English - Cattle Tyrant
Portugueses - Suiriri-cavaleiro
Latin - Machetornis rixosa
The Cattle Tyrant is a species of bird in the tyrant-flycatcher family Tyrannidae. It is the only member of the genus Machetornis. The relationships of this species and other species in the tyrant flycatcher family is uncertain.
In colour the Cattle Tyrants resemble many other species in the Tyrannidae family. Cattle Tyrants are a long legged and short winged flycatcher with brown upper-parts, a grey crown, a thin dusky eye stripe, with yellow underparts. They are about 20 cm in length and weigh up to 40 grams.
The Cattle Tyrant has a disjunct distribution. It is found in Argentina, Bolivia, Brazil, Colombia, Ecuador, Panama, Paraguay, Uruguay and Venezuela. Its natural habitats are drier open and semi-open habitats, savannah, pastureland, parkland, agricultural land and even gardens. They avoided forested and wooded areas.
Cattle Tyrants are Insectivore and usually forages in pairs or in small groups. They are semi-terrestrial, they run rapidly along the ground with an upright posture chasing prey. They feed on insects, mostly from the ground. They may follow cattle or other large animals, catching flushed up prey, or even hitch rides on these animals, and then snatching flushed up prey with a quick sally-flight. The Cattle Tyrant can also be seen hunting biting horseflies attempting to land on capybaras.
During the breeding season Cattle Tyrants build a bulky spherical nest of grass high off the ground, or, they have been known to steal the nests from other birds. The female lays 3 to 4 eggs and incubated them for 14 days. The chicks fledge after 15 days.
Cattle Tyrants are not globally threatened and are “Fairly common to common”. They can easily adapt to converted habitat. Due to deforestation, the Cattle Tyrant has recently colonised areas where it was previously absent, such as northeast Ecuador. They are classed as a species of “least concern”.
Photo No. 1 was taken at Praia da Costa - Vila Velha - Espirito Santo
Photo No. 2 was taken at Foz do Iguacu - Parana
Photo No.3 was taken at Parque Barigui - Curitiba - Parana and shows 2 Cattle Tyrants feeding on the back of a Capybara.
English - Boa Constrictor
Portuguese - jiboia-constritora
Latin - Boa Constrictor
There are several species of boas, but the most common is the Boa Constrictor. Boa Constrictors are non-venomous snakes famous for their method of subduing prey: squeezing, or constricting them to death. Though they are not as long as their relatives, anacondas and reticulated pythons, Boa Constrictors rank among the longest snakes in the world. The Boa Constrictors scientific name is ”boa constrictor”. It is unusual for a species’ English name to be the same as its scientific name.
Boa Constrictors are an exclusively New World species. They are found in tropical Central and South America. Boa Constrictors occupy a variety of habitats. Primary habitat is rainforest clearings or edges. However, they are also found in woodlands, grasslands, dry tropical forest, thorn scrub, and semi-desert. Boa Constrictors are also common near human settlements and often found in agricultural areas. They are commonly seen in or along streams and rivers in appropriate habitats. Boa Constrictors are semi-arboreal, although juveniles tend to be more arboreal than adults. Like their anaconda cousins, they are excellent swimmers, but prefer to stay on dry land, living primarily in hollow logs and abandoned mammal burrows. Boa Constrictors are nocturnal or crepuscular, though they bask in the sun to warm themselves in cool weather. They periodically shed their skins. Female boa constrictors are larger than males.
Boa Constrictors have some of the most distinctive markings of all reptiles. Depending on the habitat, they try to blend into their surroundings. Their bodies can be tan, green, red, or yellow, and display cryptic patterns of jagged lines, ovals, diamonds, and circles. Significantly smaller than anacondas, Boa Constrictors can grow up to 4 meters in length and weigh more than 45 kilograms. Their jaws are lined with small, hooked teeth for grabbing and holding prey while they wrap their muscular bodies around their victim, squeezing until it suffocates.
Boa Constrictors tend to be ambush predators. They will sit and wait from a desired tree perch or burrow and wait for prey to come along. They will eat almost anything they can catch, including small mammals like rats, squirrels and mice. They will also feed on lizard, birds and bats. The bigger Boa Constrictors can take monkeys, wild pigs and small deer. Their jaws can stretch wide to swallow large prey whole.
