Woodpeckers use drumming as a communication signal. However, specific drumming features may indicate play behaviour. Studies have shown that woodpecker species can have different drumming types (Budka 2018; Turner 2020; Dodenhoff et al. 2001; Węgrzyn and Leniowski 2020). Furthermore, studies have demonstrated that species diversity and behaviour of woodpecker are strongly influenced by tree availability and landscape (Ilsøe et al. 2017; Poblete et al. 2020; Vergara-Tabares et al. 2018). Therefore, more variations of drumming types are being discovered, even within species, through observational studies. Conducting detailed investigation of intra-specific drumming activities is necessary to understand complexity of the species behaviour. Consequently, this will help in understanding individual diversity. However, the specialty and universality of drumming types are often difficult to differentiate. They could reflect a common community-related performance, or a specific and unique activity such as playing. Furthermore, human activities, including deforestation and urbanization, capturing a butterfly, or felling a tree can severely effect wildlife (Doherty et al. 2021; Rutz et al. 2020; Shaw and Harvey 2020; Ellison et al. 2013; O’Leary et al. 2021; Cockle et al. 2017; Lammertink et al. 2019). Satoyama is a Japanese term for marginal areas between the foothills and arable land. Since it is a border, several species are not consistently observed in this region every year.
In the present study, the author studied the drumming activities of a Japanese pygmy woodpecker (Dendrocopos kizuki) in the Satoyama landscape of Japan. The Japanese pygmy woodpecker is endemic in Japan but the biology and behaviour (Garcia et al. 2020; Hamao et al. 2006; Shiina et al. 2013; Boswall 2005; Spence 2015; Gutzat and Dormann 2018) of the species is sparsely studied. To illustrate how acoustic patterns can reflect individual characteristics, the author adopted dawn recordings of an individual Japanese pygmy woodpecker for seven years.
Google searches for “woodpecker drumming metal” and “sapsucker drumming metal” yielded over 500,000 hits including numerous videos and photos of woodpeckers drumming on metal objects. Experts explain that woodpeckers choose metals for their drumming antics for two reasons: firstly, to attract mates; and secondly, to establish their territory. In natural environments, woodpeckers look for the most resonant, dry, hollow, and tall trees to make the loudest possible drums sounds in order to mark territory and attract mates. The use of metal objects for drumming in suburban areas is most likely just an extension as the loudest available substrate. Therefore, woodpeckers frequently drum on metals (Kramer 2009; Harmata 1979; Dean 1949; Morgan; Hopp 1999)
The bird has a tiny stain-like mark under the throat (see Photo 1-c), with a non-unique non-plumage characteristic such as a missing toe. However, it visited the garden field of the author from the beginning of the study period. According to the bird banding data, 723 days (Yoshiyasu 2020) is reported as the surviving period of a woodpecker, which is relatively short-term with uncertainty of the bird-capturing period. However, constantly observing this bird showed constant changes in drumming by the same bird over multiple years. Therefore, it is highly possible that the same woodpecker changed drumming behaviour according to changes in the environment.
Although drumming is common on metals, the following questions still exist: why did the bird select this metal? Does this selection prove that the birds ‘remember’ and ‘compare’ the sound of different materials? The ‘existence of the metal pole’ is important. Many videos and photos of these birds drumming on metal objects around the world were not from big cities. They were always found drumming metal poles near urbanised areas with certain density of trees like that of Satoyama.
Firstly, we can ascertain that the woodpecker already knew which side of the plate made what sound by evaluating the memory of the woodpecker between successive drumming sessions. Every time, the identified single bird hovered around the plate to explore the sound difference. Secondly, the woodpecker drummed on both sides in order to “compare” the two sounds. Generally, conclusions about the internal mental state of an animal can only be drawn after carefully controlled experiments. However, majority (almost ¾) of the videos and records indicated that the bird “intentionally” sough after the most treble sound to attract mates and repel rivals. Thus, they started visiting metals after obtaining mastery of sound ‘learned’ on different substrates.
In general, drumming is known to be a form of communication. The sound produced by drumming on metal travels further than that produced by wood, thereby facilitating communication (to repel rivals and attract mates). However, the increasing frequency of drumming on metal prompted this research.
Some reviews reveal that the choice of a woodpecker to drum on a telephone pole was because that they want to amplify the sound and was unrelated to the availability of trees (O'Brien 1983; Lee, 1992; Harness et al. 2005; Kosiński, et al. 2018; Basile, et al. 2020; Fieber 2021; Pierce II 2011; Earsom 2022; Wild Birds Unlimited Inc 2022). However, ¾ of videos and records demonstrate drumming on metal near/between the forest and human settlement. Any scientific conclusions about causality (for example, tree removal “changed” woodpecker behaviour) could be drawn from these findings rather than the usual form of a controlled experiment. Thus, comparing woodpecker behaviour before and after tree removal would imply whether causal relationships exist between tree removal and change in woodpecker behaviour.
Author studied cases with a surrounding scenery of the birds and metals. The sample size was 300, and in majority (3/4) of the cases, the birds drummed on the metal nearest to or between the forest and human settlement.
Woodpeckers worldwide may not drum on metals if they do not live in such areas. However, almost all human settlements are designed by removing trees. Thus, the dynamics of tree removal and human settlement components (including metals) play a significant role in woodpecker drumming behaviour.