Graduation Year


Date of Submission


Document Type

Campus Only Senior Thesis

Degree Name

Bachelor of Arts



Reader 1

Dr. Elise Ferree

Reader 2

Dr. Diane Thompson


Differential migration is when a subset of a population, usually an age or sex group, migrate different distances or at different times. Gambel’s White Crowned Sparrows (WCSP), have been recorded as exhibiting sex-based migration. To test the fidelity of this phenomenon we performed PCR and gel electrophoresis to determine the sex-ratio of WCSP during their non-breeding season, in the winters from 2017-22, at the Bernard Field Station in Claremont, California. Previous studies have observed a male-biased sex ratio at locations north of our study site and female-biased sex ratio at locations south of our site. Based on this latitudinal cline observed in WCSP sex-ratio, we expected to see a female-biased population. A chi-squared test was run on 193 banded individuals and a separate chi-squared test was run on the individuals observed within each year. The results showed that the ratio of males to females did not differ from 1:1. Overall or within any given year of the study 50% female and 50% male was observed in the population. Our preliminary findings suggest that there are other factors that influence inter-population spread of differential migrants. Knowledge of differential migration is important for understanding how ecological conditions in isolated areas could have unequal effects on subgroups within migrant species.

This thesis is restricted to the Claremont Colleges current faculty, students, and staff.