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21

The joint you are thinking (I assume) of is not a knee, nor is it an elbow, instead it is an ankle which is bending the same way as us humans. You can see from the below diagram that the knee - the joint between the femur and tibia - is just further up the leg normally hidden by feathers. Birds have a comparatively elongated metatarsus which gives the ...


18

The question is all about semantics. One can call reptiles whatever (s)he wants. The question is what do we define as being a reptile? And the answer is that there are two possible definitions, a common "bad" definition (Definition 1) and a phylogenetic-based "good" definition (definition 2). I think your confusion comes from the use of the same term to mean ...


17

Birds have a body part known as the nicitating membrane otherwise known as the "third eyelid". This part has become vestigial in humans, where it remains as the plica semilunaris. This image of a masked lapwing clearly shows its nicitating membrane in action, where it covers the eye in a horizontal motion. This is analogous to blinking in humans, and the ...


16

I just weighed a pigeon tail feather (~10 cm) long. The mass was 0.05 g. Although all tail feathers are not equal in length (and all pigeons are not equal in size), this is probably a good approximation. Measuring the drag coefficient is going to be very challenging, because it will vary with the orientation of the oncoming airflow. A feather falling with ...


14

I looked up winglets so I had context for this answer. I'm interpreting winglets as the vertical tips at the end of airplane wings. If so, then you are correct. The spread primary feathers of soaring birds like eagles function as winglets (Tucker 1993). Airbus has a biomimicry web page devoted to some of the biological designs, including winglets, they ...


12

This looks pretty much like a female zebra finch to me (the male have a more prominent feather pattern). See this picture: These birds are not native in Europe, this is correct. But it is always possible that birds escape captivity (or are released) and the live in countries where they originally not belong. I think this is the case with the zebra finch ...


10

This is a Cattle Egret (Bubulcus ibis), which is a heron in its breeding plumage. When not breeding, the bird is white. See the images for comparision: Breeding cattle egret with colored feathers. Nonbreeding cattle egret, completely white.


10

This phenomenon is called tonic immobility. And those speculations you've mentioned are wrong: they do get back on their feet, only remain in that state for a prolonged time, which depends on the distance and eye contact with whoever laid the chicken on its back, as stated here. From this experiment, it can be concluded, that this behavior in which the ...


9

The logical assertion "winglets have not happened in a long time, therefore they are not advantageous" is incorrect. It is possible for an advantageous trait not to evolve even when advantageous, if there is no "path" to it. The trait only occurs gradually, in small incremental steps. If intermediary steps are harmful, the trait will not occur, even if the ...


8

Most species of birds have 2 foveas, the temporal fovea and the central fovea. temporal fovea, which is like ours in the sense that it looks straight ahead and offers binocular vision (i.e. the temporal foveas of both eyes point in the same direction). But birds also have a central fovea, which points sideways and is, obviously, monocular (i.e., ...


8

There are two possibilites with evolutionary processes: The development either never went into this direction or it brought no advantages. Besides this two possibilities the claims from the other forum are wrong. Birds (not all of them though) do have winglet-like structures. If you look at big birds, you can see feathers on the end of the wings looking like ...


7

Obviously, as you point out, some birds, such as waterbirds (ducks, puffins, auks, sandpipers) are perfectly fine in the rain, as they spend much of their time in the water anyhow and have oil glands that waterproof their feathers. For other birds, rain can increase heat loss. For instance, rain increases metabolism by up to 22% in eagles (Stalmaster & ...


7

I don't know of studies specifically of boat-tailed grackle flight, so I'll focus on elongated tails in general and come back to grackles at the end. Long tails in birds are obviously interesting from the standpoint of sexual selection. Going all the way back to Darwin, one hypothesis has been that females prefer males with long tails. There seems to be ...


6

What does "evolutionary advantageous" mean? First note that is sexual selection evolutionarily advantageous? is a question that makes no sense. An allele or a trait can be evolutionarily advantageous if it increases the fitness of its carrier. If an allele, an evolutionary process or an environmental change decreases the risk of extinction for a species, ...


