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This study reports on findings about the natural history of the Cloud-forest Pygmy-Owl (Glaucidium nubicola). Recently described as a species, the general ecology of the Cloud-forest Pygmy-Owl remains poorly documented. Three banded individuals at a private reserve in the province of Pichincha, Ecuador, are used to describe its habitat use, diet items, and individual longevity. Our observations suggest this local population prefers wet primary cloud forest and appears to have a generalist diet. Multiple recaptures of a banded individual indicate a longevity record of 5 years. Additionally, ectoparasites were found on 2 out of 3 captured individuals. Received 10 April 2020. Accepted 22 July 2021. Key words: diet, habitat, lifespan, Neotropical owl, parasite, raptor, Strigidae. Este estudio reporta hallazgos sobre la historia natural del mochuelo Glaucidium nubicola. Recientemente descrito como especie, su ecología general se encuentra escasamente documentada. Usamos datos de 3 individuos anillados en una reserva privada en la provincia de Pichincha, Ecuador, para describir su uso de hábitat, ítems de su dieta y longevidad individual. Nuestras observaciones sugieren que esta población local prefiere bosques primarios húmedos y parece tener una dieta generalista. Su longevidad, según múltiples recapturas de individuos anillados, indican un récord de 5 años de edad. Adicionalmente, encontramos ectoparásitos de 2 de los 3 individuos capturados. Palabras clave: búho neotropical, dieta, hábitat, longevidad, parásito, rapaz, Strigidae., Cloud-forest Pygmy-Owls (Glaucidium nubicola) are small, range-restricted owls of the northwestern Andes (Freile and Restall 2018, BirdLife International 2021). Historically, this species was overlooked due to its parapatric distribution and [...]

The Ryukyu Scops Owl, Otus elegans, is distributed over a 1,200-km area, only inhabiting islands. Within this range, I studied this species across 20 continental islands in the Ryukyu Archipelago and two oceanic islands. Although most studies recently use quantitative continuous measurements of many specific aspects of the vocalization, I introduced a new method, 'typological analysis' to visually classify variation of spectrograms according to the shape of syllable in the owl species, examining their dialects in relation to their geographical distribution. In the typological analysis, hoot, syllable, and element types were defined according to the number of syllables, the degree of timescale overlap of the first and second elements in the second syllable, and relative differences of duration and frequency of two elements in the second syllable, respectively. Although frequencies of hoot and element types in each island population were significantly different between the island groups north and south of the Kerama Gap across the archipelago, hoot and element types were shared between the island groups. Furthermore, typological variation occurred in syllable types, however there were no differences in frequencies of syllable types between the island groups. Geographic structure in vocal parameters as steep clines with stepped variation is represented as a dialect. According to the definition, this study found that no unique dialects in hoots occurred between the different island populations of Ryukyu Scops Owls. The Kerama Gap might act as a biogeographical barrier, contributing to the differentiation between owl hoots according to spectrotemporal analyses; however, the typological analysis detected the distribution of typological characteristics of hoots on the small islands north of the Kerama Gap that contradicts this concept of a biogeographical barrier. Because the typological analysis needs to visually examine each individual by careful attention to detail, it is a good method for discovering minor geographic variations and patterns in bird vocalizations. Received 5 August 2012. Accepted 12 November 2012. Key words: biogeography, dialect, Ores elegans, sound spectrogram, typological analysis., Bird song provides a well-documented example of a culturally inherited trait in nonhuman animals (Mundinger 1980). Bird song has a micro-geographic pattern, and the patterns arise mainly from vocal copying [...]

