Águia, gavião ou falcão? Saiba identificar as espécies

Cerca de 70 espécies de aves de rapina estão distribuídas pelo Brasil; Gavião-real é a mais poderosa.

Por: Marcus Cabral - 13/02/21

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Harpia é uma das aves de rapina mais imponentes do mundo — Foto: Carlos Alberto Coutinho / TG

No mundo das aves existem aquelas espécies que literalmente reinam no céu: os rapinantes.

E, convenhamos, não é preciso ser admirador da natureza para se impressionar com a imponência desses seres alados. O tamanho do corpo, as garras, o bico e a habilidade em atacar as presas são algumas das características que marcam a força dos gaviões, falcões e águias.

No Brasil, as aves de rapina são dividas em três famílias a Falconidae, Pandionidae e Accipitridae. O primeiro grupo corresponde aos falcões, o segundo é restrito a uma única espécie - a águia-pescadora - e o terceiro engloba tanto gaviões como águias.

Pelo menos 70 espécies diferentes de rapinantes se distribuem pelo País, mas como identificá-los? Distinguir uma ave da outra não é tão fácil quanto parece, ainda mais quando elas possuem características físicas em comum.

Mas com um pouco de atenção é possível diferenciar e ainda saber se a ave avistada em campo trata-se de uma águia ou um falcão, por exemplo.

Tamanho, comportamento e voo podem ajudar na identificação — Foto: Arte TG

A primeira diferença pode ser notada pelo tamanho. As águias são os rapinantes mais imponentes, sendo consideradas de médio a grande porte. Já os gaviões e os falcões são menores, sendo de pequeno a médio porte.

As águias possuem asas largas e compridas e as garras são fortes e desenvolvidas. Apresentam uma proeminência óssea acima dos olhos, o que torna a ave com um olhar impactante.

Os gaviões são muito semelhante às águias, assim como elas, também caçam e perfuram as presas com as garras e planam em voo. A principal diferença é que são aves menores. O que pode ser notado também no tamanho diminuto da cauda.

Gavião-asa-de-telha tem face semelhante às águias e apresenta comportamento estratégico — Foto: Kleber Tadeu Jeronimo / Acervo Pessoal

Já os falcões se diferem dos outros pelo porte - que pode ser pequeno ou médio - e principalmente pelo formato da asas estreitas e pontiagudas. Além disso, esses rapinantes não planam no ar e não usam as garras para matar as presas, e sim o bico.

Diferente de muitas crenças que são pregadas a respeito da diferença destas aves, não é possível distingui-las pela coloração do bico, olhos e pés, mas sim pelo comportamento e características físicas.

Características da harpia sobressaem entre as aves de rapina do mundo — Foto: Arte TG

De acordo com o ornitólogo, Willian Menq, especialista em estudos sobre aves de rapina, a principal diferença entre as espécies se dá pelo porte e também captura das presas, mas é importante lembrar que sempre há exceção quando falamos em vida selvagem.

Uma curiosidade é que nem sempre o nome da espécie faz referência ao grupo que ela pertence, como é o caso do gavião-real, também conhecido como harpia. Apesar de ser chamada de "gavião" a espécie é uma águia, aliás, uma das mais imponentes do mundo.

"Na realidade não existe um critério taxonômico para diferenciar esses grupos de aves. Os critérios são morfológicos e ecológicos", explica Menq.

The ancestors of all modern birds, from the hummingbird to the majestic bald eagle (Haliaeetus leucocephalus, seen here as a young adult), lived on a supercontinent in the Southern Hemisphere about 95 million years ago, a new study suggests.

Wikipedia Commons/Adrian Pingstone

Asteroid impact helped create the birds we know today

O impacto de asteroides ajudou a criar as aves que conhecemos hoje

By Sid PerkinsDec. 11, 2015 , 2:00 PM

Every bird alive today can trace its ancestry to creatures that lived about 95 million years ago on a chunk of land that split off from the supercontinent Gondwana, a new study suggests. The new family tree, compiled using information from fossils and from genetic analyses of modern birds, reveals that this lineage underwent a major burst of evolution after an asteroid slammed into Earth about 66 million years ago and killed off the rest of their dinosaurian kin. But factors such as changes in global climate and the drifting of continents have played major roles in defining and shaping the diversity and distribution of bird species, too, the scientists say.

