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Blackbirds and Starlings Killed at Winter Roosts from Pa-14 Applications, 1974-1992: Implications for Regional Population Management
| Content Provider | Semantic Scholar |
|---|---|
| Author | Dolbeer, Richard A. Mott, Donald F. Belant, Jerrold L. |
| Copyright Year | 1995 |
| Abstract | The surfactant PA-14, registered with the U.S. Environmental Protection Agency (EPA) in 1973 by the federal Animal Damage Control (ADC) program, was used for 19 years (1974-1992) for lethal control of roosting blackbirds (Icterinae) and European starlings Sturnus vulgaris in the United States. In 1992, the ADC program withdrew the registration of PA-14 because of costs required to provide additional EPA-requested data. There were 83 roosts encompassing 178 ha treated with 33,300 L of PA-14 from 1974-1992. An estimated 38.2 million birds (48% common grackles [Quiscalus quiscula], 30% European starlings, 13% red-winged blackbirds [Agelaius phoeniceus], and 9% brownheaded cowbirds [Molothrus ater]) were killed, an average of 2.0 million/year. The annual kill represented ≤ 1.3% of the national winter population of blackbirds and starlings. We found no evidence using North American Breeding Bird Survey (BBS) data that PA-14 applications caused declines in regional breeding populations. Furthermore, there was no evidence of semndary poisoning or other adverse environmental effects from PA-14 applications. If regional population management of blackbirds and starlings is to be implemented to reduce agricultural damage or conflicts with native songbirds, new approaches, such as reproductive control, are needed because PA-14 alone will not be adequate. However, PA-14 could have a role in such regional programs in addition to solving localized roost problems. PA-14 was a useful management tool safely applied in human-populated areas (where most roost problems occur); its reregistration should be considered as part of an integrated management program for blackbirds and starlings. Red-winged blackbirds, brown-headed cowbirds, and common grackles, (hereafter collectively referred to as blackbirds), and European starlings (hereafter starlings) nest throughout much of the United States and southern Canada (Dolbeer and Stehn 1979). Most of these birds migrate during autumn to the southern United States (Dolbeer 1982) where they congregate in roosts during winter (White et al. 1985). A minimum of 537 million blackbirds and starlings were reported in roosts in the United States during winter 1974-1975 (Meanley 1973). Blackbirds and starlings can cause substantial economic loss to various agricultural crops (Heisterberg 1983, Hothem et al. 1988, Decker et al. 1990, Dolbeer 1990). In a recent survey, 82% of North Dakota and South Dakota sunflower producers stated that a blackbird toxicant should be 77 Proc. East. Wildl. Damage Meant. Conf. 7:77-86.1997. used to reduce the number of female red-winged blackbirds (U.S. Department of Agriculture 1995) to, decrease crop depredation. Perhaps of greater concern is the noise, fecal accumulation, general nuisance and disease threat caused by large winterroosting populations (Garner 1978, White et al. 1985). There are also concerns regarding conflicts between blackbirds or starlings and other avian species. For example, introduced starlings have been documented as a competitor of nest sites with indigenous species (Feare 1984:40). Additionally, parasitism by brown-headed cowbirds has been implicated recently as a major factor in population declines of neotropical migratory birds (Askins 1995, Robinson et al. 1995) with population reduction of cowbirds being considered as a potential means of control (Rothstein et al. 1987). The only EPA-registered chemical for lethal control of roosting blackbirds and starlings was Compound PA-14 Avian Stressing Agent, a surfactant with excellent wetting properties. PA-14, applied with water to roosting blackbirds and starlings at night, was registered by the ADC program of the U.S. Fish and Wildlife Service in 1973 (U.S. Department of Interior 1976) and used on roosts for 19 years, 1974-1992. In 1992, a decision was made within the ADC program (which was transferred to the U.S. Department of Agriculture [USDA] in 1986) not to renew the registration of PA-14 because of costs required to provide additional EPA-requested data. Garner (1978) and Heisterberg et al. (1987) summarized the results of PA-14 applications to blackbird and starling roosts from 1974-1978 and 1979-1986, respectively. Their reports provided detailed information on methods, logistics and costs of applications as well as estimates of total birds killed (but generally not by species). Our objective was to provide a complete summary of the number and characteristics of PA-14 applications and the number of birds killed (by species when possible) from 1974-1992. In addition, the number of birds killed annually was examined in relation to the estimated total winter population of blackbirds and starlings in the United States as well as to estimated breeding-season population trends of these species, 1974-1992. This document should aid in evaluating the utility of PA-14 during its 19 years of registered use and in future decisions regarding reregistration of this compound or in the development of other techniques for managing blackbird and starling populations. We thank USDA/ADC employees F. Boyd, K. M. Garner, J. . F. Heisterberg, E. P. Hill and A. R Stickley, Jr., for providing data and reviewing portions of the manuscript. We also acknowledge the efforts of these individuals and their colleagues in overseeing and evaluating the PA-14 applications reported herein. We thank personnel of the National Biological Service, Office of Migratory Bird Management, particularly B. G. Peterjohn, for providing BBS data. METHODS Summary of PA-14 Applications Relevant data for all PA-14 applications w organized into a database (available from authors Initial data for 1974-1986 were obtained fro Garner (1978) and Heisterberg et al. (1987). The authors were then asked to review the data and provide additional, unpublished data regarding roost treatments from 1974-1992. A. R Stickley, Jr. (USDA/ADC) and F. Boyd (USDA/ADC) similarly reviewed and supplemented the data. These data were then summarized to provide an overview of PA-14 use from 1974-1992 regarding the number of roosts treated by state and month, estimated total kill of birds by species, methods of application, and amount of material applied. Impact on Breeding Populations Using migration data (Dolbeer 1982), we determined that breeding distributions of blackbirds and starlings killed by PA-14 applications occurred primarily in Indiana, Michigan, and Ohio. We obtained BBS data (Robbins et. al 1986) for each species in these states from 1974-1992. We then calculated the mean number of birds observed/route/year and the mean percent annual change in relative abundance for each species for all 3 states combined. For each species, we used simple correlation analysis (SAS Inst., Inc. 1988) to determine associations between numbers of birds killed by PA-14 treatments each winter and the mean percent annual change in relative abundance during subsequent breeding seasons. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1028&context=ewdcc7 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
