Article

Malathion applied at standard rates reduces fledgling condition and adult male survival in a wild lesser kestrel population

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Abstract

The lesser kestrel Falco naumanni is a globally threatened colonial bird that has suffered a generalized population decline in Europe. Recent studies have suggested that the land-use changes linked to agriculture intensification are the main factors accounting for the population regression. However, there has been little analysis of the role of pesticide applications. In this study, we examined the consequences of a malathion treatment in a wild population of lesser kestrels, specifically its effects on breeding performance, adult survival and population size. We found that the larger the area treated with malathion around the colony, the lower the size and the body condition of the fledglings, although no effects were found on the number of fledged chicks per pair or their sex ratio. Survival of adult males, but not females, was lower in the malathion-treated areas. These results show that organophosphorus pesticides applied at standard rates might disrupt the lesser kestrel population dynamics by reducing their breeding performance and increasing adult mortality in a sex-biased way. The proportional area treated around the colony did not affect colony size in the following year, indicating that an increased adult male mortality was not enough to lead to a detectable population size reduction and/or that the arrival of immigrants could have masked it. Both the direct malathion toxic effects and the expected reduction in prey availability due to fumigation are likely to underlie the observed effects. Hence, keeping non-treated buffer areas around kestrel colony centers should be a strictly applied conservation measure to avoid the observed negative side effects of malathion applications.

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We examined the causes, costs and benefits of adoption in the altricial lesser kestrel Falco naumanni. Specifically, we tested the intergenerational conflict hypothesis, proposed to explain adoption in some birds. Adoptions involved 76% of the nests and 51% of the nestlings at a mean age of 25 days (12 days before fledging). Nest-switching nestlings were not in poorer body condition, more parasitized or younger than their siblings, and body condition and prey delivery rates of their parents did not differ from those of other parents. In the foster nest, adopted nestlings did not benefit from higher feeding rates or a prolongation of the nestling period. They did not have fewer nest-mates or achieve higher rank within the new brood. Thus, adopted nestlings did not improve their body condition and survival. Adult lesser kestrels seemed unable to finely discriminate beween their own and alien chicks. Foster parents bore the cost of an increase of prey delivery rates, although it did not affect their survival or subsequent reproductive performance. Therefore, our results do not support the intergenerational conflict hypothesis, and suggest that adoption in this species is non-adaptive. Traditionally, the lesser kestrel bred in cliffs where movement among nest-sites was restricted. Nowadays, about half of the colonies are in tiled roofs which facilitate nest-switching by nestlings. The high rate of adoptions may thus be explained as reproductive errors associated with the recent occupation of a new breeding habitat.
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The Australian Plague Locust Commission uses the organophosphorus insecticide fenitrothion to control locust population increases across 2000000 km2 of eastern Australia. Although the impact of fenitrothion on non-target invertebrates has been studied, effects on vertebrates are largely unquantified. Lethal and sublethal impacts on vertebrates are a consequence of the use of organophosphorus and carbamate insecticides. Information detailing the effects of exposure on free-living animals, particularly for herpetofauna, is lacking. This paper reviews literature concerned with the impacts of organophosphorus and carbamate insecticides on terrestrial vertebrates and highlights the need for continued research into the effects of these chemicals, especially in Australia.
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The selection of foraging habitats by nine radio-tagged adult lesser kestrels (Falco naumanni) breeding in one colony in southern Spain, was studied in 1989 and 1990. Despite individual differences in the feeding habitat, there was a general tendency for grassland to be used more, and sunflower and woodlots to be used less, than expected by their availability. 2. The relatively higher food availability (measured as the number of hovering bouts by the lesser kestrels to catch one prey) of grasslands and cereals would explain the kestrels' preference for these habitats. 3. Since the 1950s, uncultivated grasslands in the area have decreased drastically and have been replaced by new crops, such as sunflowers. If grasslands continue to decrease in southern Spain, the progressive decline of lesser kestrel populations will probably continue in those areas.
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Organophosphorus (OP) insecticides continue to be an important group of pesticides widely used worldwide in spite of the introduction of the modern synthetic pyrethroids. The success of this class of compounds as insecticides is due to three main characteristics: (1) they show a relatively low persistence in the environment in comparison with their predecessors, the organochlorine (OC) insecticides; (2) they show low accumulation by biota; and (3) they generally exhibit a high acute toxicity. OPs can be broken down by a large variety of physicochemical and biological processes, such as hydrolysis, photolysis, or microbial degradation. They present a wide range of half-lives in the environment, from a few days to several months. For instance, degradation half-lives of OPs on plant foliage ranged between 0.2 to 10.5 d while in soil the range was between 7 and 144 d, depending on the OP and soil type (Racke 1992). Half-lives in water ranged from a few hours—at high temperature or pH, or in the presence of light—to more than 6 mon (Lartiges and Garrigues 1995).
