| [ilheus arbovirus in wild birds (sporophila caerulescens and molothrus bonariensis)]. | to report the first ilheus arboviruses isolated from wild birds and analyze its public health impact. | 2001 | 11359196 |
| new data on philornis seguyi garcia (1952) (diptera, muscidae). | philornis meinert is a very interesting muscidae (diptera) genus whose larvae are associated with a wide range of bird species. the existing description of philornis seguyi garcia (1952), which was reported in argentina, so far involves only the female. during the 2000-2002 breeding seasons, we collected philornis flies from six bird species in buenos aires province, argentina. all the flies were identified as p. seguyi. based on this material, we describe the larva, puparium, adult male, and ma ... | 2005 | 16532187 |
| helminths of molothrus bonariensis (gmelin, 1789) (passeriformes: icteridae) from southernmost brazil. | information about helminths of molothrus bonariensis (gmelin, 1789) (passeriformes: icteridae) are scarce; in this sense the objective of this paper was to contribute to its knowledge. five hosts of southern brazil were examined and the helminths prosthogonimus ovatus, tanaisia valida (digenea), diplotriaena bargusinica and synhimantus (dispharynx) nasuta (nematoda) were identified. the species t. valida, p. ovatus and s. (d.) nasuta are for the first time registered for the bird in brazil. pros ... | 2016 | 27580390 |
| the nucleus mesencephalicus lateralis, pars dorsalis in neotropical passerines. | the volume of the nucleus mesencephalicus lateralis, pars dorsalis and the optic lobe were determined in 8 species of neotropical birds in the order passeriformes: pyrocephalus rubinus, pitangus sulphuratus, atticora fasciata, molothrus bonariensis, tangara nigrocincta, ramphocelus dimidiatus, euphonia xanthogaster and spinus magellanicus. the ratio of the volume of the nucleus to the volume of the optic lobe was calculated for each species, and was found to be larger in all 8 species than in a ... | 1979 | 526853 |
| formulated beta-cyfluthrin shows wide divergence in toxicity among bird species. | it is generally assumed that the toxicity of pyrethroid insecticides to birds is negligible, though few species have been tested. the oral acute toxicity of formulated beta-cyfluthrin was determined for canaries (serinus sp.), shiny cowbirds (molothrus bonariensis), and eared doves (zenaida auriculata). single doses were administered to adults by gavage. approximate lethal doses 50 (ld(50)) and their confidence intervals were determined by approximate d-optimal design. canaries were found to be ... | 2011 | 21584255 |
| sexual differences in memory in shiny cowbirds. | avian brood parasites depend on other species, the hosts, to raise their offspring. during the breeding season, parasitic cowbirds (molothrus sp.) search for potential host nests to which they return for laying a few days after first locating them. parasitic cowbirds have a larger hippocampus/telencephalon volume than non-parasitic species; this volume is larger in the sex involved in nest searching (females) and it is also larger in the breeding than in the non-breeding season. in nature, femal ... | 1998 | 24399271 |
| coevolution and avian brood parasitism: cowbird eggs show evolutionary response to host discrimination. | the rufous hornero (furnarius rufus) is an important host of the brood parasitic shiny cowbird (molothrus bonariensis) in uruguay, but not in nearby buenos aires province, argentina. eggs of the shiny cowbird are extremely variable in size, and horneros eject cowbird eggs with widths less than about 88% of the widths of their own eggs. uruguayan cowbird eggs are, on average, 12% larger than those from buenos aires, a geographic pattern in egg size that corresponds to the pattern of successful ho ... | 1986 | 28563499 |
| [reproduction of the bird mimus gilvus (passeriformes: mimidae) in maracaibo, venezuela]. | four pairs of the poorly understood tropical mockingbird mimus gilvus were captured and color banded at a grassland in maracaibo, venezuela in june 1997. throughout the following 8 months, individuals were observed two days per week for 4 hours each. we recorded courtship behaviour, nest construction, incubation, parental care, territory defense and timing of reproductive cycle. pairs lived in defined territories defended primarily by the male. both sexes participated in nest building which bega ... | 2006 | 12189795 |
| molecular tracking of individual host use in the shiny cowbird - a generalist brood parasite. | generalist parasites exploit multiple host species at the population level, but the individual parasite's strategy may be either itself a generalist or a specialist pattern of host species use. here, we studied the relationship between host availability and host use in the individual parasitism patterns of the shiny cowbird molothrus bonariensis, a generalist avian obligate brood parasite that parasitizes an extreme range of hosts. using five microsatellite markers and an 1120-bp fragment of the ... | 2016 | 27547305 |
