In a pilot study, the investigators demonstrated that Glaucous-winged Gulls lay eggs synchronously on an every-other-day schedule, but only in areas of the colony where the nest density is sufficiently dense. A mathematical model was developed based on the hypothesis that 48-hour ovulation cycles synchronize through social stimulation. This project builds on the results of the pilot study in the following three ways: 1) The mechanisms by which reproductive synchrony occurs are investigated, in which the investigators explore possible olfactory, auditory, and visual channels of communication. 2) Three classes of mathematical models are studied in order to understand the process of synchronization, the effects of synchrony on population growth and decline, and possible selective advantages of reproductive synchrony. 3) Theory is rigorously connected with data on a project involving a vertically integrated research team in which the training of undergraduates and underrepresented groups is a major focus.
Examples of synchrony have been documented in a wide variety of electrical, mechanical, chemical, and biological systems, including the menstrual cycles of women and estrous cycles of rats. Socially-stimulated ovulation synchrony in birds is analogous to menstrual synchrony in women and estrous cycles in rats, and constitutes the first example of ovulation synchrony in a non-mammalian species. Documentation of ovulation synchrony in both birds and mammals suggests the existence of taxonomically widespread and fundamental physiological and adaptive processes that deserve further attention. Analysis of this phenomenon provides insight into three new classes of mathematical models. Moreover, participation by undergraduates, especially those in underrepresented groups, at every stage of this interdisciplinary research produces young scientists literate in the techniques of quantitative biology.
In this study, we showed that every-other-day egg-laying synchrony occurs in dense areas of a seabird colony in the Pacific Northwest, with the degree of synchrony increasing with the nesting density. We used mathematics to study the system as a population of (hormone) oscillators in order to probe how egg-laying synchrony might occur, what effect it might have on population dynamics, and why it might be advantageous. Our research group focuses on training undergraduates and members of underrepresented groups in STEM research. We could not do our research without extensive undergraduate participation in data collection. Undergraduates also participate in all other areas of the research, from mathematical modeling to manuscript preparation. Most of our students are involved in coauthoring papers and giving presentations. Several of our undergraduate and masters students whose research was funded by this grant went on to PhD studies in STEM during this grant cycle. These studies led to surprising results: Increasing local sea surface temperature leads to high rates of egg cannibalism in colonial seabirds, which leads to egg-laying synchrony. If birds lay eggs on the same day that others are laying, each egg has less chance of being cannibalized. A major punchline is that a small change in a climate variable can cause an unexpected, dramatic, and rapid change in feeding and reproductive behaviors. We have shared these results with the scientific communities and the general public through many peer-reviewed publications, talks at conferences, and public lectures.
