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Parental Nest Defense on Videotape: More Reality Than "Myth"

Pamela J. Pietz and Diane A. Granfors

Predation is recognized as the primary source of nest mortality in most passerine species (e.g. Ricklefs 1969, Martin 1992a); thus, it is no surprise that parental nest defense has received considerable scientific attention (see below). By nest defense, we refer to any parental behavior that decreases the probability that a predator (or brood parasite) will harm the nest contents and that simultaneously entails some cost to the bird engaged in the behavior—either by increasing the bird's risk of injury or death (Montgomerie and Weatherhead 1988) or by at least increasing its expenditure of time and energy (Buitron 1983).

Bradley and Marzluff (2003) used an innovative combination of approaches to investigate potential nest predation by three species of rodents; in the discussion section of that paper, they made the general assertion that “nest defense by parent birds seems to be more myth than reality.” That statement is at odds with a vast scientific literature on the topic that spans several decades (e.g. Skutch 1955, reviews by Montgomerie and Weatherhead 1988, Martin 1992b, Sealy et al. 1998). A simplistic search for the phrase “nest defense” in one online database (Wildlife and Ecology Studies Worldwide) produced a list of >90 papers published on nest defense by birds for 1994-2004 alone. Fifty of those papers deal with nest defense by passerines. Although parental defense is often unsuccessful, especially in passerines, one cannot dismiss its existence or its potential value as a predator deterrent (e.g. Montgomerie and Weatherhead 1988, Martin 1992b).

Given the wealth of observational and experimental evidence of nest defense, one may wonder whether further discussion of Bradley and Marzluff's statement is even warranted. However, the authors supported their dismissal of nest defense with data from a relatively new research tool—miniature video cameras used to continuously monitor active nests. In the last several years, such cameras have provided unprecedented information on nest predators of passerines (e.g. Thompson et al. 1999, Pietz and Granfors 2000a, Granfors et al. 2001, Williams and Wood 2002, Liebezeit and George 2003, Renfrew and Ribic 2003, Stake and Cimprich 2003, Thompson and Burhans 2003, Schaefer 2004). We therefore thought it appropriate to discuss the suitability of this tool for studies of nest defense, and to present some additional data related to nest defense that we acquired with video cameras.

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This resource is based on the following resource (Northern Prairie Publication 1443):

Pietz, Pamela J., and Diane A. Granfors.  2005.  Parental nest defense on videotape: more reality than myth.  Auk 122(2):701-705.

This resource should be cited as:

Pietz, Pamela J., and Diane A. Granfors.  2005.  Parental nest defense on videotape: more reality than myth.  Auk 122(2):701-705.  Jamestown, ND: Northern Prairie Wildlife Research Center Online.  (Version 24AUG2006).

Pamela J. Pietz, U.S. Geological Survey, Northern Prairie Wildlife Research Center, 8711 37th Street Southeast, Jamestown, North Dakota 58401, USA.  E-mail:
Diane A. Granfors, U.S. Fish and Wildlife Service, Habitat and Population Evaluation Team, 21932 State Highway 210, Fergus Falls, Minnesota 56537, USA.

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