6

On a more general level it is possible for parents to influence sex-ratio of broods in a number of ways, and there are other reasons why a brood might have a sex ratio distortion. The paper I've been reading this morning is about side-blotched lizards doing just this. I'll give a quick basic answer just from the top of my head and hopefully someone can give ...


4

Richard Dawkins discusses this in his book The Greatest Show on Earth: The Evidence for Evolution. The birds, in the aforementioned example Starlings, 'know' which direction to fly and where to be by obeying simple local rules concerning the distance and spacing of other members of the flock in their immediate vicinity, without any global knowledge of the ...


4

Many birds, especially birds of prey and owls, have eyes that are proportionally much larger than that of similar-size mammals. Most birds cannot move their eyes, as with larger eyes there is little or no room for the required musculature. This, in addition to having two foveas as @The Last Word mentioned, necessitates that a bird move its head to change ...


4

Apart from one isolated group of birds in Australia (i.e., mound nesters found in Australia that use external heat for incubation - see link), all birds incubate their eggs (see link). All species that returned from land to sea have retained their reproductive cycle (marine mammals still give live birth and suckle their young) and still rely on air for ...


4

There are actually a few, the problem with these websites is that they usually cover only a part of all birds on this planet. I use: Bird identifier: Usefull website for a lot of European birds. Backyard Bird Identifier: Useful for some European birds but mostly for North American and Canadian birds. All about Birds: Useful, but needs more knowledge for ...


4

Cant be very sure about ravens but the maximum recorded flight duration is of Alpine Swift — 6 months. Pigeons can fly up to 1800km in a long flight. From this article: In the United States, the longest pigeon races involve flights of 1800 km and, because substantial financial rewards accrue to the owner of the fastest pigeon, there is severe ...


4

I don't know about the specific cues that American robins use for migration. This species is also both a short range (e.g. between states or to lower altitudes) and long range migrant (e.g. Florida & Mexico), so the cues that they use can probably differ between overwintering populations. There are also year-round populations of robins in the US, but ...


3

The order of settling depends on the resource availability in different patches (in your case the difference between high and low quality habitat), but generally speaking, the pattern you observe conforms to the ideal free distribution. The key factor in the ideal free distribution is that habitat patches are filled according to the current resource ...


3

I think it's a kingfisher. Luckily the tail is short. Some are larger, some smaller, yellow-, orange-, or brown-billed, but all with an intense stare, especially when they spot prey.


3

Crows don't lay their eggs in sparrows' nests - they lay them in crows' nests. What you're describing, though, here is brood parasitism. This relieves the parasitic parent of the responsibility of rearing young, building nests, protecting the eggs, etc. Brood parasitism is seen in a number of duck species, with females laying their eggs in the nests of ...


3

I'd go with juvenile striated heron. I ruled out others such as the chinese pond heron because of the spotted wing plumage and slightly different shape of the patch around the eye. The night heron seems to have a more red eye than the striated heron and appears to have a stubbier beak. Arkive is a good place to see a lot of pictures of birds, this is a good ...


3

Following your answer to my comment, I deduced the “yellow” color to be more brownish as there is not big bird with really bright yellow color (like the golden oriole). With these parameters I search as well in the ornitho.ch database (all observations given by ornithologist professionals and amateurs) : there was no observation of vulture or eagle in that ...


3

It seems like they are not affected by fluorescent light frequency. I did not find anything about their visual sampling rate. Their hearing is between 0-200Hz with an average of 86Hz so I guess the visual sampling rate is under this, but that's just a guess. We conclude that at the illumination levels used in this experiment, the hens did not perceive ...


3

From this paper about black-headed gulls responding to a hedgehog: The gull might peck the intruder, or strike it with its feet. Pecks were mostly directed at the hedgehog's head and might be delivered after a horizontal approach with the wings partly lifted. Although not directed at the eyes specifically, they observed the birds directing attacks ...


2

It can't be confirmed but it sounds like a pelican.


2

I am pretty sure this doesn't happen with eagles, and I have no idea why this would be written. But not so! In a flash the great mother eagle flies down, catches the little one on her back, and flies up and deposits it in the nest. ("Whew! Mom, that must have been an accident.") But it wasn’t an accident." This is flight, alright: a pure flight of ...



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