ellen

About me…

I began my trek into the world of biology at the University of Maryland at College Park. After satisfying the most essential core requirements for my first two years as a biology student, I transferred to Western State College in Gunnison, Colorado. It was a move to invoke inspiration, and it worked. Conserving wildlife has been my main aspiration since elementary school days. Being a visual learner, I suppose I needed to see in order to believe. The wilderness of the Rocky Mountains was the ideal setting for learning the fundamentals of ecology and animal behavior, and by the spring of 1997 I graduated with a B.A. degree. My academic interests are constantly "evolving," but my education has focused on the ecology and behavior of vertebrates. I enrolled in the biology graduate program at UNCW in the fall of 1998 to work with Dr. Emslie.

My Thesis Research…

I am studying the foraging ecology of breeding known-age Royal Terns (Sterna maxima). In the spring and summer, Royal Terns nest in tightly packed colonies on small islands along the southern coastal regions of the United States. Each monogamous pair usually lays one egg per season. Both parents utilize the rich food sources available in estuaries during the breeding season to raise their chick(s). They bring single, whole prey items, mostly juvenile clupeids or sciaenids, to their offspring. Therefore, their diet may be identified using binoculars rather than using invasive stomach content analysis. The primary purpose of my project is to gain baseline diet and foraging time data for Royal Terns nesting on a dredge-spoil island in the Cape Fear River, N.C. so the breeding population may be used as a bioindicator of changing environmental quality here in the future.

Marked parent feeding chick a striped anchovy

Another interesting fact about this species is that their fledglings have been banded annually with USFWS identification service bands since the late 1970’s. Many of the returning adults still wear bands, and thus are of known-age. The other purpose of my study is to understand the relationship between parental age and foraging characteristics of this long-lived species. In accordance with Lack and Ashmole’s theory concerning the evolution of deferred breeding in monogamous shorebirds, I hypothesize that parents of different ages have different foraging traits related to time management, tide cycles and diet composition.

Hoop trap used to capture adults

In order to test temporal questions, an Advanced Telemetry Systems data logging device and radio-transmitters are being used for birds nesting on Ferry Slip Island during two breeding seasons (1998 and 1999). So far, the largest constraint of this project has been determining the best method to attach radio-transmitters to birds so that they will stay fixed to parents the entire season but not hinder flight behavior. Despite trial and error setbacks with traps and transmitters, most of my data from the spring and summer of 1999 is compiled and is giving me much more to work with regarding the foraging ecology of Royal Terns than I ever imagined when I began.

Interesting Results…

As expected, the diet observations show that the type and size of prey brought to chicks changes throughout the breeding season. The time period from 6 June to 19 June marked the early hatchling stage for most of the chicks on Ferry Slip. During this time, chicks were eating smaller fish (usually 32-64 mm total length) mainly anchovy and juvenile herring. As the season progressed, the average size of prey items was in the 64-96 mm size distribution and Atlantic croaker, spot, striped mullet, and shrimp species became much more abundant in the diet of chicks. Herring species such as Atlantic menhaden were most abundant during the time period between 20 June and 4 July. Out of the fish that could not be identified to family, the trend of greater body depth (>2 mm) also increased by 35% after the hatchling stage.

Time data for birds of known-ages showed that the average foraging bout time of 46 min. did not differ by age group. Older birds took less day bouts than younger birds (p=0.0433, ANOVA), but did not spend a significantly lower percentage of the daytime on foraging trips. Next season I hope to have a larger sample size of transmitter birds, and also, I am anticipating a longer time over which the data can be compared for birds of different ages by using elastic transmitter harnesses. By increasing the time and number of subjects hopefully I can decipher the seemingly contradictory results concerning number of bouts versus the amount of time spent foraging during daylight hours.

I believe the most important contribution of this study is how it relates to the projects that Dr. Emslie’s other graduate students are conducting. My study is smaller in scale by comparison, however in order for the Royal Tern to be used as a bioindicator species in their breeding grounds, it is essential to learn the details of how their diet and foraging traits may change with age. By collecting egg contaminant load, genotoxic assault and foraging range data for subpopulations of this species along the North Carolina coast, we may be able to monitor and understand how slight environmental changes affect the breeding biology of predatory species especially in the Cape Fear River System.