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Numerous experimental studies providing extra food have concluded that food availability at the beginning of the breeding season constrains the start of egg-laying for female birds (Food Supply Hypothesis) because supplemented females usually lay earlier than nonsupplemented ones. This conclusion has recently been questioned because food addition studies may be confounded by ordered habitat selection. Ordered habitat selection occurs when territories or nests provided with extra food are chosen by individuals of higher quality that may be able to initiate breeding early, regardless of food supply (Habitat Selection Hypothesis). To test these two hypotheses, we performed an experiment using the Lesser Kestrel (Falco naumanni). To reveal effects of ordered habitat selection, extra food was provided to half of the nests in two colonies in which the other nests remained unsupplemented (mixed colonies). We provided extra food to all nests in two colonies (all-fed colonies) and to no nests in three colonies (all-unfed colonies). In these colonies, ordered habitat selection could not occur because all nests received equal treatment. In mixed colonies, fed pairs laid earlier than unfed ones. In contrast to the prediction of the Habitat Selection Hypothesis, there was no significant difference in mean laying date between unfed pairs of mixed colonies and pairs in all-unfed colonies, or between fed pairs of mixed colonies and pairs in all-fed colonies. Moreover, laying date was significantly earlier in all-fed than in all-unfed colonies. Therefore, the results support the Food Supply Hypothesis and refute the Habitat Selection Hypothesis.
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Mass increases of the levant vole (Microtus guentheri) are common in alfalfa fields in Israel. Deep ploughing, which is the main factor controlling vole numbers in other agricultural areas, is not possible in alfalfa. As alfalfa is a preferred food, voles in these fields are not attracted to poison baits and cannot be controlled by this means.A particularly striking increase of voles developed during the winter of 1975–1976 on 8 km2 of alfalfa fields in the northern Huleh Valley in Israel. This mass increase attracted large numbers of raptors and owls, mainly those wintering and on migration, but also resident species.Because the voles, which reached densities of 2400/ha, caused considerable damage to the alfalfa crop, destroying it completely in some places, the farmers sprayed the fields with Azodrin (Monocrotophos). This persistent insecticide is recommended in Israel only for the control of pests on cotton and in orchards. The dangers to wildlife described on the original label do not appear in the Hebrew translation.Due to secondary poisoning with Azodrin there was a mass mortality of raptors and owls that had fed on poisoned voles and birds on these 8 km2. 116 raptors and 29 owls were found dead during December 1975 through February 1976; 53 raptors and 16 owls were found poisoned but still alive, and were saved and later released. According to repeated counts of the black kite (Milvus migrans) population in the area it was estimated that about twice as many birds as those found were affected. Since it is probable that no poisoned birds could recover in the field, about 400 birds of prey had been destroyed on 8 km2 within three months.
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ASTCT.--Pesticides applied to control pests sometimes kill raptors. One region receiving frequent and heavy pesticide treatments is the Sahel that lies between the Sahara Desert and tropical forest areas of northern Africa. Plagues of locusts, grasshoppers, birds and rodents periodically develop in the Sahel when heavy rainfall follows periods of drought. Insecticides, avicides and rodenticides are applied over millions of hectares at rates known to kill birds. Observations indicate that many pesticide applications in the Sahel do not cause serious mortality. Only minimal raptor losses were reported following appli- cations of malathion, fenitrothion, chlorpyrifos and other insecticides for control of locusts and grass- hoppers scattered over about 14 million acres in northern Africa. Similarly, applications of zinc phos- phide bait on 430 000 ha in Sudan did not cause known losses of raptors. In contrast, use of fenthion to control Red-billed Quelea (Quelea quelea) in breeding colonies often killed or debilitated nontarget vertebrates, including raptors. A more specific avicide should be developed for quelea control. Until then, nontarget birds should be kept out of colonies for several days following avicide applications and dead quelea should be removed from treated areas.
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The effects of methyl parathion on survivability of wild northern bobwhites (Colinus virginianus) were investigated from 1986 to 1988 near Tallahassee, Florida. In three field seasons, 197 bobwhites were administered 0, 2, 4 or 6 mg/kg methyl parathion in corn oil by oral intubation, released and monitored for 14 d using radio telemetry. Bobwhites receiving 6 mg/kg methyl parathion had lower survival (P = 0.022) than control birds due to predation, not overt toxicity. There were no differences (P > 0.05) among treatment groups in activity, but methyl parathion may have influenced covey integrity. Birds that survived methyl parathion treatment had brain cholinesterase activities similar to those of control bobwhites. The results suggest that if bobwhites receive sufficiently high methyl parathion exposure in their natural habitats, then their susceptibility to predation may increase.
