Breeding bird assemblages associated with riparian, interior forest, and nonriparian edge habitats in a balsam fir ecosystem

Abstract

Riparian zones are typically viewed as the highest quality habitat available to wildlife in forested landscapes, and consequently are seen as being the most biodiverse. This perception originated largely from studies conducted in southwestern North America; however, its validity in boreal forests remains relatively untested. We surveyed breeding bird assemblages along transects in riparian edge, nonriparian edge (clearcut or access road), and interior habitat in balsam fir (Abies balsamea (L.) Mill.) forests in Newfoundland. Distinct species assemblages were associated with each of these habitat types. Notably, five species were significantly more common in interior forest than along riparian edges. Total abundance and species richness did not differ between riparian and interior forest transects, but were significantly higher on nonriparian edge than riparian transects. Distinct species were characteristic of the two edge types, and no generalist edge species were identified. Based on this and other recent studies, it is apparent that relatively high riparian biodiversity may be the exception for bird assemblages in coniferous and mixedwood forests. Interior forest species, many of which have declined in northeastern North America in recent years, formed an important component of the regional avifauna. These species are likely not afforded adequate protection in boreal forests, where conservation efforts focus on preserving riparian habitat. Resume : Les zones riveraines sont typiquement perAues comme les meilleurs habitats disponibles pour la faune dans les paysages forestiers et sont par consOquent considOrOes comme les plus diversifiOs biologiquement. Liorigine de cette perception provient en grande partie diOtudes menOes dans le sud-ouest de liAmOrique du Nord, mais sa validitO en forŒt borOale demeure relativement peu examinOe. Nous avons fait liinventaire diassemblages diespces dioiseaux nicheurs le long de transects en zone riveraine, non-riveraine (coupe ‡ blanc ou route diaccs) et dans des habitats situOs ‡ liintOrieur de forŒts de sapin baumier (Abies balsamea (L.) Mill.) ‡ Terre-Neuve. Des assemblages distincts diespces Otaient associOs ‡ chacun de ces types dihabitat. Notamment, cinq espces Otaient significativement plus communes ‡ liintOrieur des forŒts que le long des bordures riveraines. Liabondance totale et la richesse en espces ‡ liintOrieur des forŒts et le long des bordures riveraines Otaient semblables, mais elles Otaient significativement supOrieures dans les bordures non riveraines comparativement aux transects riverains. Des espces distinctes Otaient caractOristiques des deux types de bordures et aucune espce gOnOraliste de bordure nia OtO identifiOe. Selon notre Otude et diautres Otudes rOcentes, il semble quiune biodiversitO relativement OlevOe le long des rives soit liexception dans le cas des assemblages diespces dioiseaux des forŒts conifOriennes et mixtes. Les espces vivant ‡ liintOrieur de la forŒt, parmi lesquelles plusieurs ont subi un dOclin dans le nord-est de liAmOrique du Nord dans les dernires annOes, formaient une composante importante de liavifaune rOgionale. Ces espces sont probablement liobjet diune protection inadOquate en forŒt borOale, oo les efforts de conservation se concentrent sur les habitats riverains. (Traduit par la ROdaction)