Silhouettes of patrolling raptors filled skies throughout Africa as recently as a few decades ago, but it’s much less common to spot those birds of prey today. Now, new research gives an indication of just how sharp the birds’ decline has been.

According to a study published Thursday in the peer-reviewed journal Nature Ecology & Evolution, 88 percent of 42 African raptor species have suffered declines over the past 20 to 40 years, and 69 percent are either more endangered than previously thought or now meet criteria for being threatened with extinction.

“We’re looking at really iconic species in Africa that are declining significantly,” said Darcy Ogada, the African program director at the Peregrine Fund, a nonprofit conservation group that focuses on birds of prey, and an author of the study. “It’s a wake-up call.”

Raptors, carnivorous birds that feed on other vertebrates, play crucial ecological roles as both apex predators that keep other species’ populations in check and as scavengers that recycle nutrients back into the food web and limit the spread of disease around carcasses. “Losing either of those groups is going to have major trickle-down impacts to the rest of the ecosystem,” Dr. Ogada said.

Eagles, vultures and other birds of prey are particularly vulnerable because many species are long-lived, slow-breeding and wide-ranging. In Africa, like most other places, habitat loss is the biggest threat to their survival. Declines are also driven by poaching for food and ritual use, poisoning, electrocution, striking power lines and wind turbines, and climate change.

One of the most worrying findings from the new study, Dr. Ogada said, was that population losses were significant even inside national parks. While the raptor decline was more than twice as bad outside of protected areas as within them, many species inside parks are still “declining substantially,” Dr. Ogada said.

This finding can partly be explained by the existence in Africa of so-called paper parks, Dr. Ogada said, or places where protections “exist in name only and where lack of management or mismanagement is a major problem for wildlife.”

The new paper compiles data that Dr. Ogada and her colleagues had previously collected across four regions in sub-Saharan Africa. The researchers conducted hundreds of surveys by driving slowly along roads and recording every raptor they saw. Other scientists started surveying the same roads as early as 1969, allowing the researchers to draw conclusions about how populations have been doing for the past three raptor generations.

The extent of the losses was “shocking,” Dr. Ogada said. They included an estimated 85 percent decline in secretary birds and a 90 percent decline in martial eagles, one of the world’s largest and most powerful eagle species.

Only five species’ populations increased over the study time period, according to the findings, including African pygmy falcons and pale chanting goshawks. The authors only surveyed birds of prey that are active in the daytime and that live in savannas.

But they said they suspected that the continent’s other 60-plus raptor species, including nocturnal ones like owls as well as those that live in other ecosystems like forests and swamps, are very likely faring just as poorly, if not worse.

Owls are sometimes persecuted out of superstition, Dr. Ogada said, and many zones that raptors depend on are being lost at alarming rates.

Of the species identified by the authors as being in steep decline, nearly half are currently categorized on the International Union for Conservation of Nature Red List as “least concern,” a conservation status reserved for species that are common and widespread.

The fact that supposedly common species are now disappearing across Africa “suggests that habitat loss, environmental degradation and other threats have reached a tipping point,” said Amanda Rodewald, an ecologist at Cornell University who was not involved in the study.

Stuart Butchart, the chief scientist for BirdLife International, a nonprofit group that is in charge of maintaining International Union for Conservation of Nature status listings for the world’s 11,000 species of birds, said that he and his colleagues would be reviewing and, where appropriate, revising the status of each species included in the new paper.

Conservation statuses are important for setting action priorities by governments and other stakeholders, said Dr. Butchart, who was not involved in the study. Such action, he continued, would ideally entail working with local communities to protect more land in areas of high biodiversity, increasing efforts to protect raptors and making sure that new infrastructure like wind turbines is installed with minimal impacts to birds.

One key to achieving these things, Dr. Ogada said, is to engage more Africans in raptor research and conservation. “It’s extremely important to have Africans leading these studies in the future,” she said.

To promote this, the researchers launched a new education and mentorship initiative called the African Raptor Leadership Grant that supports up-and-coming scientists around the continent.

“When you open young people’s minds to what’s happening and the potential they can contribute, they get really keen to start learning about birds,” Dr. Ogada said. “There’s so many interesting topics to explore, and so much to do.”