In April 2018, a pipeline belonging to Texas-based petroleum company Andeavor ruptured near the small town of Buhl, Idaho, spilling about 7,000 gallons of diesel fuel across an area the size of five football fields, much of it ending up in a small creek and a pond used for livestock.

During the cleanup, workers discovered dead birds, internal U.S. Fish and Wildlife Service communications show. But no one appears to have looked into why the birds died, much less pursued action against anyone.

It’s the kind of incident that the federal agency charged with protecting wildlife would historically have investigated, because killing many species of migratory birds ― either on purpose or unintentionally ― violates the 1918 Migratory Bird Treaty Act (MBTA). But months earlier, in December 2017, Daniel Jojani, the top lawyer at the Department of the Interior and a longtime former adviser to the fossil fuel moguls Charles and David Koch, issued a highly controversial legal opinion that allowed all unintentional migratory bird deaths, including those caused by oil and gas operations, chemical spills, power lines and wind turbines. As long as the birds die when a company or individual means to do something else, it isn’t an issue, according to the opinion.

The move broke from decades of legal precedent, and the Trump administration has since introduced a rule to codify that change and permanently slash protections for hundreds of species of migratory birds.

It’s “an absurd, incorrect and illegal interpretation” of the law, made even more outrageous by the fact that it comes amid a global biodiversity crisis that has pushed up to 1 million species to the brink of extinction, said Erik Schneider, a policy analyst at Audubon, one of several wildlife organizations challenging Trump’s controversial policy in court.

And it has led the Trump administration to largely abandon investigating migratory bird deaths ― even in cases in which officials are unsure if the killings are unintentional, according to a batch of documents that American Bird Conservancy and other environmental groups obtained through public records requests and that were shared with HuffPost.

Staff Photographer / Reuters A pelican coated in oil stands on the beach in Ship Island, Mississippi, in July 2010, weeks after the Deepwater Horizon oil spill started.

A few days after the Andeavor spill was discovered, an employee of Fish and Wildlife’s Ecological Services Program in Boise emailed an agency law enforcement officer to provide an update on two coolers that someone dropped off at a government office that “were indicated to contain bird carcasses.” A card left with the containers included contact information for an Andeavor employee.

“You indicated that due to the new solicitors opinion regarding incidental take, if these were mortalities incidental to an oil spill, their may be no need to hold the carcasses as there would be no need for an enforcement response,” the employee wrote April 5 (names and personal information have been redacted in the documents). The staffer added that someone had mentioned the birds may have “died from gunshot wounds” and that there was “still uncertainty about the cause of death.”

The FWS special agent responded eight hours later to say that, in accordance with the new policy, the agency’s law enforcement arm is “no longer involved” in Migratory Bird Treaty Act cases involving incidental deaths.

“Please retain/dispose of the birds” as the agency’s ecological services office sees fit, the agent wrote.

Katie Merx, a spokesperson for Marathon Petroleum Corp., which later merged with Andeavor, told HuffPost via email that “2 or 3 ducks″ were found at the spill site, but it was “very clear” they had died of gunshot wounds before the incident. The dead birds were turned over to state and federal wildlife officials, but “there was no follow up because their deaths were not related to the spill,” she said

As for the coolers, Merx claims they were filled not with birds but rather dead fish.

Were they birds? Were they fish? How many and how did they die? The Fish and Wildlife Service doesn’t seem to know or to care. The agency did not respond to HuffPost’s specific questions about the Idaho case, the broader effects of the policy change or what now triggers an investigation.

The agency is “currently working on a scientific analysis to assess the potential impacts our proposed rule could have on bird populations,” an FWS spokesperson said in an email statement. Any claims that populations will be negatively impacted, they said, “would be speculative and irresponsible.”

milehightraveler via Getty Images A western kingbird, one of more than 1,000 species of birds protected by the Migratory Bird Treaty Act, perches on a fence post near a wind farm in northern Colorado.

