (auratus) auratus
Red-shafted Flicker, Colaptes (auratus) cafer
Guadalupe Flicker, Colaptes auratus/cafer rufipileus - extinct (c.1910)
Gilded flicker, Colaptes chrysoides
Fernandina's flicker, Colaptes fernandinae
Chilean flicker, Colaptes pitius
Andean flicker, Colaptes rupicola
Campo flicker, Colaptes campestris
Tribe Megapicini
Genus Campephilus
Powerful woodpecker, Campephilus pollens
Crimson-bellied woodpecker, Campephilus haematogaster
Red-necked woodpecker, Campephilus rubricollis
Robust woodpecker, Campephilus robustus
Crimson-crested woodpecker, Campephilus melanoleucos
Guayaquil woodpecker, Campephilus gayaquilensis
Pale-billed woodpecker, Campephilus guatemalensis
Cream-backed woodpecker, Campephilus leucopogon
Magellanic woodpecker, Campephilus magellanicus
Ivory-billed woodpecker, Campephilus principalis (possibly extinct)
Imperial woodpecker, Campephilus imperialis (possibly extinct)
Genus Chrysocolaptes
White-naped woodpecker, Chrysocolaptes festivus
Greater flameback, Chrysocolaptes lucidus
Genus Reinwardtipicus
Orange-backed woodpecker, Reinwardtipicus validus
Genus Blythipicus
Maroon woodpecker, Blythipicus rubiginosus
Bay woodpecker, Blythipicus pyrrhotis
Genus Gecinulus (Placement in Megapicini tentative)
Pale-headed woodpecker, Gecinulus grantia
Bamboo woodpecker, Gecinulus viridis
Genus Sapheopipo (Placement in Megapicini tentative)
Okinawa woodpecker, Sapheopipo noguchii