Date of Award:

5-2022

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Ecology

Committee Chair(s)

Clark S. Rushing

Committee

Clark S. Rushing

Committee

Frank P. Howe

Committee

Mary M. Conner

Abstract

Migratory species time their movements to follow changes in food and environmental resources throughout the year. Despite the ubiquity of migration in birds, little is still known about how birds select routes and time migrations. Recent advancements in miniaturized tracking devices now allow tracking of small birds throughout their annual life cycle, presenting opportunities for migratory ecology research at scales immeasurable in the past. Here we investigated the migratory ecology of a northern Utah, USA breeding population of Lazuli Bunting, a common songbird in western North America for which few migratory studies have been completed. We sought to compare breeding site arrival and departure of male and female buntings across an elevational gradient. We used encounter records of microchip-banded individuals visiting electronic birdfeeders to estimate migratory timings of each sex at high and low elevations. We additionally tagged a subset of birds with light sensing tags from which rough daily locations can be estimated throughout the year to determine where and how the individuals migrated.

We found males to arrive before females at low elevation, while no differences between sexes was found in birds arriving at high elevations. This difference questions traditionally held thoughts on why most male birds typically arrive earlier than females. Our results suggest arrival timing by sex may be driven by differences in constraints on migratory timing rather than evolutionary selection for earlier arrival by males. Our tracking data revealed that tagged individuals migrated south to western Mexico for the non-breeding season. We found little support for a mid-migration stopover long enough to complete an annual molt, as had been suggested for the species. During spring migration, we observed two distinct migratory patterns: a direct route north made by three individuals, and a looping route through California and Nevada made by two birds. The latter route was significantly longer in distance but not duration. These differences suggest routes may be selected by individuals to balance between length, duration, and food availability of migration routes based on individual conditions each bird experiences. Our results collectively highlight the importance of investigating migratory ecology at the individual level. Such investigations are necessary in understanding how individual birds migrate and are ultimately necessarily for effective conservation of birds throughout their annual cycles.

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