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Public Radio's Environmental News Magazine (follow us on Google News)

Tiger Sharks Dine on Migrating Birds

Air Date: Week of

The Gulf of Mexico is a migration corridor for birds throughout eastern North America. It’s also home to about 5,000 oil-drilling platforms. The powerful lights on the rigs confuse the birds, draining their energy reserves and thinning the flock. Ben Raines, an environmental reporter for the Mobile Alabama Press-Register, speaks with host Bruce Gellerman about the problem.


GELLERMAN: Something very strange is happening near oil platforms in the Gulf of Mexico. On dark and overcast nights, migratory birds become stuck in the cones of light from the powerful beacons on the drilling rigs. The birds swoop and circle overhead - flying round and round - until, exhausted - they drop into the sea.

Environmental reporter Ben Raines has written about the unusual and often deadly phenomenon for the Mobile, Alabama, Press-Register:

RAINES: You have to imagine what the platforms are down here. I mean, we’ve got 5,000 in the Gulf, and they’re out there over a formerly dark ocean, and each one is lit up with several hundred bright, bright flood lights - think of streetlights. They’re like these beacons out on the horizon. If you’ve ever been close to a bright light outside like a lantern, you look away from it and you can’t see anything and it’s the same phenomenon on these platforms.

Dutch oil companies and Royal Philips Electronics developed a green light that reduced “nocturnal migration” – birds circling a platform – by 90%. No green lights are used on the Gulf of Mexico’s 5000 oil platforms. (Photo: Nederlandse Aardolie Maatschappij)

GELLERMAN: So how does that affect the birds?

RAINES: Well, on cloudy nights in particular, where the stars are obscured, birds migrating across the Gulf, which is a long trip - a couple hundred miles, takes 20 to 30 hours - will fly and they’ll become sort of disoriented and bamboozled by the lights on the platforms, thinking that those are, you know, navigation cues like stars because they can’t see the stars.

And, so, they just start flying in a circle around these platforms, and you have to remember the platforms - some of them are very big. I mean - you know, the top deck might be the size of a football field.

GELLERMAN: So what happens to the birds? They fall onto the platform?

RAINES: Well, some fall onto the platform, some are eaten by migrating raptors - you know, hawks and things, and some are eaten by sharks. We had some scientists here that work out of the Dauphin Island Sea Lab who began dissecting sharks - tiger sharks in particular - and finding a lot of songbirds in them. Brown thrashers, scarlet tanagers, you know, birds you would associate with the woods that could only be out there - 20 and 50 miles offshore - because they are migrating.

GELLERMAN: I know that tiger sharks, they're, they’re kind of considered the garbage disposal of the sea!

RAINES: I watched them cut one open and it had a two foot shark inside it - whole! But then there was this big black mass and… it was feathers! Mixed in there were some bright yellow feathers for instance, some red feathers, which didn’t come from marine birds. There were some little bitty feet.

Scientists at the Dauphin Island Sea Lab in Alabama have removed woodpeckers, meadowlarks, swallows and other songbirds from the stomachs of tiger sharks. The birds seem to be disoriented by oil platform lights, flying in circles until dying of exhaustion. (Photo: Ben Raines)

We’re in what’s known as the Dauphin Island trans-migration throughway, which is one of the biggest bird migration corridors in the US, and this hemisphere. A tremendous number of these migrating birds definitely pass by these platforms.

GELLERMAN: How many birds are being killed by these platforms?

RAINES: Well, no one knows. It’s hard to say how big of a problem it is - if a bird flies around the platform and falls in the water, it disappears - there’s no carcass to count. But, in the North Sea, they’ve documented bird clouds, up to 100,000 birds, flying in circles.

Well, that becomes an issue if you’re migrating across the Gulf on this 30-hour flight, because you’ve only got enough energy to make it across. The US government first did a study in 2005, but as best I can tell there has been no science whatsoever since 2005, looking at this.

GELLERMAN: So the feds have known about this problem for years - seven years now!

RAINES: Yes. But the Bureau of Ocean Management put something in one of their recent lease-sale documents, which said that more platforms in the Gulf would be an adverse but not significant effect. Well, 2005, the study concluded further development of the Gulf will not be benign for migrating birds.

GELLERMAN: Isn’t there an easy fix: turn of the lights!

RAINES: Well, with OSHA rules and stuff they have to keep the lights on because it’s a working environment 24-hours a day, and you’ve got, you know 100 people on a platform. But in the North Sea, where they’ve got, you know, the same phenomenon, nocturnal circulation - birds flying in circles for hours during their migration from, you know, Finland to middle-Europe - there was an experiment done.

I believe it was on a Shell platform. And Phillips invented a light that is green and they found that it would reduce the circulation behavior by 90 percent. So, you know, it’s possible that just switching light bulbs could virtually stop the problem altogether here in the Gulf. Yet, you know, no one has tried it here.

GELLERMAN: So they want to build more platforms in the Gulf and there’s now this comment period for the environmental impact statement - have you had any further response from the federal government?

RAINES: Well, in that impact statement is several thousand pages. And on page 796 of volume 2 of the impact statement, they devote about a page to this phenomenon. They say that the platforms are good for hawks because they get to eat the tired birds that are sitting on the platforms, and they say that they will have an adverse but not significant effect on the migratory birds.

And they talk about the nocturnal circulation event, but as best as I can tell in conversations with the government - no further study has ever been done, although the earlier 2005 study called for further study. The comment I got when I called most recently was: we may look at it in 2013.

GELLERMAN: Ben Raines is an environmental reporter with the Mobile, Alabama, Press-Register.



Video of shark dissections at the Dauphin Island Sea Lab, Alabama


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