Wikipedia:Reference desk/Archives/Science/2015 August 6

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August 6

Quiet birds

Apologies for starting three sections at once.

The other day I noticed that some snow buntings had built a nest on an I beam under our building. This puts the nest about 70 cm (28 in) above the ground and better protected from predators than normal. Because finding a nest isn't common I decided to take some pictures. Every time the shutter went off the birds opened their mouths for food. However, it wasn't until later that I realised they were completely silent and still are 5 days later. Now this makes sense for birds who nest on or close to the ground. But other birds who don't quite often have young who are vocal.

So the questions are:

1. Do other ground dwelling birds remain silent until grown?
2. What advantage, if any, is there to birds who nest higher up to have young who are more vocal? CambridgeBayWeather, Uqaqtuq (talk), Sunasuttuq 04:56, 6 August 2015 (UTC)

For starters, see Altricial - high nesting birds do indeed tend to be more altricial than their ground-nesting counterparts. See also Begging_in_animals#Auditory_signals - the noisy bird (often) gets the food! SemanticMantis (talk) 13:41, 6 August 2015 (UTC)

Thanks. The chicks are still silent. I suspect that the birds don't nest close together so there is little need for them to be noisy. CambridgeBayWeather, Uqaqtuq (talk), Sunasuttuq 00:37, 7 August 2015 (UTC)

Egg laying

As it points out in the snowy owl article they lay their eggs every other day leading to a large difference in size between the first and last hatched.

So the questions are:

1. What advantage, if any, is there to laying eggs spaced out like this?
2. Are there any other animals, birds or not, that lay their eggs over a period of time? CambridgeBayWeather, Uqaqtuq (talk), Sunasuttuq 04:56, 6 August 2015 (UTC)

We have seen on BBC Springwatch examples of this across the owl family. Their resident naturalist (Chris Packham) explained it as "lay the brood - lay the food". In other words, the older chicks will eat the youngest ones during times of relative famine. This has been filmed by them. --TammyMoet (talk) 08:30, 6 August 2015 (UTC)

Just to expand on this slightly. The timing of egg laying is so that the earlier laid eggs produce significantly larger chicks. So, when times are tough and the chicks perform siblicide, one of them is it a clear advantage. This prevents equally sized chicks fighting it out and possibly both dying. Nature can be cruel, but beautiful in design.DrChrissy ^(talk) 13:48, 6 August 2015 (UTC)

Most birds do lay over a period of time. This is sort of an energetics and physiology issue. How could e.g. a mallard hold ~12 eggs inside before letting them all out at once? There is a ton of research into describing the patterns of laying period and clutch size in birds, and understanding the ecological and evolutionary forces that control them. For a general idea, try skimming /laying period clutch size interaction/ in google scholar [1]. (The abstracts are almost always free, and if you past the full title in to regular google you can often find freely accessible copies) SemanticMantis (talk) 13:47, 6 August 2015 (UTC)

I'd done some checking because the snowy owl article says they don't siblicide but it isn't referenced. Unfortunately, almost everything I found confirming that had been copied from Wikipedia. One thing I did find was this which indicates that they may regulate their egg laying based on the food supply. CambridgeBayWeather, Uqaqtuq (talk), Sunasuttuq 00:41, 7 August 2015 (UTC)

I concur with both reasons given. As for being unable to lay multiple eggs at once, in this respect they may be similar to humans. Yes, humans can have twins, triplets, etc., but the more babies at once, the smaller each one is and the more likely each will have medical problems. StuRat (talk) 03:28, 7 August 2015 (UTC)

r-k selection is also relevant to this and the question below. SemanticMantis (talk) 14:16, 7 August 2015 (UTC)

In nature, food is a precious resource and evolution has worked around the fact that food might become unavailable. So if the food dries up before all the chicks are ready to go, then the first one will have got biggest and ready to fly even though the food ran out, so not much was wasted on the small one who will die. If they was all hatched at the same time and fed equally, they would all have died when the food ran out. It is cruel but it is nature. Erunaquest (talk) 23:21, 7 August 2015 (UTC)

• Two separate issues are being conflated here. In birds with large clutches and precocial chicks, the legs are laid over a period of days for the metabolic costs mentioned above. But the brooding parent doesn't start incubating the nest until the last egg is laid. Hence they all start developing at the same time, and you get a large clutch as with Galloanseres and other usually non-predacious birds.

