Introduction of sculpins into a stream previously devoid of these predators significantly reduced drift rate of Gammarus pulex. The drift of insect larvae was not affected. High amounts of exudates after implantation of sculpins were probably responsible for the low number of drifting G. pulex specimens. Laboratory

Many units of the National Wildlife Refuge System (NWRS) in the Central Flyway of the United States were established to conserve and enhance waterfowl populations. Consistent and continuous monitoring of waterfowl abundance on refuges is critical when evaluating the performance of individual refuges as well as the refuge system on a larger scale. It is also essential for providing metrics to determine progress toward established waterfowl use and abundance goals. Despite the considerable resources the U.S. Fish and Wildlife Service spend annually on waterfowl management within the NWRS, the quality of ongoing monitoring efforts outside the breeding season has never been systematically evaluated. We evaluated the quality of historical waterfowl monitoring data at refuge sites within the Central Flyway during the migration and wintering period (Oct-Mar). Ninety-six percent of all survey data sets were classified as being of good or fair quality overall. There were, however, some serious issues with the data sets, primarily concerning consistency in survey methodology and temporal survey coverage, as well as lack of coordination among refuges. One-third of the data sets were collected without the existence of a written survey protocol, creating uncertainty regarding methodological consistency over time. Evaluation of the NWRS's benefits to waterfowl as a whole may be severely hampered by temporally inconsistent survey coverage among and within survey sites. We suggest 7 improvements for future waterfowl surveys that will enhance quality and usability of NWRS survey data. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

Globally, migration phenologies of numerous avian species have shifted over the past half-century. Despite North American waterfowl being well researched, published data on shifts in waterfowl migration phenologies remain scarce. Understanding shifts in waterfowl migration phenologies along with potential drivers is critical for guiding future conservation efforts. Therefore, we utilized historical (1955–2008) nonbreeding waterfowl survey data collected at 21 National Wildlife Refuges in the mid- to lower portion of the Central Flyway to summarize changes in spring and autumn migration phenology. We examined changes in the timing of peak abundance from survey data at monthly intervals for each refuge and species (or species group; n = 22) by year and site-specific temperature for spring (Jan–Mar) and autumn (Oct–Dec) migration periods. For spring (n = 187) and autumn (n = 194) data sets, 13% and 9% exhibited statistically significant changes in the timing of peak migration across years, respectively, while the corresponding numbers for increasing temperatures were 4% and 9%. During spring migration, ≥80% of significant changes in the timing of spring peak indicated advancements, while 67% of significant changes in autumn peak timing indicated delays both across years and with increasing temperatures. Four refuges showed a consistent pattern across species of advancing spring migration peaks over time. Advancements in spring peak across years became proportionally less common among species with increasing latitude, while delays in autumn peak with increasing temperature became proportionally more common. Our study represents the first comprehensive summary of changes in spring and autumn migration phenology for Central Flyway waterfowl and demonstrates significant phenological changes during the latter part of the twentieth century.

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Wetlands with associated avifauna can pose a substantial hazard to aviation safety, potentially increasing bird–aircraft collision (strike) risk when located near air operations areas. We modeled year‐round use by wetland avifauna of Drummond Flats Wildlife Management Area (Drummond Flats), a wetland complex located within 10 km of Vance Air Force Base (AFB), Enid, Oklahoma, USA. Our objectives were to 1) quantify seasonal avifauna abundances at Drummond Flats; 2) test a priori models reflecting use by bird species recognized as hazardous to aviation safety relative to environmental factors including flooded wetland habitat and vegetation cover; 3) use these models to predict maximal expected abundances of wetland avifauna during flood conditions; and 4) compare our findings with reported bird strikes at Vance AFB. Drought conditions influenced avian use during our study. Of the species expected to respond predictably to flooded wetland habitat, only ducks (Anatinae) occurred in numbers conducive to modeling. Using zero‐inflated Poisson models, we found that duck abundance was positively associated with permanent wetland habitat type and, excluding winter, available habitat area (i.e., standing water); whereas, >50% vegetation cover was negatively correlated with abundance. No model predicted >97.2 ducks/ha for any habitat type, except during winter. Our models also identified potential peaks in abundance not evident from raw count data, emphasizing the benefits of this approach. Identifying factors driving abundances also enables targeted management of hazardous species. Further, we found double‐sampling to be a practical method for assessing detection bias during avian surveys at wetlands. Restricting to obligate wetland species associated with Drummond Flats, we found 1 strike/184,212 flight‐hours, which was an order of magnitude lower than the average for U.S. civil aircraft (1990–2014). Thus, under drought conditions, bird use of Drummond Flats likely did not elevate strike risk for Vance AFB aircraft operations. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.