IU Journal of Undergraduate Research https://scholarworks.iu.edu/journals/index.php/iujur <p>The Indiana University Journal of Undergraduate Research (IUJUR) is a student organization supported by the Office of the Vice Provost for Undergraduate Education. It aims to create a student-run, faculty-mentored, annual undergraduate research publication for all of the IU campuses. For more information, including a detailed submission guide, please see&nbsp;<a href="https://iujur.iu.edu" target="_blank" rel="noopener">iujur.iu.edu</a>. ISSN&nbsp;2379-5611.</p> Indiana University Bloomington en-US IU Journal of Undergraduate Research 2379-5611 <p>Authors who publish with this journal agree to the following terms:</p> <ol type="a"> <li class="show">Ownership of the copyright shall remain with the Author, subject to <em>IUJUR</em>’s use and the rights granted by the Creative Commons license assigned by the Author. A Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) license will be applied to the published work unless otherwise indicated in the Student Author Contract. The CC BY-NC 4.0 license (https://creativecommons.org/licenses/by-nc/4.0/) lets others remix, tweak, and build upon the published Work non-commercially, and although the new works must also acknowledge the original <em>IUJUR</em> publication and be noncommercial, they don’t have to license their derivative works on the same terms.Authors are able to enter into separate, additional contractual arrangements for the non-exclusive distribution of the journal's published version of the work (e.g., post it to an institutional repository or publish it in a book), with an acknowledgement of its initial publication in this journal.</li> <li class="show">Authors are permitted and encouraged to post their work online (e.g., in institutional repositories or on their website) prior to and during the submission process, as it can lead to productive exchanges, as well as earlier and greater citation of published work (See&nbsp;<a href="http://opcit.eprints.org/oacitation-biblio.html" target="_new">The Effect of Open Access</a>).</li> </ol> Breeding Latitude and Annual Cycle Timing in a Songbird https://scholarworks.iu.edu/journals/index.php/iujur/article/view/26407 <p>In spring, songbirds undergo physiological changes such as migratory fattening and gonadal recrudescence in response to increasing day length. Past research suggests that the day length required to initiate physiological changes, known as the photoperiodic threshold, can vary by breeding latitude. In this study, we explored whether migrants breeding at higher latitudes require longer days in spring before physiological changes occur (i.e., whether breeding latitude of origin predicts photoperiodic threshold). We caught and housed male migrant and resident dark-eyed juncos (Junco hyemalis) in an indoor aviary. Photoperiod was increased incrementally from nine to sixteen hours over fourteen weeks. During each photocycle, morphological measurements of mass, subcutaneous body fat, and cloacal protuberance were measured as indicators of migratory and reproductive condition. Stable isotope signatures of hydrogen were used to estimate breeding latitude as an index of migratory distance. Our results show that migrants and residents differed in physiological changes, as migrants accumulated more subcutaneous fat, increased body mass, and displayed a significant delay in gonadal recrudescence relative to residents. Additionally, individuals breeding at higher latitudes deposited fat at a faster rate than individuals breeding at lower latitudes. These results supported our hypothesis that migratory strategy and breeding latitude may predict differences in photoperiodic threshold for both migratory and reproductive timing. Our findings contribute to the understanding of regulation of timing in annual cycles and improve predictions of how species might respond to changing environments.</p> Susan M Reed Ellen Ketterson, PhD ##submission.copyrightStatement## https://creativecommons.org/licenses/by-nc/4.0/ 2019-08-15 2019-08-15 10.14434/iujur.v5i1.26407