The diving ducks obtain food by diving underwater. To facilitate diving, the feet are set far back on the body. They have large feet with a lobed hind toe. They tend to patter or walk on the surface of the water as they take off. When swimming, they keep the tail close to the water.
An area referred to as the Prairie Pothole region is a prime breeding area for ducks. The region is 1,000 miles long and about 300 miles wide extending from South Dakota northward to Saskatchewan and Alberta.
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On or pertaining to the belly or abdomen
Applied to ventral fins when inserted far behind pectorals.
Non-living. Climate is an abiotic component of ecosystems.
Frictional erosion by material transported by wind and waves.
Total number of eggs in a female.
absolute mean sea level change
An eustatic change in mean sea level relative to the geographic center of the Earth.
A particularly deep part of the ocean, between 4,000 and 7,000 m depth.
A device used in wave buoys for measuring acceleration.
Tidal datums and Greenwich high and low water intervals obtained through primary determination or simultaneous observational comparisons made with a primary control tide station in order to derive the equivalent of a 19-year value.
The accumulation of (beach) sediment, deposited by natural fluid flow processes.
acoustic Doppler current profiler (ADCP)
A current measuring instrument employing the transmission of high frequency acoustic signals in the water. The current is determined by a Doppler shift in the backscatter echo from plankton, suspended sediment, and bubbles, all assumed to be moving with the mean speed of the water. Time gating circuitry is employed which uses differences in acoustic travel time to divide the water column into range intervals, called bins. The bin determinations allow development of a profile of current speed and direction over the entire water column. The ADCP can be deployed from a moving vessel, tow, buoy, or bottom platform. In the latter configuration, it is nonobtrusive in the water column and thus can be deployed in shipping channels.
The specialized larva of a surgeonfish (Acanthuridae).
A margin consisting of a CONTINENTAL SHELF, a CONTINENTAL SLOPE, and an oceanic trench.
A type of natural resource management that implies making decisions as part of an on-going process. Monitoring the results of actions will provide a flow of information that may indicate the need to change a course of action. Scientific findings and the needs of society may also indicate the need to adapt resource management to new information.
Fatty. Used, for example, in 'adipose fin' found in some primitive bony fishes.
A small fleshy fin without rays found on the back behind the dorsal fin of some primitive teleost fishes such as the lizardfishes (Synodontidae), salmonids (Salmonidae), or characids (Characidae).
Analog to Digital Recording tide gauge. A float or pressure actuated tide gauge that records the heights at regular time intervals in digital format.
Fish that have fully developed morphological and meristic characters and that have attained sexual maturity.
An insect that's fully mature and capable of reproducing.
Soil transported from one area to another by wind.
Wind-deposited sediments, such as sand DUNES.
The process of adding pure oxygen or air into water for the purpose of increasing the dissolved oxygen content.
Removing logs from a timber harvest area by helicopter. Fewer roads are required, so the impact to an area is minimized.
Modified pectoral or pelvic fins used for gliding in some fishes.
The natural environment that exists at the present time in an area being analyzed.
1. a group of animals in a population with approximately the same age (i.e., fawn, yearling, adult). 2. An age grouping of trees according to an interval of years, usually 20 years. A single age class would have trees that are within 20 years of the same age, such as 1-20 years or 21-40 years.
age of diurnal inequality
The time interval between the maximum semimonthly north or south declination of the Moon and the maximum effect of the declination upon range of tide or speed of the current. The age may be computed from the harmonic constants by the formula: age of diurnal inequality = 0.911(K1
age of Moon
The time elapsed since the preceding new Moon.
age of parallax inequality
The time interval between perigee of the Moon and the maximum effect of parallax upon range of tide or speed of the tidal current. This age may be computed from the harmonic constants by the formula:
age of parallax inequality = 1.837(M2
age of phase inequality
The time interval between new or full Moon and the maximum effect of these phases upon range of tide or speed of the tidal current. This age may be computed from the harmonic constants by the formula:
age of phase inequality = 0.984(S2
age of tide
Same as age of phase inequality.
the number of individuals of each age within the population.
Same as double tide.
The geologic process by which various parts of the surface of the earth are raised in elevation or built up by the deposition of material transported by water or wind.
An Indian Ocean current setting southwestward along the southeast coast of Africa.
air acoustic ranging sensor
A pulsed, acoustic ranging device using the air column in a tube as the acoustic sound path. The fundamental measurement is the time it takes for the acoustic signal to travel from a transmitter to the water surface and then back to the receiver. The distance from a reference point to the water surface is derived from the travel time. A calibration point is set at a fixed distance from the acoustic transducer and is used to correct the measured distance using the calibrated sound velocity in the tube.
air temperature sensors
Sensors located in the protective well for the purpose of verifying uniformity of temperature for measurements taken by the air acoustic ranging sensor.
