Wikipedia:Reference desk/Archives/Science/2022 May 22

= May 22 =

What makes some daytime birds wake up so early?
Why do they sometimes tweet about 2 hours before sunrise and before astronomical dawn? Sagittarian Milky Way (talk) 08:12, 22 May 2022 (UTC)


 * Well some birds are nocturnal, but others may be affected by light pollution and other disturbances, or maybe they just feel like tweeting. Shantavira|feed me 08:52, 22 May 2022 (UTC)


 * Dawn chorus (birds) gives a vague hint with it is common for different species to do their dawn singing at different times. This might be saying that they're taking turns, basically, to stay out of the airtime of the other species, but that's a guess and the article lacks references and information, especially in the section Dawn chorus (birds). Card Zero  (talk) 11:12, 22 May 2022 (UTC)


 * If birds are going to spend some part of the day singing, during the night has the advantage that it does not take time away from when they might be feeding or doing other things that require better illumination. There have been quite a range of other hypotheses and experiments in the behavioural ecology literature concerning why dawn is an especially advantageous time to sing, such as because migrants tend to migrate at night so that the intended audience of unpaired females are commoner at that time, as are rival males looking for a territory. Another idea is that sound carries better in the still air of dawn. And another that some species are forced to sing earlier than they otherwise would because there are too many other species drowning them out at the ideal time. One influential hypothesis is that birds usually have a surfeit of fat reserves before dawn to expend on singing, because they have stored up fat the previous day to survive a worst-case cold night that rarely materialises. Generally explanations can be divided into those focussing on the special properties of dawn, and those resulting from the fact that there are dark and light parts of the day, with some processes favoured at the transition point between them. Most of the explanations are not contradictory. Lastly, be aware that birds have better low-light vision than humans, so it starts to get usefully light earlier for a bird than for us. The latest review is by Gil & Llusia (2020), available here. An example of my own modelling work on this topic is available here. Jmchutchinson (talk) 11:59, 22 May 2022 (UTC)
 * That is some really fascinating computational bird modeling and it's really sparked a few insights into the finely-tuned and highly optimized complex system that is biologically-evolved behavior! Thank you for sending the link!  To your knowledge, did anyone ever follow up with experimental observation to validate the modeling efforts?  Nimur (talk) 15:55, 23 May 2022 (UTC)
 * Nimur, that is very nice of you to say. Yes, behavioural ecologists are testing these models in at least a qualitative way, particularly, but not only, by manipulating light levels. This relates to the hot topic of light pollution in cities. I can't provide an authoritative review as I am largely out of this field myself now. One suggestion is to look at the Gil & Llusia article cited above and another is to skim the titles of articles that cite my article as revealed by Google Scholar: it records over 60 citations. Jmchutchinson (talk) 14:54, 26 May 2022 (UTC)
 * Since birds with 4+ cone types have UV cones maybe the light pollution here in New York City doesn't obliterate their zodiacal light? It's just sunlit solar system dust after all, if the dust reflects enough UV maybe they can see the triangle? Sagittarian Milky Way (talk) 00:22, 24 May 2022 (UTC)
 * Some considerations:
 * Many birds, in particular those with small eyes, don't see very well at night. It's too dark to forage, but they can spend the time singing. Other birds don't forage at night because their prey is hiding.
 * Lack of sun-driven convection means that there's less mixing of air close to the ground with the air higher up. Consequently, the wind speed at the surface drops and there's less rushing of the wind in tree branches, so less background noise.
 * At night, humans are less active, so less background noise.
 * At night, the air close to the surface is colder than a bit higher up, bending sound back to the surface. The sound reaches farther.
 * Some predators may be less dangerous at night. Some can't see the bird or the tree branches where they're hiding, some are inactive as they're cold-blooded.
 * BTW, no astronomical dawn here this time of the year; the sun never gets below -18° less than a month from midsummer at 52°. PiusImpavidus (talk) 12:12, 22 May 2022 (UTC)
 * Aren't birds warm-blooded? --←Baseball Bugs What's up, Doc? carrots→ 15:28, 22 May 2022 (UTC)
 * That's talking about some of the predators as I read it. Mikenorton (talk) 15:31, 22 May 2022 (UTC)
 * Not exactly a cite, but round here the kookaburras arc up about 15 minutes before the songbirds dawn chorus. Greglocock (talk) 22:39, 22 May 2022 (UTC)
 * The early 'burra catches the vermin. --←Baseball Bugs What's up, Doc? carrots→ 23:31, 22 May 2022 (UTC)
 * Most diurnal birds have far superior eyesight to humans. They started up singing here about 20 minutes ago (can't sleep) and looking at the sky now, it's just starting to lighten a little bit. The sky does start to lighten before the sun appears over the horizon.
 * Fun fact - if you have a pet parrot and you forget to keep the curtains drawn at night, they do a dawn chorus too. But in this case, it's earsplitting 4am squawking, designed to carry over several miles of rainforest that doesn't stop until you get out of bed and show them that you survived the night. Iloveparrots (talk) 03:12, 24 May 2022 (UTC)
 * Quality of eyesight has many aspects: size of the eye, sensitivity, colour resolution, spatial resolution, temporal resolution, sensitivity to polarisation, dynamic range. Human eyesight is quite good. There is room for improvement, but not much without sacrificing one aspect for another. By increasing the ratio of rods over cones, light sensitivity can be improved a lot, but this sacrifices colour resolution. Nocturnal animals tend to have rather poor colour resolution. Rewiring the light sensitive cells into larger groups also increases sensitivity, but lowers spatial resolution. Increasing persistence of vision is also good for sensitivity, but bad for temporal resolution, making it a bad idea for fast animals, like flying animals. The big eyes of owls gather a lot of light, so they see well at night, but hummingbirds, who are tiny and need good colour vision to find their food, don't. They spend the night sleeping.
 * They say that biology is the science of the possible and physics is the science of the impossible. Physics tells us that it's impossible to get information from less than one photon, giving an upper limit to the quality of eyesight. We only need a few photons to see something. PiusImpavidus (talk) 09:45, 24 May 2022 (UTC)
 * It appears from the sources and our article nightingale that the singing is done by males.  The neighbour whose garden backed onto ours used to keep a cockerel.   Despite the height of the fence we soon found out... 92.19.175.5 (talk)  — Preceding undated comment added 11:28, 27 May 2022 (UTC)