Ralph and others 



Chapter! 



Overview of Ecology and Conservation 



and Hamer, this volume a; Nelson and Peck, in press); see 

 Paton (this volume) for details on the survey method and its 

 caveats. We compared for each region (table 1), the site, 

 stand, and tree attributes that have been shown to be correlated 

 with nesting behavior. Among the most consistently observed 

 of these attributes are the presence of large diameter conifer 

 trees and associated nest platforms and covering limbs. The 

 use or presence of large diameter conifers is pervasive 

 throughout the studies in this volume. Occasional sites with 

 only a few old-growth trees have been found in Oregon to 

 have murrelets present (Nelson, pers. comm.). Further, as 

 Grenier and Nelson (this volume) point out, stand structure 

 is probably more important than stand age itself. However, 

 as stands mature, they generally gain the characteristics 

 necessary for nesting. These observations support the idea 

 that it is the presence of adequate nesting platforms that 

 defines suitable nesting habitat. The species of conifer is less 

 important than its structural ability to support nest platforms 

 (Burger, this volume a). 



Limiting Factors and Relative Importance in Old-Growth 

 Several factors appear related to the preference for 



old-growth, including temperature, predation, stand and tree 



structure, and accessibility. 



Temperatures in old-growth forests are lower than in 



open, second-growth areas. This may be very important for a 



thickly-feathered species primarily adapted for diving for 

 food in cold ocean waters. 



Old-growth stands may also provide more protection 

 from inclement weather by providing greater cover around 

 branches. 



Predation apparently has a pervasive influence on murrelet 

 reproductive success, as we detail below. Nelson and Hamer 

 (this volume b) found that most studies of avian predator 

 abundance or influence support the idea that modified forests 

 have higher predator populations than older, undisturbed 

 forests. In contrast, Rosenberg and Raphael (1986) found 

 that predator populations were not greater in second growth, 

 as compared to old-growth forests. Although more work 

 needs to be done on this issue, it seems likely that predation 

 could well be a principal limiting factor for selection of 

 nesting habitat and reproductive success. 



The presence of old-growth in an area does not assure 

 sufficient substrate for nesting. Though old growth appears to 

 be a necessary condition, some old-growth stands may have 

 relatively few deformed or broad-limbed trees, possibly limiting 

 the availability of nest sites. The physical condition of a tree 

 appears to be the important factor in determining its suitability 

 for nesting. Specifically, the murrelet, a bird with high wing 

 loading, prefers high and broad platforms for landing and 

 take-off, and surfaces which will support a nest cup (see 

 Hamer and Nelson, this volume b). Accessibility of the stand, 



Table 1 Site, stand, and tree attributes important to Marbled Murrelets 



Region 



Important attributes 



Source, this volume 



Nesting stands in: 

 Alaska 



British Columbia 

 Washington 



Oregon 

 California 



Nest trees in: 



All areas 



Epiphyte cover, nesting platforms, 

 large diameter trees, old-growth forests. 



Old-growth forests, low elevation, large trees. 

 Old-growth forests, stand size, large sawtimber. 



In old-growth forests: nest platforms, 

 moss cover, slopes, stem density, large 

 d.b.h.. western hemlock, low elevation, 

 lack of lichen, low canopy cover. 



Older forests and large diameter trees. 



Density of old-growth trees, lower 

 elevation, topography, redwood. 



Large diameter, old-growth forests, and 

 decadent trees with mistletoe, deformations, 

 and moss on limbs. 



Kuletz and others 



Burger (a) 

 Raphael and others 

 Hamer 



Grenier and Nelson 



Miller and Ralph 

 Paton and Ralph 1990 



Hamer and Nelson (b) 



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



