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Multiple density-dependence mechanisms regulate a migratory bird population during the breeding season
Nicholas L Rodenhouse1, T Scott Sillett, Patrick J Doran
1Department of Biological Sciences, Wellesley College, Wellesley, MA 02481, USA. nrodenho@wellesley.edu
Proceedings. Biological Sciences
|October 17, 2003
Summary
Bird population regulation is complex. This study shows migratory songbirds, like the black-throated blue warbler (Dendroica caerulescens), are controlled by multiple density-dependence factors operating at different scales.
Area of Science:
- Ecology
- Population Biology
- Ornithology
Background:
- Mechanisms regulating bird populations are poorly understood.
- Density dependence is a key factor in population dynamics, but its multiple mechanisms are debated.
Purpose of the Study:
- To investigate the density-dependence mechanisms regulating the black-throated blue warbler (Dendroica caerulescens) population.
- To determine how crowding and site-dependence operate at different spatial scales.
Main Methods:
- Time-series analyses of population density (1969-2002).
- Experimental removal of individuals from territories to assess crowding effects.
- Monitoring of territory quality and demography to identify site-dependence.
Main Results:
- Population density remained stable, indicating strong regulation.
- Fecundity decreased with higher warbler density, and increased with higher recruitment.
- Experimental removals nearly doubled fecundity, showing local crowding.
- Site-dependence was evident through inverse relationships between population size and territory quality.
Conclusions:
- Crowding and site-dependence mechanisms act simultaneously at different spatial scales to regulate bird populations.
- Understanding these mechanisms is crucial for conservation and managing migratory songbirds.