Master of Science
Environment and Sustainability
Morbey, Yolanda E.
Differential migration by sex and age is commonly observed in passerines. Previous studies have found differences in wing morphology between sex and age classes which could affect their movement ecology. In this thesis, I examine whether migratory stopover duration and nocturnal flight speeds differed between age and sex classes in 89 Black-throated Blue Warblers (Setophaga caerulescens) using movement data obtained by Motus Wildlife Tracking System and meteorological data from the NCEP/NCAR Reanalysis II project. Second year birds (hatched during the previous breeding season) had longer stopovers but similar post-departure movements to after second year birds (hatched before the last breeding season). There were some differences in morphological characteristics between age and sex classes. Second year birds had more wing wear than ASY birds, and females had smaller wings than males. Overall, there was no evidence that morphological differences influenced flight characteristics, but flight performance was dependent on wind conditions.
Summary for Lay Audience
Songbirds can vary in physiological, morphological, and behavioural traits depending on their age and sex, affecting individual movement patterns. Little is known about how these differences can affect migratory flight characteristics in songbirds. In my thesis, I examined age and sex differences in stopover duration (amount of time spent at locations where birds stop between migratory flights) and wing morphology to see if these factors could influence flight speed, distance, and duration.
In the spring of 2014, 2015, and 2021, Black-throated Blue Warblers (Setophaga caerulescens) were caught using nets (designed to capture birds) at Long Point Bird Observatory. Birds were carefully extracted from nets. They were banded, and morphological measurements (e.g., wing length, mass) were taken. Birds were tagged with tiny radio transmitters (< 5 % of the bird's weight) to track their movements during migration. The transmitters were placed on the bird with a harness around its legs. The harness did not interfere with the bird's movement or flight. For all years, weather data and the data collected by the radio transmitters were used to calculate stopover duration and flight speeds. In 2021, feather lengths were measured, and photographs of the bird's wings were taken to analyze wing shape.
In 2021, I found that age and sex classes differ in some morphological characteristics but not all. Despite morphological differences individuals displayed similar flight characteristics suggesting that wing morphology does not influence flight performance. Younger birds had longer stopovers but similar post-departure movement to older birds.
My study is one of the first to compare flight speeds between age classes of songbirds using radiotelemetry. It is also one of the first studies to examine differences in wing morphology between age and sex classes and the effects of wing morphology on migratory flight characteristics in songbirds. My study provides individual-based data on migratory movements improving our understanding of songbird migration. This information is essential for piecing together complete migratory journeys and identifying critical habitats to support migratory songbirds.
Rokitnicki, Patricia, "Age and Sex Differences in Stopover Behaviours and Flight Performance in Black-throated Blue Warblers" (2023). Electronic Thesis and Dissertation Repository. 9307.
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