Dr. Hans Slabbekoorn

Birdsong, speciation, and conservation in a noisy world. 

Dr. Hans Slabbekoorn
Institute of Biology, Leiden University

 
Birdsong is a secondary sexual trait, which may play an important role in species recognition. Therefore, song variation between populations of the same species may affect the rate and probability of speciation. Birds rely on song for defending a territory and attracting a mate. Singing loud, long, complex, or familiar, may signal qualities of a singer to anyone hearing the song. However, target receivers may be at a distance at which the original sound has attenuated and degraded while breeding areas are often quite noisy. Natural 'soundscapes' are determined by abiotic sound sources and the local vocal community, but more and more human activities make anthropogenic noise almost omnipresent. Consequently, the signal function of singing depends heavily on signal-to-noise ratios, and noise conditions are getting worse and worse. Several counter strategies in producing sounds, related to adjustments in loudness, pitch, and timing, could help out under rising noise conditions. Such acoustic flexibility may be key to efficient use of the 'left-over acoustic space' and may determine whether individual birds can maintain their territory and breed successfully. Variation in flexibility among species may explain which birds will remain widespread in our noisy world and which will be pushed back into 'silent' habitat pockets. At the same time, urbanization provides a natural experiment of global scale, which allows the investigation of intra-specific song variation and the associated potential for behavioural barriers to gene flow. So, if we look at the bright side of life: understanding the impact of anthropogenic noise may yield fundamental insights into the process of ecological speciation.

1986-1993: Biology study at Utrecht University

1994-1998: PhD-project at Leiden University

1998-2001: Post-doctoral Fellow at San Francisco State University (SFSU) at the Center for Tropical Research, now at UCLA: http://www.ioe.ucla.edu/CTR/

1999-2001: Research Associate at the California Academy of Sciences (CAS)

http://www.calacademy.org/research/bmammals/
2002-2004: Post-doctoral Fellow at Leiden University (NWO-PULS-grant) http://biology.leidenuniv.nl/
2004-: Assistant Professor at the Institute of Biology at Leiden University (IBL) http://biology.leidenuniv.nl/ibl/S8/S8PeopleInfo.php?PeopleID=143

Summary of research interest

The central theme of my research concerns the assessment of environmental impact on the evolution of acoustic signals. Within this theme, I am specifically interested in the role behavioural processes play in: 1) the emergence of geographic structure in sexual signals, and 2) the rise of reproductive barriers leading to speciation (Slabbekoorn & Smith, Philosophical Transactions 2002). Over the last five years, I have studied patterns of song variation among individual birds within a single urban population (Slabbekoorn & Peet, Nature 2003), and among different populations across Europe (Slabbekoorn & den Boer Visser, Current Biology 2006). The first paper showed individual variation in the frequency use correlated to local urban noise levels. The second paper confirmed that urban birds across Europe have diverged from nearby forest birds in several parameters. In 2007, I received an Open Competition research grant from NWO to further develop this line of research. Anthropogenic noise in human-altered habitat provides an excellent work space for fundamental research, but also yields insights potentially valuable to conservation (Slabbekoorn & Ripmeester 2008). The great tit work has taken a lead in what seems to develop rapidly into an independent sub-discipline, which has been labeled: "Mechanistic Urban Ecology" (Katti & Warren, TREE 2004; Shochat et al. TREE 2006), and has raised the public awareness of the negative consequences of noise pollution.

Key publications

Slabbekoorn, H. & Smith, T.B. 2002. Bird song, ecology, and speciation.  Philosophical Transactions of the Royal Society, London, B. 357: 493-503.
Slabbekoorn, H. & Peet, M. 2003. Birds sing at a higher pitch in urban noise.  Nature 424: 267.
Marler, P. & Slabbekoorn, H. 2004.  Nature’s Music. The Science of Birdsong. Hardcover, 504 pages, including 2 CD’s. Academic Press/Elsevier, San Diego. http://www.elsevier.com/wps/find/bookdescription.cws_home/703036/description#description
Slabbekoorn, H. & den Boer-Visser, A. 2006. Cities change the songs of birds. Current Biology 16: 2326–2331 .
Slabbekoorn, H. & Ripmeester, E.A.P. 2008. Birdsong and anthropogenic noise: implications and applications for conservation. Molecular Ecology 17: 72-83. http://www3.interscience.wiley.com/journal/119411284/issue

Teaching at the Institute of Biology, Leiden University (IBL)
Among other things:

·  Annual 4 weeks field-course in Behavioural Biology for 2nd year students.

This course addresses fundamental approaches to conducting science outdoors in a discipline founded by the Nobel-prize winning Ethologist Niko Tinbergen, who also had his roots in Leiden. There is a strong focus on bioacoustic techniques and experimental design, and birdsong is used as the main model system to investigate behavioural and evolutionary processes (Next course will be in May/June 2009).
·     Biannual MSc-Seminar series on Behaviour and Conservation for 3rd to 5th year students. In this course, participants prepare presentations about book chapters and articles, and they discuss the ways in which behavioural data are, or could be, contributing to conservation efforts. Acoustic data is only one of many types addressed during this course, which is in English, and takes thirteen Wednesday afternoons (Next course will likely be October/December 2009).  

Information: studieadviseur@biology.leidenuniv.nl

Slabbekoorn 2002
Slabbekoorn 2003
Slabbekoorn 2006
Slabbekoorn 2006 suppl