|
Post by brobear on Jul 9, 2021 15:31:00 GMT -5
Ornimegalonyx. Artwork by Roman Uchytel… The Cuban giant owl or giant cursorial owl is an extinct genus of giant owl that measured 1.1 metres in height. It is closely related to the many species of living owls of the genus Strix. It was a flightless or nearly flightless bird and it is believed to be the largest owl that ever existed. It lived on the island of Cuba. The first fossil specimen was mistakenly described as a bird in the family Phorusrhacidae, in part because the bones were so large. In 1961, Pierce Brodkorb reviewed the findings and placed them properly, with the owls. Remains have been abundant throughout the island, in cave deposits from the Late Pleistocene period (10,000’s of years ago) and at least three nearly complete skeletons have been found. Oscar Arredondo estimated the height of Ornimegalonyx to have been 1.1 meters tall and it probably easily exceeded 9 kilograms. It had very long legs for its size, but was bulky overall and probably short-tailed. The modern owl that most resembles the Cuban giant owl in proportions is probably the dainty burrowing owl, the only surviving owl closely tied to the ground. This implies similar adaptations to the terrestrial lifestyle, but not a close phylogenetic relationship. One of the largest living owl, the Eurasian eagle owl (Bubo bubo), reaches 4 kg in weight, and Peters (page 188) has reported them taking roe deer fawns that weigh 17 kg as prey. This suggests that Ornimegalonyx could have killed prey of 35 kg or more. Modern owls are known to use a pouncing strategy - where they drop from elevated perches onto prey, spreading their wings only just before hitting their target. The modern kakapo (Strigops habroptila) is a flightless island parrot and is convergent, in some ways, with owls. Like Ornimegalonyx, it is the largest and heaviest member of its order, it has reduced wings, and a reduced keel of the sternum, but it can parachute by leaping from trees with its wings outspread, potentially covering several meters at an angle of descent less than 45 degrees. The legs and feet of the Cuban giant owl appear to be very large and powerfully built. This supports the theory that they were strong runners, hence the alternate name, cursorial. The keel of the sternum was reduced and the owl may have been capable of short burst of flight. It is probable that, like a modern wild turkey, the owl only took flight when extremely pressed, more often choosing to run. The Cuban giant owl is believed to have preyed principally on large rodents including Heteropsomys, Capromys, Geocapromys, and Macrocapromys (the size of modern nutria or capybara) and the ground sloths Cubanocnus, Miocnus, Mesocnus, and Megalocnus. It was probably an ambush predator that would pounce on unsuspecting prey with its crushing talons. WORLD OF PREHISTORIC CREATURES:
|
|
|
Post by brobear on Jul 18, 2021 1:14:58 GMT -5
|
|
|
Post by OldGreenGrolar on Jul 18, 2021 18:27:40 GMT -5
Same here with the Australian Budgie which is normally green and yellow but is blue and white using rare mutation.
|
|
|
Post by brobear on Jul 22, 2021 10:37:32 GMT -5
|
|
|
Post by brobear on Jul 22, 2021 10:38:21 GMT -5
*Between the birds, the bats, and the pterosaurs, which ( in your opinion ) were the best fliers? 1- speed. 2- maneuverability. 3- distance / time in the sky. 4- height.
|
|
|
Post by OldGreenGrolar on Jul 25, 2021 18:26:41 GMT -5
*Between the birds, the bats, and the pterosaurs, which ( in your opinion ) were the best fliers? 1- speed. 2- maneuverability. 3- distance / time in the sky. 4- height. Bats and pterodactyls are the most manuverable exceeded only by some species of falcons. Falcons, eagles, and vultures are among the highest flying and longest soaring birds.
|
|
|
Post by tom on Jul 26, 2021 8:04:55 GMT -5
What is the fastest flying bird in the world? If you guessed peregrine falcon you are correct. In a dive it can reach speeds up to 200 mph. Incredible... earthsky.org/earth/fastest-bird/
|
|
|
Post by brobear on Jul 29, 2021 12:17:07 GMT -5
*Between the birds, the bats, and the pterosaurs, which ( in your opinion ) were the best fliers? 1- speed. 2- maneuverability. 3- distance / time in the sky. 4- height. Bats and pterodactyls are the most manuverable exceeded only by some species of falcons. Falcons, eagles, and vultures are among the highest flying and longest soaring birds. Is there any more maneuverable than a hummingbird?
