Oil does two categories of things to birds: First, it makes their feathers unable to do what they're supposed to do, which is keep the bird waterproof, warm, and buoyant, and allow it to fly. It does this by penetrating into the feathers, matting them and keeping the barbules from latching together properly. Water penetrates directly to the skin and quickly chills the bird (even 95-degree Gulf water is cooler than a bird's typical body temperature). In hot climates like the Gulf of Mexico, oiled feathers also hinder a bird's ability to keep cool, by losing their ability to insulate against the heat.
Second, oil poisons birds, either from fumes the bird breathes in or from oil it ingests while feeding, preening, scavenging other oiled wildlife, etc. Oil irritates the digestive tract causing vomiting, diarrhea, and hemorrhaging as well as disrupting normal cell functions. Some of the compounds in oil (particularly the class of pollutants known as polyaromatic hydrocarbons) continue to harm the birds after absorption into the blood, causing anemia, compromising the liver and immune system, and, even at low levels of exposure, changing hormone levels and increasing egg abnormalities or making them inviable.
These effects vary with the type of oil the bird encounters, with heavier or more weathered crude having more effects on feathers and lighter or less weathered oil affecting the respiratory system.
Oil threatens most of the birds that spend time in the Gulf's coastal ecosystems. These species fall into five general categories: beach nesters, saltmarsh residents, migrating shorebirds, wintering waterfowl, and pelagic (open-ocean) species.
Beach Nesters place their nests just feet away from, and mere inches above, the Gulf's waters. In normal years they are vulnerable to flooding by high tides and storm surges; this year adults and especially chicks at several colonies have been exposed to oil as well. These include species such as Sandwich, Royal, Caspian, and Least terns, Wilson's and Snowy plovers, American Oystercatcher, and Black Skimmer.
Saltmarsh Residents skulk in the vast, low grasses, or wade through estuaries and tidal flats of the Gulf Coast. They include small birds that nest and forage in the grasses, such as Seaside Sparrows, Common Yellowthroats, Boat-tailed Grackles, Least Bitterns, and Clapper Rails, as well as many species of larger wading birds such as Snowy and Great egrets, Tricolored, Louisiana, and Great Blue herons, Roseate Spoonbills, White Ibis, and Black-crowned and Yellow-crowned night-herons. These wading birds, along with Brown Pelicans, nest in colonies on islands just behind the barrier beaches, where they and their chicks can be vulnerable to oil slicks washing ashore.
Pelagic Seabirds live out in the open ocean and forage by diving or picking prey from the water. Open-ocean species are not as numerous in the Gulf of Mexico as they are in the larger oceans, but they are at risk because their feeding grounds are offshore, where most of the oil has remained. Losses of pelagic species will be very hard to estimate because they are difficult to count and bodies are unlikely to be recovered. Gulf of Mexico species include Wilson's and Band-rumped storm-petrels, Audubon's and Cory's shearwaters, Masked and Brown boobies, and Northern Gannets, as well as Bridled, Sooty, Common, and Black terns.
Wintering Waterbirds include the millions of ducks that spend winters along the Gulf, including scaup, teal, Redheads, and Canvasbacks, as well as Common Loons and several grebe species. Immature loons may spend one or more years in Gulf waters before migrating back to their breeding grounds. These species are at risk directly, from floating oil, as well as indirectly, from contamination of their plant, invertebrate, and fish food sources.
Migrant Shorebirds, of many species and hundreds of thousands of individuals, pass through the Gulf Coast on migration, using barrier beaches, tidal flats, and wet fields for foraging and resting. Many species continue across the Gulf to wintering sites in Central and South America, including Marbled Godwits, Western, Semipalmated, and Least sandpipers, dowitchers, yellowlegs, and Black-necked Stilts. Others spend the winter here, including up to about 40 percent of North America's population of the threatened Piping Plover.
For an illustrated, downloadable poster of this information see our Summer 2010 issue of BirdScope.