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Ultra low volume (ULV) aerial spraying of the organophosphorus insecticide malathion is widely used in Spain to control Tortrix viridana, the most important lepidopteran pest of Spanish holm oak forests (Quercus ilex) A field study was carried out in spring 1988 to analyze the short term effects of a standard application rate of malathion (1,160 g a i /ha) on the breeding success of the blue tit (Parus caeruleus) Several blue tit reproductive parameters and seasonal variation of arthropod densities in canopy trees (focusing on caterpillars, the main food resource for breeding blue tits) were compared between a mal-athion-treated plot and a control plot None of the breeding parameters (nest abandonment, nest success, hatching success, nestling mortality, daily survival rate, and nestling weight) showed differences between the treated and the control plots Malathion spraying caused nearly a 100% mortality of the target pest Tortrix viridana, but it did not reduce availability of another Tortricidae (Archips xylosteana), with the result that food supply was similar or higher in the treated plot than in the control plot The main conclusion of this study is that a forest standard application of malathion did not cause adverse short-term effects on breeding blue tits Moreover, this work focused on the indirect effects of insecticides via food depletion, its results suggest that in these kinds of studies it is more important to assess the abundance of arthropods remaining alive after treatment than the degree of arthropod mortality caused by the insecticide
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The analysis of habitat selection underlies many conservation recommendations. Different researchers use different methods, therefore there is a need to examine whether the results are consistent. This study examined habitat selection by lesser kestrels, Falco naumanni, a globally threatened species, using two methods: visual sighting data from a 35-km transect and radio-telemetry of 33 birds. Habitat use and spatial ecology were studied across all of the breeding season in a pseudo-steppe area, where traditional agro-grazing systems are still present but some areas have been transformed into pine plantations. Telemetry data indicate that, in good quality habitat, lesser kestrels prefer to forage close to the colony. Furthermore, the home ranges obtained were smaller than those for lesser kestrels using intensively managed habitats or more forested areas. Habitat availability was determined within a 4-km radius of the colony and habitat preferences were determined using compositional analysis. Both methods were found to produce similar results, but telemetry provided a larger number of significant differences between habitats. Before the chicks hatched, lesser kestrels preferred grazed fallows, ploughed fields and cereal, while after hatching cereal stubble was the preferred habitat. In steppe habitats the protection of such foraging habitats within a 3-km radius from the colonies could be a very effective conservation measure.
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The lesser kestrel is a Globally Threatened Species which large decline has been related to recent agricultural changes in Euro-pean pseudo-steppes. Irrigation is considered as one of the major threats for this and other steppe birds, but the actual effects of irrigation on foraging habitat selection have been scarcely examined. We studied the selection of traditional dry cereal farming and irrigated habitats by foraging lesser kestrels during the breeding cycle, paying especial attention to possible differences among crop types. Field margins were the scarcest but the most positively selected habitat, and different stages of cereals cultivated follow-ing traditional practices were selected depending on the breeding and agriculture cycles. Effects of irrigation were dual. While irri-gated maize and other crop types were avoided, alfalfa was used in proportion to its availability and later highly selected after harvesting. Moreover, field margins in irrigated land were selected in a similar way than in traditional dry farmland. Therefore, although maintaining low-intensity farming is still the main recommendation for this species, new management options arise when social pressure makes irrigation unavoidable. Further agri-environmental schemes in these circumstances should thus promote cul-tivation of alfalfa with a low input of biocides while avoiding maize, together with increasing field margins, to make compatible irrigation with lesser kestrel conservation.
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Summary1.The role of individual experience vs. the use of conspecific cues on breeding dispersal decisions have seldom been determined in colonial birds. We studied causes of breeding dispersal in the lesser kestrel (Falco naumanni), a species that breeds in colonies of variable size as well as solitarily. During a 6-year study in Spain, we gathered information on 486 subsequent breeding attempts and on 26 explanatory variables which evaluated individual experience, conspecific cues in terms of breeding performance and colony size, and different ecological and populational characteristics.2.Two decisions were separately analysed: whether or not to disperse, and how far to move. Generalized Linear Mixed Models (GLMMs) allowed us to identify the relative contribution of each explanatory variable while controlling for the non-independence of individual dispersal decisions across years.3.Females seemed to disperse more often than males (34% vs. 19%), and both sexes apparently dispersed less with age. However, a GLMM showed that experience (i.e. the number of years a bird bred in a particular colony) was the only factor influencing breeding dispersal. Birds showed higher site fidelity the greater their experience in a colony, which could be related to benefits derived of increased local familiarity. A second GLMM showed that, before birds acquired experience in a particular colony, individual nest failure due to predation and proximity to other colonies increased the probability of dispersal, dispersal being also higher in colonies with poor conspecific breeding success. Furthermore, solitary nesting birds were more prone to disperse and dispersal probability decreased the larger the colony of origin, according to fitness expectations associated with colony size.4.A GLMM explaining dispersal distances retained two variables – birds dispersed farther the lower the breeding density in the surroundings, and the larger the distance to the nearest colony. Dispersing birds tended to settle within their previous foraging areas (median dispersal distance = 1·6 km), being constrained by the availability of nearby colonies.5.Lesser kestrels mainly cue on their own breeding performance and experience in a particular colony at the time of taking a dispersal decision. However, inexperienced birds also partially cue on the size and breeding success of their own colonies (but not on the size or breeding performance of other colonies), and birds moved larger distances when dispersing from areas of low populational density. These results support some degree of conspecific attraction.
