Turdus Grayi Research Articles

A potential consequence for urban birds’ fitness: Exposed anthropogenic nest materials reduce nest survival in the clay-colored thrush

Urban bird dwellers survive and reproduce in highly urbanized ecosystems. Some individuals adjust to these novel conditions by changing natural nesting materials for artificial materials, thus making nests more conspicuous in the environment. The consequences of using artificial materials for nesting remain poorly understood, especially from a nest-predator perspective. We studied if exposed artificial materials on bird nests affect the daily survival rate in a common dweller species, the clay-colored thrush (Turdus grayi). We used previously collected nests with a different area of exposed artificial materials and placed them with clay eggs on the main campus of the Universidad de Costa Rica. During 12 days of the reproductive season, we monitored the nests using trap cameras located in front of each nest. We found that nest survival decreased as the proportion of exposed artificial materials increased in the nest and, unexpectedly, that the principal predators were conspecifics. Thus, artificial materials used in the outer layer of nests make them more susceptible to predation. The use of artificial materials likely reduce reproductive success and population size in urban clay-colored thrush, but further field experiments measuring the effect of waste in birds' nests on the reproductive success of urban birds are needed.

Nest daily survival rate of six Costa Rican urban birds

The advance of urbanization in Neotropical countries has drastically changed or eliminated extensive areas of natural habitats. Despite these changes, some species breed in cities and adapt to urban conditions. Several variables, such as the type of nest, substrate, and height, as well as the distance to buildings at which nests are constructed, may affect nesting success of birds in urban habitats. Here we tested how these variables affect nest daily survival rate (DSR) of 6 bird species that constructed 3 different types of nests in a high human-density suburb of San José, Costa Rica. The first type includes platform nests built by 3 species of columbids, where at least 1 parent is always present at the nest; the second type includes cup-shaped nests, where both parents can be absent from the nest simultaneously, and is represented by a single species, the Clay-colored Thrush (Turdus grayi); the third type includes closed nests built by 2 species where at least 1 parent is always present. Species with all 3 types of nests display protective behaviors. We quantified nest variables (e.g., type of nest, substrate used to construct the nest, nest height, distance to buildings). The nests differed in their DSR, with a higher nest survival for columbids (3 species; 0.969, SE 0.011), followed by Clay-colored Thrush (0.942, SE 0.009) and closed-nest species (2 species; 0.942, SE 0.028). We found that nesting substrate was the most important variable explaining the DSR in columbids, but none of the variables had a significant effect explaining the DSR in the remaining 2 nest types.

RESPONSES OF POTENTIAL HOST SPECIES TO SIMULATED BRONZED COWBIRD PARASITISM AT TWO SITES IN COSTA RICA

To assign responses of acceptance and rejection of potential hosts to parasitism by the Bronzed Cowbird (Molothrus aeneus), in Costa Rica, 110 egg manipulations were performed at nests of 17 species, from which 10 responses, by three species, were scored as ejections (Pitangus sulphuratus, Cyclarhis juganensis, Turdus grayi) and nests were deserted by three species (Zonotrichia capensis, Arremenops conirostris, Piranga bidentata). None of the artificial eggs removed from nests at which they were accepted exhibited peck marks that would indicate attempted ejection. Additional experiments are necessary to determine whether mixed responses of acceptance and rejection by individuals of the same species is more common in tropical environments.

Human waste used as nesting material affects nest cooling in the clay-colored thrush

The internal temperature of nests largely depends on the materials used in their construction because the characteristics of each material affect the isolation of nest walls. In urban environments, the availability of natural materials for nest building decreases, while the availability of artificial materials increases. Therefore, many urban bird species use more artificial materials for nest building inside cities, which may affect the thermal properties of the nest. We conducted an experiment to measure the effect of artificial materials included as part of the nest structure, on nest thermoregulation. We used as a model, nests of the clay-colored thrush (Turdus grayi), an urban bird species that have been reported using artificial nest materials. In our experiment, we measured how variation in artificial materials mass affects the nest cooling rate in a climate-controlled room. We found that artificial materials increased the cooling rate of clay-colored thrush nests, compared with nests with only natural materials. This result is especially relevant because showed a negative direct effect of the use of artificial material for nest building in birds. Considering that the availability of artificial material is increasing in urban areas, while natural material is decreasing, it is expected that the negative effect of using artificital material for nest construction would increase in the clay-colored thrush and other city bird species.