“This is one of the most comprehensive studies that attempts to date when these evolutionary divergences happened,” says Luis Chiappe, a vertebrate paleontologist at the Natural History Museum of Los Angeles County in California, who wasn’t involved in the new research.
Modern birds, a group called Neornithes (a name that combines neo and a variant of ornis, the Greek words for “new” and “bird,” respectively) are the most diverse and widespread vertebrates on Earth today. Previous studies that used only information from genetic analyses of current species have suggested that birds arose anywhere from 72 million to 170 million years ago. But the new study, which includes anatomical data extinct species preserved in the fossil record, narrows that window considerably, says Joel Cracraft, an ornithologist at the American Museum of Natural History in New York City.

He and museum colleague Santiago Claramunt, also an ornithologist, didn’t include well-known ancient birds such as Archaeopteryx and Confuciusornis, which belonged to lineages that eventually died out. They only looked at species that belonged to the three major groups of birds alive today: Palaeognathae (ostriches and their close relatives), Galloanseres (waterfowl, pheasants, and their close kin), and Neoaves (all other birds).

The team’s genetic information came from analyses of two particular genes from 230 species representing all major subgroups of modern birds. (Mutations in those genes, which are related to basic biochemical processes that take place in all cells, helped the researchers estimate when those groups arose or diverged from their closest relatives, Cracraft says.) Anatomical data from 130 extinct species that had once lived worldwide helped the team figure out when and where those groups originated, as well as how quickly they evolved.

The results suggest that the last common ancestor of all modern birds—in other words, the species at the base of the evolutionary family tree that includes all living bird species—lived in West Gondwana, a landmass that included what are now fragments of South America and large portions of Antarctica, about 95 million years ago. What’s more, all three major groups—Palaeognathae, Galloanseres, and Neoaves—had already arisen by the time the dino-killing asteroid smacked our planet 66 million years ago, the researchers report online today in Science Advances. So although the resulting die-offs may not have triggered the original diversification of birds, by eliminating many ecological competitors, the extinction provided opportunities for survivors to diversify and spread, Cracraft says.

In eras since the asteroid impact, changes in global climate significantly affected how quickly new species evolved, the researchers found. When global climate cooled, areas experiencing what are today considered tropical conditions shrank back toward the equator, and the net rate of species appearance (the number of new species that evolved minus the number that went extinct) increased. When global warmth returned, those newly minted species could then spread worldwide—as long as they didn’t run into gaps between continents too big for them to fly across. Birds stuck on landmasses that had drifted into isolation due to the long-term movement of Earth's tectonic plates, such as Australia and New Zealand, were consigned to evolve in isolation.

The team’s results are “reasonably convincing, and their new insights make sense,” says Edward Braun, an evolutionary biologist at the University of Florida in Gainesville.

Among those new insights is a notion of how birds spread throughout the ancient world. Whereas some groups spread southward through the fragments of Gondwana to reach what are now Australia and New Zealand, others spread north to what is now North America. From there, some species spread eastward into Eurasia and Africa and others moved westward, across occasional land bridges exposed when global sea levels were low, to eastern Asia. In particular, the new data “better match the origins of certain groups of birds once thought to have arisen in Africa,” Braun says.

Although the new study answers many questions, it poses many more, Chiappe says. Among them: Why did a large class of now-extinct birds called Enantiornithines (which were superficially similar to modern birds) die out? That’s especially mysterious because Enantiornithines were exceptionally abundant (they apparently outnumbered the ancestors of modern birds before the asteroid struck) and had presumably played the same ecological roles as the ancestors of modern birds, which survived the mass extinctions.

*Correction, 14 December, 11:42 a.m.: New information has been added to note the major influences that global climate and continental drift have had on the diversity and distribution of bird species.

Posted in:

• Plants & Animals

doi:10.1126/science.aad7562