Document Type

Thesis

Degree

Master of Science

Major

Biology

Date of Defense

11-3-2006

Graduate Advisor

Patricia G. Parker

Committee

Bette Loiselle, PhD.

Patrick Osborne, PhD.

Abstract

The foraging behavior of bird assemblages at Rubus niveus was determined over two seasons in the agricultural zone of Santa Cruz Island, Galapagos in order to identify effective seed dispersers of the species and understand the factors that aid invasion of fleshy fruited weeds. A total of seven bird species were observed feeding on R. niveus fruits. In both seasons, the small ground finch (Geospiza fuliginosa), the introduced smooth-billed ani (Crotophaga ani ) and the small tree finch (Camarhynchus parvulus) were the most common visitors. Mean number of seeds removed per visit was higher for anis than for Geospiza and Camarhynchus. Finches fed on pulp and juice of ripe fruit and predate seeds. Anis swallowed entire fruits, suggesting that they handle seeds more effectively than finches. Additionally, 57% of seeds recovered from anis¿ feces were viable using a 2,3,5-triphenyl tetrazolium chloride test. Forty-four percent of those seeds germinated in a greenhouse experiment from May to October. In contrast, finches rarely passed viable seeds of R. niveus. Effective seed dispersal may be an important factor contributing to the rapid naturalization and invasion of R. niveus since its introduction on Santa Cruz 20 years ago, and represents one potential mechanism by which this species may be dispersed to adjacent islands.

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