I had never thought about this until last week, when I saw a humorous panel on the subject in an anthology from Mad. Granted, bats’ echolocation helps them find insects or avoid fixed objects, so they don’t rely so much on their eyesight; but how do birds and flying insects cope with fog?
That’s an interesting question. I also wonder about overcast nights.
I think a lot of insects (not including moths) don’t really navigate celestially, they probably navigate by smell. I.e., sniff sniff, there’s a warm-blooded animal, sniff, there’s its flesh, mmmm tasty blood, sniff sniff, there’s a pond to lay my eggs on. No celestial navigation needed.
Birds will sometimes get killed by circling radio towers in fog. They circle and circle until they collide with one another or with objects on the ground, and then get counted by grim-faced grad students. If the lights weren’t on at all, they probably would just sit tight.
I wonder about non-celestial navigation … do we know if there are any birds that navigate inertially or magnetically? (My sig line should be taken with a grain of salt…)
- Boris B, Hellacious Ornithologist
There’s some speculation that some birds, especially species that migrate along the continental coasts, can detect the low frequencies caused by shore break and use this to oreintate themselves in a north/south migration. This point can up in an avian physiology lecture when the topic was the structure and function of the ear. I’d have to check the references (latest edition of Sturkie’s), though, before I completely buy into this.
I’m not going to get this exactly right but it’s something like this.
Bees can detect the polarization of light, which varies over the sky depending on where the sun is. Although overcast skies block most of the light, what remains is still polarized and the bees solar navigation is still operable.
One of the components of the honeybee’s famous “wiggle dance” is the angle of the path to the food source with respect to the sun, so solar location is important to the little guys.
How’s that for hard science?
Let’s see. I lathered and I rinsed. But did I repeat?
I believe many species of insects and birds have the ability to detect the earths magnetic field. I also read somewhere that fluid in eye capillaries are fixed at a certain pressure at birth, and as the organism moves further from it’s birth place it can detect the pressure changes, giving it “homing” ability.
I have also read somewhere that migratory geese make an inexplicable turn in crossing the great lakes. Speculation is that a huge iceburg existed there for so long that the change in direction is programed in their brains.
Magnetic Sense Helps Billions of Moths on an Australian Migration
Researchers say this is the first reliable evidence that insects can use Earth’s magnetic field for navigation. (NYTimes article today)
I like that the Times headline cites “billions.” Otherwise, we might question the newsworthiness or the veracity of the report.
19 year zombie!
Not sure if the OP was asking about migration and general orientation, as opposed to general day-to-day “how to get from here to there sufficiently to feed, mate, avoid danger…”
I suspect many birds are less active in inclement weather, and that fog would increase the incidence of them striking objects.
On EDIT - good heavens, why didn’t I notice the age?
Good Heavens indeed! What’s more, you skipped MY post! 
ETA: You’re right about specific OP. But it was either this thread or one how cows line up to post this.
I’ve read that too, and I can see where it would be important in migratory flights across long distances.
But I can’t see that the earths magnetic field can vary that much from one side of by back yard to another. Or that small birds or insects can contain sufficiently delicate detection systems to note such minuscule variations. I think that ‘local’ travel must be based on direct senses, like smell, sight, etc.
Full text:
Electric Fields Elicit Ballooning in Spiders
Erica L. Morley, Daniel Robert
Summary
When one thinks of airborne organisms, spiders do not usually come to mind. However, these wingless arthropods have been found 4 km up in the sky [1], dispersing hundreds of kilometers [2]. To disperse, spiders “balloon,” whereby they climb to the top of a prominence, let out silk, and float away. The prevailing view is that drag forces from light wind allow spiders to become airborne [3], yet ballooning mechanisms are not fully explained by current aerodynamic models [4, 5]. The global atmospheric electric circuit and the resulting atmospheric potential gradient (APG) [6] provide an additional force that has been proposed to explain ballooning [7]…
Altogether, the evidence gathered reveals an electric driving force that is sufficient for ballooning. These results also suggest that the APG, as additional meteorological information, can reveal the auspicious time to engage in ballooning. We propose that atmospheric electricity adds key information to our understanding and predictive capability of the ecologically important mass migration patterns of arthropod fauna [8].
Lay article:
**Spiders Can Fly Hundreds of Miles Using Electricity
**