Say what? On the transmission of acoustic signals in a Neotropical green city

Cities do not only represent noisy systems, but also limit acoustic communication given the complex array of artificial structures through which signals can be trapped or obscured. In this study we performed a field experiment to evaluate the loss of energy of a standardized acoustic emission (generated with notes and a call of the Clay-colored Thrush – Turdus grayi). For this, we emitted the acoustic signal and recovered it at increasing radial distances from 26 fixed emission points (i.e., 10 m, 20 m, 40 m, 80 m, 120 m, 160 m) located across the city of Xalapa (Mexico). Our results show that the emitted signal was not recorded beyond 80 m from the emission point. The number and height of the assessed physical obstacles between the emitted signal and the receiving equipment showed to drive our main result, with built elements representing a major barrier than vegetation ones in terms of the recovered energy of the emitted signal. Interestingly, we found that, for both types of physical obstacles, a height of ~7 m was a common threshold influencing the recovered energy of the emitted signal.

Arizona Bird Committee Report, 2018–2020 Records

From 2018 to 2020 the Arizona Bird Committee reviewed 195 reports and updated the Arizona bird list through 2020, adding two species—the White-throated Thrush (Turdus assimilis) and Clay-colored Thrush (Turdus grayi)—bringing the Arizona state list to 567 species in good standing.

First Record of Total Leucism in the Clay-colored Thrush (Turdus grayi, Aves, Passeriformes, Turdidae)

We present the first record of total leucism for the Clay-colored Thrush, Turdus grayi, and the fourth case of chromatic aberration for this species. From April 2019 to August 2020, we observed an adult individual characterized by a lack of pigmentation with completely white plumage and eyes of normal color. The locality of occurrence corresponds to the tropical humid forest of the Lancetilla Botanical Garden, 250 meters from the city of Tela, on the north coast of Honduras. Documenting these cases in the Neotropical region is important to better understand pigment abnormalities, and studies are necessary to evaluate the survival and reproductive success of birds that present a lack of pigmentation.

The frugivory network properties of a simplified ecosystem: Birds and plants in a Neotropical periurban park.

Frugivory networks exhibit a set of properties characterized by a number of network theory‐derived metrics. Their structures often form deterministic patterns that can be explained by the functional roles of interacting species. Although we know lots about how these networks are organized when ecosystems are in a complete, functional condition, we know much less about how incomplete and simplified networks (such as those found in urban and periurban parks) are organized, which features are maintained, which ones are not, and why. In this paper, we examine the properties of a network between frugivorous birds and plants in a small Neotropical periurban park. We found a frugivory network composed of 29 species of birds and 23 of plants. The main roles in this network are played by four species of generalist birds (three resident, one migratory: Myiozetetes similis, Turdus grayi, Chlorospingus flavopectus, and Dumetella carolinensis) and three species of plants (one exotic, two early successional: Phoenix canariensis, Phoradendron sp., and Witheringia stramoniifolia). When compared to reference data from other locations in the Neotropics, species richness is low, one important network‐level metric is maintained (modularity) whereas another one is not (nestedness). Nestedness, a metric associated with network specialists, is a feature this network lacks. Species‐level metrics such as degree, species strength, and module roles, are not maintained. Our work supports modularity as the most pervasive network‐level metric of altered habitats. From a successional point of view, our results suggest that properties revealed by species‐level indices may be developed at a later time, lagging the acquisition of structural elements.

