Date of Thesis

Spring 2018

Thesis Type

Honors Thesis

Degree Type

Bachelor of Science

Major

Animal Behavior

Minor, Emphasis, or Concentration

Environmental Studies

First Advisor

Morgan Benowitz-Fredericks

Keywords

seabird, microclimate, climate, Gulf of Alaska, animal behavior, reproduction and development

Abstract

Seabirds are marine top predators, and as such are often studied as bioindicators of climate shifts (Oswald and Arnold 2012). Though many studies have analyzed the effect of macroclimatic variation on marine prey species availability and thus seabirds, few have analyzed effects of microclimate - fine spatial patterns of climate (Mantua and Hare 2002; Hatch 2013; Kim and Monaghan 2005a). I tested the hypothesis that localized temperature and humidity at nest sites interact with food availability to alter black-legged kittiwake (Rissa tridactyla) nest site quality, chick body condition during growth and development, and reproductive parameters including Julian lay date, number of eggs laid, and the proportion of chicks fledged per nest.

All black-legged kittiwakes were located in physically accessible nests along the exterior of an abandoned radar tower that now serves as a converted seabird laboratory. Nests were located on “panels” with distinct compass orientation, insolation, and exposure to wind and rain along the exterior of this polyhedral radar tower. Panels housed ~27 nests, alternating between supplementally fed (n = 4; all nests offered ad libitum food 3x/day) and unfed panels (n = 3). The supplemental feeding status of each nest remained unchanged for the duration of the dataset with the exception of panel G, which had supplemental food removed in the latter third of the breeding/chick rearing season. I recorded temperature and humidity at individual nest sites during egg laying and chick rearing (May-August 2017) on Middleton Island, AK using rainproof wireless sensor tags (Cao Gadgets, LLC). Measurements of chick developmental morphology (weight, wing, tarsus, culmen, headbill) were collected every five days. Nest site quality was determined by analyzing the number of chicks fledged at individual nests over several years, therefore providing an historic analysis as well.

Microclimate varied across the tower, with warmest and driest panels being panels A through C and cooler more humid panels being panels D through G. Humidity and temperature were inversely related. Nests at fed panels maintained higher average temperatures and greater nest site quality than adjacent unfed panels. Microclimate minimally influenced egg laying of breeding adults and body condition of chicks. Warmer and drier nests tended to maintain earlier Julian lay dates and greater quantities of eggs laid. While food availability had a greater impact on growth and reproductive success, the data suggest that microclimate, specifically temperature and humidity, does explain some amount of variation in reproductive success.

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