Use of corridor-like landscape structures by bird and small mammal species

We investigated the use of corridor-like structures by birds and rodents in coastal San Diego County, California, USA, in areas characterized by dense residential development and small remnant habitat fragments. In 1992 and 1 993 we compared the use. of remnant strips of coastal sage scrub habitat an d revegetated highway rights-of-way (ROW) with that of larger remnant patch es of coastal sage scrub habitat to which these strips were connected. Usin g live trapping we compared rodent species composition, percent of females reproducing, and recapture frequency among the three site types. Rodent spe cies richness did not differ significantly among the three site types. One species, Peromyscus eremicus was significantly more abundant in ROW sites, while several other species, Rheithrodontomys californicus, Chaetodipus cal ifornicus and C. fallax showed a similar, though non-significant trend. Per omyscus californicus was most abundant in remnant strips while Neotoma fusc ipes used ROW sites less than remnant strips or patches. No significant dif ferences were detected among the three site types in recapture frequency or proportion of females in reproductive condition. Common bird species were a priori divided into two categories based on previous research in this reg ion: fragmentation-sensitive and fragmentation-tolerant. Species richness i n remnant strips of habitat was similar to that in remnant patches for both categories of species. Species richness of the fragmentation-sensitive spe cies was significantly lower in ROW sites than in remnant strips or patches by a factor of 4-10. Species richness in fragmentation-tolerant species wa s significantly lower in ROW sites in 1993 by less than a factor of two. Th e greater reduction in fragmentation-sensitive species suggests they have m ore stringent corridor requirements than do fragmentation-tolerant species. The species richness per site for fragmentation-sensitive bird species was significantly correlated with the percent cover of native shrubs in 1993 i n patch and remnant strip sites. Fragmentation-tolerant bird species showed no consistent trend with shrub cover. Rodent species richness trended high er with increasing shrub cover in five of six site-type/year combinations, but none of the correlations were, significant. Within the range of width a nd length examined there was no correlation between bird or rodent species richness and length or width of these corridor-like structures. These resul ts indicate that remnant strips of habitat and revegetated highway ROW have potential to serve as habitat linkages for native rodents and fragmentatio n-tolerant bird species, but only remnant habitat strips appear suitable fo r fragmentation-sensitive bird species. (C) 2001 Elsevier Science Ltd. All rights reserved.