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American kestrels (Falco sparverius), eastern screech-owls (Otus asio), and northern bobwhites (Colinus virginianus) were given single acute oral doses of four widely diverse anticholinesterase pesticides: EPN, fenthion, carbofuran, and monocrotophos. LD50s, based on birds that died within 5 d of dosage, were computed for each chemical in each species. Sex differences in the sensitivity of northern bobwhites in reproductive condition were examined. American kestrels were highly sensitive to all chemicals tested (LD50s 0.6–4.0 mg/kg). Eastern screech-owls were highly tolerant to EPN (LD50 274 mg/kg) but sensitive to the remaining chemicals (LD50s 1.5–3.9 mg/kg). Northern bobwhites were highly sensitive to monocrotophos (LD50 0.8 mg/kg) and less sensitive to the remaining chemicals (LD50s 4.6–31 mg/kg). Female bobwhites (LD50 3.1 mg/kg) were more sensitive to fenthion than males (LD50 7.0 mg/kg). Mean percent depression of brain cholinesterase (ChE) of birds that died on the day of dosing exceeded 65% for all chemicals in all species. The response of one species to a given pesticide should not be used to predict the sensitivity of other species to the same pesticide. The need for research on several topics is discussed.
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The ecological risks of pesticides to wildlife are assessed by the United States Environmental Protection Agency with a simple quotient model. A risk factor is calculated by dividing the estimated dietary concentration by the chemical’s dietary toxicity. The risk factor, which can be used to predict population mortality, serves as a regulatory criterion to identify compounds that could pose unacceptable risk. Under the “New Paradigm,” the Environmental Protection Agency recently cut by 50% the critical risk factor, yielding more-rigorous decision-making criteria by decreasing acceptable wildlife mortality from 50 to 8.8% following one pesticide application and by increasing the number of pesticides that pose unacceptable risk to wildlife. The quotient model depends on at least one implicit and approximately 11 explicit assumptions; deviations from these assumptions may bias outputs and consequent regulatory decisions. To correct error-prone assumptions we present three modifications that improve ecological risk estimates. We used the agency’s quotient model to survey risks to a regional avifauna (Florida birds) in relation to mosquito pesticide exposure (fenthion, malathion, and naled). Certain groups (small-bodied, insectivorous passerines) were predicted to face the highest ecological risk due to taxonomy, diet, and body mass. Finally, we performed a risk assessment for Black-whiskered Vireos (Vireo altiloquus barbatulus) exposed to fenthion. The results revealed that this species could potentially suffer 42% mortality in a population exposed to one application of fenthion. Ecological risk assessments increasingly will be based on mathematical models. To improve predictions of the effects of xenobiotic compounds on wildlife, biologists-especially conservationists-should work with ecotoxicologists to improve current models, develop new models, and provide data to parameterize models. Equally important, conservationists should participate in defining regulatory levels of ecological risk for wildlife. Los riesgos ecológicos de los pesticidas para la fauna silvestre son evaluados por la Agencia de Protección Ambiental de los Estados Unidos con un simple modelo de cociente. Se calcula un factor de riesgo dividiendo la concentración dietética estimada por la toxicidad dietética química. El factor de riesgo que puede ser usado para predecir la mortalidad poblacional, sirve como un criterio regulador para identificar compuestos que podrían representar riesgos inaceptables. La Agencia de Protección Ambiental recientemente ha reducido en un 50% el factor de riesgo crítico, creando un criterio más riguroso para la toma de decisiones al disminuir la mortalidad aceptable de la fauna silvestre, después de una aplicación del, pesticida del 50% at 8.8% y al aumentar el número de pesticidas que representan riesgos inaceptables para la vida silvestre. El modelo del cociente depende de, por lo menos, un supuesto implícito y aproximadamente 11 supuestos explícitos; desviaciones en estos supuestos podrían sesgar los resultados y las consiguientes decisiones reguladoras. A los efectos de corregir supuestos propensos a errores, presentamos tres modificaciones que mejoran las estimaciones del riesgo ecológico. Usamos el modelo del cociente de la Agencia para evaluar el riesgo para una avifauna local (las aves de la Florida) en relación con la exposición a los pesticidas contra mosquitos (fenthion, malathion y naled). Se predijo que ciertos grupos (pequeños paserinidos insectívoros) enfrentan un riesgo ecológico más alto debido a taxonomía, la dieta y masa corporal. Finalmente llevamos a cabo su una evaluación del riesgo para Vireo altiloquus barbatulus expuesto al fenthion. Los resultados revelaron que esta especie podria sufrir potencialmente un 42% de mortalidad en una población expuesta al fenthion. Para mejorar las predicciones de los efectos de compuestos xenobióticos sobre la fauna silvestre, los biólogos (especialmente los conservacionistas) deben trabajar con ecotoxicólogos para mejorar los modelos corrientes, desarrollar nuevos modelos y proveer datos para parametrizar los modelos. De igual importancia es que los conservacionistas participen en la definición de los niveles de regulación del riesgo ecológico para la fauna silvestre.