The MBTA was enacted a century ago to combat overhunting of bird species fueled in part by the commercial trade of feathers for high-end hats. In the 1970s, the federal government began prosecuting timber, fossil fuel and mining companies under the law for unintentional but often avoidable bird deaths caused by industrial activity. The most notable example is the $100 million in fines that BP agreed to pay over damage from the 2010 Deepwater Horizon oil spill in the Gulf of Mexico, which killed an estimated 1 million birds.

Jorjani’s sweeping reinterpretation means MBTA now prohibits only the purposeful hunting, capturing or killing of bird species. In other words, if an activity or operation ― drilling for oil, constructing a building, spraying chemicals or cutting down trees ― is not intended to kill birds, then any resulting bird deaths are not a violation of the law.

The effects have been far-reaching.

In July 2017, FWS opened an investigation into the death of an osprey that was found electrocuted and dangling from a power line in Paris, Tennessee. In a report on Jan. 3, 2018, less than two weeks after Jorjani’s legal opinion, an FWS official wrote that “due to recent Solicitor’s opinion M-37050 no further investigative action is needed and [special agent] recommends closing case.”

Similarly, when the U.S. Coast Guard notified FWS in January 2018 of a tugboat that spilled oil off Cape Cod, Massachusetts, killing at least 29 birds, a wildlife officer responded that the agency is operating under the new opinion and “there is currently no enforcement action planned.”

In the five years before the Trump policy change, FWS law enforcement completed 152 investigations into MBTA-protected bird deaths from industrial activities including oil, gas, solar and wind energy, according to agency law enforcement data. Since the legal opinion in late 2017, FWS has closed at least seven industrial investigations, only one of which was opened after the policy took effect and which was later closed without prosecution.

Barcroft via Getty Images Snow geese wintering in Bosque del Apache National Wildlife Refuge in Rio Grande, New Mexico.

It’s not just that investigations have come to a halt. Agencies have also discouraged companies from taking precautionary measures to prevent bird deaths and from reporting fatalities to officials, a recent New York Times investigation found.

In rolling out the rule to cement the changes last month, FWS Director Aurelia Skipwith said a primary goal is to ensure private industry can “operate without the fear and uncertainty that the unintentional consequences of their actions will be prosecuted.”

Fossil fuel, mining and agricultural interests will no doubt be the biggest beneficiaries, a reality that was confirmed by an FWS press release last month that included 28 glowing reactions, many of them from industry organizations that lobbied for the changes. David Klinger, a former FWS public affairs official, sent a letter to Skipwith urging her to disavow and withdraw the release, calling it a “blatant attempt to ‘steer’ a rulemaking action to a predetermined conclusion.” A 45-day public comment period on the proposed rule ends March 19.

The proposed rule itself acknowledges that some companies are likely to “reduce or curtail” current efforts to prevent bird deaths in response to the change, as E&E News first reported. Still, the industry-friendly administration trusts industry to do right by birds.

“Many businesses will continue to take actions to reduce effects on birds because these actions are best management practices for their industry or are required by other Federal or State regulations, there is a public desire to continue them, or the businesses simply desire to reduce their effects on migratory birds,” the 43-page rule states.

That prediction appears to be based on little more than a hunch. FWS notes in its proposal that it has not tracked the extent to which companies have continued or scrapped mitigation efforts in the three years since Jorjani’s legal opinion.

MCT via Getty Images A pit containing fresh water or fresh water with chemicals sits next to a drill site in Butler County, Penn.

Critics argue that the Trump administration’s overhaul muddies MBTA enforcement and opens the door to gross negligence ― or worse. The proof, they say, can be found in the agency’s own guidance.

In an April 2018 memo, FWS attempted to clarify how staff should implement Jorjani’s opinion by providing several hypothetical situations. One example given is a state transportation department pressure-washing barn swallow nests off a bridge before painting it. While purposefully removing the nests would require a permit, FWS added that “if the intent was to simply paint the bridge and the nests were accidentally destroyed incidental to that process, that destruction would not violate the MBTA.”

