Nelson and Haroer 



Chapters 



Nest Success md Effects of Predatioo 



Table 5 Characteristics of successful Marbled Murrelet tret nests compared with those that failed because of predation 



1 1 = successful, = failed. 



2 Edge = Distance to nearest unnatural edge (road or clearcut ). 

 -' Data not available. 



* P. Jones, pers. comm. 



b Hamer. unpublished data. 

 c Ritchie, pers. comm. 



- Nelson, unpublished data; Nelson and Peck, in press. 

 e Singer and others 1991. 



f Singer and others, in press. 



Habitat Characteristics and Predation of Nests 



The effect of predators on avian nesting success can 

 vary significantly with geographic location, and is dependent 

 upon the species of predators present, accessibility of nests, 

 type and dimension of the habitat, topography, and vegetative 

 complexity (vertical and horizontal diversity) (Chasko and 

 Gates 1982; Martin 1992; Marzluff and Balda 1992; Paton 

 1994; Reese and Ratti 1988; Yahner 1988; Yahner and others 

 1989). For example, alcids nesting on islands relatively free 

 of mammalian predators, or on cliffs inaccessible to terrestrial 

 predators, experience lower predation rates than species 

 nesting in accessible sites and with abundant predators (Ainley 

 and Boekelheide 1990; Hudson 1985). Because many species 

 of birds have evolved in association with predators, the long 

 term impacts of predation on avian nesting success are 

 expected to be minimal in natural situations. However, rapid 



and unnatural changes, such as the introduction of mammalian 

 predators (cats, goats, mice, pigs, raccoons, rats) and habitat 

 modification, can have significant impacts on nesting success 

 of seabirds (Bailey and Kaiser 1993; Ewins and others 1993; 

 Gaston 1992; Murray and others 1983), and neotropical 

 migrants (Chasko and Gates 1982; Martin 1992), respectively. 

 In these cases, predation can be a major factor affecting 

 avian population viability (Martin 1992). 



Significant changes have occurred in the forested 

 landscapes of the United States over the past century, including 

 loss of late-successional forests, habitat fragmentation, and 

 increases in the amount of edge (Hansen and others 1991; 

 Harris 1984; Morrison 1988; Perry, this volume; Thomas 

 and Raphael 1993). These changes have affected the 

 abundance and distribution of many avian predators and 

 forest nesting birds. For example, populations of corvids and 



USDA Forest Service Gen. Tech. Rep. PSW-152. 1995. 



95 



