President’s Message

Thank Geology for the Birds

I would like to use this opportunity, in my last message as President, to meld two themes which have been longstanding interests of mine – birds and geology. Over the past two years, I’ve penned a number of newsletter articles highlighting many aspects of the diversity of birds. Yet, how did birds achieve such great diversity and ecological success? Through recent fossil finds and new analytical techniques coupled with an in-depth understanding of fundamental geological processes, the origin and evolution of birds is now one of the best understood transitions in the history of life.

Where did birds come from? Until recently, this was a subject of hot debate. The first hint that birds might be related to reptiles came from the discovery of an exquisitely preserved fossil in Germany in 1861. Called Archaeopteryx, it possessed a curious mixture of feathers and wings as well as claws and a long bony tail. It is now widely accepted that birds evolved from dinosaurs – specifically a group of dinosaurs called theropods, many carnivorous members with which you may be familiar, including Tyrannosaurus (e.g. T. rex!), Allosaurus, and Velociraptor. Birds first appear in the fossil record a long time ago – namely 165-150 million years ago (which on the Geologic Time Scale, is referred to as the Jurassic Period). Moreover, the oldest birds were small, probably chicken-sized, lightweight, long-armed, winged, and feathered. The first major diversification of birds occurred not long after (geologically speaking!) – about 130-120 million years ago, during the Early Cretaceous – but the true modern birds result from later diversification after a now well-known mass extinction event at the end of the Cretaceous Period. Sixty-six million years ago, a large meteorite struck the earth (just off the eastern coast of Mexico in the Gulf of Mexico) which triggered a global cataclysm – earthquakes, tsunamis, wildfires, acid rain, and climate change – wiping out all non-avian dinosaurs and many other organisms. This sudden change in the world order gave other groups, such as birds and mammals, an explosive opportunity to grow, evolve, and diversify.

Beyond providing fossils and meteorites, however, geology has played other key roles in the evolution of birds.

Modern birds can be divided into effectively two main groups – flightless birds and all other birds. Biologists knew that flightless birds were generally found only in the Southern Hemisphere, e.g. moas* and kiwis (New Zealand), emus (Australia), cassowaries (Australia and New Guinea), ostriches (Africa), rheas (South America), dodos* (Mauritius), and elephant birds* (Madagascar) [note: * = now extinct]. But how did a group of flightless birds end up scattered across the Southern Hemisphere? This puzzle was finally solved with the theory of plate tectonics, when it was realized that, 200 million years ago, the southern landmasses were all part of a single supercontinent called Gondwana (which means “forest of the Gonds”, a region in central India). Notably, the ancestors of these flightless birds must have thrived throughout Gondwana, but geologists think this supercontinent broke up into different pieces (“plates”) of the Earth’s crust and underlying mantle (causing the separation of South America from Africa, and Australia from Antarctica, for example, and resulting in the creation of smaller landmasses and continents that gradually drifted apart to where they are today).

Many of us may not have realized that Australia appears to have played a particularly key role in bird evolution. Songbirds are the most successful group of birds on the planet. Consisting of more than 5000 species globally, they comprise about half of the world’s known bird species and are found on all continents except Antarctica. Often known as perching birds, they have three toes pointing forward and one pointing backward, allowing them to cling to trees and branches. Of course, we love them for their birdsong. Until recently, most ornithologists believed that many bird groups evolved in the north, only later spreading to Australia, possibly biased by the widespread 19th-century colonial notion at the time that Terra Australis was “empty”, void of anything. However, the earliest known songbird fossil comes from the Eocene (54 million years ago) in southeastern Queensland, and it is not until 24 million years later (in the early Oligocene, 30 million years ago) that we find the oldest songbird fossil in the Northern Hemisphere (in southern Germany). Songbird fossils first show up in the New World some 7-15 million years after that (early/middle Miocene, 23-15 million years ago). The rise of DNA analysis now seems to suggest that much of the early evolution of songbirds took place in Australia and they radiated outward from there. But why?

The answer is geology. The tectonic break-up of Gondwana led to the gradual separation of Australia from Antarctica, commencing ~85 million years ago, with Australia starting to drift northwards. During this time, Australia became more and more isolated from the rest of the world by large stretches of open sea, and researchers think that this allowed songbirds to diversify for millions of years in isolation. Changing climates within the continent as it drifted north created dramatically different ecosystems ranging from lush rainforests to arid grasslands, forcing Australian birds to adapt and diversify. By 30 million years ago (Oligocene), Australia was completely separated from any other landmass. While diversification continued, however, the explosion of global diversification did not appear to happen until the Miocene (~12 million years ago) when volcanic islands forming close to Australia (likely New Guinea – again, geology in action!) allowed the songbirds to move offshore to colonize Asia and beyond. This theory is also consistent with the fact that Australia and Indonesia are the top two countries with the most endemic bird species, i.e. birds found nowhere else. For example, out of the 850 species in Australia, 45% are endemic! It’s truly an amazing detective story to try and piece together, but it is clear that without geology, it wouldn’t be possible.

In closing, it has been a privilege serving as President of the SNS for the last two years. During this time, I must thank the enthusiastic and very capable members of the Board, with whom it has also been a delight to work. I am particularly pleased that we have such strong community engagement across all ages (through our Young Naturalists and Kids-in-Nature programs, our varied field trips throughout the year, and the wonderful Golden Eagles program) and reinforced our linkages with like-minded organizations like the Nature Conservancy of Canada (through our partnership with the Asquith Complex) and with the Meewasin Valley Authority and local Saskatoon nature-based initiatives (through our rejuvenated Conservation Committee). Finally, I hope this article has provided a greater understanding of why we should all thank geology for our morning songbird chorus. And now you also know why birds really rock.

Jim Lee

Saskatoon Nature Society

Connecting People and Nature

Saskatoon Nature Society
Box 27013 Grosvenor Park
Saskatoon, SK S7H 5N9

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Saskatoon Nature Society
Box 27013 Grosvenor Park
Saskatoon, SK S7H 5N9