It is well-known that woodpeckers provide cavities for secondary cavity nesters. Cavity nesters form cavity webs, which consist of primary cavity nesting species, weak cavity nesters, secondary cavity nesters and bark nesters. Woodpeckers within the nest web can therefore by regarded as key-stone species. Woodpeckers are highly susceptible to habitat changes. One important reason for this is that woodpeckers are dependent on dead wood for foraging and excavating cavities, and many woodpecker species require specific forest habitats. Because of their susceptibility to habitat changes, woodpeckers can be considered general indicators to forest biodiversity (Virkkala 2006).
The green woodpecker (Picus viridis) is described as being closely bound to cultivated land and deciduous forests, mainly due to its summer diet composed of ants (Hymenoptera: Formicidae) found on meadows and pastures. The Picus genus, including a dozen Asian species, presumably originated in oriental broad-leaved forests. Except for the grey-faced woodpecker (Picus canus), none of the species are regarded as regular inhabitants of boreal forests. Selection of habitat can be attributed to origin in the sense that birds choose environments similar to the region in which the species once originated (Rolstad et al. 2000).
One of the most fascinating woodpecker adaptations is its tongue. Unlike the tongues of humans, which are primarily muscular, the tongues of birds are rigidly supported by a cartilage-and-bone skeleton called the hyoid apparatus. All higher vertebrates have hyoids in one form or another, the human hyoid bone serves as an attachment site for certain muscles of our throat and tongue. The Y- shaped hyoid apparatus of birds, however, extends all the way to the tip of their tongues. The fork in the “Y” sits just in front of the throat, and it is in this area that most of the muscles of the hyoid attach. Two long structures, the “horns” of the hyoid, grow backwards from this area and provide insertion sites for protractor muscles which originate on the lower jaw. Thus, the twin horns of a bird’s hyoid serve only as an attachment site for muscles which actually originate in the lower jaw – contraction of these muscles pulls the horns, and the whole hyoid apparatus, forward and against the skull, thrusting the tongue out of the mouth like a spear (Ryan 2003).
Reference List:
- Rolstad.J., Loken.B., & Rolstad.E., (2000) Habitat selection as a hierarchical spatial process: the green woodpecker at the northern edge of its distribution range. Oecologia, 124, 116-129.
- Ryan.R., (2003) Anatomy and Evolution of the Woodpecker’s Tongue. URL: http://www.talkorigins.org/faqs/woodpecker/woodpecker.html#ref1 [08/08/2012].
- Virkkala.R., (2006)Why Study Woodpeckers? The Significance of Woodpeckers in Forest Ecosystems. Annual of Zoology, 43, 82-85.