In groups like waterbirds or raptors where two eggs are laid, and the chick must be fed a burdensome amount, then you find neglect of the smaller chick (which was laid as an insurance policy, in case the big egg didn't hatch) and siblicide is common. (In the medium sized clutches of altricial birds like many song birds, there may be a runt which cannot compete for sufficient food and dies, even if it is not actively murdered.) But in large clutches you usually get twelve chicks of almost identical size, regardless of when they were laid, and not a set of matryoshka dolls. μηδείς (talk) 16:45, 10 August 2015 (UTC)

Disappearing wildlife

Normally in the spring we (Cambridge Bay) get hundreds of geese on either side of the road to the airport and hundreds more in the large pond at the end of the runway. However, this year there were very few. Wondering if I was just imagining it I checked and others had noticed it too. I then realised that other bird species like the snow buntings, small brown birds (official name), gulls, terns and even the ever present ravens were visible but in much smaller numbers. Then a couple of days ago we were down on our local beach, frolicking in the Arctic Ocean, when someone commented that there were very few mosquitos. This also applies to regular flies, which I don't mind at all, that normally number in the hundreds in one of our buildings. So what would cause the sudden lack of these animals? I know that we had a early spring and July seems to have been very wet but would that factor into it? Sorry again for three sections. CambridgeBayWeather, Uqaqtuq (talk), Sunasuttuq 04:56, 6 August 2015 (UTC)

When a wife disappears, the default suspect is the husband. When the wildlife disappears, it's usually your fault. "You people", anyway. Harder to pin down the specifics, but the way my wildlife fell just a few years after the West Nile panic sprayings has my spidey senses tingling. Still a ton of mosquitoes (and new big, crunchy yellow ones), so it's not like they're going hungry. I just don't think this new kind of bug is very healthy. Only one piece of the puzzle, though, even if true. InedibleHulk (talk) 07:35, 6 August 2015 (UTC)

Well, the lack of mosquitos and other food sources could be a an example of bottom-up control. See e.g. here [2] for a quick primer, here [3] for some hard science papers, and our scant WP coverage is at Top-down_and_bottom-up_design#Ecology. You can play with this interactive mapping tool [4] to see how mosquitos are currently doing. They generally do worse in harsher winters and dryer springs, not sure what you had this year.

Also keep in mind all populations fluctuate in their natural conditions, sometimes wildly. A famous example comes from your neck of the woods (roughly), elucidated by trapping data from the Hudson Bay company, showing the boom/bust cycle of lynxes and hares [5]. Finally, the weather is weird in much of the world this year, a likely record-breaking ENSO is already pushing temp and precip patterns around the word far from their seasonal norms. Many birds do " facultative migration," meaning they stay or go based on how good their current locale feels. So maybe some of these birds are just staying elsewhere this season. As far as specific scientific explanations of causes for this phenomenon this year, you'll have to wait a year or so, collected and analyzing such data takes time. SemanticMantis (talk) 13:38, 6 August 2015 (UTC)

FWIW, further south in Ontario we've had bumper crops of mosquitoes this year. You're quite welcome to come collect as many as you need to feed your birds. :) 64.235.97.146 (talk) 14:05, 6 August 2015 (UTC)

I think a more famous example of population fluctuations are these animals. Although are winter was mild, and they have been for several years, in that the temperature didn't drop below −40 °C (−40 °F), spring came early. We had warm above 0 °C (32 °F) for a while and then a drop below freezing for 2 weeks. June wasn't too bad for rain but July was very wet. Even after the rain stopped there were few mosquitoes around. CambridgeBayWeather, Uqaqtuq (talk), Sunasuttuq 00:50, 7 August 2015 (UTC)

Since Canada geese are migratory, the obvious answer is that they've migrated on. If it's now warmer there than normal, they might have migrated farther north to take advantage of the food up there. StuRat (talk) 03:23, 7 August 2015 (UTC)

See the "Ugly duckling" section just below. Nyttend (talk) 04:12, 7 August 2015 (UTC)

Can the hairs and the fingernails be regarded as a "benign growth", according to its scientific definition?