We estimated annual return rate, fidelity, and breeding dispersal in a migratory population of Flammulated Owls (Otus flammeolus) in central Colorado. Return rates, based on capture-recapture histories of 39 males and 52 females from 1981 to 2003, were higher for males (84%) than for females (45%). Annual recapture probability was higher for females, because breeders are easier to capture than nonbreeders and females always attempted to nest, whereas some males were unpaired (did not nest) for up to four years. Territory fidelity was male biased (92%, vs. 56% for females, adjusted for undetected emigration), and mean tenure on territories was more than twice as long for males as for females. Females, but not males, had lower return rates to territories in the year following nesting failure compared with females whose nests were successful. Most males appeared to occupy one territory their entire reproductive lives, countering predictions of habitat-selection models that individuals should move to higher-quality habitats when they become available. We estimated that 74% of pairs retained the same mate in consecutive nesting attempts, but mates that bred together for multiple years had no reproductive advantages over mates that bred together for the first time. In most cases, females dispersed from territories if their mates did not return. When females dispersed, they went to territories where total productivity over the study and lifetime reproductive success of new mates were higher than on original territories, which supports the hypothesis that dispersal by females increases individual fitness. Key words: breeding dispersal, Flammulated Owl, mate fidelity, Otus flammeolus, return rates, site fidelity, territory fidelity. Estimamos la tasa de retorno anual, la fidelidad y la dispersion reproductiva en una poblacion migratoria de Otusflammeolus en el centro de Colorado. Las tasas de retorno, basadas en las historias de captura-recaptura de 39 machos y 52 hembras desde 1981 a 2003, fueron mayores para los machos (84%) que para las hembras (45%). La probabilidad anual de recaptura fue mayor para las hembras, debido a que las aves reproductivas son mas faciles de capturar que las aves no reproductivas y que las hembras siempre procuran nidificar, mientras que algunos machos permanecieron sin pareja (no nidificaron) por periodos de hasta cuatro anos. La fidelidad al territorio estuvo sesgada hacia los machos (92%, vs. 56% para las hembras, ajustado por la emigracion no detectada), y la ocupacion media de los territorios fue mas de dos veces mas prolongada para los machos que para las hembras. Las hembras, no los machos, presentaron tasas de retorno mas bajas a los territorios en el ano que siguio el fracaso del nido, comparado con las hembras cuyos nidos fueron exitosos. La mayoria de los machos parecio ocupar un mismo territorio durante la totalidad de sus vidas reproductivas, contradiciendo las predicciones de los modelos de seleccion de habitat que indican que los individuos deberian moverse a ambientes de mayor calidad cuando estos se vuelven disponibles. Estimamos que el 74% de las parejas mantuvieron el mismo consorte en intentos de nidificacion consecutivos, pero los consortes que nidificaron juntos por multiples anos no tuvieron ventajas reproductivas sobre los que nidificaron juntos por primera vez. En la mayoria de los casos, las hembras se dispersaron de los territorios si sus consortes no retornaron. Cuando las hembras se dispersaron, se fueron a territorios en donde la productividad total a lo largo del estudio y el exito reproductivo total de vida de los nuevos consortes fueron mayores que en los territorios originales, lo que apoya la hipotesis de que la dispersion por parte de las hembras aumenta su adecuacion biologica individual.

In February 2004, we collected 104 long-eared owl (Asio otus) pellets from beneath a large pine tree in northern Wichita, Kansas that served as a winter roost for approximately four [...]

Survival and behavior of 131 radio-tagged tawny owls, Strix aluco during the post-fledging dependency period were studied for each of three yeas with high food abundance and three years of poor food supply in Danish deciduous woods. Thirty-six percent of the young from control broods died between fledging and independence, primarily due to predation from raptors and mammals.

According to Breeding Bird Survey data, grassland birds are among the most imperiled species in North America. Within this group, grassland owls show steep population declines across the United States. Despite these declines, questions still remain regarding the seasonal and geographic distribution of grassland owls. On San Clemente Island (SCI), California, grassland owls are known to occur, but nothing is known about their distribution or abundance. To increase our understanding of owl populations on SCI, we used night-time spotlighting to survey for grassland owls from October 2001 to October 2002. We recorded 733 detections of three species of owls: Barn Owl (Tyto alba), Burrowing Owl (Athene cunicularia), and Short-eared Owl (Asio flammeus). Barn (8.3 ± 0.8 owls/hr) and Burrowing owls (2.2 ± 0.7 owls/hr) were the most frequently detected species, whereas Short-eared Owls were rarely detected (0.2 ± 0.1 owls/hr). We detected owls during all nighttime hours surveyed and detected Barn Owls in every month of the study. We detected Burrowing Owls only from October to March and Short-eared Owls from December to April, suggesting that they are winter visitors. Despite the bias of increased detectability using roadside surveys, spotlighting from a vehicle enabled us to efficiently cover a large proportion of the island (compared to walking surveys) and survey multiple grassland species using one survey technique. Received 8 August 2003, accepted 22 February 2005., Grassland birds are among the most imperiled wildlife in North America (Peterjohn and Sauer 1999, Sauer et al. 2004), and, within this group, owls are considered species of conservation concern [...]

