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Direct and Indirect Effects of Insecticide Applications on Growth and Survival of Nestling Passerines
Author(s) -
Howe Frank P.,
Knight Richard L.,
McEwen Lowell C.,
George T. Luke
Publication year - 1996
Publication title -
ecological applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.864
H-Index - 213
eISSN - 1939-5582
pISSN - 1051-0761
DOI - 10.2307/2269609
Subject(s) - biology , passerine , sparrow , ecology , nest (protein structural motif) , malathion , pesticide , biochemistry
We conducted an experiment in 1989 and 1990 to determine the effects of malathion ultra‐low volume (ULV) aerial spray on reproduction of passerine birds in shrub‐steppe habitat of southern Idaho. The experiment consisted of reducing the insect food base with malathion, a broad‐spectrum insecticide, while monitoring nestling growth variables and daily nest survivorship. Relative arthropod abundance and biomass were reduced on the treatment plot in 1989 and 1990 (F. P. Howe et al., unpublished manuscript). Wing and tarsus lengths of nestling Sage Thrashers (Oreoscoptes montanus) were shorter on the treatment than on the control plot after malathion application in 1989 but not in 1990. Nestling Brewer's Sparrow (Spizella breweri) wing length and mass were lower on the treatment plot in 1990 but not in 1989. Primary length and foot length were unaffected for either species in either year. Multivariate ANOVA indicated that nestling Brewer's Sparrow size (a combination of five growth variables) was smaller on the treatment than on the control site after the 1990 treatment, but similar between sites after the 1989 malathion application. Sage Thrasher nestling size was smaller on the posttreatment malathion plot in 1989, but similar between plots in 1990. The percentage of eggs hatched and percentage of nestlings fledged were unaffected for either species. No differences were detected in Mayfield estimates of nest survivorship for either species in either year. The mean number of Sage Thrashers fledged per nest attempt was lower on the treatment than on the control plot in 1989, but not in 1990. The mean number of Brewer's Sparrows fledged per nest attempt was not affected on the treatment plot. No adult mortality for either species was observed, and nestling mortalities could not be attributed to malathion. Thus, few differences were detected in nestling growth variables and nest survivorship between the control and treatment plots, and these differences were not consistent across years. Under the conditions of this study, malathion had no observable direct effects, and only marginal indirect effects, through food‐base reduction, on Brewer's Sparrow and Sage Thrasher nestling growth and survival.