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Interspecific competition among canids can result in mortalities and spatial displacement of smaller canids by larger canids. To investigate mortalities and spatial relationships of swift foxes (Vulpes velox) and coyotes (Canis latrans), we captured and radio-tracked both species at Rita Blanca National Grasslands in northwestern Texas. At least 89% of swift fox mortalities were caused by coyotes, resulting in a relatively low annual survival of 0.47 for swift foxes. Annual home ranges of swift foxes occurred near the periphery and outside coyote home ranges, and did not overlap or only slightly overlapped coyote core areas. Thirty-three of 36 known swift fox dens occurred outside coyote core areas. When swift foxes established dens within coyote core areas (n = 3), they were killed by coyotes shortly thereafter. Our data indicated that spatial displacement of swift foxes was not due to behavioral avoidance of coyotes but rather to increased killing of swift foxes within coyote core areas. Most mortalities caused by coyotes occurred in the immediate vicinity of swift fox dens, suggesting that coyotes made an active effort to kill swift foxes.

BackgroundEuropean starlings (Sturnus vulgaris) are an invasive bird species known to cause damage to plant and animal agriculture. New evidence suggests starlings may also contribute to the maintenance and spread of diseases within livestock facilities. Identifying and mitigating the risk pathways that contribute to disease in livestock is necessary to reduce production losses and contamination of human food products. To better understand the impact starlings have on disease transmission to cattle we assessed the efficacy of starling control as a tool to reduce Salmonella enterica within a concentrated animal feeding operation. We matched a large facility, slated for operational control using DRC-1339 (3-chloro-4-methylaniline hydrochloride, also 3-chloro p-toluidine hydrochloride, 3-chloro-4-methylaniline), with a comparable reference facility that was not controlling birds. In both facilities, we sampled cattle feed, cattle water and cattle feces for S. enterica before and after starling control operations.ResultsWithin the starling-controlled CAFO, detections of S. enterica contamination disappeared from feed bunks and substantially declined within water troughs following starling control operations. Within the reference facility, detections of S. enterica contamination increased substantially within feed bunks and water troughs. Starling control was not observed to reduce prevalence of S. enterica in the cattle herd. Following starling control operations, herd prevalence of S. enterica increased on the reference facility but herd prevalence of S. enterica on the starling-controlled CAFO stayed at pretreatment levels.ConclusionsWithin the starling-controlled facility detections of S. enterica disappeared from feed bunks and substantially declined within water troughs following control operations. Since cattle feed and water are obvious routes for the ingestion of S. enterica, starling control shows promise as a tool to help livestock producers manage disease. Yet, we do not believe starling control should be used as a stand alone tool to reduce S. enterica infections. Rather starling control could be used as part of a comprehensive disease management plan for concentrated animal feeding operations.

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We radio tagged and tracked 50 European starlings between December 2008 and January 2009 at 3 feedlots in the northern Texas Panhandle. Daily fidelity to sites of capture (home feedlots) was different among the 3 radio-tagged cohorts. Cohorts from Sites A and C were recorded at home feedlots on 48 and 59% of tracking days, respectively. The Site B cohort was at its home feedlot 95% of days. There were qualitative differences in use of home feedlots between cohorts A and C. The former were nearly obligate in their use of concentrated animal feeding operations (CAFO), whereas the latter tended to balance their use between CAFO and a nearby urban center. Six birds (12%) used either one or both of the counterpart home feedlots. Of these, 5 permanently switched from their home feedlots and used counterpart home feedlots; one bird captured at Site B alternated between Sites A and C after abandoning its home feedlot. Use of roost sites depended on habitat composition surrounding the study feedlots. Urban habitats were used as roosts by several birds from Sites A and C, whereas birds using Site B roosted at a petroleum refinery and a reservoir. Some Site B individuals used both roost sites during the study period; however, the reservoir was the preferred roost site. Daily activities in habitats away from the home feedlot generally occurred ≤5 km from the home feedlot. For birds from Sites A and C, offsite habitats were mainly urban areas and small CAFO. Increased habitat heterogeneity, as exemplified in our study by urban habitats and CAFO near Sites A and C, seemed to reduce rates of daily use of home feedlots. Heterogeneous environments can complicate management strategies that use DRC-1339 Concentrate for reducing starling numbers at infested CAFO. First, starlings may be erratic in their daily use of a CAFO in complex environments. Secondly, urban areas, when present, may be used as refuges by poisoned birds, leading to adverse public exposure.