Geoscience Reference
In-Depth Information
scale dinosaur traces, ecological echoes of the interplay between dinosaurs seeking
their respective sustenance.
Worldly Traces: Birds, Pollination, Seed Dispersal, and Hitchhiking Animals
As modern dinosaurs, birds have surely changed the world in small ways through
their extremely varied behaviors and their resultant traces. Bird tracks, nests, bur-
rows, beak probes, drillholes, cough pellets, gastroliths, feces, and tools certainly
constitute bird calling cards, letting you know that individual birds have visited al-
most everywhere you look. Yet bird behaviors and their vestiges have also changed
the face of terrestrial environments, resulting in the ultimate trace of their reign as
Cenozoic dinosaurs.
Glance at nearly any landscape, and then look more carefully for a flowering
plant in it, which you will likely find without much searching. (Hint: all grasses are
flowering plants.) Chances are good that a bird was somehow involved in the evol-
utionaryheritageofthatplantforatleastthepast65millionyears.Nowthinkabout
how flowering plants range in habitat from seashores to mountains, from deserts to
freshwater ponds, and from Arctic tundra to tropical rainforests. Also consider how
flowering plants often dominate those ecosystems through sheer numbers, or play
integral roles as keystone species: remove certain flowering plants, and some eco-
systems become ghosts of their former selves.
How did birds influence this situation, helping flowering plants to live almost
everywhere on the land? Much of this world-altering activity came about through
the special relationship between birds and these plants. Coincidentally (or not),
early birds and flowering plants expanded and diversified at about the same time,
which was in the middle of the Cretaceous Period (about 100-125
mya
). Although
paleontologists cannot say for sure that birds helped with the spread and evolution
of flowering plants during the last half of the Cretaceous, or that flowering plants
aided bird evolution, or that a combination of the two happened, the ecologically
tight relationship we see today between these two suggests that they did indeed co-
evolve.
