PARENT SESSION
Contributed Oral Session 18: Avian Communities and Populations
Monday, August 8, 8:00 AM - 11:30 AM, Meeting Room 524 C, Level 5, Palais des congrès de Montréal
Assessing species co-occurrence patterns at multiple temporal scales for wetland birds during migration.
Brennan, Elisabeth *,1, Smith, Loren1, McIntyre, Nancy2, 1 Dept. of Range, Wildlife and Fisheries Management, Lubbock, TX, US2 Department of Biological Sciences, Lubbock, TX, US
ABSTRACT- Interspecific competition is considered to be among the most influential forces in community ecology and is one of the underlying assumptions of species assembly rules. Community assembly rules are frequently tested by comparing species co-occurrence patterns at different spatial locations to those generated from the null hypothesis of a community assembled by chance. However, few studies have examined temporal patterns of species co-occurrence at multiple scales. Therefore, the objective of this study was to determine if species co-occurrence patterns differed from randomly generated co-occurrence patterns at several temporal scales. We surveyed 40 wetlands for migratory wetland birds biweekly from mid-February to mid-May 2004 at a major migratory stopover site in southern Nebraska. Using EcoSim, we generated random co-occurrence matrices and compared the C-scores of observed co-occurrence patterns to the C-scores of those expected in a random community assembly. These analyses were evaluated at three separate temporal scales: weekly, monthly, and over the entire migratory period. For the overall migration period, the observed C-score did not differ from the simulated C-score (P = 0.2). However, we did detect higher observed C-scores than simulated C-scores in one of three months (P < 0.01) and five of 13 weeks (P < 0.05), indicating less species co-occurrence than expected by chance during these time intervals. Four of the five months in which C-scores were larger than random occurred during peak migration, when abundance and species richness were highest. Our preliminary results support the idea that avian communities will be non-random at times and locations when competition is structuring communities. By testing species co-occurrence at finer temporal scales than traditionally examined, we detected community assembly patterns that are not apparent at coarser scales.
Key words: Co-occurrence, Wetland, Birds, Community