Exploring Biotic and Abiotic Constraints on Competition for Signal Space Within Birdsong Communities

Date of Award


Degree Name

Doctor of Philosophy


Biological Sciences

First Advisor

Sharon A. Gill, Ph.D.

Second Advisor

Devin D. Bloom, Ph.D.

Third Advisor

Maarten J. Vonhof, Ph.D.

Fourth Advisor

Jason T. Weir, Ph.D.


Acoustic niche partitioning, anthropogenic noise, migratory species, Parulidae, signal space, species interactions


With the acceleration of climate change and the conversion of natural ecosystems to human-dominated landscapes, there is concern for the persistence of biodiversity amid novel biotic and abiotic factors. An important outcome of shifting species distributions and environmental disturbance is the formation of novel assemblages. For animals that vocalize for mate attraction and resource defense, the introduction of new species into communities may alter availability of acoustic space for signaling and affect detection of signals by conspecifics. Thus, to minimize signal overlap, species should partition signal space and thereby inhabit well-defined acoustic niches. Yet mixed evidence exists regarding signal space partitioning even in undisturbed communities and little is known about how novel selective pressures may influence competition for signal space.

I use observational and experimental methods to understand how singing bird communities share limited signal space and whether partitioning patterns among species vary depending on community composition and anthropogenic noise. In Chapter 1, I review relevant literature on bird communication within a community context. In Chapter 2, I show that a whole breeding community partitions signal space, resulting in song divergence across species, but more closely related species have more similar songs due to phylogenetic constraints on signal structure. In Chapter 3, I focus on a single bird family (Parulidae; hereafter “warblers”) and show that male warblers commonly sing during migratory stopovers. Migratory song differs from breeding song, and variation in singing rates across species could reflect physiological readiness to breed. In Chapter 4, I show that singing migratory warbler species were present in the southwest Michigan community for two-thirds of the breeding season, overlapping the signal space of locally breeding species during their critical period of mate attraction and territorial defense. By coexisting temporarily with breeding species, singing migrants also may act as acoustic competitors, imposing additional constraints on song detection and selection for partitioning in signal space. Finally, in Chapter 5, I introduced anthropogenic noise to warbler communities and showed that noise alters community-wide partitioning of signal space. Species varied in how they modified their songs in noise, leading to changes in acoustic niche area that were idiosyncratic; some species expanded their niches during noise exposure, while others contracted their niches. Noise-driven song adjustments may bring species that had acoustically partitioned into novel vocal competition. By understanding how ecological, evolutionary, and behavioral processes drive partitioning of signal space within communities, we can better predict which communities and/or species are most vulnerable to novel vocal competitors that shift their ranges in response to climate change. Furthermore, understanding the effects of anthropogenic noise on community-wide shifts of acoustic niches will reveal patterns of behavioral plasticity within a songbird family, which will improve our understanding of factors that may drive the persistence of species or communities in noise-polluted areas and the evolution of signals in noisy environments.

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