Variation in dark-eyed Junco (Junco hyemalis) nest mass and nest size across an elevational gradient in Southeastern British Columbia Lee, Joanna K.
I explored the variation in dark-eyed junco (Junco hyemalis) nest mass and nest size across an elevational gradient in Revelstoke, BC. I predicted that mean monthly temperature during the breeding season would be lower at high elevation compared to low elevation. I also predicted that nest mass and external diameter would be greater at higher elevation compared to low elevation, while there would be no elevational difference in internal cup diameter or internal cup depth. Results show that high elevation temperatures were significantly colder than low elevation temperatures throughout the breeding season (P<0.005) but nest mass and external diameter were not different. Nests at one of the two low elevation sites were heavier and wider externally than those at both the single high elevation site and the second low elevation site (P<0.005), suggesting that factors other than temperature may influence nest construction. When comparing nest mass and dimensions in Revelstoke with nests elsewhere in North America, I found no apparent trends in mass, external diameter, internal diameter or internal cup depth, suggesting that as a ground nesting species, dark-eyed juncos may modify nest construction in relation to temperature gradients less than has been observed in other species. An unexpected eight tree nests were discovered at high elevation during the 2014 field season but not during the 2013 field season, indicating that dark-eyed juncos can inter- and intra-seasonally alter their nesting behavior depending on site conditions. Further research on nest composition and placement with relation to a broader suite of environmental factors may provide better models on the drivers of nest construction along elevational and environmental gradients.
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