Extreme Heat Events and Cassin’s Auklets



San Jose State University and POINT BLUE Graduate Student:
Extreme Heat Events and Cassin’s Auklets

Please join us in congratulating Emma Kelsey, a graduate student with Scott Schaffer at San Jose State University, who presented her MS thesis last Friday. She used artificial eggs to study Cassin’s Auklet incubating behavior at the Farallon National Wildlife Refuge.  She found that auklets using unshaded nest boxes work harder than those in natural burrows to keep their eggs cool.  This information is important as we start working on designing new artificial nesting habitat on the Farallon Islands to help mitigate the effects of extreme heat events on these birds. The title of her thesis and abstract can be found below.

Title: Turn of events: How environmental temperatures and artificial nest habitats influence incubation behaviors of Cassin’s auklets (Ptychoramphus aleuticus)

Abstract: Nest attendance behaviors, such as egg turning and temperature maintenance, are critical to proper hatching success for most bird species.  The details of avian incubation behaviors are still not well understood, especially for species that nest in burrows and crevices where their nests cannot be observed.  Cassin’s auklet  (Ptychoramphus aleuticus) is a small, burrow-nesting seabird found throughout the northeastern Pacific Ocean.  Artificial nest boxes are used to monitor the Cassin’s auklet population located on Southeast Farallon Island, California.  Higher air temperatures on Southeast Farallon (SEFI) have indicated that extreme heat events can increase temperatures in un-shaded nest boxes to lethal temperatures for the auklet nesting inside.  However, the effects of these elevated temperatures on the incubation behaviors and egg viability are not clear.  In this study, I used egg data loggers, containing an accelerometer, magnetometer, and heat thermistor, to measure the egg temperatures and turning rates of auklet eggs in natural burrows, nest boxes covered with a shade, and un-shaded nest boxes on SEFI during the 2012 and 2013 breeding seasons.  Nest temperatures were highest, and most variable, in un-shaded nest boxes.  Egg temperatures were also highest in un-shaded boxes and lowest in natural burrows.  Average egg turning rates were 2 turns/hour.  Diurnal incubation patterns were seen, with increased egg turning rates and decreased egg temperature during the night.  Egg turning rates were positively correlated with egg temperatures during daytime periods.  These results show that nest habitat can influence auklet incubation behaviors and suggest that auklets may compensate for elevated nest temperatures with their incubation behaviors.  The results indicate that increasing environmental temperatures can affect breeding Cassin’s auklets and ways to further mitigate these effects should be considered.

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