turn 



Chapter 10 



Defining Detections and Behavior at Inland Sites 



daytime feedings 82 and 150 minutes after sunrise (Naslund 

 1993a, see also Nelson and Hamer. this volume a). 



Below are some relevant definitions useful to biologists 

 studying Marbled Murrelets, based on Ralph and others (1994): 



Potential Nesting Habitat (1) mature or old-growth 

 coniferous forests: mature forest can be with and without an 

 old-growth component (see Ralph and others 1994, Raphael 

 and others, this volume); (2) younger coniferous forests that 

 have large, deformed trees or structures suitable for nesting. 



Forest Stand a group of trees that forms a continuous, 

 relatively homogeneous, potential nesting habitat with no 

 gaps >100 m. 



Survey The process of determining the presence, 

 absence, and occupancy of Marbled Murrelets in a forest 

 stand. Surveys generally are conducted during the morning 

 hours, when detection rates are greatest (Paton and others 

 1990; Ralph and others 1994; Rodway and others 1993b). In 

 addition, surveys generally occur from May through July 

 when detection rates peak (e.g., Rodway and others 1993b); 

 however, murrelets are known to visit inland forest stands 

 throughout the year (Naslund 1993b; O'Donnell 1993; 

 O'Donnell and Naslund, this volume). 



Intensive Survey Designed to determine the probable 

 presence, absence, or occupancy of Marbled Murrelets in a 

 specific tract of land. When conducting an intensive survey, 

 the observer surveys from one point for the entire morning 

 survey period. Under most forest conditions, observers can 

 see murrelets within 100 m. and hear them within 200 m 

 (Ralph and others 1994). Therefore, approximately 12 ha (x 

 x [200 m] 2 = 12.6 ha) can be adequately surveyed from a 

 single point for auditory detections, while only 3.14 ha can 

 be monitored for visual detections. Under certain conditions, 

 visual and auditory ranges are reduced (e.g., next to a stream 

 or under a dense forest canopy). Surveys generally are 

 conducted from 45 minutes before sunrise to 75 minutes 

 after sunrise (Paton and others 1990, Ralph and others 1994), 

 although surveys at northern latitudes start and end earlier 

 (e.g., Kuletz and others, this volume; Rodway and others 

 1993b). The exact methodologies for Intensive and General 

 Surveys are detailed in Ralph and others (1994). 



General Survey A survey designed to determine the 

 geographic distribution of Marbled Murrelets over large 

 tracts of land (e.g., states, counties, basins). General surveys 

 are exploratory in nature and cannot be used to confirm 

 murrelet absence from specific forest stands. These surveys 

 consist of a transect of 8-10 stations surveyed during a 2- 

 hour period each morning. Stations are spaced 0.5-1.0 km 

 apart, depending on terrain, with each station surveyed for 

 10 minutes. 



Survey Area the entire area being surveyed. 



Survey Visit a single morning's visit. 



Survey Site an area containing >1 survey station. 



Survey Station the exact location where an observer 

 stands to survey murrelets. 



Occupied Stand a forest stand, consisting of potential 

 nesting habitat, where murrelets were observed exhibiting 



subcanopy behaviors associated with nesting. Quantitative 

 information on murrelet behavior near nests is scarce; 

 however, some data are available from Naslund (1993a), and 

 Nelson and Hamer (this volume a). Data collected by Naslund 

 (1993a) suggests that only 6-21 percent of the detections 

 <100 m from known active nests represent "occupied 

 behaviors" (see below), while most detections near nests 

 were birds flying above the canopy. The proportion of 

 detections which were categorized as occupied behaviors 

 was not affected by weather conditions (i.e. cloud cover, 

 ceiling), although the total number of detections increased 

 significantly on cloudy days (Naslund 1993a, Rodway and 

 others 1993b). 



Evidence for Nesting: 



Seven different categories are considered indicators of 

 nesting. They are listed below with varying degrees of certainty 

 that murrelets are nesting in a particular forest stand. Only 

 categories 1-3 listed below provide confirmation of breeding, 

 whereas categories 4-7 are occupied behaviors, which are 

 behaviors that suggest that murrelets could be nesting in a 

 specific forest stand. 



Confirmation of breeding: 



(1) Discovery of an active nest either with an incubating 

 adult, brooding adult and chick, or pre-fledged chick. 



(2) Obvious signs of recent nesting activity such as 

 fecal rings surrounding the nest or eggshell fragments in a 

 nest scrape. 



(3) Discovery of a chick or eggshell fragments on the 

 forest floor see Becking 1991, and Ralph and others 

 1994 for detailed information on the characteristics of 

 murrelet eggs. 



Occupied behaviors: 



(4) Birds flying below the top of the forest canopy (also 

 called subcanopy behaviors; Ralph and others 1994) This 

 refers to murrelets either flying through the stand, into or out 

 of the stand, or adjacent to a forest stand, the weakest evidence 

 in this category (O'Donnell and Naslund, this volume; Rodway 

 and others 1993b). Because tree heights can vary, a bird 

 observed at or below the height of the top of the tallest tree 

 visible to the observer would be classified as a subcanopy 

 detection. Based on observations at active nests, only silent 

 birds are probably near an active nest (Naslund 1993a, but 

 see Nelson and Hamer, this volume a). This category includes 

 birds flying over or along roads, young stands, or recently 

 harvested areas adjoining potential nesting habitat. In these 

 latter two instances, only the adjacent potential nesting habitat 

 should be classified as occupied. Subcanopy behaviors are 

 currently thought to be the strongest indirect evidence of 

 nesting in a stand (Ralph and others 1994). 



(5) Birds circling above the forest canopy at any radii 

 Circling is common flight behavior over occupied sites. 

 However murrelets have also been observed circling over 

 young or non-forested habitats (Hamer and Cummins 1990, 



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



115 