Article
European pseudo-steppes have suffered from extensive changes in agricultural practices during the past decades with the disappearance of field margins and fallow systems and the increase of biocide treatments. The negative effect on wildlife has led to the adoption by the European Union of policies more compatible with environmental conservation, but decisions about optimal land use are difficult to make because of lack of information. We studied habitat use by the Lesser Kestrel (Falco naumanni), a globally vulnerable species, in a Spanish pseudo-steppe (Los Monegros) where traditional agro-grazing systems are still being practiced, and we compared the results with those of another Spanish pseudo-steppe where modern and intensive agriculture has been implemented. We focused on the use by Lesser Kestrels of habitats subject to changes provoked by recent agricultural policies. Habitat availability was determined in a 3-km radius around 11 colonies, where 23 Lesser Kestrels were radio-tracked during the chick-rearing stage. Habitat selection was determined through compositional analysis. The rank of selected habitats was similar for all kestrels, considering both habitats surveyed and habitats where kestrels hunted. Kestrels selected field margins and cereal fields and rejected abandoned crops and scrubland. This selectivity seemed to be due to prey availability. In the intensively cultivated areas the kestrels selected similar habitats but used only small foraging patches and obtained smaller prey than in the traditional agro-grazing systems, probably because of the irregular distribution of prey resources as a result of the intensive biocide treatments. Consequently, in intensively cultivated habitats Lesser Kestrels had larger home ranges (63.65 km2) than in those with traditional systems (12.36 km2). These differences are reflected in the productivity and population trends of both populations. Thus, the best strategy for conserving the Lesser Kestrel seems to be the maintainance of traditional cereal cultures with low biocide treatments and numerous field margins. Both agricultural intensification and marginal land abandonment (with subsequent scrubland invasion) have detrimental consequences for this and probably for other pseudo-steppe species. Positive management steps can be encouraged by recent agro-environmental regulations such as the 2078/92 European Union Reglament, which favors the creation of programs in which agricultural practices accord with wildlife conservation.Conflictos Entre la Conservación del Cernícalo Priniilla y la Politica Agraria Comunitaria Determinados por Estudios Sobre Uso del HábitatDurante las últimas décadas, las prácticas agrícolas en las pseudo-estepas europeas han sufrido fuertes cambios; los márgenes entre campos y los sistemas de barbechado han tendido a desaparecer mientras se incrementaba el uso de biocidas. Estas tendencias se aceleraron con la puesta en marcha de la Política Agraria Comúniteria (PAC) de la Unión Europea (UE). Sus efectos negativos sobre la vida silvestre han determinado que la UE adoptara políticas más compatibles con la conservación del medio, pero las decisiones acerca del uso óptimo del suelo son difícles de tomar debido a la carencia de información. Nosotros hemos estudiado el uso del hábitat por el cernícalo primilla, una especie amenazada a nivel mundial, en una pseudo-estepa española (Los Monegros) donde se mantienen sistemas tradicionales agro-pastorales; los resultados se comparan con los obtenidos en otra pseudo-estepa española altamente transformada. Nos centramos en el uso de hábitats sujetos a cambios determinados por políticas agrarias recientes. La disponibilidad de hábitat se midió en torno a 11 colonias de cernícalo primilla, donde se siguieron mediante radiotelemetría 23 adultos durante la crianza de pollos, y su selección se determinó mediante el análisis composicional. El rango de los hábitats seleccionados fue similar en todos los individuos, tanto considerando la selección a nivel de hábitats prospectados como de hábitats donde obtuvieron presas. Los cernícalos seleccionaron márgenes de campos y cereales y evitaron campos abandonados y matorral; ello parece ser debido a diferentes rendimientos (disponibilidad de presas). En pseudo-estepas transformadas en áreas de cultivo intensivo los cernícalos seleccionaron hábitats similares pero sólamente usaban pequeñas parcelas para cazar, obteniendo presas de menor tamaño que en pseudo-estepas no alteradas; ello probablemente es debido a la irregular distribución de los recursos como consecuencia de los tratamientos con biocidas. Consecuentemente, en pseudo-estepas transformadas, los cernícalos primillas necesitaron áreas de campeo mayores (63,65 km2) que en aquellas con cultivos tradicionales (12,36 km2). Estas diferencias se reflejaron en la productividad y tendencias de ambas poblaciones. La mejor estrategia para conservar el cernícalo primilla parece ser el mantenimiento de los cultivos cerealistas tradicionales con bajos tratamientos y la potenciación de los márgenes entre campos. La intensificación de la agricultura y el abandono de tierras (con la subsecuente invasión de matorral) son negativos para ésta y probablemente para otras especies esteparias. Las medidas de manejo pueden incentivarse a través de las recientes regulaciones como el Reglamento 2078/92 de la UE que favorece prácticas agricolas respetuosas con la conservación de la fauna silvestre.
