Bad News and Good News for Bird Nests at Reservoirs

[rdeatsman]

(June 24, 2015, The Condor: Ornithological Applications)—A 6-year study published this week in The Condor: Ornithological Applications found that while some nests fail due to flooding as the Arrow Lakes Reservoir in British Columbia fills up in the spring, higher water levels actually provide benefits for the nests that survive. Researchers from Cooper, Beauchesne and Associates and Simon Fraser University monitored Yellow Warbler (Setophaga petechia) and Willow Flycatcher (Empidonax traillii) nests, and they found that while 28% of warbler nest failures and 50% of flycatcher nest failures were caused by flooding when water inundated their nesting habitat, the overall survival rate did not differ between flooded and unflooded areas. The researchers speculate that rising water levels actually helped protect the nests that survived from predators, so that while they were more likely to fail due to flooding, they were less likely to fail due to other causes. Many bird species rely on riparian habitat, building their nests in the vegetation that lines rivers and streams, but whether they can find success nesting on the shores of reservoirs that are drained and flooded according to the needs of water storage rather than the needs of wildlife has remained largely an open question. Read the full paper, which provides the first assessment of how shrub-nesting birds fare in reservoir drawdown zones, at http://www.aoucospubs.org/doi/full/10.1650/CONDOR-14-154.1.