Predation and nutrients drive population declines in breeding waders

Area of Science:

• Ecology
• Population Dynamics
• Conservation Biology

Background:

• Allee effects describe reduced fitness at low population densities.
• Nest predation can decrease breeding wader population size by causing dispersal.
• Environmental factors like nutrients and water levels influence population dynamics.

Purpose of the Study:

• To investigate the effects of nest predation and nutrient levels on breeding wader population size.
• To test the hypothesis that predation negatively impacts population density and nutrients positively impact it.
• To identify management strategies for enhancing breeding wader populations.

Main Methods:

• Nest predation was monitored for 4,745 nests across five wader species from 1987-2015.
• Statistical analyses examined relationships between predation rates, population density, and environmental factors.
• Environmental factors included ground water level, grazing, mowing, and nutrient levels.

Main Results:

• Predation rates were negatively related to conspecific and heterospecific densities but positively to overall wader community density.
• High nest predation (one-year lag) correlated with low breeding population density; high nutrients correlated with higher density.
• Ground water level, grazing, and mowing reduced nest predation rates.

Conclusions:

• Nest predation can reduce population density via negative density dependence and emigration.
• Total nitrogen in adjacent waters can increase population size by enhancing vegetation and food availability.
• Management of ground water, grazing, and mowing can mitigate nest predation and benefit breeding waders.