Assessment of waste grain densities to aid waterfowl conservation in the Klamath Basin of northeastern California and southeastern Oregon

Abstract

Post-harvest waste seed from cereal grains is a major dietary component of waterfowl in the Klamath Basin in northeastern California and southeastern Oregon, a region that plays host to over a million waterfowl annually. Understanding food abundance is critical to local waterfowl management, therefore we conducted a study in 2008 to investigate waste grain densities in barley, oat and wheat fields. We used hierarchal mixed effect models to assess several factors that may affect waste grain densities post-harvest. We also compared the effects of residue management practices to measure the effect of these treatments. To understand the scope of post-harvest practices, we conducted a weekly road survey to document treatments applied to fields in our study area. We found that, region, best explained the variance of post-harvest waste grain in barley fields, where the Tule Lake region had 89% greater densities than Lower Klamath. Neither harvester age or baling affected waste grain in oats fields. In wheat fields, the model containing region and lodging ranked highest, where the Tule Lake region had 66% greater waste densities than Lower Klamath and lodging increased waste grain by 70%. Burning did not reduce waste grain in barley or oat fields. Chisel-disking reduced waste grain by 94% in wheat fields, compared to post-harvest. Our field treatment survey found that 70% of barley fields were untreated while 18% were disked and 13% were burned and flooded. We estimated that 82% of oat fields were burned post-harvest while 18% were burned and flooded. In wheat, 61% of fields were left untreated, while 16% were disked, 8% were chisel-plowed and 7% were flooded post-harvest. Flooding and burning occurred primarily on National Wildlife Refuges while disking, chisel-plowing and post-harvest irrigation occurred solely on private properties. Our results indicate that reducing tillage treatments would boost accessibility of cereal grain food resources to waterfowl in the Klamath Basin, and incentives to flood grain fields on private properties should be considered for the same purpose when and where possible.