The act of oiling refers pretty much to what it sounds like. It is the application of oil to the wings and feathers during preening or through water contact.
Air sacs are a section of a bird's respiratory system. They are attached to lungs and extend throughout the body cavity. Depending on the species, can temporarily store large amounts of air to cool the body and maximize oxygen intake.
A Field mark refers to distinctive characteristics used by a birder to identify particular birds in the wild. Field marks can be coloring, shapes, size and so on.
Birds are often cleaning themselves. This act is referred to as preening. Each species handles it differently, but a common characteristic is the use of the beak to clean wings and such. Not to be confused with anting.
The brood is somewhat of a catch all term meaning either the young birds hatched from a clutch of eggs or the act of incubating eggs in the nest. It can also refer as a verb to the act of keeping chick warm.
Photoperiodism refers to the reaction of birds as well as other animals and plants to the changing amounts of sunlight in a day during the year. Breeding periods and migration are believed to be triggered by it.
Bird designated as dabblers are ones that sit on the water and tip down to eat food, whether plants or animals, below the surface. Ducks are classic dabblers.
Dabbling is the act of a bird sitting on the water and feeding by moving its head below the water line to access plants, bugs, animals and whatever it happens to eat.
The speculum is a marketing area found on a duck. Many ducks have a patch of color on their wings. The color distinction and shape can be used for identification purposes.
Moulting refers to the process whereby birds shed their feathers to be replaced by new ones. Most species moult once a year, but not all.
Nalospi is a measurement that helps in the classification of sighted birds. The Nalospi is the distance between the tip of the bill and the forward edge of the nostril. It is not always easy to see and calculate.
The act of foot-raking is distinct to a classification of birds that feed in the water. The term refers to their moving their feet about in the water to get animals to move so they can feed upon them.
The wattle is one of the easier markers on bird. It is the structure on the top of the head. It can be a comb, gathering of feathers or bone structure. Identify the wattle, and you are on your way to identifying the bird.
Being able to speak Birdinese is important, but hardly the key to enjoying your time on sighting trips. If you feel overwhelmed by the terms, forget them and just enjoy yourself.