| different recognition cues reveal the decision rules used for egg rejection by hosts of a variably mimetic avian brood parasite. | brood parasitism imposes several fitness costs on the host species. to reduce these costs, hosts of avian brood parasites have evolved various defenses, of which egg rejection is the most prevalent. in the face of variable host-parasite mimicry and the costs of egg discrimination itself, many hosts reject only some foreign eggs. here, we experimentally varied the recognition cues to study the underlying cognitive mechanisms used by the chalk-browed mockingbird (mimus saturninus) to reject the wh ... | 2012 | 22627806 |
| brood parasite eggs enhance egg survivorship in a multiply parasitized host. | despite the costs to avian parents of rearing brood parasitic offspring, many species do not reject foreign eggs from their nests. we show that where multiple parasitism occurs, rejection itself can be costly, by increasing the risk of host egg loss during subsequent parasite attacks. chalk-browed mockingbirds (mimus saturninus) are heavily parasitized by shiny cowbirds (molothrus bonariensis), which also puncture eggs in host nests. mockingbirds struggle to prevent cowbirds puncturing and layin ... | 2012 | 22158956 |
| do shiny cowbird females adjust egg pecking behavior according to the level of competition their chicks face in host nests? | interspecific brood parasites, like the shiny cowbird (molothrus bonariensis), lay eggs in nests of other species. shiny cowbird females peck and puncture eggs when they parasitize host nests. this behavior increases the survival of cowbird chicks when they have to compete for food with larger nestmates. however, cowbird chicks may benefit from smaller nestmates as they increase food provisioning by parents and the cowbird chicks secure most extra provisioning. we investigated whether egg-peckin ... | 2012 | 22119844 |
| partial host fidelity in nest selection by the shiny cowbird (molothrus bonariensis), a highly generalist avian brood parasite. | obligate avian brood parasites can be host specialists or host generalists. in turn, individual females within generalist brood parasites may themselves be host specialists or generalists. the shiny cowbird molothrus bonariensis is an extreme generalist, but little is known about individual female host fidelity. we examined variation in mitochondrial control region sequences from cowbird chicks found in nests of four common argentinean hosts. haplotype frequency distributions differed among cowb ... | 2007 | 17714308 |
| a novel method of rejection of brood parasitic eggs reduces parasitism intensity in a cowbird host. | the hosts of brood parasitic birds are under strong selection pressure to recognize and remove foreign eggs from their nests, but parasite eggs may be too large to be grasped whole and too strong to be readily pierced by the host's bill. such operating constraints on egg removal are proposed to force some hosts to accept parasite eggs, as the costs of deserting parasitized clutches can outweigh the cost of rearing parasites. by fitting microcameras inside nests, we reveal that the neotropical ba ... | 2013 | 23485877 |
| host-parasite coevolution beyond the nestling stage? mimicry of host fledglings by the specialist screaming cowbird. | egg mimicry by obligate avian brood parasites and host rejection of non-mimetic eggs are well-known textbook examples of host-parasite coevolution. by contrast, reciprocal adaptations and counteradaptations beyond the egg stage in brood parasites and their hosts have received less attention. the screaming cowbird (molothrus rufoaxillaris) is a specialist obligate brood parasite whose fledglings look identical to those of its primary host, the baywing (agelaioides badius). such a resemblance has ... | 2012 | 22648157 |
| the shiny cowbird, molothrus bonariensis (gmelin, 1789) (aves: icteridae), at 2,800 m asl in quito, ecuador. | the shiny cowbird, molothrus bonariensis gmelin, 1789, is a brood parasite of hundreds of small-bodied birds that is native to south american lowlands. within the last 100 years this species has been expanding its range throughout the caribbean, towards north america, but has rarely been seen above 2,000 m asl. | 2016 | 27226760 |
| sex differences in retention after a visual or a spatial discrimination learning task in brood parasitic shiny cowbirds. | females of avian brood parasites, like the shiny cowbird (molothrus bonariensis), locate host nests and on subsequent days return to parasitize them. this ecological pressure for remembering the precise location of multiple host nests may have selected for superior spatial memory abilities. we tested the hypothesis that shiny cowbirds show sex differences in spatial memory abilities associated with sex differences in host nest searching behavior and relative hippocampus volume. we evaluated sex ... | 2015 | 26248015 |
