Life in Boxes and Burrows

         

From March through August, Southeast Farallon is bustling with seabird activity, some more obvious than others.  The presence of the Western Gulls is undeniable, and it is pretty hard to miss the 250,000 or so Common Murres milling about as you approach the island.  But some species here on the island, being more reclusive and mysterious, don’t make their nesting presence as obvious. One such species is the Cassin’s Auklet.  They nest primarily in burrows and rocky crevices underground and come and go from the island only under the cover of darkness.  Luckily for us, they can also be found nesting in little wooden boxes with PVC pipe entrances and shaded roofs, which are scattered around the island, tucked in among the Farallon weed, lavatera and rocks. 

Cassin’s Auklet in a nest box, photo courtesy of Annie Schmidt.

         PRBO researchers began building and installing these artificial nest boxes in the early 70’s in order to provide additional nesting habitat and to make it easier to monitor the nesting phenology, breeding success, and chick growth rates of the auklets. Since then, the use of artificial nest boxes to monitor the breeding biology of burrow nesting seabirds has become a widely embraced technique.  But, for those of us researchers who depend on these nest boxes for our monitoring purposes; it is important for us to know that the boxes are, indeed, providing an adequate environment for the birds nesting within them.  I am here on SEFI to help PRBO and FNWR consider just that.

A Cassin’s Auklet nest box with shade cover.

Environmental temperatures on the Southeast Farallon Island were exceptionally warm during the 2008 and 2009 Cassin’s Auklet breeding seasons.  These anomalously warm temperatures meant that the artificial nest boxes turned into little hotboxes, which was distressing to some of the auklets nesting within.  In 2009, to help mediate this problem, PRBO researchers created shade structures for all occupied nest boxes and started a pilot study to better understand the differences in temperature experienced by the auklets in artificial and natural burrows.  Initial results showed that natural burrows were significantly cooler than nest boxes but putting shades on nest boxes decreased the nest box temperature notably.  Since 2009, all nest boxes with auklets nesting in them are covered in shades. 

The goal of my project is to take this study one step further.  I want to see if the adult auklets in nest boxes are able to control egg temperature when nest box temperatures are elevated, and how this may affect their hatching success.  

Reaching into an auklet home to switch out an egg.

For my project, I put devices that recorded temperature in hollow artificial Cassin’s Auklet eggs.  I then put the artificial egg in the auklets nest for a couple days to record egg incubation temperature.  The goal of the project was to compare the incubation temperature of auklets in different nest types- natural burrows, shaded nest boxes, and unshaded nest boxes.  Once I have chosen the nests where my artificial eggs were to be deployed, I diligently babysat the auklets real egg in a poultry incubator while the temperature loggers were deployed for seven days. 

 

Cassin’s Auklet eggs, safe and warm in the incubator.

I started my study a year ago and successfully made three deployments of egg temperature loggers during the 2012 auklet breeding season.  Based on my results so far, I have found that the eggs in artificial nest boxes are significantly warmer than those found in natural burrows that there is a significantly correlation between burrow habitat temperature and egg temperature.  However, these variations in egg temperature do not seem to significantly affect reproductive success of the auklets.  In other words, the nest habitat conditions in the artificial nest boxes may be warmer than in natural burrows but this doesn’t seem to be having negative effects on the overall breeding success of the birds.  My sample size is small enough thus far that it is difficult to say for sure though.
 

An artificial egg, ready to go inside a Cassin’s nest box.

The artificial eggs and wire pulling lubricant.

Beyond the science, this study has also given me the opportunity to learn about a lot more than just Cassin’s Auklet incubation temperature.  How do you make a fake Cassin’s Auklet egg?  You ask an art student (many thanks to Kat McKinnon and Philip Priolo of the San Jose State University art and industrial design departments!).  How do you incubate a Cassin’s Auklet egg?  You follow the directions for incubating quail eggs in the incubator package instruction manual.  How do you make a fake egg feel realistic enough so an auklet will want to incubate it without interfering with the temperature of the egg?  You fill it with wire pulling lubricant (don’t know what wire pulling lubricant is?  Don’t worry, I didn’t either until recently). 

This project has also given me the amazing opportunity to spend the season participating in all the other seabird studies that are carried out on this SEFI.  I have learned so much and made some wonderful memories out here.

I just arrived on SEFI for my second season deploying Cassin’s Auklet eggs, in which I hope to increase my sample size and get a better idea of the differences in incubation temperature between natural and artificial nest habitats and how the auklets may mitigate for this.  It is our hope that the results of this study could lead to the design and implementation of new and improved nest boxes of the Cassin’s Auklets on SEFI.  In the meantime, I am so happy to be back out here on this incredible island and I look forward to whatever the season has in store!

Emma Kelsey

PRBO research assistant and graduate student at San Jose State University