Bird – Evolution and Ecology Study Guide


Evolution is the process of living things changing over a period of time. Science teaches us that humans can trace their development from early single-celled organisms to vertebrates and, much later, apes and modern humans throughout billions of years. Similarly, all other living organisms have an evolutionary history stretching back to millions or billions of years.

Bird evolution:

Birds are one of the most recognizable and diverse groups of modern vertebrates. Over the past two decades, a wealth of new fossil discoveries, phylogenetic and macro-evolutionary studies have drastically changed our understanding of how birds originated.

Many in the scientific fraternity firmly believe that the evolution of birds can be traced back to dinosaurs. Several finds in recent years have seemed to support the hypothesis that birds descended from the two-legged, running, meat-eating, Dinosaurs, which are called theropods.

This was based on the discovery of a 150-million-year-old fossilized bird creature Archaeopteryx, in a swamp in Germany in the 1860s, and it is the oldest bird fossil in history. Birds belong to the biological class Aves, and the earliest known species of class Aves is Archaeopteryx lithographica.

Most biologists have accepted that dinosaurs sired birds. ‘Archaeopteryx’ is the first bird. Archaeopteryx had feathers along its arms and tail, but unlike living birds, it also had teeth and a long bony tail.

Evolutionary history of birds:

Overwhelming evidence indicates that birds evolved within the clade Dinosauria. The bird clade Dinosauria is further subdivided into two groups, Saurischia (“lizard hips”) and Ornithischia (“bird hips”). Despite the names of these groups, modern birds did not come from the bird-hipped dinosaurs. Rather, the Saurischia group further diverged into two groups. The second group, bipedal predators called theropods, gave rise to birds. The other group included the long-necked herbivorous dinosaurs, such as Apatosaurus.

Bird evolution chart

Bird evolution chartSource

Bird evolution tree

The tree (in the figure below) explains pictorially the evolution of birds that began in the Jurassic Period, with the earliest birds derived from a clade of theropod dinosaurs.

Bird evolution treeSource

Ecology of a bird

The ecology of birds describes how they fit into the environment, where they live and coexist with other organisms. There are two main aspects in the ecology of birds: feeding ecology and breeding ecology.

a) Feeding ecology:

Birds have a wide-ranging food source, including flower, berry, seed, nectar, fish, worm, crab, mouse, or even another bird. There are a few forms of life that birds do not eat. The shape of a bird’s beak indicates what a bird eats. With so many different types of food, many birds have beaks adapted to specific types of food or specific methods of foraging.

b) Breeding ecology:

During breeding, birds have many varied interactions with the animals and plants around them and other aspects of the environment. For successful breeding, birds require a place to build their nest and materials for the nest, adequate food for their young and a secure place to protect their young from potential predators or other sources of danger. Birds usually breed when there is an optimum chance for their young ones to survive, and therefore the breeding coincides with the time of the year when food for the young birds is most abundant.

Like many other organisms, birds help maintain sustainable population levels of their prey and predator species and, after death, provide food for scavengers and decomposers. Many birds act as pollinators or seed dispersers, playing an important role in plant reproduction and food production.

Birds occupy a wide range of ecological positions and are important members of every environment they live in. Environmental changes affect all areas of a bird’s life. Therefore, environmental changes can be assessed based on many indicators of this change as seen by observing birds and their ecology.

✅ Conclusion:

  • As one of the most recognizable and diverse groups of modern vertebrates, birds’ evolution has intrigued scientists for many years.
  • Fossil discoveries and macro-evolutionary studies have enhanced the scientific understanding of how birds have evolved.
  • Birds play a key role in the environment: as pollinators or seed dispersers, they determine and influence plant reproduction and food production; help maintain sustainable population levels of their prey and predator alike.
  • Climatologists study birds and their ecology to ascertain the environmental changes in a given region.


1. What is the ecology of a bird?

The ecology of birds describes how they fit into their environment and their co-existence with other organisms. Further, there are two main aspects of the ecology of birds: feeding ecology and breeding ecology.

2. What is the evolutionary history of birds?

Birds evolved from theropod dinosaurs during the Jurassic Period(165–150 m). Their classic small, lightweight, feathered, winged body structure has gradually evolved over tens of millions of years.

3. How is ecology and evolution related?

The traditional view has been that ecology shapes evolution. The environment defines a template for evolution: natural selection shapes organisms to fit that template. However, some studies suggest that evolutionary processes reciprocate by influencing ecology.

4. How does ecology play a role in evolution?

Ecological processes, such as species interactions and environmental changes, can influence evolutionary change by altering natural selection. This, in turn, can alter the genetic frequency underlying phenotypic traits.

5. Why is ecology important to evolution?

Biologists are aware that ecology plays a significant role in forming new species and modifying living ones (Ecology – the interaction between organisms and their environment). The environment defines a template, and the process of evolution by natural selection shapes organisms to fit that template.

6. Why do ecologists need knowledge of evolution?

Evolution enables a better understanding of the interactions of organisms with their environments. Evolution is a process that results in changes in the genetic content over time.

7. Is evolution an ecology?

Evolution is the development of changes that can be passed genetically over the history of an organism. Ecology is the study of the interactions between an organism and its environment. Evolutionary ecology studies how environmental factors cause changes in an organism throughout its history.

8. How does the environment affect evolution?

Environmental change and the isolation of organisms play an important role in evolution. Change in an organism’s environment forces the organism to adapt to fit the new environment, eventually causing it to evolve into a new species.

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  1. Evolutionary History of Birds Accessed on 6 Dec 2021.
  2. The Origin and Diversification of Birds Accessed on 6 Dec 2021
  3. Ecological roles of birds Accessed on 6 Dec 2021
  4. Bird Evolution Accessed on 6 Dec 2021
  5. Bird Ecology Accessed on 6 Dec 2021

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