| egg-laying behaviour by shiny cowbirds parasitizing brown-and-yellow marshbirds. | we studied the laying behaviour of shiny cowbirds, molothrus bonariensis, parasitizing brown-and-yellow marshbirds, pseudoleistes virescens. shiny cowbirds lay two egg morphs, spotted and white immaculate. brown-and-yellow marshbirds eject the white egg morph but accept the spotted morph. the incidence of parasitism in this host was 66.5%, and half of the parasitized nests had more than one shiny cowbird egg. there was a positive relationship between the number of parasitic events and the availa ... | 1999 | 10512661 |
| the decline of an adaptation in the absence of a presumed selection pressure. | the colonial nesting village weaver (ploceus cucullatus) lays eggs that vary in ground color and pattern, but individual females lay similar eggs each time. tests on captive african stocks have shown that females reject eggs of other cohorts if such eggs are sufficiently different. the village weaver may have evolved rejection behavior and variable eggs in response to cuckoo parasitism in africa. the village weaver was introduced into hispaniola from africa as early as the 18th century. before t ... | 1989 | 28568503 |
| plasma cholinesterase activity in wild birds from undisturbed woodlands in the central monte desert. | plasma cholinesterase activity is a biomarker sensitive to the effect of organophosphate and carbamate pesticides, and its enzymatic levels have been previously unknown for most of the wild birds analyzed in the present study. our objectives were to establish plasma acetylcholinesterase levels in songbirds of 2 undisturbed sites in the central monte desert (argentina). we also examined the influence on cholinesterase activity of age, sex, body condition, feeding and migratory habits, and species ... | 2019 | 31063226 |
| female and male rufous horneros eject shiny cowbird eggs using a mental template of the size of their own eggs. | hosts of interspecific brood parasites often evolve antiparasitic defences, like the recognition and rejection of parasite's eggs. most hosts use differences in coloration and maculation to discriminate between their own and parasitic eggs, but there are a few cases of hosts using the size of eggs as a cue. to recognize parasite eggs, hosts may require the presence of their own eggs and use a discordancy rule or may use a mental template of their own eggs. females are responsible for egg rejecti ... | 2020 | 32473280 |
| parasites of the shiny cowbird, molothrus bonariensis, and the austral blackbird, curaeus curaeus, (passeriformes: icteridae) in chile. | comparative studies of parasites in sympatric bird species have been generally scarce. parasitic infection/transmission can be spread in a number of ways that suggests possible direct and indirect, horizontal transmission between avian hosts. in order to determine whether two sympatric icterids from central and southern chile share their parasite fauna (ecto- and endoparasites), we examined parasites of 27 shiny cowbirds, molothrus bonariensis, and 28 austral blackbirds, curaeus curaeus, includi ... | 2020 | 32609244 |
| sex differences in the use of spatial cues in two avian brood parasites. | shiny and screaming cowbirds are avian interspecific brood parasites that locate and prospect host nests in daylight and return from one to several days later to lay an egg during the pre-dawn twilight. thus, during nest location and prospecting, both location information and visual features are available, but the latter become less salient in the low-light conditions when the nests are visited for laying. this raises the question of how these different sources of information interact, and wheth ... | 2020 | 32980971 |
| variation in multicomponent recognition cues alters egg rejection decisions: a test of the optimal acceptance threshold hypothesis. | the optimal acceptance threshold hypothesis provides a general predictive framework for testing behavioural responses to discrimination challenges. decision-makers should respond to a stimulus when the perceived difference between that stimulus and a comparison template surpasses an acceptance threshold. we tested how individual components of a relevant recognition cue (experimental eggs) contributed to behavioural responses of chalk-browed mockingbirds, mimus saturninus, a frequent host of the ... | 2019 | 30967077 |
| parasitic egg rejection decisions of chalk-browed mockingbirds mimus saturninus are independent of clutch composition. | obligate avian brood parasites lay their eggs in nests of other host species, which assume all the costs of parental care for the foreign eggs and chicks. the most common defensive response to parasitism is the rejection of foreign eggs by hosts. different cognitive mechanisms and decision-making rules may guide both egg recognition and rejection behaviors. classical optimization models generally assume that decisions are based on the absolute properties of the options (i.e., absolute valuation) ... | 2018 | 29372341 |