Roberto Firmino Jersey Sale<\/a><\/p>\nThat information should give us pause as we continue to change our planet. As humans artificially brighten the sky, and as we launch more satellites into orbit that outshine even stars, we may be messing with the cognitive compasses of untold numbers of creatures.<\/p>\n
Birds … in a planetarium?<\/p>\n
Emlen\u2019s experiments read like something out of a scientifically curious little kid\u2019s dreams. When he was a graduate student at the University of Michigan, Emlen was given the keys to the Longway Planetarium in Flint, Michigan, where he could reign free at night.<\/p>\n
\u201cThe director closed the planetarium at 10:30, and they gave me the key,\u201d Emlen recalls. \u201cI became nocturnal.\u201d Between experiments conducted there, and later at Cornell University, he pieced together a theory for how the birds navigate. <\/p>\n
When Emlen started his work, some things were already known. A husband-and-wife duo from Germany, Edgar Gustav Franz Sauer and Eleonore Sauer, had worked out in the decade prior that migratory birds \u2014 which sometimes fly thousands of miles in a single season \u2014 look to the stars to get a sense of direction. <\/p>\n
The Sauers put birds in outdoor arenas where the only thing they could see was the night sky. And with just the sky as their guide, the birds attempted to fly in their expected migratory direction. They wouldn\u2019t do so on a cloudy night. The Sauers repeated the experiment in a German planetarium, and it worked there, too. Which was amazing: Birds could use information they found in the sky \u2014 even man-made replicas of the night sky \u2014 to navigate. <\/p>\n
But there were still unanswered questions. What were the birds looking at in the night sky, and how were they figuring out the right way?<\/p>\n
There were several hypotheses. Some argued that the birds were using an internal clock of sorts to orient themselves to the stars. Stars change their positions over the course of the night, and when viewed from the northern hemisphere, they appear to rotate around Polaris, the static North Star. Perhaps they\u2019re born with an innate sense of time and learn where the stars should be at a given moment. (Similarly, humans know that around sunset, they can find the sun by looking to the west.)<\/p>\n
Emlen wasn\u2019t sure that was true. So he decided to find out \u2014 with the help of the planetarium, North American indigo buntings, and a special cage he invented with the help of his father (who was also a biologist).<\/p>\n
The cage was in the shape of a funnel, and the buntings \u2014 a beautiful, sparrow-sized songbird that migrate at night \u2014 were placed in the narrow bottom of the funnel. This design, illustrated below, ensured that the birds could only look at what was above them (i.e, the \u201csky\u201d). <\/p>\n
The upper part of these funnels was covered in paper, and the bases of the cages \u2014 \u201cjust aluminum pudding pans,\u201d Emlen says \u2014 featured an ink pad that turned the birds\u2019 feet into stamps. Little avian footprints would appear on whatever side of the funnel the bird attempted to fly toward. The top of the funnel was covered with plexiglass or a wire screen, so the bird wouldn\u2019t get out \u2014 hence, no poops in the planetarium.<\/p>\n
In the planetarium, Emlen could tinker with the cosmos. He started by setting the stars to a different time of night than it actually was, throwing off the birds\u2019 biological clocks. Yet the birds would still orient themselves in the right direction of their migration. \u201cThey were not using a clock,\u201d Emlen says. <\/p>\n
So the birds could orient themselves regardless of the time of night. It meant they were focusing on some other aspect of the night sky. But what? <\/p>\n
Emlen started on a painstaking process of elimination. As he describes, he \u201cattacked\u201d the expensive planetarium projector, blacking out certain stars systematically. \u201cLet me block the Big Dipper,\u201d he remembers thinking. \u201cLet me block Cassiopeia.\u201d No matter the constellations omitted from the cosmos, the birds could still orient themselves. <\/p>\n
\u201cI couldn\u2019t link it to any particular star pattern,\u201d he says. \u201cI had to block out pretty much everything within about 35 degrees of the North Star. And when that happened, the birds acted as though they were clueless.\u201d<\/p>\n
The clueless birds were a big clue for Emlen. He knew then that the orientation had something <\/em>to do with the area around the North Star \u2014 but didn\u2019t rely on any of the particular stars around it. <\/p>\nMaybe it was the spot in the sky that doesn\u2019t rotate at all. <\/p>\n
A further, ambitious experiment would prove this hypothesis correct. This time, Emlen didn\u2019t just bring birds to a planetarium \u2014 he raised some of them inside one. Again, he altered the planetarium projector, not by blocking out stars but by changing the axis of the Earth. He chose a new stationary \u201cNorth Star\u201d \u2014 Betelgeuse \u2014 for his chicks to observe. <\/p>\n
Remarkably, the birds raised under this altered sky would orient themselves toward Betelgeuse, as it was the fixed point, when they were ready to migrate.<\/p>\n
The experiment showed that the birds are primed for nighttime navigation not by an inborn star map, Emlen says, but by paying \u201cclose attention to the movement of the sky. They\u2019re hardwired to pay attention to something, which then takes on meaning.\u201d<\/p>\n
Emlen is still not sure if the birds look for some sort of constellation to point their way north, once they\u2019ve learned where it is from the motion of the stars. We humans often use the Big Dipper to find north. <\/p>\n
\u201cDifferent birds might use different star configurations,\u201d says Roswitha Wiltschko, a German behavioral ecologist who has conducted similar experiments on bird navigation. \u201cAnd apparently there is some individual difference in it. This is a part of orientation where we do not know the details yet.\u201d<\/p>\n