The number is in the tens of millions. It's difficult to know exactly how many birds live in a large region such as the Gulf of Mexico, let alone which of those can be considered at risk. Agency scientists have estimated the number of shorebirds alone that pass through the northern Gulf at nearly 1.5 million. There are also several hundred thousand to a million colonial-nesting terns, shorebirds, herons, egrets, spoonbills, and ibis in the Louisiana Delta alone. Numbers of wintering ducks and geese can reach nearly 15 million in the Gulf Coast region in some years, according to Ducks Unlimited. In addition, many millions of landbirds migrate over the Gulf between North American breeding grounds and tropical wintering grounds. These birds may be at less risk than shorebirds and waterfowl, but they may encounter reduced food availability or contaminated habitats when they stop over along the Gulf.
Because in cases involving lightly oiled birds or oiled birds in nesting colonies, rescues are likely to cause more disturbance and damage than leaving the birds alone.
Attempting to aid lightly oiled birds is difficult and can endanger them. Birds are wild animals and they don't know they need help; they see rescuers as threats. Many oiled birds can still fly, and even flightless chicks are agile runners. If rescuers were to enter a nesting colony to chase down these birds, many other birds might leave their nests, be driven into the water, or otherwise come to harm through stress or exposure to predators. The biologists at the U.S. Fish and Wildlife Service and Lousiana Department of Wildlife and Fisheries have the unenviable task of making these decisions, and we fully support the work they're doing.
We've written more about this dilemma and the way biologists are approaching it on our blog, here and here .
Cleaning an oiled bird is a difficult and risky process that must only be attempted by a trained and well-equipped cleaning team. If well-intentioned people try to clean birds on their own, the birds are very likely to die. That's why bird rescue hotlines have been set up—to get the birds into the hands of experts.
After rescue, oiled birds are taken to a rehabilitation center, where they are first stabilized for several days. When they are strong enough, they are cleaned by a group of trained workers. Afterward, they are monitored for a week or longer until it's clear they are in good health and their feathers are fully waterproofed. Finally, they're released into the wild. Because the spill and its damage is ongoing, most released birds have been moved to the Atlantic or Texas coasts in an attempt to keep them from returning to the oil.
Practices for rehabilitating oiled birds have been worked out in detail over the past several decades. Techniques have been carefully refined and evaluated. As a result, survival rates, though still variable, have improved substantially. Here's some more detail on what happens during the 2-week process:
Because of oil's toxicity, just-rescued birds tend to be suffering from dehydration, hypothermia, malnourishment, and illness or infection. The birds are typically too weak to survive immediate cleaning. They are held in pens for 2-5 days and monitored closely. During this time they are kept warm, given antibiotics, and tube-fed a nutritional slurry and rehydrating liquids up to four times per day. The birds are also evaluated as to their likelihood of surviving cleaning; severely ill or oiled individuals may be euthanized at this point---a difficult but humane decision.
Once a bird recovers some of its strength (as evaluated by rehab staff), it's ready for washing by a team of two or three people. Birds covered with especially sticky oil may be pre-washed in warm canola, olive, or mineral oil. Water for washing is kept between 104 and 106 degrees Fahrenheit and contains 1-2 percent Dawn dishwashing detergent. Workers carefully clean oil from feathers and skin by hand or with a toothbrush or water spray. The washing water is changed frequently until the bird no longer has any oil on it and the water is clean. Then it's given a warm rinse and placed in a heated drying pen.
After the bird has dried off it still needs to recover its strength and its waterproofing abilities. This typically takes about a week of care and monitoring. The birds stay in outdoor enclosures with pools of warm water, where they can resume natural swimming and diving behavior. Workers closely monitor them for signs of hypothermia, which may be a sign of incomplete cleaning. Weak birds may still be tube fed, but most graduate to eating whole fish at this point. Before release, the birds are thoroughly examined by veterinary staff.
The two main rescue organizations have more information on their websites: International Bird Rescue Research Center and Tri-State Bird Rescue and Research .
This debate was the subject of several media stories during the first months of the oil spill. Both sides make persuasive arguments: Those against rehab say it helps only a tiny fraction of birds, many of those don't survive long after they've been cleaned, and the money spent on rehab would be better spent on other approaches such as cleaning up oiled habitat. People in favor of rehabilitation argue that today's techniques give a much higher post-release survival rate to cleaned birds, that saving even a small percentage of oiled birds is better than nothing, and funds for rehabilitation don't take away from funds for habitat restoration.
