A principal objective of this project was the study of the diversity of bird communities in different seral stages of the aspen ecosystem in the Sub-boreal Spruce (dk subzone) of the Prince Rupert Forest Region. In the spring of 1991 and 1992, I examined clearcuts (under 7 years), sapling aspen (7-23 years), mature aspen (50-60 years), old aspen with 100-year-old veterans, and mixed aspen-conifer stands. A preliminary survey of some conifer stands was also conducted. I counted birds over the 2 years using a modified point count method. One aspen stand was also examined by spot mapping.
Results showed a tendency for bird species richness, abundance, and diversity to all increase with increasing ecological age of the seral stage. Analysis of variance showed that differences in species numbers, bird abundance, and diversity between seral stages were significant for both breeding birds and total bird use. Numbers of breeding species, their abundance, and diversity indices were significantly lower in clearcuts than in sapling stands. Species abundance and diversity of breeding birds were greater in mixed aspen-conifer stands than in old and mature pure aspen combined. The number of breeding species in mixed stands was greater than that in pure aspen only in the second year of the study. Old aspen stands contained more birds and the species diversity was greater than in mature stands. The overall abundance of birds differed significantly between the 2 study years.
Analysis of the data using a Detrended Correspondence Analysis ordination procedure revealed that the bird communities in clearcuts and one of the three sapling stands were similar to each other, but quite different from those found in the other seral stages examined. The bird communities in the remaining stages were not distinct from each other, but rather there was an overlap from one bird community to another as the stands aged and the vegetation changed and became more complex.
Habitat relations of the 16 most abundant species were analyzed by multiple regression. Results suggest that most changes in bird abundance were species specific, and relate to changes in the proportions of the different layers of vegetation in the seral stages.
Lack of sufficient information on habitat requirements precludes the assignment of a single management indicator species for each stage. However, species that could potentially be used for managing different seral stages, or habitat components therein, are proposed.
The report suggests that removal of aspen, either commercially or by land clearing, might affect breeding birds using the different seral stages.
Keywords: biodiversity, bird, birds, aspen, sub-boreal spruce, dk subzone, Prince Rupert Forest Region.
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Updated May 03, 2007