Article
Free-living female red-winged blackbirds (Agelaius phoeniceus) were captured on their nests and given oral doses of 0, 2.37 or 4.21 mg/kg methyl parathion in a propylene glycol carrier during incubation. Birds were released immediately after dosing and observed for 5 h to document behavioral effects, amount of time spent off the nest after dosing and time spent incubating. Each nest was monitored until nestlings fledged or until all nestlings died or disappeared. For each nest, the time of abandonment, hatching success and fledging success were determined. In addition, prefledging weights were obtained for all nestlings in nests at 8 d after hatch. Although methyl parathion caused ataxia, lacrimation and lethargy and significantly depressed cholinesterase activity (>35%) at 4.21 mg/kg, there were no apparent adverse effects on reproduction. Females receiving 4.21 mg/kg methyl parathion were able to return to their nests, resume incubation, successfully hatch their clutch and rear their young. Nestlings of poisoned females did not have significantly different body weights at 8 d compared to controls, indicating that methyl parathion did not disrupt the females' ability to forage and deliver adequate food to nestlings. Band returns from the following year indicated that treatment birds returned and nested in nearly the same proportion as did controls and other red-winged blackbirds occupying the ponds. There was no indication that a single oral dose of methyl parathion (2.37 or 4.21 mg/kg) decreased over-winter survival.
Article
Indirect effects of pesticides, operating through the food chain, have been proposed as a possible causal factor in the decline of farmland bird species. To demonstrate such a link, evidence is needed of (1) an effect of food abundance on breeding performance or survival; (2) an effect of breeding performance or survival on population change; and (3) pesticide effects on food resources, sufficient to reduce breeding performance or survival, and hence to affect the rate of population change. Evidence under all three categories is only available for one species, the Grey Partridge Perdix perdix, although data showing effects of pesticides on food resources and relationships between food resources and breeding performance are also available for some other species. This paper reports on recent work investigating the effects of pesticides on Yellowhammer Emberiza citrinella and Skylark Alauda arvensis during the breeding season. The probability of brood reduction in Yellowhammer was affected by the proportion of the foraging area around the nest which was sprayed with insecticide. No significant effects of pesticides were recorded on Skylark chick condition or growth rate, but sample sizes were small. Invertebrate food abundance affected chick condition (Skylark) and the number of chicks fledging (Yellowhammer and Corn Bunting Miliaria calandra; relationship for the latter derived from re-analysis of data from an earlier study). Other recent work is briefly reviewed and the current evidence for the indirect effects of pesticides is summarized. Significant knowledge gaps are identified and some of the issues involved in resolving these are discussed.
Article
Lesser kestrels (Falco naumanni) lay clutches which appear excessive as only 3% of them yield as many young as eggs laid. Four hypotheses may explain the adaptive value of producing surplus eggs: (1) the bet-hedging hypothesis assumes that the environment varies unpredictably and surplus eggs serve to track uncertain resources; (2) the ice-box hypothesis suggests that surplus offspring serve as a reserve food during a period of shortage; (3) the progeny choice hypothesis says that parents produce surplus offspring in order to choose these with higher fitness; and (4) the insurance-egg hypothesis proposes that extra eggs are an insurance against the failure of any egg. To test the significance of this strategy in the lesser kestrel, an experiment manipu-lating brood size at hatching was carried out over 2 years, with good and bad feeding conditions. The experiment consisted of adding a chick to experimental broods where one egg failed to hatch or removing a randomly selected chick from experimental broods where all eggs had hatched. Independently of annual food availability, pairs with brood sizes reduced by one chick fledged more nestlings than pairs with brood size equalling their clutch sizes. Body condition of young was also better in the former group, but only in 1993 (a high-food year). Independently of year, mean local survival of parents with complete broods at hatching was lower than for parents raising reduced broods. These results supported only the insurance-egg hypothesis which says that surplus eggs may be an insurance against the failure of any egg, but parents may suffer reproductive costs when all eggs hatch.
Article
Young rats have been shown in several laboratories to be more sensitive to the neurotoxic effects of acute exposure to chlorpyrifos. To examine the neurobehavioral effects of chlorpyrifos as a function of age and dose, we conducted dose–response and time-course assessments in rats of three different ages (postnatal day, or PND, 17, 27, and adults). Doses were selected to span the effective dose range in each age group: PND17 — 4, 10, 20 mg/kg; PND27 — 10, 25, 50 mg/kg; adult — 10, 50, 100 mg/kg. Rats were tested at the time of peak effect on the day of dosing, and again at 1 and 3 days, and at 1 and 2 weeks after a single oral dose. There were age- and sex-related differences in the recovery of these behavioral effects; the adult males recovered from the behavioral effects more quickly than the other age groups, and the adult females showed the slowest recovery (up to at least 3 days). Although these doses had been shown previously to produce a similar degree of cholinesterase inhibition, the neurobehavioral alterations fell into the following three patterns of effect as a function of age. (1) Some endpoints (e.g., gait abnormalities, tremor) showed a dose–response curve that was shifted to the right in the older animals. Calculated ED50 values indicated that the PND17 rats were three- to five-fold more sensitive than the adults. (2) Some measures showed less effect in the youngest rats; for example, maximal motor activity decreases were half as great as with adults. (3) A few effects that were typically observed in adults, e.g., salivation, were not seen at all in the PND17 rats. Thus, differential responses on these neurobehavioral endpoints were observed as a function of age. These data suggest that, for some endpoints, young rats are more sensitive to a range of chlorpyrifos doses; however, the magnitude of age-related differences depends on the specific endpoint and time of assessment, as well as age and sex of the test subject.