Passage Through a Bird’s Gut Confers a Germination Head Start to the Seeds of the Nightshade Witheringia stramoniifolia

In frugivory networks, birds offer plants the advantage of dispersing their seeds away from the parent plants in exchange for macronutrients, primarily sugars, and water. The benefits for birds are clear, as they obtain food and water from fruits, and highly variable for plants, as birds may act in ways that vary from effective dispersers to seed predators. We studied two common species that interact frequently in the frugivory network of a Neotropical, periurban park: The clay-colored thrush ( Turdus grayi) and a nightshade ( Witheringia stramoniifolia), in order to evaluate the advantage of passing its seeds through a bird’s gut. We set up an investigation using captive thrushes that we fed with fruits of W. stramoniifolia. We had four experimental treatments: in two of them, seeds that had passed through the digestive tract of thrushes were germinated under greenhouse and controlled conditions; in the remaining two treatments, we germinated seeds that were not consumed by thrushes and were likewise germinated under greenhouse and controlled conditions. W. stramoniifolia seeds consumed by birds had a germination onset that was 1 to 2 weeks earlier than nonconsumed seeds. Mean germination rate and final germinability, however, did not differ significantly among treatments. In our study, passage through a bird’s gut accelerates the germination onset of seeds, an advantage that possibly enhances seedling establishment, but is not indispensable, for the dispersal of W. stramoniifolia. This bird–plant relationship ultimately accounts to a true mutualism.

Aspectos de la Biología de Psarocolius decumanus y Turdus grayi en la Estación Agraria Cotové, Santa Fé de Antioquia, Colombia

Se estudiaron aspectos de la biología de la oropendola crestada Psarocolius decumanus y la mirla parda Turdus grayi en la Estación Agraria Cotové de la Universidad Nacional de Colombia. La estación está ubicada en el municipio de Santa Fe de Antioquia, área geográfica del bosque seco tropical. La Estación funciona con un sistema silvopastoral, que integra el uso de árboles y pastizales en la producción ganadera, conservando así hábitats para especies silvestres. Se realizaron seis muestreos de campo entre diciembre de 2009 y octubre de 2010, cada dos meses. Se realizaron registros de la presencia de estas dos especies en los diferentes hábitats disponibles. De esta manera se hizo evidente el papel que los fragmentos de bosque y los sistemas de silvopastoreo desempeñan en favor de la conservación de la diversidad de aves, y en particular de la oropéndola crestada y la mirla parda. Psarocolius decumanus y Turdus grayi utilizan la Estación Agraria como lugar de forrajeo y predominan en bordes boscosos. Las dos especies son muy susceptibles a la perdida y fragmentación del bosque natural y a la transformación de estos ecosistemas en tierras dedicadas a la agricultura y ganadería, principalmente la oropéndola crestada especie que no registró actividad reproductiva durante el estudio. Por su parte, Turdus grayi registró actividad reproductiva en los meses de abril y junio de 2010.

Video Surveillance of Nesting Clay-colored Thrushes in South Texas

Video Surveillance of Nesting Clay-colored Thrushes in South Texas

Leucismo parcial del yigüirro (Turdus grayi) en la Estación Biológica La Selva, Costa Rica

Las anormalidades pigmentarias en aves son escasas en estado silvestre pero comunes en ambientes modificados por impacto antropogénico. Reportamos un caso de leucismo parcial en el yigüirro (Turdus grayi) en la Estación Biológica La Selva, Costa Rica. El yigüirro es un ave de amplia distribución geográfica, común en hábitats con diversos grados de alteración por cambio de uso de suelo en bosques tropicales desde México hasta Colombia. Los reportes de casos de aves con anormalidades pigmentarias contribuyen para una mejor interpretación del fenómeno como su frecuencia y detección de poblaciones y localidades donde ocurren estas alteraciones.

Nestling feeding, nest success, and notes of parental care in the Clay-colored Thrush (Turdus grayi): the role of females and males

ABSTRACT Females often invest more in parental care than males, but in socially monogamous systems, males invest as much as females in caring for their offspring, and male contribution is believed essential for reproductive success in these systems. Here we describe the number of visits, the feeding rate to their nestlings, and the time on the nest invested by each sex of the socially monogamous songbird, the Clay-colored Thrush (Turdus grayi), for 16 nests in San Jose, Costa Rica. Both males and females fed their nestlings at a similar rate, but females visited the nests more frequently than males. The feeding rate of both females and males was also similar when controlled by age of nestling. The feeding rate was highly variable across males (minimum 1, maximum 15 visits per 2 h), possibly related to the probability of males fathering the offspring of the attended nest. Females spent more time on the nest than males, but males tended to remain near the nest to defend it from predators. Moreover, male con...

