USING AUTOMATED RADIO-TELEMETRY TO ASSESS SPRING MIGRATORY ECOLOGY AND SURVIVAL OF IPSWICH SPARROWS (PASSERCULUS SANDWICHENSIS PRINCEPS)

Abstract

Songbird behaviour during migration is consequential because it can affect survival and ultimately population size. Behaviour during spring migration may be particularly important because it affects condition and timing of arrival, which affects subsequent breeding. Population-level differences in behaviour can occur due to various factors. Intrinsic factors such as age and sex lead to differences in experience and sexual maturity. Extrinsic factors like landscape features such as ecological barriers can influence movement patterns and the spatial location of mortalities. I used three years of radio-telemetry data to assess the behaviour and survival of a range-restricted songbird, the Ipswich Sparrow (Passerculus sandwichensis princeps), during spring migration. I tracked 153 sparrows migrating along the Atlantic Coast between wintering grounds in the eastern USA to breeding grounds on Sable Island, Canada, and used those data to evaluate how various intrinsic and extrinsic factors affected behaviour. In Chapter 2, I assessed the temporal and spatial patterns of spring migration in the context of optimal migration theory to determine if sparrows followed a time- or energy-minimizing strategy. I found that sparrows followed an energy-minimizing strategy, travelling relatively slowly, making short nightly flights, and making frequent refueling stopovers. I found no evidence that strategy varied with age or sex. In Chapter 3, I assessed behaviour at two overwater ecological barriers, the Gulf of Maine (GOM) and part of the Atlantic Ocean (AO). I also estimated daily survival probability in different spatial legs of the Atlantic Coast during migration. Sparrows both crossed and circumvented the GOM. Juveniles, in particular, also made non-migratory movements and abandoned flights before the AO but not elsewhere during migration, suggesting some difficulty crossing this barrier. Juvenile bearings to Sable Island were also less direct than adult bearings. There was no evidence that these behaviours varied with sex. Daily survival probability was variable across legs of the Atlantic Coast, being highest in the GOM and lowest in eastern Nova Scotia and crossing the AO to Sable Island. Collectively, these results have conservation implications for the Ipswich Sparrow. There is a need for broad-scale protection of stopover sites that support the frequent refueling needs of sparrows along the coast. This may be especially important in Nova Scotia adjacent to the AO where non-migratory movements, abandoned flights, and low survival suggest that passing this barrier is a particularly challenging leg of migration. These results also provide insight into how migratory behaviour develops across age and sex classes. By spring, the behaviour of juvenile sparrows is largely, but not completely, consistent with the behaviour of adults. This is likely attributable to individual learning by juveniles over the previous year. A lack of sex-related differences in behaviour suggest that males and females are under similar selection pressures or may be in similar condition during spring migration.