While banding Cactus Ferruginous Pygmy-Owls (Glaucidium brasilianum cactorum) in Arizona, we removed three Protocalliphora sialia (Diptera: Calliphoridae) from the wing margin of one nestling. Subsequent inspection of nest material revealed an additional 119 Hesperocimex sonorensis (Hemiptera: Cimicidae), another hematophagous parasite. All nestlings (n = 3) fledged successfully, but on day 8 postfledging, two fledglings were found dead and one was missing. Although unsubstantiated, the subclinical effect (e.g., anemia) of these hematophagous parasites may have contributed to the fledglings' demise. This is the first published record of P. sialia parasitizing Ferruginous Pygmy-Owls and the first documented infestation of H. sonorensis for nesting Ferruginous Pygmy-Owls. Received 2 August 2004, accepted 23 February 2005., Cactus Ferruginous Pygmy-Owls (Glaucidium brasilianum cactorum, hereafter pygmy-owl) are secondary obligate cavity nesters that require mature trees, including large columnar cacti, for nesting (Proudfoot and Johnson 2000). In March 1997, [...]

Over a seven-year period, we used mark-recapture in a population of Flammulated Owls (Otus flammeolus) in the Zuni Mountains, New Mexico, to estimate adult breeding-site fidelity, mate fidelity, natal philopatry, and dispersal distances. We also used DNA fingerprinting to examine the genetic population structure of Flammulated Owls among four mountain ranges in New Mexico and one range in Utah. Mark-recapture revealed that adults are site-faithful and tend to maintain pair bonds between years, whereas juveniles show little natal philopatry. DNA fingerprinting revealed very low differentiation among populations, even between the New Mexico and Utah ranges, with population subdivision ([F.sub.ST]) estimates ranging from 0.00 to 0.04. Heterozygosity values were high within each mountain range and, together with the low [F.sub.ST] values, suggest that this Neotropical migrant may have long-distance natal dispersal and frequent intermountain dispersal. Received 3 May 2004, accepted 21 October 2004. Key words: dispersal, DNA fingerprinting, Flammulated Owl, gene flow, New Mexico, Otus flammeolus, ponderosa pine, population structure. A 10 largo de un periodo de siete anos, usamos tecnicas de marcado y recaptura en una poblacion de Otus flammeolus en las montanas Zuni, New Mexico, para estimar la fidelidad de los adultos a los sitios de cria, la fidelidad de las parejas, la filopatria natal y las distancias de dispersion. Tambien usamos huellas dactilares de ADN para examinar la estructura genetica poblacional de O. flammeolus entre cuatro cadenas montanosas de New Mexico y una de Utah. El marcado y recaptura revelo que los adultos son fieles a sus sitios y que tienden a mantener vinculos con sus parejas entre anos, mientras que los juveniles muestran poca filopatria natal. Las huellas dactilares de ADN revelaron una diferenciacion muy baja entre las poblaciones, incluso entre las montanas de New Mexico y Utah, con estimaciones de subdivision poblacional ([F.sub.ST]) que oscilaron entre 0.00 y 0.04. Los valores de heterocigocidad fueron elevados dentro de cada cadena montanosa y, junto con los bajos valores de [F.sub.ST], sugieren que este migrante Neotropical puede presentar dispersion natal de larga distancia y dispersion frecuente entre montanas.

