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Brady, Ryan S. – Nest lining behavior, nest microclimate, and nest defense behavior of Burrowing Owls. 2004.

Adult Female Burrowing OwlMy M.S. thesis research focuses on a unique nesting behavior exhibited by burrowing owls (Athene cunicularia). During the breeding season, burrowing owls locate and gather mammalian dung, typically from livestock, which they distribute within their nest chamber and tunnel, as well as around the nest burrow’s entrance. However, despite the prevalence of this behavior across this species’ range, the function of dung in burrowing owl nests has not been tested experimentally and remains poorly known. Therefore, to help elucidate the role of this unusual behavior, I am conducting a series of field and natural experiments on burrowing owls nesting in and around the Snake River Birds of Prey National Conservation Area in southwestern Idaho in 2001 and 2002.

 

Dung piles next to burrowMy study specifically tests the following hypotheses:

Anti-predation: Dung masks the scent of owls and their nest contents and thus deters terrestrial predators

Optimal microclimate: Dung creates a more suitable burrow microenvironment for adult owls and their developing young by:

providing thermal insulation

reducing relative humidity within nest chambers

reducing levels of carbon dioxide within nest chambers

Anti-ectoparasite: Dung reduces ectoparasite loads on adult and nestling owls

After one year of research, my initial results indicate:

Chicks RaspingThere was no relationship between amount of dung at owl nests and likelihood of nest predation.

Dung volume in nest chambers tended to correlate with lower temperatures, higher relative humidity, and lower carbon dioxide concentrations.

There was no relationship between ectoparasite load of adult female or nestling owls and volume of dung in nest chambers.

Therefore, my results suggest that dung potentially alters microclimates of burrowing owl nests. Determining if and how this benefits burrowing owls is part of my continuing research.

Thesis Abstract

Publications:

Moulton, C.E., R.S. Brady, and J.R. Belthoff. 2006. Associations between wildlife and agriculture: underlying mechanisms and implications in Burrowing Owls. Journal of Wildlife Management 70(3):708-716.

Moulton, C.E., R.S. Brady, and J.R. Belthoff. 2005. A comparison of breeding season food habits of Burrowing Owls nesting in agricultural and nonagricultural habitat in Idaho. Journal of Raptor Research 39(4):429-438.

Moulton, C.E., R.S. Brady, and J.R. Belthoff. 2004. Territory defense of nesting Burrowing Owls: responses to simulated conspecific intrusion / Defenza territorial de individuos nidificantes de athene cunicularia: respuesta a la presencia simulada de congéneres. Journal of Field Ornithology 75(3):288-295.