Treesearch

Lack of clear, unambiguous criteria that distinguishes a linear habitat patch as a corridor contributes to controversy over the value of corridors for wildlife conservation. The definitions of biological corridors have been vague or inconsistent, and often they confound form and function. Explicit criteria that can differentiate between a linear habitat patch and a biological corridor have not been formulated. We reviewed the use of the term “corridor-’ in the ecological literature. and attempted to clarify the concept of biological corridor.

Estimates of instantaneous growth rates (A) of spotted owl (Strix occidentalis) populations have been based on demographic data that uniformly assumed an equal sex ratio among fledglings. In this study, sex ratios of subadults, banded as juveniles, and fledgling California spotted owls (S. o. occidentalis) were observed and compared to an assumed 1 : 1 ratio. The sensitivity of lambda (A) to variations in fledgling sex ratio was then examined. The sexes of 73 fledgling spotted owls from 1993 and 1994 were 42:3 1 (ma1es:females) in the Sierra National Forest (SNF) and Sequoia and Kings...

We compiled 86 breeding records of eggs, downy young,and fledgling Marbled Murrelets (Brachyramphus marmoratus) for which the fledging date could be estimated. Records were collected from California (n = 25), Oregon (n = 13), Washington (n = 13), British Columbia (n = 23), and Alaska (n = 12). The number of young fledging increased rapidly from 6 June to 19 July and peaked by the 10-day period beginning 19 July. A second peak in the number of young fledged was observed for the 10-day period beginning 18 August, with a rapid decrease in late August and early September. From these results, a...

There are a variety of systems in use that employ a camera at a bait station to detect wildlife. We will describe three that are widely used and with which we are most familiar. They can be divided into two major categories according to the type of camera used. The first employs automatic, 35-mm cameras and can be further divided into two types that differ by the mechanism that triggers them. We will refer to these types as "single sensor" (Kucera and Barrett 1993, 1995) and "dual sensor" (Mace and others 1994). The second major category is a line-triggered system that uses a manual, 110-...

Marbled Murrelets (Brachyramphus marmoratus) are comparable to most alcids with respect to many features of their reproductive ecology. Most of the 22 species of alcids are colonial in their nesting habits, most exhibit breeding site, nest site, and mate fidelity, over half lay one egg clutches, and all share duties of incubation and chick rearing with their mates. Most alcids nest on rocky substrates, in earthen burrows, or in holes in sand, around logs, or roots. Marbled Murrelets are unique in choice of nesting habitat. In the northern part of their range, they nest on rocky substrate;...

Identification ofPeromyscus species in the field can often be time consuming and inaccurate. Determination of several morphological characteristics is usually required for reliable identification. Characteristics may differ only slightly, can be highly variable, or can overlap among species. In oak woodlands of the southern Sierra Nevada in Fresno county, most identifying characteristics of the two dominant Peromyscus species, brush mouse (P. boylii) and California mouse (P. californicus) overlapped considerably. Weight, body length, tail length, hind foot length, dorsal tail-stripe width,...

This chapter summarizes terminology and methodology used by Marbled Murrelet (Brachyramphus marmoratus) biologists when surveying inland forests. Information is included on the types of behaviors used to determine if murrelets may be nesting in an area, and the various types of detections used to quantify murrelet use of forest stands. Problems with the methodology are also discussed.

We present here an overview of the ecology, abundance, and distribution of the subspecies of the Marbled Murrelet inhabiting the coasts of Asia. In most regards, the species is similar to the North American race with respect to its feeding, breeding, molt, and habitat ecology. It is, however, a migratory species, moving into southern parts of its range in the Sea of Okhotsk during the winter. The population has not been censused, but may number in the tens of thousands. Populations in Asia are threatened by logging of breeding habitat, oil pollution, and gill nets.