By Emily Elderbrock, Department of Biological Sciences, University of Memphis
Let’s pretend for a moment that someone was able to convince you to stick your hand into an underground hole and pull out the critter that lived inside. What would you expect to find? A rabbit? A snake? It’s probably safe to say that a bird would not be at the top of your list. However, for researchers on Kent Island, removing Leach’s storm-petrels from an underground burrow is a frequent activity, one they’ve been doing for over 55 years. Using long-term data collected on the island, Dr. Robert Mauck and his colleagues, Dr. Chuck Huntington and Dr. Paul Doherty, are investigating the impact of climate change on this seabird’s survival and reproductive success.
In the late 1940s, not long after Cunningham first began his study, Dr. Chuck Huntington, a biologist, visited the island. By 1954, he had begun studying what would become his life’s work and passion. His interest was the large population of Leach’s storm-petrels that nest on Kent Island. These seabirds are pelagic, meaning they return to land only to breed. A male and female pair will lay a single egg in an underground burrow and then alternate taking turns caring for the egg or young. To avoid predators, the storm-petrels leave the burrow during the night. During daylight hours, researchers may approach a burrow, reach inside, and briefly remove the bird in order to take measurements for their study. Huntington identified individuals by putting bands on their legs and monitored each bird’s reproductive success, tracking how many pairs attempted to nest and how many of these chicks survived to adulthood. Storm-petrels are known to survive for over 30 years, but Huntington’s research has outlasted even the longest-lived individual in his population, with over 6000 birds being banded during a span of more than 55 years.
When Mauck began working on the island in 1990, Huntington had collected over 30 years of data on the storm-petrels. When combined with Cunningham’s long-term weather monitoring program, this provided a unique situation. “A 50 year data set can detect small changes that a few years’ worth of data would not find,” Mauck stated. He looked for patterns with the expectation that if annual temperatures were higher or lower, the environment may impact the petrels’ ability to successfully raise young or even just to survive. His primary interests were the temperatures on Kent Island and on the sea surface of nearby bodies of water where the petrel’s feed. This included the Gulf of Maine where Kent Island is located and Georges Bank which separates the Gulf from the Atlantic south of the island. He then decided that although it may be longshot, he’d add global temperatures into his study as well.
It may have been a longshot, but it worked. “I didn’t believe it at first”, Mauck said when his results showed that global temperatures were in fact impacting the petrels’ lives. The long-term data sets revealed that when local island temperatures, sea surface temperatures, and global temperatures were warmer, the petrels had increased reproductive success, meaning they had a greater chance of successfully mating, laying an egg, and raising their offspring to adulthood. However, warmer temperatures were not necessarily always good for the petrels, because Mauck also found that when local, sea surface, and global temperatures were cooler, the birds survived better as adults. This means that over the last 50 years, warmer temperatures were better for reproduction, but cooler temperatures were better for survival. Mauck is currently looking into further detail on how the demographic of the petrel population is being affected, but a relatively simple explanation may exist for these seemingly contradictory results.
These findings may suggest that the ideal environment for the storm-petrels is similar to that of Goldilock’s desires in the nursery rhyme: not too hot or too cold, but somewhere in between is “just right”. In warmer temperatures, birds have a better chance of successfully raising offspring, but also face a greater chance of dying. In contrast, they survive better in colder weather, but have less success at raising offspring. The ideal temperature for the petrels may be a constant point somewhere in the middle of the extremes, allowing for both maximum survival and reproduction at the same time. These findings are only the start, as Mauck hopes to continue looking at effects of temperature with data he has collected throughout his time at Kent Island. This will include more detailed information on reproduction, such as the date petrels first begin laying eggs each year, the date the eggs hatch, and the growth rate of the offspring within the nest.
Thanks to the enduring research efforts of Huntington and Cunningham, future scientists have a great amount of history on both the storm-petrels that breed on Kent Island and on the island itself. As Mauck and I talked over coffee in January, his phone rang. It was Huntington. Now 93, Huntington is still involved in the research on Kent Island. It must be a passion for the research, the birds, and the island, that keeps these researchers returning year after year. Or perhaps it’s just as Mauck’s daughter announced years ago following a trip to Florida: “Kent Island is way more fun than Disneyworld”.
Emily Elderbrock developed an interest in avian endocrinology while working with Eastern bluebirds as a student at the College of Wooster in Ohio. She is now pursuing a masters degree in the lab of Dr. Stephan Schoech at the University of Memphis. Emily spends her winters and springs in sunny southern Florida, where she is studying the effects of developmental stress on the physiology and behavior of Florida scrub-jays.