By Rachael Orben, Research Associate, Department of Fisheries and Wildlife, Oregon State University
In late May, I returned to St. George Island, Alaska to study the foraging ecology of red-legged kittiwakes using a mix of high-tech biologging tags, physiology measurements, and observations. The study was designed to identify differences in behavior and physiology between birds that reproduce successfully and birds that don’t and then to see how this might carry over to the winter season (and vice versa). Things didn’t go as planned.
This was my fourth spring on the island, and like prior seasons we arrived in late May, when birds should be building nests. However, unlike previous seasons, red-legged kittiwake’s didn’t look like they had done much nest building. I was accompanied by Abram Fleishman, a superstar MS student from San Jose State who is studying the winter spatial ecology of red-legged kittiwakes in relationship to mercury concentration in their feathers.
We immediately set about recapturing birds that had carried geolocation data loggers over the winter. We wanted to catch as many as possible before eggs were laid, so that their blood samples would represent the pre-lay period. The weather was wonderful, so it wasn’t until three weeks after we arrived that we had our first day-off. It was at about this time that I finally lost my optimism and realized the majority of red-legged kittiwakes were not going to lay eggs. By late June kittiwakes are usually incubating eggs. We only saw a handful of eggs and very few of these were being incubated. Most birds didn’t even build nests, or if they did, the nest was dismantled by other birds when the nest building pair didn’t stick around to guard their pile of mud and moss.
When I designed the study, I thought collecting enough data to answer my questions about successful versus failed breeders would be hard, since failed breeders would be challenging to work with and red-legged kittiwakes typically have high breeding success, meaning that sample sizes of failed breeders would be small. Instead our three seasons occurred with progressively worse breeding success and we will now have to shift the focus of our analysis to see if we can find differences between birds that laid eggs and birds that didn’t, if we have the sample sizes! With ~80% laying success in the 9 years preceding the beginning of our study in 2015, this is something I would never have expected! The egg laying failure of 2017 is unprecedented in the productivity monitoring time series collected by the Alaska Maritime Wildlife Refuge.
Seabirds are often touted as indicator species of marine health (Cairns 1988, Piatt et al 2007), and while there are always caveats and additional questions to be answered, seabirds are reliant on the ocean for food and observing their behavior and condition tells us something about how easy (or hard) it is for them to find food.
So, what do I think the red-legged kittiwakes told us this year? I think they were squawking loud and clear, that they were not able to find myctophid fishes within their foraging range to the south and west of the Pribilofs. Myctophids are small fatty mesopelagic bioluminescent fish that come to the surface at night where red-legged kittiwakes catch them.
Besides just observing the laying failure, we were able to GPS track a few birds, collect a few diet samples, catch birds for blood and feather samples, and resight banded individuals. It is these pieces of information that I will be analyzing in the coming months to try to understand why some individuals were able to lay eggs during our study years, while most were not. These years should also help us understand what capacity red-legged kittiwakes have to cope (or not) with changes in prey availability. However, after three years, I still don’t know what a ‘good’ year looks like for red-legged kittiwakes. Fingers crossed next season is finally a decent year for this sentinel seabird of the pelagic Bering Sea.
You can read more about our red-legged kittiwake research in a series of blog posts written for the Seabird Youth Network, a partnership between the Pribilof School District, the Aleut Community of St. Paul Island, the City of St. Paul, Tanadgusix Corporation, the St. George Traditional Council, St. George Island Institute, the Alaska Maritime National Wildlife Refuge, and the wider scientific community. The network creates opportunities for youth to learn about seabirds with the aim of building local capacity for the collection of long-term seabird monitoring data on the Pribilof Islands.
Whatof the mercury concentration in the feathers of the red legs, what is the level if any? As a life long resident of St.George..I would be keenly interested in future findings of your on going research…thank you
Hi Victor, Thanks for your interest in our research! All the kittiwakes (both red-legged and black-legged) that we have sampled do have measurable levels of mercury, but generally the levels have been on the lower side. However some birds do have higher concentrations. We are sampling blood and feathers, which isn’t directly equivalent to muscle. This years samples are heading to the lab for analysis so we should have more results to share sometime this fall.