|
|
|
Post by brobear on Jul 29, 2021 15:45:02 GMT -5
|
|
|
Post by brobear on Aug 7, 2021 3:22:40 GMT -5
www.sci-news.com/paleontology/ichthyornis-dispar-brain-09931.html Birds today are the most diverse group of land vertebrates, and understanding why living birds alone among dinosaurs survived the end-Cretaceous mass extinction is crucial to reconstructing the history of life. Hypotheses proposed to explain this pattern demand identification of traits unique to the living birds. However, this identification is complicated by a lack of data from non-avian birds. “Living birds have brains more complex than any known animals except mammals,” said Dr. Christopher Torres, a researcher at the University of Texas at Austin and Ohio University. “This new fossil finally lets us test the idea that those brains played a major role in their survival.”
|
|
|
Post by OldGreenGrolar on Aug 7, 2021 9:50:30 GMT -5
/\ It is really hard to keep track of all bird species. For example just as when you think you have discovered all blue birds, another one appears.
|
|
|
Post by OldGreenGrolar on Aug 7, 2021 9:52:42 GMT -5
|
|
|
Post by OldGreenGrolar on Aug 7, 2021 9:53:37 GMT -5
This little mountain bluebird will always be my fave.
|
|
|
Post by brobear on Aug 10, 2021 6:37:53 GMT -5
|
|
|
Post by OldGreenGrolar on Sept 20, 2021 10:24:33 GMT -5
Surprisingly there is not much difference in size between make and female kestrel.
|
|
|
Post by OldGreenGrolar on Sept 20, 2021 10:26:53 GMT -5
Karearea (male left, female right) - New Zealand falcon -Falco novaeseelandiae The size difference between the male and female falcon is clear in this photo. My series on the falcon Zeason at Zealandia is drawing to a close. The chick is close to fledging now. Perhaps another month to fledge and learn the skills of survival before his parents send him on his way. www.flickr.com/photos/stevex2/6196756171
|
|
|
Post by OldGreenGrolar on Sept 20, 2021 10:28:30 GMT -5
|
|
|
Post by OldGreenGrolar on Sept 20, 2021 10:39:44 GMT -5
Females favour smaller males:Third, sex role differentiation hypotheses focus on the distinct parental roles evident in raptors. They argue that smaller males have been favored for their greater foraging efficiency or superior territorial defense, whereas larger female size allows more effective incubation, larger egg/clutch sizes, and/or better nest defense (Balgooyen, 1976; Hakkarainen and Korpimäki, 1991, 1995; Hakkarainen et al., 1996; Lundberg, 1986; Reynolds, 1972; Selander, 1972). Clearly the intensity of nest defense by brown falcons was unrelated to body size in either sex, and this, along with the fact that small males are the main defender of nest sites in many other raptors exhibiting marked RSD (Andersson and Wiklund, 1987; Simmons, 2000; Wiklund and Stigh, 1983), indicates nest defense is unlikely to influence the maintenance or evolution of RSD in raptor populations. Prey delivery rates by male brown falcons were also unrelated to body size, indicating smaller males were not more effective hunters. Further, larger female brown falcons did not hatch a greater proportion of their eggs or lay larger eggs, indicating increased egg volume is also not likely to be a significant influence upon RSD in raptors. Despite this, female brown falcons with larger feather scores were more likely to fledge nestlings within their brood and had a greater chance of reproductive success, providing some support for the hypothesis that larger female size has evolved to improve a females brooding ability (see Snyder and Wiley, 1976). However, this hypothesis is not likely to provide a general explanation for the existence of RSD in raptors as it cannot explain the degree of dimorphism evident between raptor species, the existence of both RSD and NRSD in species such as the Ninox owl genus, and the lack of RSD in many other bird groups. A possible role of larger feathers in facilitating more successful brooding of young by female brown falcons during inclement weather is more likely to be a consequence of recruitment favoring increasing female structure size, and thus RSD, than the principal factor responsible for the evolution of RSD. Fourth, hypotheses centered around the effects of sexual selection can be divided into two types: those that suggest RSD is maintained by (1) intersexual selection in which females select smaller, more agile males that are capable of performing more attractive display flights and are better hunters (Hakkarainen and Korpimäki, 1991, 1995; Hakkarainen et al., 1996; Jehl and Murray, 1986; Safina, 1984; Simmons, 2000; Widén, 1984); and (2) intrasexual selection that favors an increase in size of females that compete for a scarce resource, a male holding a territory that is ready to breed (Olsen and Olsen, 1984, 