The properties and potential signal value of Atlantic puffin bill colouration

Kochvar, Katja Helgeson (2023) The properties and potential signal value of Atlantic puffin bill colouration. Masters thesis, Memorial University of Newfoundland.

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Abstract

Conspicuous features in species with mutual ornamentation may be overlooked, especially concerning their potential adaptive function. Recent work has demonstrated that selection may act to produce and maintain features that are present in both sexes, but careful investigation is required to elucidate which selective force(s) are at play. The life history characteristics of the species, as well as the properties of the trait itself, are fundamental to generating informed hypotheses on what the adaptive function may be. In this thesis I explore the function of the colourful bill and rosette of Atlantic puffins (Fratercula arctica), a long-lived seabird with obligate bi-parental care. In Chapter 2, I assess whether bill colour aligns more closely with a signal of identity or quality based on three key properties: lability, condition-dependence, and degree of sexual dichromatism. My analysis had mixed results; bill colour was highly dynamic within individuals throughout the late breeding season, but no aspect of colour was condition-dependent and the sexes were monochromatic based on a model of avian visual perception. Although bill colour does not correspond to a traditional quality signal (i.e., correlation with body condition), it may signal a different aspect of individual quality, which I explore in Chapter 3. Specifically, I ask whether bill colour is related to parental quality, as reflected in offspring hatch date and growth patterns. Several aspects of maternal bill and rosette colouration predicted chick growth but not hatch date. Instead, timing of hatch itself was an important factor in determining patterns of offspring mass and wing growth. While these results provide a more nuanced picture of the colourful bill’s role in Atlantic puffins, there is ample room for further investigation, as discussed in Chapter 4.

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