PARENTAL NEST DEFENSE ON VIDEOTAPE: MORE REALITY THAN “MYTH“

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