Male Boa Constrictors are polygynous; each male can mate with multiple females. Females may also have more than one mate in a season. Females are usually widely scattered and courting males must invest energy into locating them. Most female Boa Constrictors do not appear to reproduce annually. They are likely to become reproductive only when they are in good physical condition. Female Boa Constrictors incubate eggs inside their bodies. The gestation period lasts around 4 to 8 month and they can give birth to around 60 live hatchlings. Once born, the hatchlings are fully independent. Their length is around 2 feet at birth and their appearance doesn’t change much as they age, though their colours may fade a bit.
With the high demand for Boa Constrictors skins and meat in the past and now with the over collection of Boa Constrictors for the pet trade and the needless persecution of them has had an impact on some Boa Constrictor populations in the wild. Some populations have been hit harder than other, and various wild populations are now endangered, particularly those on offshore islands. Furthermore, habitat loss and road mortality have also reduced populations. Boa Constrictors are not listed on the International Union for Conservation of Nature’s Red List of Threatened Species. However, they are on the Convention on International Trade in Endangered Species (CITES) Appendix II, which means they are not currently under threat of extinction but that may change if the trade of these animals is not carefully controlled.
Photos of the Boa Constrictors were taken at Parque das Aves - foz do Iguacu - Parana.
English - Screaming Cowbird
Portuguese - Vira-bosta-picumã
Latin - Molothrus rufoaxillaris
The Screaming Cowbird is an obligate brood parasite belonging to the Icteridae family of birds. It is also known commonly as the short billed cowbird.
The Screaming Cowbird has a mildly iridescent black plumage; the lesser under-wing coverts are rufous. The female is slightly duller in colour than the male. The legs are black and the iris is reddish brown. Adult body length is around 21 cm in length and weighs up to 58 g. The call of the Screaming Cowbird was first described as “impetuous screaming notes”, however, a more useful description for field identification is noisy, explosive and piercing with rasp like calls. Screaming Cowbirds are mostly seen in pairs or small flocks.
The Screaming Cowbird is found in South America. It is found In parts of Argentina, Bolivia, Brazil and throughout Paraguay and Uruguay. Its natural habitat is pastureland but can also can be found in open areas in cities, parks, gardens, etc.
Similar to other species of cowbirds, the Screaming Cowbird forages predominantly on the ground, eating invertebrates such as spiders and a variety of insects that have been disturbed by grazing stock. where it forages amongst grazing animals such as cows, hence the name “cowbird”.
Screaming Cowbirds are monogamous and form stable pairs for the duration of the breeding season. As obligate brood parasites, they do not build their own nests, and instead, parasitise the nests of other species, predominantly the Bay-winged Cowbird.
Most Bay-winged Cowbird nests are parasitised by the Screaming Cowbird. The Screaming Cowbird is also known to parasitise the nests of Brown and Yellow Marsh bird and the Chopi Blackbird. Screaming cowbird eggs are spotted like those of their main host, the Bay-winged Cowbird, but do vary in shape, background colour and markings. Although this may be obvious when they appear in the host nest during pre-laying, they can be difficult to detect in a nest full of eggs. Screaming Cowbirds can lay 6-20 eggs in a Bay-winged Cowbird nest but usually one pair will lay only 2 eggs in the host nest. Up to 12 female Screaming Cowbirds can parasitise the same Bay-wing Cowbirds nest. Screaming Cowbird adults frequently pierce the eggs of their hosts as well as previously laid parasite eggs. Screaming Cowbirds can distinguish between their eggs and those of other species. The purposes of egg puncture behaviour are not clearly understood but one reason could be to reduce nestling competition and to enhance survival of the Screaming Cowbirds offspring. Screaming cowbirds nestlings deceive their main host with superb visual chick mimicry and calling, in addition, they can beg for longer and at a higher intensity. This more intense begging does not reflect greater hunger demands; instead, reflects a hard-wired behaviour to ensure adequate nourishment and survival. They are the only avian brood parasite to exhibit this trait. There are slight differences in skin and bill colour of nestling Screaming Cowbirds and the host nestlings but this is only obvious for the first 4–5 days. They then remain almost identical in size and appearance until they become nutritionally independent.
The global population size has not been quantified, but this species is described as ‘fairly common’. The distribution of the screaming cowbird has increased significantly in recent decades due to habitat alteration caused by deforestation and by following its hosts into new ranges. It is considered that the Screaming Cowbird is a species “of least concern”.
Photos of the Screaming Cowbird were taken at Parque Barigui - Curitiba - Parana.
