Andy Adcock
Worst person on Birdforum
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Losing the night (1 Viewer)
- Thread starter Andy Adcock
- Start date
Paul Longland
Well-known member
This raises some very interesting points.
The most obvious one is as the article states the potential effect of night time migration. Another thought struck me however. Whilst there are many triggers for migration, it has long been thought that it is daylight hours that is one of the major factors that birds use to time their migration. If the amount of light pollution is spreading in some of the traditional wintering grounds for many of our summer visitors could this lead to them setting off too earlier only to arrive here whilst there may still be cold weather and hence less insect food available. Alternatively the opposite may occur and late arrival reducing the available time to rear their young?
Another thought also occurs to me. I have noticed that the urban tawny owl has decreased significantly over recent years. Could the type of lighting now being used in our towns and cities have an effect here also (maybe light frequency as against actual brightness)?
In conservation terms we always look to loss of habitat, changes in farming methods etc etc but maybe far more research is needed in this type of area.
It has long been known that street lighting can have an effect of feeding patterns of Bats. Some observers have also noted that urban peregrines have adapted to use silhouettes cast by migrating birds to prolong their hunting times into dusk.
Light will often attract insects such as moths. are we going to see urban nightjars?
The most obvious one is as the article states the potential effect of night time migration. Another thought struck me however. Whilst there are many triggers for migration, it has long been thought that it is daylight hours that is one of the major factors that birds use to time their migration. If the amount of light pollution is spreading in some of the traditional wintering grounds for many of our summer visitors could this lead to them setting off too earlier only to arrive here whilst there may still be cold weather and hence less insect food available. Alternatively the opposite may occur and late arrival reducing the available time to rear their young?
Another thought also occurs to me. I have noticed that the urban tawny owl has decreased significantly over recent years. Could the type of lighting now being used in our towns and cities have an effect here also (maybe light frequency as against actual brightness)?
In conservation terms we always look to loss of habitat, changes in farming methods etc etc but maybe far more research is needed in this type of area.
It has long been known that street lighting can have an effect of feeding patterns of Bats. Some observers have also noted that urban peregrines have adapted to use silhouettes cast by migrating birds to prolong their hunting times into dusk.
Light will often attract insects such as moths. are we going to see urban nightjars?
kb57
Well-known member
You are correct about the wavelength change and its possible ecological effects. We have moved away from the longer-wavelength 'yellow' light of sodium lamps in favour of LED lighting - both because of energy efficiency concerns and the more 'natural' (i.e. closer to daylight) spectrum. These are both understandable aims but appear to be having unintended consequences, as the BBC article which Andy highlighted points out.
I've seen scientific papers replicating effects of sodium and LED lighting on a hedgerow using portable lighting columns, which found a greater effect on bat activity of the LED lights. Not aware of any comparable replicated studies on birds, but it would make sense that lighting which most closely matched the daylight spectrum would have a more disruptive effect on light-induced behaviours. On the positive side, I think I've mentioned before on BF that a study involving 'green' lighting on a North Sea gas platform proved less disruptive to nocturnal migrants, while also providing a safe working environment for staff due to the good contrast levels produced.
Obviously some urban birds like peregrines can exploit a higher light environment and extend their foraging period - I've seen studies on shorebirds which suggests that lighting can be similarly positive in some circumstances. And I believe some species of nightjar do occur in urban environments and feed off moths attracted to lights. But maybe for species like tawny owls which are well adapted to forage in darkness, the high contrast environment of LED lighting just tips the balance in favour of their prey.
Andy Adcock
Worst person on Birdforum
There's a site in Suffolk where ringers used to catch plenty of rarities (Landguard I think it was) which is near the port of Felixtowe. The port changed it's lighting system and it's totally changed the catch there, we hardly ever hear of a rarity there these days.
A
A
Nutcracker
Stop Brexit!
Possible yes, but I'd suspect decreased human tolerance of rats, and consequent increased use of rodenticides, might be more significant. Particularly also as warfarin (much used in the past, but not much now, since rats have evolved resistance) has very low avian toxicity compared to other more recent rodenticides.
I work on various North Sea installations, and to say they are very brightly lit is an understatement. I have observed that the thrush species never land on a rig but will spend all night circling it, generally in poor weather. That is a lot of energy wasted. I have seen similar behaviour by woodcock. But....lots of migrant thrushes and woodcock do make it across every year so maybe their stamina levels are enough to endure these overnight interludes.
Hi Mudman,
I've read about exhausted birds often landing on brightly lit ships in poor weather, so maybe if they ran really low on energy, they would also land on oil rigs out of desparation.
Heligoland of course is an important stepstone for birds migrating over the North Sea, and apparently the lighthouse beam helps them to find it, but on the other hand, I seem to remember that there also are a lot of birdstrikes on the lighthouse.
A couple of years back, I read a study about gulls nisting on Helogoland being fitted with GPS trackers to determine their feeding habits. The researchers correlated the birds' GPS tracks with the tracks of the fishing vessels (which apparently are required to provide their position at all times for legal reasons), and found that while the gulls in daylight tended to favour the vicinity of fishing vessels somewhat over other North Sea areas, at night, almost none of the gulls ever moved farther away than something like 1 km from a fishing vessel.
