LE3 .A278 2021

2021

Mallory, Mark
Craik, Shawn

Acadia University

Master of Science

Masters

Biology

Biology

Patterns of habitat use do not necessarily reveal optimal choice, so habitat selection studies should relate habitat use to reproductive success to reveal processes critical to the evolution of habitat choice behaviour. In Lobster Bay, Nova Scotia, I conducted a study of habitat use and selection by Common Terns (Sterna hirundo), Arctic Terns (S. paradisaea), and Roseate Terns (S. dougallii) at two spatial scales: 1) island-level selection, and 2) nest-site selection. For four years and across 97 similar islands, the absence of trees was the most important factor predicting island use by terns and used islands were also generally less elevated than those not used. I studied the amount of lateral cover, the number of different sized rocks, and the amount of inter and intraspecific nest density from 292 nests in a colony of Common, Arctic, and Roseate Terns. I examined whether the species partitioned habitat at a fine spatial scale and I compared these characteristics between used sites and available sites and between successful and unsuccessful nests for each species. My results indicated that all three species partitioned habitat based on physical characteristics like lateral cover and large rocks and biological features (nearby density of nesting terns). I found that high lateral cover was an important feature for nest site selection of both Common Terns and Roseate Terns. Common Terns had higher nest success with greater interspecific nest density (i.e. density of Roseate and Arctic tern nests) within 2 m, possibly via reduced predation pressure by gulls (Larus spp.) in areas with dense tern nesting. A similar trend was observed for Roseate and Arctic terns, although it was much less pronounced than in Common Terns. Overall, my results suggest that mixed species colonies of terns can provide fitness advantages to each species, and that Common, Arctic, and Roseate Terns nesting in the Northwest Atlantic have evolved habitat preferences that serve to reduce competition in dense colonies.

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https://scholar.acadiau.ca/islandora/object/theses:3647