Spring Migration Phenology Of Four North American Insectivorous Bird Species In Relation To Climatic Variables

Abstract

This thesis describes the relationships between the timing of spring migration (phenology) of four bird species and eight environmental variables which could influence migration. Different bird species respond differently to various cues, and research in this area has shown a wide range of results. Some species respond strongly to weather (often shorter distance migrants) while others do not (often longer distance migrants). If environmental conditions continue to change as recently observed, bird species may respond in different ways, potentially leading to ecological mismatches. Historical First Arrival Date observations were obtained from the North American Bird Phenology Program and compared with weather data. Approximately 2,000 total records of First Arrival Date observations from 1899 to 1962 were included in the analyses. Purple Martins (Progne subis, April 16 ± 12.6 days) and Tree Swallows (Tachycineta bicolor, April 18 ± 14.1) arrived earliest, followed by Barn Swallows (Hirundo rustica, April 25 ± 9.07) and Bank Swallows (Riparia riparia, May 3 ± 10.4). Multiple regression and stepwise regression were conducted to describe relationships between weather and arrival timing. Two species (Bank Swallow and Purple Martin) responded with no significant influence imposed on arrival timing by weather or climate conditions. This follows expectations due to their long distance migration patterns. The two other species studied did not respond as expected. Tree Swallow, despite being the shortest distance migrant examined responded to very few environmental parameters, mainly the Southern Oscillation Index. Barn Swallow, a mid- to long-distance migrant, was unexpectedly the most responsive to weather and climate, responding to all types of weather parameters, including temperature, precipitation, Southern Oscillation Index, and Northern Atlantic Oscillation Index.