Article
Cereal steppe habitat is a low intensive system that is rapidly disappearing as a result of changes in agricultural practices, and has the highest number of bird species with an Unfavourable Conservation Status of any habitat in Europe. A logistic regression model showed that the lesser kestrel, a globally threatened species, prefers to forage close to colonies, selects fields with livestock and avoids tree plantations. The conservation of this species is dependent on maintenance of extensive agriculture characterised by a rotation of cereal and grazed fallow. Abandonment of traditional agriculture and recent changes in agri-environmental programme support, which favour afforestation, are jeopardising the future of cereal steppes. Agri-environment measures are likely to be the most effective means of retaining the specific characteristics of cereal steppe habitat.
Article
Intensification of agriculture is believed to have caused declines in farmland bird populations. One of the key elements of recent agricultural intensification is the increased use of pesticides. However, studies elucidating relationships between individual management practices and responses in bird populations remain rare. Here, evidence is presented of indirect effects of pesticides on behaviour and nestling condition of yellowhammers (Emberiza citrinella L.). Insecticide use was associated with reduced abundance of invertebrate food at the field scale resulting, early in the season (when nestlings were fed exclusively on invertebrates), in a negative correlation with yellowhammer foraging intensity. There was also a negative relationship between insecticide use and nestling body condition. While cumulative effects of repeated spraying can have impacts, the occurrence of any insecticide spraying in the breeding season may be more detrimental than multiple sprays at other times. Minimising applications of persistent broad-spectrum insecticides during March–June, the provision of alternative unsprayed foraging habitat and advice on mitigating indirect effects of pesticides to advisers and users are likely to benefit nesting yellowhammers.
Article
House sparrows, Passer domesticus, dermally exposed to ‘Rid-A-Bird’ perches and solution (active ingredient: 11% fenthion) under realistic but controlled conditions, were offered to American kestrels, Falco sparverius, in a laboratory setting in groups of four birds comprised of one fenthion-exposed and three unexposed birds. In 15 of 30 predation trials, kestrels captured a sparrow and were considered successful. Kestrels captured the fenthion-exposed sparrows in 12 of these cases, demonstrating a significant differential selection of contaminated sparrows. Kestrels captured five of six sparrows obviously affected by fenthion that were displaying aberrant behaviour at the time of capture. Behavioural effects as a result of fenthion exposure may have made treated house sparrows more conspicuous to kestrels, influencing kestrel prey choice. Selective predation on fenthion-exposed prey by raptors may amplify any existing risk of secondary poisoning in a field situation.
Article
Bobwhite quail (Colinus virginianus) that received either 0, 2, 4, or 8 mg/kg methyl parathion (O,O-dimethyl o-p-nitrophenyl phosphorothioate) treatment were investigated as to their susceptibility to predation by a cat (Felis domesticus) predator. Four hours after receiving methyl parathion (MP), physical activity levels were monitored in quail and included the number of seconds spent still, walking, running, or flying before and after a cat was introduced into an experimental arena. The cholinesterase (ChE) activity for each quail on experiment was determined. Quail that were captured exhibited significantly greater inhibition of brain ChE activity and spent significantly more time being still than noncaptured birds. Birds receiving MP at 8 mg/kg spent more seconds being still than those in other treatment groups and had ChE activity reduced to 42.8% of normal activity. There was a tendency for quail at increasing treatment levels to be more susceptible to capture by the cat predator. The neurological and behavioral effects of methyl parathion may have important ecological ramifications.
Article
Physiological and toxicological effects of p.o. methyl parathion (0.375-3.0 mg/kg) or fenvalerate (1000-4000 mg/kg) were examined over a 10-h period in American kestrels (Falco sparverius) maintained in thermoneutral (22 degrees C) and cold (-5 degrees C) environments. Methyl parathion was highly toxic (estimated median lethal dose of 3.08 mg/kg, 95% confidence limits of 2.29-4.14 mg/kg), producing dose-dependent inhibition of brain and plasma cholinesterase activity, hyperglycemia, and elevated plasma corticosterone concentration. Brain and plasma cholinesterase inhibition in excess of 50% was associated with transient but pronounced hypothermia 2 h after intubation, although the magnitude of this response was variable. Fenvalerate, at doses far exceeding those encountered in the environment, caused mild intoxication and elevated plasma alanine amino-transferase activity. Cold intensified methyl parathion toxicity, but did not affect that of fenvalerate. Thus, it would appear that organophosphorus insecticides pose far greater hazard than pyrethroids to raptorial birds.
