It is a spring morning in my garden. The clouds are still kissing the ground and everything is bathed with tiny droplets of water. In the sky shines the first glimmer of sunlight and the birds are chirping fervently. A couple of resident hummingbirds come to drink their early nectar ration. In silence, I admire their movements as I sip my tea. How graciously they hover around the lavender bushes and the few remaining peach blossoms. How easy they make it seem.
As in every other story of evolution, this one involves many forces and takes place over a long period of time, far longer even than humanity. It began to come about in the early Cenozoic era. Cenozoic – meaning ‘recent life’ – is the term used to describe the third major era of Earth’s history, which began approximately 66 million years ago and extends to the present. It is during this time period that the continents assume their modern distribution on the world map. For the first time in the Earth’s history large glaciers form, lowering the sea levels, and life emerges as we know it.
By the beginning of the Cenozoic, flowers had been around for almost 100 million years forging stable partnerships. Some still relied on wind or water to reproduce, but most of them had developed exclusive relationships with insects. In the low altitudes and warm climates where flowers usually grew, there was an abundance of hungry insects eager to serve as pollinators in exchange for nectar. The flower-insect relationship was a successful one; in many cases, it continues to be. But the Earth was experiencing major changes and, for some flowers, surviving meant they needed to change with it.
At the dawn of the Cenozoic Era, the Andes mountains began to rise. This event altered completely the landscape of the South American continent and consequently, the life that inhabited these evolving ecosystems. One of the reasons why the Earth’s landscapes and ecosystems change is the interaction of tectonic plates as they undergo geological processes. These are the processes in which mountains and bodies of water both form and vanish. Similar to the rise of the Sierra Nevada and the Coastal Ranges in North America, the Andes were formed in a major tectonic collisions between the Nasca and the South American plate.
As the Andes rose, flowers were taken to higher altitudes where insects were no longer abundant nor reliable messengers for their seeds. Unlike mammals and birds, insects are cold blooded animals. Even in places where it gets warm during the day, the night and early morning cold makes them lethargic. As winters became colder in the rising mountains, flowers there found themselves in need of a new partner.
We don’t know exactly how or when it happened, but around 50 million years ago, somewhere in the damp forested mountains of South America, flowers found a bird that was up for the challenge. The original hummingbirds, with their heavier bills and relatively large bodies, were rather clumsy and fed on spiders and other insects. As the topography of the region changed and insects became scarce in the higher regions, early hummers started visiting nectar-bearing flowering plants, thus beginning their complementary evolution.
It turns out that reaching for nectar inside of a flower while hovering in the air, supporting your own weight, is not at all easy. It requires extraordinary precision and balance, as well as copious amounts of energy. In order to endure this lifestyle, hummers became smaller and lighter over time. Their beaks got thinner, their tongues grew longer and more agile to better search the flowers for nectar. Their legs and feet grew ever smaller, until they could no longer walk or even hop, only perch on branches or fly.
Since hummingbirds were the only reliable pollinators, being able to fly in all weather conditions, flowers developed loyal strategies to protect their nectar from insects and other birds. Some flowers became longer and thinner making the nectar impossible to reach without the hummingbird’s hovering ability and long beak. Others, knowing that bees do not differentiate between red and green, produced red pigments to resemble leaves in the bees’ eyes.
Not only have flowers and hummingbirds overcome infinite changes together, they have also followed each other to distant places. If you look at a map of the Americas today, they can be found everywhere between Tierra del Fuego – the southernmost tip of the South American continent – all the way north to Alaska. Throughout the centuries, it has been their relationship what propels them forward and what has allowed them to survive in places where neither of them could have survived alone.
By Ana Lucia Ralda