Riqueza de especies y abundancia de aves residentes y migratorias en parques urbanos de San José, Costa Rica

Con la excepción de unas pocas ciudades grandes, hay poco conocimiento sobre las aves urbanas de América Latina. Utilicé transectos lineales en 15 parques urbanos en la ciudad de San José entre setiembre y diciembre de 2009 y encontré 40 especies, la mayoría Tyrannidae (n=10) y Parulidae (n=9). Hubo 23 residentes (principalmente Tyrannidae), 15 migrantes del norte (en su mayoría Parulidae) y un migrante del sur. Las especies más representativas fueron Contopus sp. y Setophaga petechia. Zenaida asiatica, Turdus grayi y Quiscalus mexicanus estaban muy extendidos, al igual que la paloma Columba livia, que podía llegar a 122 individuos por parque. La diversidad y la abundancia fueron determinadas por el tamaño del parque, la complejidad de la vegetación y la proximidad a los fragmentos de vegetación. Los parques urbanos están siendo utilizados como áreas transitorias y permanentes por las aves migratorias y las características biofísicas de algunos parques favorecen a Columba livia y Quiscalus mexicanus, generando competencia, depredación y desplazamiento de otra especie, así como daños a la infraestructura. Estas áreas verdes podrían usarse para la observación y educación de aves.

Depredación oportunista sobre Turdus grayi (Passeriformes: Turdidae) por Dasyprocta punctata (Rodentia: Dasyproctidae) en San Vito, Costa Rica

El 05 de junio de 2016 (08h00), observamos un evento de depredación de este roedor sobre un ave canora en el Jardín Botánico Wilson de la Estación Biológica Las Cruces en San Vito, Provincia de Puntarenas, Costa Rica (8.785, -82.95916;1200 msnm). Inicialmente un macho de D. punctata se alimentaba de frutos y raíces, pero repentinamente tras desplazarse sigilosamente se abalanzó sobre un pichón de yigüirro o mirlo pardo (Turdus grayi). Tras capturarlo con sus patas delanteras, el roedor lo mató con sus dientes incisivos, y posteriormente se desplazó algunos metros hasta empezar a consumirlo (Figura 1). La posiciónque usó la Guatusa para depredar y posteriormente consumir el ave es la misma que usa para alimentarse de semillas; sentándose en sus patas traseras y manipulando el alimento con las delanteras (Mora & Moreira 1984). Tras unos 15 minutos el roedor había consumido parte del ave incluyendo músculos, vísceras e incluso su cabeza. Finalmente, el roedor huyó sin dejar restos de la presa en el sitio al llevarse parte de la carcasa en el hocico

Song plasticity over time and vocal learning in clay-colored thrushes.

Songbirds have been traditionally classified into close-ended or open-ended learning species according to the length of the sensitive period during which birds are able to memorize new vocalizations. Closed-ended learners are generally not capable of changing their song after the first year of life, while open-ended learners show song plasticity as adults. A few Turdus species have been suggested to be open-ended learners, but no long-term study has been conducted to investigate their song plasticity over time. We analyzed the songs of clay-colored thrushes, T. grayi, over four successive breeding seasons to assess song plasticity in their syllable repertoires within and between breeding seasons. A total of 16,262 syllables were classified through visual inspection of spectrograms and multidimensional scaling analysis based on spectrogram correlations. On average, 563±153 (SD) syllables per male per breeding season were analyzed. Male repertoire size was 9-20 syllable types. Males were capable of modifying their syllable repertoire between the initial and final periods of the breeding season. Song plasticity within breeding seasons may be associated with imitation between neighboring males, suggesting song learning in males that were ≥2years old. This short-term plasticity is not enough, however, to explain the high proportion of change (mean=65% syllable types) in repertoire composition between breeding seasons in adult males. Song plasticity resulting from annual changes in repertoire composition could be explained by open-ended learning, but another mechanism, extended memory and re-expression, could also explain long-term plasticity. Experimental studies controlling the acoustic environment are needed to determine which mechanism is responsible for such a high level of song plasticity.

Does low daily energy expenditure drive low metabolic capacity in the tropical robin, Turdus grayi?

