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Observations at a Nest of the Black-and-White Hawk-Eagle
... Diet and hunting tactics are poorly described, but it is known to feed manly upon reptiles and birds caught in the canopy by long flights from perches or by stooping from the sky (Willis, 1988;Robinson, 1994). Its breeding behavior is known only by observation of few nests (Brown & Amadon, 1968;Strauch, 1975;Anderson et al., 2004;Canuto, 2008b;Phillips, 2009;Canuto et al., 2012). ...
... The Black Hawk-Eagle and Ornate Hawk-Eagle were extensively studied during the Maya Project, which was developed by The Peregrine Fund in Belize and Guatemala during the 1980s and 1990s, and which acquired much information about their diet, breeding biology, habitat requirements, territory size, and so on (Whitacre et al., 2012a,b). Most of the biology of Black-and-white Hawk-Eagle is basically unknown (Strauch, 1975;Willis, 1988;Robinson, 1994;Canuto, 2008b;Kohler & Rezinni, 2013;Menq, 2015 My objective in this paper is to present novel information about these three species of hawk-eagles at the southern limits of their distribution in the Atlantic Forest in southern Brazil. Here I present estimates of the distribution and abundance of these three hawk-eagles in the states of Rio Grande do Sul and Santa Catarina, and report observations about the breeding biology, diet and behavior of Ornate and Black-and-white Hawk-Eagles. ...
... The copulation observed in mid-July at BGHPS fits with Canuto's (2008b) observation, suggesting that Black-and-white Hawk-Eagle starts it breeding cycle during the winter in the Southern Hemisphere. Also fits with observations in Central America, where breeding starts at the end of the rainy season (September; Strauch, 1975) and beginning of the dry season (January and February; Anderson et al., 2004, Phillips, 2009, since winter corresponds with the dry season for most of Brazil. ...
Neotropical hawk-eagles (Spizaetus spp.) are large forest raptors, having low population densities and high sensitivity to human disturbance. The three species of Brazil’s Atlantic forest (S. ornatus, S. melanoleucus, S. tyrannus) are threatened and little is known of many aspects of their biology, such habitat requirements, nesting behavior, and food habitats. Here I present data about the breeding biology, diet and behavior of the Ornate Hawk-Eagle (S. ornatus; OHE) and the Black-and-white Hawk-Eagle (S. melanoleucus; BWHW), and estimations of distribution - extent of occurrence (EOO) - and population sizes for the three hawk-eagles of the southern Atlantic Forest. I compiled data from nine years of field studies done in Rio Grande do Sul and Santa Catarina combined with data from the literature (n = 191 records). I calculated the total amount of forest available for each species by GIS analyses and estimated population sizes based on species density data from the literature. The EOO was 123,551 km² for BWHE, 92,512 km² for OHE, and 67,824 km² for Black Hawk-Eagle (S. tyrannus; BHE). All species experienced more than 30% shrinkage in their historical distribution (before the year 2000). Forest remnants comprise 32% of BHE’s EOO and around 20% for other hawk-eagle species. Population sizes estimated for the southern region were 869 pairs for BHE (1,684 individuals), 1,532 pairs for BWHE (2,849 individuals), and 2,020 pairs for OHE (1,192 individuals). Population size estimates based only on forest patches larger than 10 km² were 542 pairs for BHE (RS = 48 pairs; SC = 494 pairs), 818 pairs for BWHE (RS = 67 pairs; SC = 751 pairs), and 1,178 pairs for OHE (RS = 67 pairs; SC = 1,111 pairs). I recorded displays and copulation of BWHE in July; the nest was built in an inaccessible, emergent tree in the hillside of a valley. Two nests of OHE were found in emergent trees (20 m and 30 m height) measured 138 x 115 x 45 cm and 132 x 100 x 100 cm; one egg was found (64.5 x 51.1 mm). Spizaetus seems to have very variable breeding cycles and begin breeding in the austral winter. I estimated egg laying occurs from July to September with fledging happening 3-4 months later. Diet of OHE consisted mostly of birds (90%) but also some mammals. Individuals of Spizaetus require large, unbroken forest areas to live, and my data reinforce the critical situation of hawk-eagles in southern Atlantic forest. All three species have lost habitat and their distributions have shrunk over the past decades. The estimated population sizes suggest concern and a need for conservation actions. Conservation of large raptors in the Atlantic Forest is not a simple task, requiring the need to preserve and limit the disturbance of remaining forests, establish connectivity among fragments and reduce direct threats to raptors (e.g., persecution). We also need to better understand the ecological requirements of hawk-eagles and establish public policies to protect both species and their habitats.
... Its breeding biology and nest have not yet been described in Brazil. Strauch (1975) pub-lished the only work describing some features of a nest site, found in Panamá. ...
Primeira descrição do ninho do Gavião Pato (Spizaetus melanoleucus) na Floresta Atlântica Brasileira, sudeste do Brasil.