How many animals look to the stars? <\/p>\n
In the decades since these experiments, ornithologists have learned a lot more about how birds navigate. They don\u2019t just use a star compass \u2014 they also have a magnetic compass, a sun compass, and even a smell compass. It\u2019s incredibly complex. \u201cAll these things intermingle,\u201d Emlen says, and scientists still aren\u2019t sure precisely how these different navigational systems all work together. (They\u2019re especially unsure about how animals use these inputs to inform their mental map of where they are going.)<\/p>\n
Scientists don\u2019t have a precise accounting of how many different species of bird navigate by starlight, but experts suspect it is a huge number. More broadly, biologists don\u2019t know how many other species look at starlight. Based on discoveries in the past several years, this ability has already shown up in surprising places. <\/p>\n
Consider the dung beetle, which takes its name from its favorite food, namely, um, excrement. <\/p>\n
These critters have a very limited visual field, but can actually see the Milky Way in a dark night sky. One particular type of dung beetle lives in South Africa, scavenges for dung, and rolls it into balls away from the source, to protect its food. <\/p>\n
This sounds simple. \u201cBut for one thing, you have to bear in mind that this ball is usually bigger than the beetle itself,\u201d says James Foster, who studies dung beetles at the Universit\u00e4t W\u00fcrzburg. \u201cSo it\u2019s quite challenging to keep that on course.\u201d <\/p>\n
Here\u2019s the amazing part: \u201cThey really don\u2019t get lost unless you build them a tiny hat and put that over their head,\u201d Foster says. \u201cThey can\u2019t just look around at the ground and work out where they\u2019re going. They really need to be able to see the sky.\u201d<\/p>\n
Like Emlen, Foster\u2019s colleagues brought beetles into a planetarium and started switching stars on and off, systematically. They found that on nights where there is a moon, the beetles use it to orient themselves. But if there is no moon, \u201cif you switch off everything else and turn the Milky Way on, then they\u2019re oriented again. So that was what led us to think that they\u2019re using the Milky Way.\u201d <\/p>\n
That\u2019s pretty astounding stuff. Starlight from tens of thousands of light-years away, still has enough power to excite the nervous system in the limited eyes of the lowly dung beetle, helping it know where to go.<\/p>\n
But this ancient navigation system is also threatened by city lights. \u201cArtificial light … can completely obscure the kind of things that the animals are looking for,\u201d Foster says. \u201cIf you put dung beetles on the roof of a building in the middle of Johannesburg, then they become completely lost. It\u2019s just far too bright for them to be able to see the Milky Way, which is the thing they need.\u201d<\/p>\n
Foster isn\u2019t sure how many animals on Earth can orient themselves with the stars \u2014 no one is \u2014 but he suspects it might be more common than currently appreciated. Seals, moths, and of course humans have been shown to use stars. But it stands to reason that changing the night sky \u2014 with electric lights and bright, near-Earth satellites that outshine the stars \u2014 could continue to mess up the navigation of untold numbers of creatures.<\/p>\n<\/div>\n<\/div>\n
Recently, Emlen saw something astonishing in the night sky. \u201cIt was a whole stream of these major bubbles that passed through the sky,\u201d he says. \u201cEvery one of those blobs was more intense than the brightest planet in the sky.\u201d <\/p>\n
He says the blobs were SpaceX satellites, recently launched to deliver Internet to remote areas from low-Earth orbit. In the future, there could be tens of thousands of these bright objects launched into the night. \u201cI do think that will completely screw up birds that are up there at night,\u201d he says. <\/p>\n
We do know that there are some things that birds can adapt to. The Earth\u2019s axis actually wobbles slightly, which means Polaris won\u2019t be the North Star forever. In fact, in around 13,000 years, the star Vega will take the position. We know from the buntings in the planetarium that birds will learn to spot it. They\u2019ll pay attention to changes in the stars, Emlen says, \u201cand lock into whatever works.\u201d<\/p>\n
<\/p>\n","protected":false},"excerpt":{"rendered":"
\u201cNo, no, no, no, Brian. No, no, no, no.\u201d I had asked Stephen Emlen, a Cornell emeritus professor of neurobiology and behavior, what seemed to me an obvious question: When he brought birds into planetariums in the 1960s and 70s, did they ever, um, make a mess in there? \u201cNo poops in the planetarium,\u201d Emlen…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[],"class_list":["post-9793","post","type-post","status-publish","format-standard","hentry","category-news"],"_links":{"self":[{"href":"https:\/\/googmn.com\/index.php?rest_route=\/wp\/v2\/posts\/9793","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/googmn.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/googmn.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/googmn.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/googmn.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=9793"}],"version-history":[{"count":0,"href":"https:\/\/googmn.com\/index.php?rest_route=\/wp\/v2\/posts\/9793\/revisions"}],"wp:attachment":[{"href":"https:\/\/googmn.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=9793"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/googmn.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=9793"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/googmn.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=9793"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}