LE3 .A278 2016

2016

Mallory, Mark

Acadia University

Master of Science

Masters

Biology

Biology

CHAPTER 2: Abstract. Auks, a group of diving seabirds, share ecological similarities, and are often found in sympatrically-nesting assemblages at suitable nesting sites. Despite these similarities, it is expected that co-existing species have evolved strategies that reduce niche overlap in response to resource competition. The presence of Atlantic puffins (Fratercula arctica), razorbills (Alca torda), thick-billed (Uria lomvia) and common murres (Uria aalge) at the Gannet Islands, Labrador, is an opportunity to study interspecific interactions among the four main and similar species of a seabird assemblage. I compared the foraging movement of adult birds, and chick and adult diet inferred from stable isotopes, as dimensions in the foraging niche among these four auks. My results revealed that puffins and thick-billed murres headed offshore to forage, while razorbills and common murres were more coastal heading towards mainland Labrador. The patterns of spatial segregation found among the coastal and the pelagic birds were mirrored by their stable isotope ratios, with a group of species foraging on a higher trophic level of an inshore food web, and the other foraging on a lower trophic level of an offshore and pelagic food web. The 'pelagic' species segregated on prey choice for the chick while differential alternate prey selection was the source of segregation between the 'coastal' species. My 17 findings are more evidence that segregation, in at least one or more dimensions of the foraging niche, is a key mechanism that potentially reduces interspecific competition among co-existing and closely related seabirds, explaining the persistence of such seabird assemblages through time. Chapter 3: Abstract. In animal populations, there are individuals that are highly consistent while others are highly flexible in their behavioural strategy. Since seabirds forage in an environment regulated by bottom-up mechanisms, their foraging behaviour is expected to be more plastic in response to changing environmental conditions that might affect the distribution of their preferred prey. I was interested in looking at how short-term individual consistency in different foraging behaviours varies across species of an important seabird assemblage nesting in sympatry: Atlantic puffins (Fratercula arctica), razorbills (Alca torda), common murres (Uria aalge) and thick-billed murres (Uria lomvia). I looked at the repeatability in foraging effort (maximum distance and duration) as well as in foraging locations of individual foraging trips to assess the various levels of individual consistency for those given behaviours. Observed individual repeatability for all behaviours varied considerably by species. Puffins proved to be highly flexible, contrasting with razorbills that were highly consistent, while a range of individual consistencies were revealed in thick-billed murres and to a lesser extent in common murres. These interspecific differences were likely promoted by differences in specific optimal prey availability and perhaps were reflecting individual strategies such as specialization for particular prey items. Because there is a need to better understand 57 individual foraging decisions and how consistency in behaviour influences or is influenced by an individual’s intrinsic characteristics, I related individual consistency with individual physiological and body condition in thick-billed murres. I found strong correlations both positive and negative between individual-level repeatability indices and individual intrinsic components suggesting that individual consistency in foraging effort and flexibility in foraging location are intrinsically linked to individual capacities and constraints.

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