The explanation suggested by the study was that the brightly lit fishing vessels provided excellent fishing opportunities for the gulls, making their vicinity even more attractive than in daylight, when the gulls could feed on the waste thrown overboard, but not have any advantage to their own fishing activities.
Regards,
Henning
I've read about exhausted birds often landing on brightly lit ships in poor weather, so maybe if they ran really low on energy, they would also land on oil rigs out of desparation.
Heligoland of course is an important stepstone for birds migrating over the North Sea, and apparently the lighthouse beam helps them to find it, but on the other hand, I seem to remember that there also are a lot of birdstrikes on the lighthouse.
A couple of years back, I read a study about gulls nisting on Helogoland being fitted with GPS trackers to determine their feeding habits. The researchers correlated the birds' GPS tracks with the tracks of the fishing vessels (which apparently are required to provide their position at all times for legal reasons), and found that while the gulls in daylight tended to favour the vicinity of fishing vessels somewhat over other North Sea areas, at night, almost none of the gulls ever moved farther away than something like 1 km from a fishing vessel.
The explanation suggested by the study was that the brightly lit fishing vessels provided excellent fishing opportunities for the gulls, making their vicinity even more attractive than in daylight, when the gulls could feed on the waste thrown overboard, but not have any advantage to their own fishing activities.
Regards,
Henning
Nutcracker
Stop Brexit!
Or opportunities to catch light-entranced thrushes?
Hi Nutcracker,
An exhausted thrush dropping into the water probably would be a welcome snack for any large gull, but I'm not sure the gulls would actively go after it in flight ;-)
However, I'm sure there are predators that exploit the new opportunities created by artifical light for hunting. Someone mentioned urban nightjars as hypothetical example - the only time I ever saw nightjars hunting, it was over the streetlights of a newly-constructed mall district.
I was quite impressed by a visit to Bergedorf near Hamburg, home of a large astronomic observatory. The entire city of Bergedorf is built with conscious concern for minimizing light pollution to preserve the darkness of the sky, with considerable attention to detail. Works great, no shortage of illumination in the streets, only the yellow tint of the ubiquitious Sodium-vapor lamps takes some getting used to.
Regards,
Henning
An exhausted thrush dropping into the water probably would be a welcome snack for any large gull, but I'm not sure the gulls would actively go after it in flight ;-)
However, I'm sure there are predators that exploit the new opportunities created by artifical light for hunting. Someone mentioned urban nightjars as hypothetical example - the only time I ever saw nightjars hunting, it was over the streetlights of a newly-constructed mall district.
I was quite impressed by a visit to Bergedorf near Hamburg, home of a large astronomic observatory. The entire city of Bergedorf is built with conscious concern for minimizing light pollution to preserve the darkness of the sky, with considerable attention to detail. Works great, no shortage of illumination in the streets, only the yellow tint of the ubiquitious Sodium-vapor lamps takes some getting used to.
Regards,
Henning
Nutcracker
Stop Brexit!
They do - I've seen (during daylight) Herring and GBB Gulls chase, catch, and eat migrating thrushes incoming into the coast here. They grab them by a wing, knock them into the sea and drown them. If the thrush is strong, it can outfly the gulls, but exhausted thrushes are easy prey for them.
Hi Nutcracker,
Thanks a lot for the explanation, I hadn't been aware of this feeding strategy! Amazing that the gulls can pull off a manoeuvre I'd normally only have expected from specialized aerial hunters - I'm impressed!
Regards,
Henning
Thanks a lot for the explanation, I hadn't been aware of this feeding strategy! Amazing that the gulls can pull off a manoeuvre I'd normally only have expected from specialized aerial hunters - I'm impressed!
Regards,
Henning
As far as I can remember I have never seen a thrush sp. actually on a rig, many other species yes but not the thrushes, they seem content to circle all night ( and it is a long night) before departing with the first pre dawn light.
The big gulls are no doubt big predators of migrating birds and I have seen them fly down and eat thrushes. They just sit on the rig until a suitable candidate flies by before a short chase and splash gulp. Gulls have really learnt how to use these man made structures to their advantage, although they are not here year round, their attendance seems closely linked to the migration season.
I have seen raptors make a good living on a rig for a few days before they too move on. One notable time their were at least two sparrowhawks, a peregrine and two great grey shrikes onboard. Bits of passerine littered the deck if you knew where to look.
The big gulls are no doubt big predators of migrating birds and I have seen them fly down and eat thrushes. They just sit on the rig until a suitable candidate flies by before a short chase and splash gulp. Gulls have really learnt how to use these man made structures to their advantage, although they are not here year round, their attendance seems closely linked to the migration season.
I have seen raptors make a good living on a rig for a few days before they too move on. One notable time their were at least two sparrowhawks, a peregrine and two great grey shrikes onboard. Bits of passerine littered the deck if you knew where to look.
