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J.3-4: Accounting for the effects of water depth on energy availability estimates for ducks in northeastern Colorado

Presented by Adam Behney - Email: adam.behney@state.co.us

Habitat management and planning strategies for nonbreeding ducks are focused on providing enough energy to support population goals. Therefore, regional estimates of energy availability are required to determine if sufficient habitat exists. I sampled duck food in six types of water features in northeastern Colorado during three sampling occasions throughout nonbreeding seasons, 2015-2016 and 2016-2017. I also estimated the percentage of each water feature that was shallow enough to facilitate feeding by dabbling ducks as a way to correct overall energy density to reflect availability to ducks. I found that emergent wetlands contained the greatest food (fall actively managed = 688 kg/ha, fall passively managed = 684 kg/ha) and energy density, followed by playas (189 kg/ha) and sloughs (186 kg/ha), and reservoirs contained little food or energy (large reservoirs = 16.1 kg/h, small reservoir 29.5 kg/ha). Fall depletion of food was greatest in actively managed emergent wetlands and spring depletion was greatest in sloughs and passively managed emergent wetlands. Mean percentage of passively managed emergent wetlands, actively managed emergent wetlands, small reservoirs, large reservoirs, and sloughs shallower than 50 cm was 37, 77, 10, 4, and 83%, respectively. These estimates can be directly incorporated into Joint Venture energetic carrying capacity model and will result in reduced estimates of energy availability for the region, potentially below what is needed to support population goals. Furthermore, my method of estimating and accounting for water depth can be used elsewhere to reduce bias in food availability estimates.
Session: Habitat Management (Friday, August 30, 13:20 to 15:00)