One way to make sense of the debate is to regard rehab as either an ecological question or a humanitarian one. In stark ecological terms, saving a very small percentage of a population is unlikely to make a large impact on the survival of the population as a whole. But in humanitarian terms, it's very difficult to hold back the sense of responsibility and empathy that many people feel when they see animals injured or killed through our own actions. Even without official bird-rescue stations, people will attempt to rescue birds in distress, so it's probably a good idea to have that work done by professionals. Also, rehabilitators have refined their techniques during past oil spills—acquiring levels of expertise that can be very important in cases where oil strikes endangered populations that simply must be saved.
At the same time, the visible rescue of individual oiled birds should not distract attention from the very important work of saving bird populations. This will require a much longer and less obvious commitment of time, money, and people to trace the effects of oil through the affected ecosystems (primarily open ocean, inshore waters, intertidal areas, barrier beaches, and saltmarshes). The Cornell Lab is committed to providing science support to efforts to monitor and restore these ecosystems, so that the Gulf's incredible shorebird and seabird populations can thrive again.
Many thousands of concerned people signed up through a variety of organizations to help in the Gulf. The volume of the response swamped out the limited number of opportunities for people to help. This was particularly true for wildlife rescue and research operations, which require specially trained and equipped personnel. Other ways to help include supporting nonprofit organizations working in the Gulf and contributing your own data to oil-spill initiatives started by two of our citizen-science projects, eBird and NestWatch .
We are not directly involved in bird rescue or rehabilitation. Cleaning oiled birds is an involved procedure that requires special equipment and training. It can be dangerous for both birds and people. Our expertise lies in studying wild birds and is quite different from the veterinary skills needed to safely rehabilitate oiled birds. Two organizations with decades of experience in saving oiled birds, the International Bird Rescue Research Center and Tri-State Bird Rescue and Research , have been managing the situation since the beginning of the spill. We are focusing our attention on providing science support to efforts to monitor and recover the region's bird populations.
Human-caused oil spills have been happening since the beginning of the twentieth century, giving scientists ample opportunity to learn about what happens after a spill. In particular, the Exxon Valdez spill in 1989 was extensively studied and produced many findings. Some of the important lessons include:
Preparation for spills tends to be inadequate. This was one of the most basic findings of research after Exxon Valdez—that Exxon did not have enough cleanup equipment on hand in case of a spill. The same pattern was seen after major spills in the United Kingdom, France, and Spain in the 1990s and early 2000s. Though this sounds like an obvious lesson and one that should be straightforward to address, it's clear that there was not nearly enough prevention or cleanup capability on hand to deal with the Deepwater Horizon spill.
Spilled oil remains in ecosystems for decades. When spilled oil gets buried in sediments, it is sheltered from decomposition but still able to affect wildlife. As late as the 2000s, scientists were still finding buried oil from spills in 1969 (Florida barge, Massachusetts), 1979 (Ixtoc I, Gulf of Mexico), and 1989 (Exxon Valdez, Alaska). In 2007, fiddler crabs were still showing effects from the buried oil in the Massachusetts spill, and in 2009 Harlequin Ducks in Prince William Sound still tested positive for direct exposure to Exxon Valdez oil.
The long-term impacts to wildlife can outweigh the short-term impacts. At the time of the Exxon Valdez spill, biologists thought the majority of impacts happened in the first months after a spill. For that spill, those direct impacts included casualties such as an estimated 250,000 dead seabirds, 2,800 sea otters, and 14 of Prince William Sound's 36 orcas (killer whales). But as years passed, scientists were shocked to see spill impacts actually worsening in many species. Even 20 years on, populations of three bird species (Barrow's Goldeneye, Black Oystercatcher, and Harlequin Duck) have yet to return to normal, and another species (Pigeon Guillemot; along with the area's herring stocks), is not recovering at all.
Very small amounts of oil can harm birds or increase their vulnerability to other stresses. After the majority of oil has dissipated, remaining oil traces can harm birds. Research shows that a thin smear of oil can cause eggs to fail to hatch in at least 10 species (in Sandwich Terns, less than 1/1000th of an ounce was enough to reduce hatching success by 56%.) Because oil contains compounds that interfere with hormones, traces of oil can hinder development or cause deformities in growing chicks, and can upset or mistime normal reproductive cycles in adults. And birds exposed to low levels of oil over long periods have lower body weight and are less resilient in the face of adverse conditions such as extreme cold.
