So what are these four similar looking birds who have similar habits (tail wagging and bobbing), and very similar habitats?
|Bird #2 - Spotted Sandpiper|
Birds 3 and 4 are waterthrushes - the Northern Waterthrush and Louisiana Waterthrush, respectively. They belong to the order “Passeriformes” - the perching birds. If you are able to watch either waterthrush for a period of time, you may occasionally see him leave the downed log or the damp pondside and sing his resounding, musical notes while perching on a low tree branch.
|Bird #4 - Louisiana Waterthrush (J.J.Audubon)|
Confused? Don’t be. Classifying species is an art form masquerading as science, although in fairness to the biologists who try to do the classifying, DNA testing is making species classification much more scientific that it use to be.
Though not related, these two sandpipers and two waterthrushes occupy similar habitat, have similar habits, and are similar in appearance. “Convergent evolution” is the term used when unrelated species have, through time, come to look alike, think alike, and live alike.
In a very broad sense, the development of the forearm into a wing in bats and birds is an example of convergent evolution. In the Northern Hemisphere there is the auk family (e.g. Atlantic Puffin) while in the Southern Hemisphere there are the penguins with a similar life style and similar habitats - another example of convergent evolution.
Along our streamsides and ponds we may be able to see convergent evolution up close in the resident Spotted Sandpiper and the transient Solitary Sandpiper, and in the warblers which don’t look like warblers: Northern Waterthrush and Louisiana Waterthrush.
|Bird #3 - Northern Waterthrush (Belize)|
|Bird #1 - Spotted Sandpiper (non-breeding)|
Learning about the habits and relationships of the birds can be very illuminating. Watch the closely and see what you notice. Start with the birds at your feeders. Good Birding!