El estudio de sitios reproductivos es de especial importancia para entender los requerimientos de hábitat y el comportamiento de especies, y para planear estrategias de conservación eficientes. Realizamos una revisión bibliográfica de la localización de los nidos conocidos del Águila Viuda (Spizaetus melanoleucus) para el continente Americano. Luego reportamos el primer nido activo con reproducción exitosa de esta especie para la Argentina. El primer nido descubierto fue en Panamá en 1972, pero la primera descripción completa fue 36 años después en Brasil. Encontramos que hasta el momento se conocían 17 nidos. La plataforma de nidificación encontrada en Argentina se descubrió en octubre de 2019 el Parque Provincial Salto Encantado, en la provincia de Misiones. El 13 de octubre de 2022 se confirmó la presencia de un pichón de 20-25 días de edad y una hembra adulta en el interior del nido, ubicado en un Sabuguero (Aralia warmingiana) de 25 m de altura en la ladera de un valle de pendiente pronunciada, que lo destaca del dosel. En el siguiente monitoreo, en noviembre de 2022 se observó al pichón con 60 días de edad realizando vuelos en la cercanía del nido junto a sus padres. El descubrimiento de este sitio de nidificación es de importancia para tomar medidas directas para la conservación de la especie. El estudio de las variables ambientales del sitio y el comportamiento reproductivo de estos individuos generará información importante para mejorar la detección de sitios de interés y plantear estrategias de conservación eficientes para esta especie amenazada.
The two main ecological groups of Amazonian forest birds consist, respectively, of species inhabiting the terra firme forest and of species inhabiting vegetation zones along the river courses (sandbar scrub, riveredge forest, flood forest). Species in both groups are either rather widespread or fairly localized in distribution. Localized species of both ecological groups cluster in several areas of endemism located in peripheral portions of Amazonia (Napo, Inambari, Imerí, Rondônia, Guiana, Belém).
Broad river courses are formidable barriers to dispersal for bird species of the forest interior but are insignificant barriers for birds of the forest canopy and for species inhabiting the vegetation zones along river courses.
Geographical exclusion of numerous parapatric members of species pairs along well defined contact zones probably is due to ecological competition, although no field studies have been carried out so far to substantiate this assumption. Some of the regionally parapatric species are sympatric in certain areas and here occupy different habitats (terra firme forest and várzea forest, respectively).
Birds of the forest interior are restricted to varyingly narrow vertical feeding zones, especially near the forest floor and in the canopy. Insect eaters use much time in the search of their more or less evenly and rather thinly spread prey. This may be the reason why they are mostly monogamous and territorial. In contrast, most fruiteating birds are able to satisfy their daily food requirements in a short time. This was probably an important precondition for the development of arena courtship systems in some families of fruiteating birds. In view of their role as effective seed dispersal agents birds are important for the maintenance of the spatial heterogeneity and taxonomic diversity of humid tropical forests.
The main breeding season of birds along the Amazon River and in southern Amazonia falls in the months of the southern spring (September–November). A less conspicuous increase of breeding activity has been recorded near Manaus in central Amazonia during January and February and near Belém at the mouth of the Amazon River during the months May–June. Going north from central Amazonia, the subordinate peak of breeding activity during the first half of the year probably becomes increasingly more conspicuous until it represents the main breeding season as is the case in northern South America (Venezuela, Trinidad, Guyana).
The current knowledge of the phenology and ecological background of periodical migrations of certain Amazonian forest birds is still very meagre. These migrations indicate that the food supply of the species involved becomes temporarily uncertain in their breeding areas. Birds which inhabit river margins and islands or which fish in shallow water retreat to other portions of the Amazon river system during periods of high water level in their home range. Only few migrant birds from the north Temperature Zone spend the winter in Amazonia where they are restricted to secondary vegetation and forest borders.
The bird fauna of the open vegetation formations (campina, caatinga) is relatively poor in species number compared to the forest avifauna. Among waterbirds ducks (Anatidae) are represented in Amazonia by less species than in extratropical areas. On the other hand, local forest bird communities in Amazonia are 5–6 times richer in species than those of north Temperate Zone forests. However, individual Amazonian species are comparatively rare. On a test plot in upper Amazonia, species of median abundance had a density of only three pairs per 100 ha. More than 100 species in this community were represented by fewer pairs per 100 ha. A forest reserve of 30 km2 would be required to protect a minimum population of 100 pairs of the species of median abundance. Larger areas are needed for the numerous rarer species. The size of forest reserves to protect raptors and seminomadic fruiteaters with particularly low population densities is estimated at several thousand km2.
Some of the ecological mechanisms responsible for the maintenance of the high tropical species richness are the formation of narrower ecological niches compared to species of the higher latitudes as well as the occurrence of a higher number of predators in the tropics which keep the population densities of the various prey species low. The historical cause of the development of the high tropical species richness was a prolific species differentiation probably combined with a relatively lower extinction rate of the species compared to the faunas of the higher latitudes. In this way species in tropical faunas may have “accumulated” during the course of the Tertiary and Quaternary periods, i. e. over the last 60 Million years.
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