HOOTmag (talk) 06:48, 6 August 2015 (UTC)

I don't know what sort of science you trust, but by this medical dictionary, they're disqualified for not being abnormal. Definitely "benign", unless you develop a new form of fingernail or hair cancer. InedibleHulk (talk) 06:58, 6 August 2015 (UTC)

• Terms are distinguished by not only what they include, but also by that which they exclude. See genus–differentia definition. The term benign in medicine is differentiated from malignant, and these are subgroups of tumors; that is, abnormal growths. If you are going to call hair "benign", you will end up having to call kidneys, teeth, lungs, etc., benign on the same basis. You've removed the essential genus "abnormal growth" and simply defined benign to mean anything non-cancerous. Of course you are free to use your own definitions, but if you go to the doctor and tell him to remove your malignant hair, he is not going to give you a nice hairdo. μηδείς (talk) 17:08, 6 August 2015 (UTC)

What is "scientific definition"? Is it different from the dictionary definition somehow? The answer can therefore be both yes and no depending on who is being asked. Erunaquest (talk) 23:18, 7 August 2015 (UTC)

Well, not only have you indented improperly, Erunaquest, but your skeptical equivalence is simply wrong. Most scientific and medical terms are pretty well defined, and there is no doubt medically what is the difference between a benign and a malignant tumor, although the former can convert to the latter. You don't earn a degree in medicine by playing post-modern deconstructional games. μηδείς (talk) 03:32, 8 August 2015 (UTC)

What prism would neither rotate nor invert an image after 90 degrees reflection?

What prism would neither rotate nor invert an image after 90 degrees reflection? Imagine that two persons are sitting at an angle of 90 (considering their gaze). One of them is looking at an object directly. What prism should the other have to look at exactly the same image? I know that a roof pentaprism + mirror would do the trick. But what about an optical component without mirror? --3dcaddy (talk) 20:19, 6 August 2015 (UTC)

If I'm reading pentaprism correctly, that would not require an additional mirror (note: "pentaprism" not "roof pentaprism"). Also, in these contexts, a prism is just a block of glass, some of whose internal surfaces act as mirrors. An optical arrangement of interest might easily be mappable from "mirror" to "prism" (or "extension of existing prism") by filling the space in front of the mirror surface with glass. DMacks (talk) 20:46, 6 August 2015 (UTC)

In the case of the pentaprism, the internal sides are coated to be mirrors. They don't just reflect the light internally through total refraction. Pentaprisms can even be substituted by pentamirrors. --Scicurious (talk) 22:05, 6 August 2015 (UTC)

Given a Rolleiflex, or any similar camera with waist-level viewfinder, could the camera incorporate a prism to let the photographer see the image as it would see it using an SLR?

I understand that the lens of the camera flips the image both top-down and left-right, and the mirror flips the image top-down. That leaves us with an image which is flipped only left-right in the case of the Rolleiflex. And a correct image, in the case of the SLR which has a lens + mirror + roof pentaprism. Couldn't a prism instead of the mirror correct this problem for the Rolleiflex?

If I understand correctly, having a pentaprism (not the roof pentaprism or a SLR) instead of a mirror, would flip the image top-down and left-right, leaving us with a correct image. Is that correct?

I wonder too why doesn't an upmarket camera like the Rolleiflex incorporate then a pentaprism instead of a mirror. --3dcaddy (talk) 01:20, 7 August 2015 (UTC)