1987). This hypothesis posits that male size is driven by natural selection. The results from the present study have demonstrated that smaller male brown falcons were not more successful hunters. Moreover, neither size nor condition-mediated assortative mating with larger females favoring smaller males was apparent within the population (McDonald PG, unpublished data), indicating mate choice was not a primary factor in determining settlement patterns and thus RSD. Most other studies have also failed to find a female preference for small males in field-based assessments (Bowman, 1987; Marti, 1990; Palokangas et al., 1992; Warkentin et al., 1992). Together, these results suggest that the intersexual selection hypothesis does not appear likely to be a significant factor in maintaining RSD. academic.oup.com/beheco/article/16/1/48/205777
|
|
|
Post by OldGreenGrolar on Sept 20, 2021 10:40:33 GMT -5
|
|
|
Post by OldGreenGrolar on Sept 20, 2021 10:43:41 GMT -5
Size and Sex in Raptors.
In most birds, males are larger than females, but in some birds, such as many shorebirds and birds of prey, the reverse is true. No one is certain why there is this "reversed sexual size dimorphism" in raptors, but a number of interesting hypotheses have been advanced. All are based on a well-established correlation this size difference between the sexes is less pronounced in species that pursue sluggish prey than in those that pursue birds. Vultures, whose prey are least agile of all, show little sexual size difference. Mammal-hunting buteos, such as the Red-tailed Hawk, evolved males that are somewhat smaller than females, whereas in bird-hunting accipiters and falcons, females may be half again as heavy as males. One explanation for the females' larger size suggests that it protects them from aggressive males that are well equipped with sharp talons and beaks, and the killer instincts to go with them. According to this theory, over evolutionary time, females have preferred to mate with smaller, safer males -- in fact, the female may have to be able to dominate the male for proper pair bonding to occur and for the male to remain in his key role as food provider to both female and young. Such a system would involve sexual selection for smaller size in males. Bird-hunting raptors are assumed to show aggression most suddenly, and to represent the greatest threat to their mates, and they are the ones exhibiting the greatest size difference. In experimental pairings set up so that male American Kestrels were the larger of the pair, Cornell ornithologist Tom Cade found that the females did not suffer from an avian version of wife abuse. The size difference in kestrels was not very great, however, so this may not be a definitive test of the hypothesis. It seems that while sexual selection may play a role, there probably is more to it. Another hypothesis proposes that the size differences allow the two sexes to hunt different prey and thus reduce competition for food. Competition is thought to be more severe among bird hunters than among other hawks, since their small agile prey are able to flee in three dimensions and are thus effectively scarcer than, say, carrion or ground squirrels. Indeed, there are data indicating that the hunting success of bird-chasing raptors is only about half that of raptors preying on mammals, and only a sixth that of raptors eating insects. Tom Cade has suggested that, for bird eaters, available food supply in the nesting territory can become limiting, making it adaptive for the male to specialize on small prey and for the female to specialize on large prey. The male feeds the female and young at the beginning of the nesting season; the female becomes an active hunter when the nestlings are larger, and the adults then tend to partition the prey resource in their territory. But if reducing intersexual competition for food is the reason for the size difference in raptors, why aren't males sometimes the larger sex? One possible reason is that females need to be larger because they must accumulate reserves in order to produce their eggs. Another is that females do not forage for a substantial period while incubating eggs and brooding young. They avoid the risks of the hunt during that time, but they must rely on the small male to feed the entire family. Small fleet prey, aerial or terrestrial, are more abundant than large sluggish prey, so that over time smaller male bird-eating raptors would be favored over larger, less agile ones, because they would be better providers. For species that take more sluggish prey, however, small males would not be so advantageous, which might explain the relationship between prey speed and the male-female size discrepancy. web.stanford.edu/group/stanfordbirds/text/essays/Size_and_Sex.html
|
|