We estimated concentrations of fecal reproductive steroid metabolites in free-ranging California Spotted Owls (Strix occidentalis occidentalis) during the breeding season. We collected fresh fecal samples (n = 142) from 65 individual owls in the Sierra Nevada during April-August of 2001. We developed and validated radioimmunoassay procedures to quantify fecal estrogen metabolites and fecal testosterone metabolites. We used an information-theoretic approach to identify factors that might influence fecal estrogen (E), fecal testosterone (T), and fecal estrogen:testosterone ratio (E:T ratio) levels during the owl's breeding season. We hypothesized that factors related to sampling procedures, owl characteristics (sex, reproductive status), and habitat might influence fecal reproductive steroid levels. Our analyses suggested that sampling factors and owl characteristics, but not habitat variables, were related to fecal reproductive steroid levels in Spotted Owls. Our most supported models explained Key words: California Spotted Owl, estrogens, glucocorticoids, noninvasive, testosterone, physiology, Strix occidentalis occidentalis.

We summarized records of hybridization between Barred Owls (Strix varia) and Northern Spotted Owls (S. occidentalis caurina) in Washington and Oregon through 1999. A total of 47 hybrids were observed, including 17 F1s that were first detected as adults, 4 F1s that were banded as juveniles and subsequently recaptured as adults, 10 F1 juveniles, and 16 F2 juveniles. All confirmed cases of hybridization between Barred and Spotted owls involved male Spotted Owls paired with female Barred Owls. Ten F1 hybrids that backcrossed with Barred Owls produced a total of 15 young; 6 F1 hybrids that backcrossed with Spotted Owls produced only 1 young. Those differences may indicate that some combinations of sex and species are more compatible or more fertile than others, but more documentation is needed. Because F2 hybrids and subsequent generations are difficult to distinguish in the field from Barred or Spotted owls, genetic comparisons of blood or tissue samples may be needed to identify hybrids beyond the first generation. The small number of F1 hybrids detected during many years of extensive banding studies of Spotted Owls suggests that the isolating mechanisms that separate Barred and Spotted owls are normally sufficient to avoid hybridization between them. Direct competition between the two species for food and space is probably a much more serious threat to the Spotted Owl than hybridization.

Abstract.--Pellets from a pair of barn owls were collected from May 1995 through May 1996 to identify types of prey taken from coastal prairie and salt marsh habitats on the [...]

Eyespots (color patterns resembling eyes) are present in many taxa and often have important ecological functions. In some taxa, potential functions of eyespots have not been extensively examined, as is the case with pygmy-owls (Glaucidium spp.), many of which bear a conspicuous eye-like pattern on their nape. Using wooden replicas of Northern Pygmy-Owls (G. gnoma), with and without eyespots, we tested one potential function: whether eyespots affect mobbing behaviors of small forest birds. We measured the orientation of mobbing behaviors (where birds perched and flew at the model) and intensity of mobbing bouts (duration of bouts and number of mobbing individuals). Eyespots affected the most proximal behavior, close passing (flights directly at the model, resulting in an approach within 0.5 m). When eyespots were present, mobbers shifted away from eyespots, providing the first empirical evidence for a link between eyespots and avian mobbing.

Plumage patterns of known-sex nestling and juvenile Short-eared Owls were examined to develop a sexing technique. Markings on secondary feathers varied depending on sex, and differences can be observed from around 10-15 days of age. Aging formulas were developed based on mass for nestlings up to 15 days of age and on wing length for older nestlings.

