Continental and regional distribution and abundance patterns of boreal cardueline finches - influences of conifer seed availability

Wren, L. Sarah (2001) Continental and regional distribution and abundance patterns of boreal cardueline finches - influences of conifer seed availability. Masters thesis, Memorial University of Newfoundland.

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Abstract

The mature boreal forest provides essential resources for conifer seed-eating cardueline finches. These resources are important on regional and stand level scales, and on landscape or continental scales, as cardueline finches move nomadically or irruptively in search of conifer seeds. Regional and temporal changes in conifer seed availability and cardueline finch abundance were examined with seed trap sampling and point counts in three mature conifer forests on insular Newfoundland. Seed rain phenology and finch abundance over time varied among the forests. On a landscape scale, analyses of continent-wide distributions of seed-eating finches using Christmas Bird Counts from 1970 - 1997 illustrated inter-annual fluctuations in abundance of six species of cardueline finches. These data encompass key boreal habitat in Canada that had been omitted from previous map-based studies of finch irruptions. The pattern of fluctuating continental abundance was close to biennial in some species like the common redpoll [Canluelis tlammea). There was a significant effect of boreal cone crop magnitude on annual boreal finch abundance. Abundances of boreal finches were also examined from CBC counts in varied boreal forest habitats in Newfoundland. On such a regional scale. CBC counts are a useful tool for the analysis of population trends between and within habitats, as illustrated by the CBC data that indicate a recent and precipitous decline of the Newfoundland red crossbill, Loxia curvirostra percna. Understanding the relationship between boreal finches and conifer resources on small and large scales is essential for gaining insight into how recent landscape-level changes affect such highly specialized feeders.

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