Date of Award



© 2015 Jenna Cava

Document Type


Degree Name

Master of Science in Biological Sciences

First Advisor

Steven Travis

Second Advisor

Noah Perlut

Third Advisor

Margaret Friar

Fourth Advisor

Bethany Woodworth


Knowledge of which cues attract natal dispersers back to natal areas is important for conservation because these cues could be used to attract breeders to source habitat or discourage breeders from settling in sink habitat. We examined the influence of intrinsic and extrinsic variables on natal philopatry using two metrics, short-distance natal dispersal and the probability of philopatry to the natal field, in two obligate grassland bird species breeding in an agricultural landscape: the Bobolink (Dolichonyx oryzivorus) and Savannah Sparrow (Passerculus sandwichensis). We also measured heritability and evolvability of morphological traits in the Savannah Sparrow. During 2002-2014 we detected 90 and 129 locally hatched Savannah Sparrows and Bobolinks breeding as adults on or near their places of origin (mean±SD dispersal distances: Savannah Sparrows 917 ± 851m; Bobolinks 1,251 ± 839m). Natal dispersal distance was genetically influenced, i.e., partially heritable for Savannah Sparrows (h2=0.153 ± 0.087), but there was no detectable heritability for Bobolinks. The probability a Savannah Sparrow was philopatric increased as fledge date increased, while the probability decreased if there was an opposite sex parent or sibling present on the natal field or the field was under a late-hay management scheme. None of the variables considered explained variation in Bobolink natal philopatry. Natal philopatry and short-distance natal dispersal in these species appear to be influenced by factors that are difficult to manage. Heritabilities varied from low to high (Bill Width: 0.160±0.182 to Tarsus: 0.651±0.155), while evolvabilities were low across all traits except mass, which was six times higher than the second highest measured in this study (Wing: 0.035±0.013 to Tarsus: 0.064±0.019; Mass: 0.399±0.280). While most of the traits examined have low evolutionary potential in our study population, body mass has relatively high potential; furthermore our previous work indicated that they may be under strong selection from agricultural management that influences mating and reproductive success.


Master's thesis.

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