I studied the systematic relationships of the three large owlet-nightjars (Aegothelidae) to determine the taxonomic status of a fawn-colored lowland form currently classified as Aegotheles insignis tatei. I examined most of the existing specimens of A. i. insignis (n = 158) and A. crinifrons (n = 23) and all known specimens of A. i. tatei (n = 4). I also examined specimens of A. albertisi (n = 70), A. archboldi (n = 25), A. bennettii (n = 55), A. cristatus (n = 50), A. savesi (n = 1), and A. wallacii (n = 21). Aegotheles i. tatei was distinguishable from A. i. insignis and A. crinifrons by its small size and in seven plumage characters. Aegotheles i. tatei was further distinguishable from one or the other of these taxa by four additional characters. Unique among owlet-nightjars, A. i. tatei has the shortest tarsi, does not have recurved filamentous tips on its facial feathers, and has stiffer feathers on the auricular area and throat. My search of museums revealed two new specimens of A. i. tatei, expanding the known geographic range of this taxon 1,000 km eastward along the southern coast of Papua New Guinea from the upper Fly River to Nunumai, near the Ulamanu River. Unlike the montane A. i. insignis, A. i. tatei inhabits lowland forests where rivers emerge from foothills of the main cordillera. I propose that tatei be elevated to species status and that the name Starry Owlet-Nightjar be adopted based on the bird's markings. Aegotheles crinifrons, A. insignis, and A. tatei pass through a previously unrecognized but distinctive rufous juvenal plumage. These are the only owlet-nightjars known to exhibit this plumage, which calls for reexamination of generic limits within the Aegothelidae.

A Boreal Owl survey was conducted in the New Mexico and Arizona mountains to determine the bird's distribution patterns, potential habitat in other locales, breeding within occupied habitat and southern breeding limits. The survey was also done to determine residency of the bird in the region. Twenty records of the Boreal Owl between 1987 and 1993 establishes the bird as a resident in the mountain areas of New Mexico.

The Least Pygmy-Owl (Glaucidium minutissimum) complex comprises 10 described taxa that inhabit tropical and subtropical forests. Consistent song differences among taxa in this complex, supported by morphometric, plumage, and habitat data, indicate that, in addition to the recently described G. hardyi and G. parkeri, four species can be recognized in the Least Pygmy-Owl complex: G. palmarum of western Mexico (includes the described subspecies palmarum, oberholseri, and griscomi); G. sanchezi of northeastern Mexico; G. griseiceps of southeastern Mexico, Central America, and the Pacific slope of northern South America (includes the described subspecies griseiceps, rarum, and occultum); and G. minutissimum of southeastern Brazil and adjacent Paraguay. Received 8 Nov. 1993, accepted 9 May 1994., The genus Glaucidium comprises a number of species of small owls widespread in the Americas, Eurasia, and Africa. Four groups of mainland New World Glaucidium are generally recognized: the G. [...]

A new species of pygmy-owl (Glaucidium parkeri sp. nov.) from the eastern slope of the eastern Andes of Ecuador and Peru is described. This subcanopy dwelling species appears to be uncommon in subtropical forest on outlying ridges of the main Andean chain between 1450 and 1975 m elevation. Plumage and vocalizations indicate that it is allied to the Least Pygmy-Owl (G. minutissimum) complex. Received 8 Nov. 1993, accepted 8 May 1994., In 1969 and 1970, John Weske and John Terborgh mist-netted two pygmy-owls along the eastern slope of the Andes in central Peru (Deptos. Ayacucho and Huanuco) that were identified as [...]

A study of hawk-owls in the southwestern Yukon, Canada, revealed prey selection and availability to directly influence the species' population density, thereby indicating the importance of prey composition in specific habitats in their survival. This species sustained itself mainly on voles, including Microtus, and depended on larger prey during nesting stages.

California spotted owls in the Sierra Nevada selected forests withlarger trees and canopy closures of at least 40%. Discriminant function analysis showed that the number of vegetative strata, large-tree basal areas and canopy closure were the most important characteristics of owl microhabitats. The median home range size was 1,439 hectares, similar to that of the northern spotted owl.

The development of a cheap alarm-equipped bow net for capturing wildlife is described. The system is shown to have been effectively used to signal the capture of American kestrels, loggerhead shrikes and pygmy owls in Texas over a three year period.

A conservation strategy for the Northern Spotted Owl (Strix occidentalis caurina) proposes relatively large blocks of habitat suitable for multiple breeding pairs. These habitats should be distributed throughout the current range of the subspecies. They should be separated by distances consistent with observed dispersal distances of juvenile owls. All these should be embedded in a landscape of habitat that allows foraging, resting and cover by birds dispersing between flocks. Researches on important topics of conservation planning must be undertaken to help endangered species.