In terrestrial environments, predator body size is largely correlated with prey body size. The opposite is found for many predators in the marine environment – baleen whales in particular comprise some of the world’s largest mammals and yet they feed on something far smaller (plankton). The leopard seal is unusual in that it feeds both at the top and at the bottom of the food chain, consuming large prey, such as penguins and other seals, and small prey, such as krill, an abundant basal component of the Antarctic food web. While leopard seals are well known as raptorial predators with a ‘grip and tear’ feeding styles, a large portion of their diet (krill) is too small to be eaten in this way. For this, they use filter feeding to separate the krill from seawater.
Seabirds are well adapted to acquire their prey. Those that feed on bivalves close to the surface have short, strong bills to break into shells and access molluscan meat, and those that feed on bivalves buried deeper in the sand have much longer, slender bills to access their prey. The association between bill morphology and the prey type of different bird species is a frequently cited example of niche differentiation, where animals living in close proximity have evolved distinct feeding strategies which prevent them from being in direct competition with each other (known as resource partitioning).
Birds are living, breathing, tweeting dinosaurs. That is scientific knowledge backed up by overwhelming evidence, but the evidence basis for it grows strong all the time. We know that they are related from a host of morphological evidence from the last 150 million years or so. Our understanding of the origins of feathers and flight are developing too – each new finding is a piece that slots into a puzzle, where we already have a pretty good idea of what the picture we’re trying to recreate is. The evidence is mounting too with each new discovery – findings from China are rewriting the way we think about the evolution of feathers and flight, and the evolution of early birds from their dinosaurian ancestors.
The origin of bird flight is one of the greatest stories evolution has ever told us in the history of life on this planet. To imagine how organisms that once ran around on the ground have descendants that soar through the skies is truly phenomenal, and represents a truly great leap in increasing the awesomeness of these animals. The secret of how it came about though is hidden away in the fossil record, with the mysterious tale ever-shifting as our understanding of early birds and feather precursors evolved.