Cleanup activities must be carefully designed and monitored. In an attempt to remove oil from Prince William Sound's rocky beaches, cleanup crews spray-washed the rocks with hot water. Only later did scientists learn that the scalding water had damaged microbes and algae that live on the rocks, slowing recovery of the beaches and the animals that live there. The Gulf Coast's saltmarshes are analogous: they are fragile ecosystems held together by the intertwining roots of marsh grass, and oil cleanup has to balance the benefits of removing oil against the damage that those efforts cause.
Public involvement after a major oil spill can produce meaningful changes. The Exxon Valdez spill happened in 1989, spurring Congress to pass the Oil Pollution Act in 1990, making stiffer safety requirements for oil tankers including phasing in requirements for double-hulled designs. Because tankers move between countries, these new regulations helped to usher in safer ships worldwide.
The Exxon Valdez Oil Spill Trustee Council published a useful and very readable summary of research findings 20 years after the spill.
Once spilled, oil can remain in the environment for four decades or more. After 21 years, there's still an estimated 21,000 gallons of oil from the Exxon Valdez spill along the Prince William Sound shoreline. And more than 40 years after a spill in Cape Cod, Massachusetts, oil remains buried in the saltmarshes, where it is still keeping fiddler crabs from digging burrows to their usual depth. See the previous question (What have we learned from past spills?) for more details.
As soon as spilled oil reaches the water surface, its most volatile and toxic components begin to evaporate. The remaining oil is sticky; it collects particles floating in the water. Slowly, this oil gets more dense and eventually sinks, to come to rest either in the deep ocean or along the beaches, intertidal zones, and saltmarshes.
Certain microbes that occur naturally in ocean water also help to break down the oil. They use up oxygen as they do this, and when oxygen in the water or sediment is used up, this process of breakdown stops. This oxygen limitation is the reason why oil persists for so long after it gets buried in sediment. Bacteria can't digest the oil, but burrowing invertebrates can still encounter the oil and slowly pass it up the food chain.
Yes. Damage to the habitats of the Gulf is perhaps the single most important aspect of this disaster. Birds exist near the top of their food webs. Just as it will take time for people to recover from the spill, effects on birds won't become entirely apparent until the oil has done its damage to plankton, seaweed, marsh grasses, fish eggs, shellfish beds, marine larvae, and so on.
At the Cornell Lab, we believe that long-term research and monitoring of the Gulf Coast's habitats are imperative for us to fully understand the damage done to the region, and to plan for its recovery.
Very little is known about the effect of oil dispersants on birds or other animals, particularly in the amounts used during the Deepwater Horizon oil spill (about 2 million gallons). We know that dispersants are toxic chemicals, though they're less toxic than crude oil. There's also the physical effect that dispersants have on the oil: they break up large slicks into tiny blobs that may travel farther and be more easily consumed by invertebrates, fish, and birds. Dispersed oil can remain deep in the water, where it's essentially unavailable to birds, though it may have grave consequences on fish.
The question of dispersants' ecological effects will be one very important area of research in the aftermath of the oil spill.
In the early days of this disaster, Cornell Lab director John Fitzpatrick wrote this moving op-ed that spells out the takeaway lesson: that we as a people must weigh our energy choices against the very real ecological damage they can cause.
And in June, in Birds & Blooms magazine, director of conservation science Ken Rosenberg said, "This is a real catastrophe that happened because the energy companies and the government agency that was supposed to be regulating them just were not prepared technologically for this sort of disaster. Yet they were taking risks mining the seabed for oil. This explosion and leak could have happened somewhere else; it could happen again. As much as our country does want oil and as much as our economy depends on it, we have to take a very serious, long-term look at what the risks are and make sure we're prepared to deal with worst-case scenarios like the one we're facing now."
This spill is so large that it may seem as if it's beyond the ability of any individual person to help repair. But public pressure in response to the Exxon Valdez oil spill spurred Congress to pass strict legislation just one year later—you can make a difference by voicing your concerns about drilling safety and energy policy to your politicians.
Find answers to questions about bird behavior, bird feeding, molt, helping injured birds, the nesting cycle, and more at our main FAQ page.