Article
We propose a model for sex-ratio adjustment complementary to that of Trivers and Willard. In addition to the three basic assumptions of the Trivers-Willard model, our model assumes that the sex with more variable reproductive success (normally male) is also the sex less constrained for reproduction. This assumption seems realistic, because several studies have demonstrated that poor-condition males may adopt alternative mating strategies and sire some offspring, whereas females have physiological constraints for gestation or egg production that cannot be avoided. Thus, under these circumstances, sons of both poor and good condition would be more valuable for parents than daughters, whereas daughters would be relatively more valuable than sons at intermediate condition. This model predicts, therefore, a U-shaped relationship between parental condition and offspring sex ratio. We present a case study for the monogamous lesser kestrel (Falco naumanni) that fulfills the assumptions and predictions of the model. The minimum body condition for breeding, measured as pectoral thickness, was lower for sons than for daughters. Below this minimum, males had a higher chance of breeding than females. Above this minimum, however, the lifetime reproductive success was condition dependent in males but not in females. Thus, males in better body condition attain, on average, higher reproductive success than females. Offspring sex ratio varied with the size of the father's ornaments and mother condition according to the U-shaped pattern predicted by the model.
Article
The fall in body temperature and inhibition of hypothalamic cholinesterase induced by rivastigmine (a pseudo-reversible carbamate inhibitor) were compared in male and female rats. In males, 1.5 mg/kg lowered body temperature by 1 degrees C and in females by 3.2 degrees C (P<0.001) and inhibited cholinesterase by 65% and 74%, respectively (P<0.05). Pilocarpine (20 mg/kg) decreased body temperature by 1.1 degrees C in males and 1.9 degrees C in females (P<0.05). Orchidectomy, but not ovariectomy, abolished the sex difference in the hypothermic effect of pilocarpine and the enzyme inhibition induced by rivastigmine, but not in its effect on body temperature. Testosterone (10 mg/rat) decreased the cholinesterase inhibition and the temperature reduction induced by rivastigmine in gonadectomised males and females, but that induced by pilocarpine in males only. In conclusion, rivastigmine causes less inhibition of cholinesterase because testosterone may interfere with its entry into the brain. Testosterone may further decrease the temperature-lowering effect of rivastigmine and acetylcholine receptor agonists in males by an action at a receptor level.
Article
This study reviews the toxic effects of organophosphate (OP) pesticides on the immune systems and immune functions of invertebrates, fish, and higher vertebrate wildlife. The fundamental features and mechanisms of OP-induced immunotoxicity are illustrated with reference to parathion, chlorpyrifos, malathion, and diazinon. Immunotoxicity may be direct via inhibition of serine hydrolases or esterases in components of the immune system, through oxidative damage to immune organs, or by modulation of signal transduction pathways controlling immune functions. Indirect effects include modulation by the nervous system, or chronic effects of altered metabolism/nutrition on immune organs. Immunotoxicities are varied and include pathology of immune organs, and decreased humoral and/or cell mediated immunity. Altered non-specific immunity, decreased host resistance, hypersensitivity and autoimmunity are also features of immunotoxicity; although not all of these have been conclusively demonstrated in terms of pollutant exposure and immunotoxic effects in wildlife within individual experiments. Immunotoxicological biomarkers and biological monitoring tools are urgently needed to assess the extent of immunotoxicity in wildlife. Selection of universal biomarkers is hampered by the physiological diversity of immune systems in animals. However, by drawing on evidence from human epidemiology and tiered approaches in mammalian immunotoxicity evaluation, a selection of generic biomarkers of immunotoxicity in animals is suggested. Priorities for future research are also identified.
Article
Organochlorine, organophosphorus, carbamate, pyrethroid and neonicotinoid insecticides and organomercury fungicides are all neurotoxic and therefore have the potential to cause behavioural disturbances in birds. A number of studies have described behavioural effects caused to captive birds by neurotoxic pesticides, but it is very difficult to measure such effects in the field, which is a serous limitation given their potential to cause adverse effects at the population level. The mode of action, and the neurotoxic and behavioural effects of these compounds are briefly reviewed before considering evidence for their effects in the laboratory and field. Behavioural effects may cause adverse changes at the population level either directly or indirectly. Direct effects upon avian populations may be due to disturbances of reproduction, feeding, or avoidance of predation. Indirect effects on predators may be the consequence of direct action upon the prey population leading to either (1) reduction of numbers of the prey population, or (2) selective predation by the predator upon the most contaminated individuals within the prey population. Attention is given to the historic evidence for neurotoxic and behavioural effects of persistent organochlorine insecticides, raising the question of retrospective analysis of existing data for this once important and intensively studied class of compounds. Less persistent pesticides currently in use may also have neurotoxic effects upon birds in the field. Sometimes, as with some OPs, their effects may outlast the persistence of their residues, and the ecotoxicity and persistence of some may be affected by interactions with other environmental chemicals. The development of new mechanistic biomarker assays could improve understanding of behavioural effects and possible associated effects at the population level caused by such compounds in the field.