Western University Scholarship@Western Electronic Thesis and Dissertation Repository 3-28-2018 2:00 PM Nest Predation by brown-headed cowbirds (Molothrus ater) David C. Swan The University of Western Ontario Supervisor Zanette, Liana Y. The University of Western Ontario Graduate Program in Biology A thesis submitted in partial fulfillment of the equirr ements for the degree in Doctor of Philosophy © David C. Swan 2018 Follow this and additional works at: https://ir.lib.uwo.ca/etd Part of the Biology Commons Recommended Citation Swan, David C., "Nest Predation by brown-headed cowbirds (Molothrus ater)" (2018). Electronic Thesis and Dissertation Repository. 5274. https://ir.lib.uwo.ca/etd/5274 This Dissertation/Thesis is brought to you for free and open access by Scholarship@Western. It has been accepted for inclusion in Electronic Thesis and Dissertation Repository by an authorized administrator of Scholarship@Western. For more information, please contact
[email protected]. Abstract The reproductive success of parasites is entirely dependent on their ability to encounter suitable hosts. Obligate brood parasitic birds may increase host encounter rate, and consequently their reproductive output, if they cause unsuitable late-stage host nests to fail thereby stimulating the host to create another nest that they can parasitize. I tested key predictions of this ‘farming’ hypothesis for the brown-headed cowbird (Molothrus ater). I found evidence that cowbird attacks are not uncommon, a basic requirement of the hypothesis. Furthermore, I found multiple lines of evidence that cowbird attacks are not indiscriminate, but directed at non-parasitized nests and at those at a developmental stage too late to be suitable for parasitism.