Rapid assessment of rice seed availability for wildlife in harvested fields

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

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.

Waste Rice Seed in Conventional and Stripper-Head Harvested Fields in California: Implications for Wintering Waterfowl

Waste rice seed is an important food for wintering waterfowl and current estimates of its availability are needed to determine the carrying capacity of rice fields and guide habitat conservation. We used a line-intercept method to estimate mass-density of rice seed remaining after harvest during 2010 in the Sacramento Valley (SACV) of California and compared results with estimates from previous studies in the SACV and Mississippi Alluvial Valley (MAV). Posterior mean (95% credible interval) estimates of total waste rice seed mass-density for the SACV in 2010 were 388 (336–449) kg/ha in conventionally harvested fields and 245 (198–307) kg/ha in stripper-head harvested fields; the 2010 mass-density is nearly identical to the mid-1980s estimate for conventionally harvested fields but 36% lower than the mid-1990s estimate for stripped fields. About 18% of SACV fields were stripper-head harvested in 2010 vs. 9–15% in the mid-1990s and 0% in the mid-1980s; but due to a 50% increase in planted rice area, total mass of waste rice seed in SACV remaining after harvest in 2010 was 43% greater than in the mid-1980s. However, total mass of seed-eating waterfowl also increased 82%, and the ratio of waste rice seed to seed-eating waterfowl mass was 21% smaller in 2010 than in the mid-1980s. Mass-densities of waste rice remaining after harvest in SACV fields are within the range reported for MAV fields. However, because there is a lag between harvest and waterfowl use in the MAV but not in the SACV, seed loss is greater in the MAV and estimated waste seed mass-density available to wintering waterfowl in SACV fields is about 5–30 times recent MAV estimates. Waste rice seed remains an abundant food source for waterfowl wintering in the SACV, but increased use of stripper-head harvesters would reduce this food. To provide accurate data on carrying capacities of rice fields necessary for conservation planning, trends in planted rice area, harvest method, and postharvest field treatment should be tracked and impacts of postharvest field treatment and other farming practices on waste rice seed availability should be investigated.