It’s easy to see how that might allow someone to falsely claim that removing the nests was an accident and that their sole focus was giving the bridge a fresh coat of paint. The question then is what prevents someone from, say, cutting down a tree where a nuisance bird of prey has its nest and then telling authorities they were simply trying to get rid of an unwanted tree? At what point would FWS launch an investigation? (Again, FWS did not respond to HuffPost’s specific questions.)

In addition to creating confusion among government employees about how to respond to incidents, the policy change has placed the burden on underfunded federal agencies to prove intent, said Schneider, the Audubon policy analyst. And not only when it comes to large industrial hazards.

“In cases where someone might know that they’re killing birds, how do you actually prove it was truly some unintentional act?” he asked.

Audubon believes more birds will die because of the policy change, although putting a number on it is difficult, Schneider said.

Perhaps most significant, the rollback strips government of a key tool to leverage against industry, leaving companies with little incentive to work with wildlife officials and proactively mitigate bird deaths that, while unintentional, may not be unforeseeable. Though fossil fuel, agriculture and other industries claim MBTA has been used as a “weapon” to target and delay their activities, it is those very industries that pose some of the biggest threats to birds.

Poisoning from pesticides and other toxic chemicals kills an estimated 72 million birds per year in the U.S., according to FWS data. More than 25 million die annually in collisions with electrical lines, while an estimated 750,000 are killed after landing on fluid-filled waste pits at oil production operations. Wind turbines kill a much smaller number, about 234,000 birds each year, still, Trump has repeatedly overstated their harm, calling turbines “bird graveyards” that “destroy” populations.

Trump’s nuts rant about wind energy: “I never understood wind. You know, I know windmills very much... Gases are spewing into the atmosphere. You know we have a world, right? So the world is tiny compared to the universe. So tremendous, tremendous amount of fumes & everything.” pic.twitter.com/DvkJq9NbWg — Aaron Rupar (@atrupar) December 23, 2019

William Woody, who for 16 years served as the top law enforcement chief at both FWS and the Bureau of Land Management before the Trump administration removed him as director of BLM’s Office of Law Enforcement last June, said enforcement under MBTA has long been about promoting compliance and working with industry to avoid criminal prosecution. And though he hopes that private industry continues to implement best practices to avoid killing birds, only time will tell.

“You’re going to have some bad actors in there, no doubt about it,” Woody said.

An FWS spokesperson said the “overwhelming majority” of the agency’s work with industry on MBTA issues has been voluntary.

“Together, we have developed industry best practices and helped proponents of numerous, diverse projects reduce their impacts to birds,” they said. “This work will still continue.”

Like many of the Trump administration’s priorities, weakening MBTA was at the top of the oil industry’s wish list. Trump has even parroted a story about dead birds that oil billionaire Harold Hamm has been telling for years, as The Washington Post reported back in 2016. Hamm’s firm, Continental Resources Inc., faced criminal charges in 2011 after dead birds were discovered in unlined oil waste pits. A federal judge ultimately tossed out the case in 2012, ruling that inadvertent bird deaths from legal industry activities do not violate the MBTA ― a decision that the Trump administration highlights in its proposed MBTA rule. Other courts, however, have held that the law does criminalize the incidental killing or harming of birds.

Three years after Jorjani’s legal opinion, top administration officials are still struggling to answer basic questions about what the MBTA change would mean in the event of a catastrophic oil spill.

At a congressional hearing this month, Sen. Chris Van Hollen (D-Md.) asked Interior Secretary David Bernhardt, a former oil and gas lobbyist, if it is true that the proposed rule would have made it impossible for the federal government to collect the $100 million in fines from BP for bird deaths related to Deepwater Horizon.

“I’d have to go back and look at that particular settlement agreement,” Bernhardt said. “I wasn’t here when it was done.”

Perplexed at Bernhardt’s response, Van Hollen accused the agency chief of “acting like BP’s lawyer.”

“You’re eliminating the legal basis that was used for getting this fine,” Van Hollen said. “That’s a reality.”