Temperate and tropical birds possess divergent life history strategies. Physiological parameters including energy metabolism correlate with the life history such that tropical species with a slower 'pace of life' have lower resting and maximal metabolic rates than temperate congeners. To better understand the physiological mechanisms underlying these differences, we investigated the relationship of metabolic capacity, muscle oxidative capacity and activity patterns to variation in life history patterns in American robins (Turdus migratorius), while resident in central North America and Clay-colored robins (Turdus grayi) resident in Panama. We measured summit metabolism [Formula: see text] in birds from both tropical and temperate habitats and found that the temperate robins have a 60% higher metabolic capacity. We also measured the field metabolic rate (FMR) of free-living birds using heart rate (HR) telemetry and found that temperate robins' daily energy expenditure was also 60% higher. Thus, [Formula: see text] and FMR both reflect life history differences between the species. Further, both species operate at a nearly identical ~50% of their thermogenic capacity throughout a given day. As a potential mechanism to explain differences in activity and metabolic capacity, we ask whether oxidative properties of flight muscle are altered in accordance with life history variation and found minimal differences in oxidative capacity of skeletal muscle. These data demonstrate a close relationship between thermogenic capacity and daily activity in free-living birds. Further, they suggest that the slow pace of life in tropical birds may be related to the maintenance of low activity rather than functional capacity of the muscle tissue.

Host Selection of Potential West Nile Virus Vectors in Puerto Barrios, Guatemala, 2007

The selection of vertebrate hosts by Culex mosquitoes relative to West Nile virus (WNV) transmission in neotropical countries such as Guatemala is not described. This study determined the feeding patterns of Cx. quinquefasciatus and Cx. nigripalpus and estimated the relative contribution of two common and frequently infected wild bird species, Turdus grayi and Quiscalus mexicanus, to WNV transmission. Engorged mosquitoes were collected from rural and urban habitats after the dry and wet seasons in the Department of Izabal in 2007. Host selection by Cx. nigripalpus varied significantly between urban and rural habitats. Both Cx. quinquefasciatus and Cx. nigripalpus fed predominantly on chickens and other domestic animals. Blood meals from wild birds were rare, accounting for 1.1% of blood meals identified from Cx. quinquefasciatus and 6.5% of blood meals from Cx. nigripalpus. Transmission of WNV by these two mosquito species may be dampened by extensive feeding on reservoir-incompetent hosts.

Repertoire Size and Syllable Sharing in the Song of the Clay-Colored Thrush (Turdus grayi)

Song repertoire size and extent of song sharing provide information about social interactions that occur in songbird species. We recorded the songs of eight male Clay-colored Thrushes (Turdus grayi) in San José, Costa Rica during the 2008 breeding season. We classified 695 songs and 5,032 syllables using visual inspection of spectrograms and spectrogram correlation analysis to measure repertoire size and syllable sharing among a local group of males. Male repertoire size was 10–17 syllable types. Males shared on average 28 ± 15% (SD) syllable types from their repertoires with other males, but a larger proportion of syllable types remained unique to particular males. Extent of repertoire sharing and distance between singing males were not related. Presence of shared and individually unique syllables in the repertoires indicate that imitation, and perhaps improvisation, contribute to development of the song of Clay-colored Thrushes.

West Nile Virus Infection of Birds, Mexico

West Nile virus (WNV) has caused disease in humans, equids, and birds at lower frequency in Mexico than in the United States. We hypothesized that the seemingly reduced virulence in Mexico was caused by attenuation of the Tabasco strain from southeastern Mexico, resulting in lower viremia than that caused by the Tecate strain from the more northern location of Baja California. During 2006-2008, we tested this hypothesis in candidate avian amplifying hosts: domestic chickens, rock pigeons, house sparrows, great-tailed grackles, and clay-colored thrushes. Only great-tailed grackles and house sparrows were competent amplifying hosts for both strains, and deaths occurred in each species. Tecate strain viremia levels were higher for thrushes. Both strains produced low-level viremia in pigeons and chickens. Our results suggest that certain avian hosts within Mexico are competent for efficient amplification of both northern and southern WNV strains and that both strains likely contribute to bird deaths.