PhD Candidate, Wake Forest University
I collected data for my dissertation research on Isla Española in the Galápagos Archipelago, ~ 600 miles off the coast of Ecuador. Our lab, led by my adviser, Dr. David Anderson, has intimately studied the breeding behavior and ecology of a large seabird, the Nazca booby (Sula granti), since 1984, making this a very valuable long-term natural study.
Over the course of one season, we monitor daily more than 2,000 nests to collect information on the parents, egg lay date, hatch date, and chick survival. We put a uniquely-numbered metal band on the leg of all chicks to follow individuals over their whole lifespan, helping compile a long-term database on the birds’ breeding behavior. Nazca boobies experience actuarial senescence -- the probability of surviving to the next year decreases with advancing age. They also experience reproductive senescence, with older birds producing fewer chicks than younger birds. My research investigates foraging behavior as a proximate mechanism to explain the observed reproductive senescence in Nazca boobies. I use GPS, TDR (time-depth recorders), and accelerometers to identify where individual birds forage, how deep a bird dives, and how their foraging behavior can change during a foraging trip. Specifically, I am interested in how environmental factors and individual factors (age and sex) affect foraging behavior.
Where does an animal forage?
We can figure that out with biologgers
The most exciting development in the field of foraging ecology is the advancement of biologgers, these small pieces of technology that can be attached to animals without harming the animal. They can provide information about an animal’s behavior and even the environment that the animal moves through. For example, I can attach a GPS—similar to the one in your smart phone or activity tracker and tells you how many steps you have taken today—that can give me information on where a bird travels when it isn't on the nest. An accelerometer can tell tell us when a bird flaps its wings and at what frequency. This technology has greatly increased what we know about how an animal forages, providing details on behaviors that take place where humans can’t observe them.
How does foraging behavior change with environment?
Maybe it's harder to forage when it's cloudy
Animals have a limited amount of time to forage and we assume they have an optimal foraging strategy that lets them obtain food from the environment in the most efficient way possible. In modern societies, humans have an optimal foraging strategy of finding the quickest route from home to the grocery store, and back. Whereas grocery stores tend to be well stocked with food the majority of the time, animals have to search for food that can be unreliable and widely spaced apart. Seabirds, like the Nazca booby, can travel hundreds of kilometers in search of food. The primarily prey on fish and squid species and can use cues from other foraging animals (i.e., tuna and dolphins) to alert them of prey. But we don’t have a firm understanding of how other environmental variables, like sea surface temperature (SST), influence where a bird chooses to forage. Nazca boobies are visual predators, plunge-diving when they spot prey, so changes in cloud cover and therefore light intensity may affect their foraging success.
Does age influence foraging behavior?
Nazca boobies can live to 27 yrs
Studying aging effects in wild animals can be difficult because it requires following an individual across its lifespan. We know that in humans, athletic performance declines with age, and this decline is usually associated with decreased muscle strength and function. Research shows that greyhounds and horses show a similar racing performance decline; older individuals don’t run as fast as younger individuals. High foraging performance is critical for survival and raising young, but how does that change with age? In some species, foraging location differs between age groups or predatory behavior declines with age. I’m interested in exploring how the foraging behavior -- and especially the flight performance -- of Nazca boobies changes with age.
Sleep in Nazca boobies?
We can look at posture in camera trap photos
Sleep is ubiquitous across many taxa, including elephants, humans, and jellyfish. While the functions of sleep remain unclear, sleep may function to reduce metabolism and decrease energy expenditure. However, sleep increases an animal’s risk to predation by making the animal immobile and limits an animal’s ability to forage for food. Nazca boobies can forage for multiple days and we are unsure how much an individual can rest on the water. Sleep after a foraging trip may be critical for a bird to recover and be a successful breeder. I have mentored three undergraduate students in their study of sleep in Nazca boobies. Our first goal was to identify if Nazca boobies sleep, and then ask questions about how sleep changes in individuals, depending on the age and sex of the bird.