English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Seasonal changes in food choice by migratory birds often reflect changes in relative food abundance and increased energetic demand. Hermit Thrushes (Catharus guttatus) in southeastern Louisiana are highly frugivorous during winter but forage exclusively on arthropods just prior to spring migration. We hypothesized that this switch to an exclusively arthropod diet would lead to an increase in fat reserves compared to a frugivorous diet, and that fat birds would initiate migration sooner and display more migratory activity than lean birds. We tested these hypotheses on captive Hermit Thrushes maintained on either an arthropod only diet or a mixed fruit and arthropod diet and measured changes in fat score, body mass, and nocturnal migratory activity (Zugunruhe) from February to April 2000. We found that the arthropod-only treatment led to greater body mass and greater amounts of subcutaneous fat than the mixed fruit and arthropod treatment by the third week of the experiment. Despite those differences, body mass was not correlated with intensity of Zugunruhe. We also did not find a significant difference in intensity or onset of Zugunruhe between treatments. We concluded that because Hermit Thrushes are short-distance migrants, large fat reserves are not crucial for their migration. Consequently, fruit and arthropods appear to be equivalent with respect to migratory behavior.

Diet and Preparation for Spring Migration in Captive Hermit Thrushes (Catharus Guttatus)