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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 ...


16

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 ...


15

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 ...


13

Various features of brain,skull and beak anatomy help to achieve protection. A paper was published in PLoSOne in 2011 on this very topic: Why do woodpeckers resist head impact injury: a biomechanical investigation There is also a very readable summary on the BBC website. I advise that you read the whole article, but here is a quotation which lists the ...


11

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.


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

Definitions of adaptation Unfortunately, there is not such thing as a single, standard definition of adaptation. But for most cases the accurate definition the author is using is not of much importance as all of the usual definitions totally fit in the sentence without changing the meaning of the concept they want to express. In you case however, the ...


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

This is a story I have been told as well when I was a kid. Usually this is related to the foreign smell that the humans leave on the chick. However, this seems to be an urban legend, as birds have not a great sense of smell. Snopes says about this: However, Mother birds will not reject their babies because they smell human scent on them, nor will ...


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

There is a classification of birds called Soaring birds. Soaring Birds In definition, some land birds, such as vultures and certain hawks, sustain flight for long periods without flapping their wings. They take advantage of updrafts produced when the wind blows over hills and mountain ridges or make use of rising columns of warm air called ...


6

Gibson (2006) identified three characteristics that help woodpeckers avoid brain injury: their small size, which reduces the stress on the brain for a given acceleration the short duration of the impact, which increases the tolerable acceleration the orientation of the brain within the skull, which increases the area of contact between the ...


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 ...


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, ...


5

A trait is said to be adaptive when it causes fitness to increase. Fitness is generally understood as the (relative) contribution to future generations in terms of offspring or genes. The trait is selected for by the environment and hence increases fitness. In the paper of Dey et al. this is the fitness of the parent birds. Hatching asynchrony causes size ...


5

Your questions mean basically the same. Birdcare.com says: The situation in which all the eggs in a clutch do not hatch at (more or less) the same time, as is more usual among birds, but have their hatching spread over several days. It is well seen in the various types of raptor, and is an adaptation to a type of food supply which may fluctuate. During ...


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 ...


4

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 ...


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

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 ...



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