A geographic area that shares the same air.
Specialized prehensile spines near the disc edge in all male skates (Rajoidea).
A North Pacific Ocean current setting counterclockwise along the coasts of Canada and Alaska in the Gulf of Alaska.
A North Pacific Ocean current setting westward along the south side of the Aleutian Islands. It is an extension of the Alaska Current.
typically pelagic colonial nesting seabirds that feed on fish by diving under the water surface to pursue their prey. Species include auklets, guillemots, murres, murrelets, and puffins.
a food fish of the herring family that is very abundant on the Atlantic coast; the alewife entered the Great Lakes through the Welland Canal in the 1940s and frequently die-off in large numbers because they are not well adapted to life in freshwater.
Large and heterogenous group of plants living in aquatic or damp terrestrial habitats.
Reef top surface feature dominated by algae cover, usually brown algae (e.g., Sargassum, Turbinaria).
A chemical used to control algae.
A term applied shelves that presently experience deposition of river-derived sediments.
allotment (range allotment)
The area designated for use by a prescribed number of livestock for a prescribed period of time. Though an entire Ranger District may be divided into allotments, all land will not be grazed, because other uses, such as recreation or tree plantings, may be more important at a given time.
Detrital material which is transported by a river and deposited – usually temporarily – at points along the floodplain of a river. Commonly composed of sands and gravels.
Parallel to and near the shoreline; same as longshore.
An instrument that determines its distance above a particular surface.
An instrument that determines altitude by measuring the length of time needed for a pulse of coherent light to travel from the instrument to the surface and back, and multiplies half this time by the speed of light to get the straight-line distance to the surface.
See altimeter, laser, and lidar.
Three feathers springing from the base of the primaries. Synonym(s): alular quills.
alular quill coverts
Feathers overlying the bases of alula.
Three feathers springing from the base of the primaries. Synonym(s): alula.
The natural temperature of the water.
A point of no amplitude of the observed or a constituent tide.
An area surrounding an amphidromic point from which the radiating cotidal lines progress through all hours of the tidal cycle.
One-half the range of a constituent tide. By analogy, it may be applied also to the maximum speed of a constituent current.
Species of fish that mature in the sea and migrate into streams to spawn.
As used in the National Ocean Service, a continuous measurement or a continuous graphic display of data. See ADR gauge and marigram.
See harmonic analysis.
See harmonic analyzer.
angle of repose
The maximum slope (measured from the horizon) at which soils and loose materials on the banks of canals, rivers or embankments stay stable.
One who uses a rod and reel to catch any species of fish.
angular velocity of the Earth's rotation
Time rate of change of angular displacement relative to the fixed stars. It is equal to 0.729,211 x 10^-4 radian/second.
Seasonal variation in water level or current, more or less periodic, due chiefly to meteorological causes.
Pertaining to the periodic return of the Moon to its perigee or the Earth to its perihelion. The anomalistic month is the average period of the revolution of the Moon around the Earth with respect to lunar perigee, and is approximately 27.554,550 days in length. The anomalistic year is the average period of the revolution of the Earth around the Sun with respect to perihelion, and is approximately 365.259,6 days in length.
As applied to astronomy, the anomaly is the angle made at any time by the radius vector of a planet or moon with its line of apsides, the angle being reckoned from perihelion or perigee in the direction of the body's motion. It is called the true anomaly when referred to the actual position of the body, and mean anomaly when referred to a fictitious body moving with a uniform angular velocity equal to the average velocity of the real body and passing perihelion or perigee at the same time.
Antarctic Circumpolar Current
Same as West Wind Drift.
Arising from human activities, as opposed to natural origin.
A mechanism that prevents the spool or handle of a reel from spinning in reverse.
A meander breaking off from the main current and spinning in a clockwise direction in the northern hemisphere (counter-clockwise in southern).
A North Atlantic Ocean current setting northwestward along the northeast coasts of the Bahama Islands.
The point in the orbit of the Earth (or other planet, etc.) farthest from the Sun.
apogean tides or tidal currents
Tides of decreased range or currents of decreased speed occurring monthly as the result of the Moon being in apogee. The apogean range (An) of the tide is the average range occurring at the time of apogean tides and is most conveniently computed from the harmonic constants. It is smaller than the mean range, where the type of tide is either semidiurnal or mixed, and is of no practical significance where the type of tide is predominantly diurnal.
The point in the orbit of the Moon or man-made satellite farthest from the Earth. The point in the orbit of a satellite farthest from its companion body.
apparent secular trend
The nonperiodic tendency of sea level to rise, fall, or remain stationary with time. Technically, it is frequently defined as the slope of a least-squares line of regression through a relatively long series of yearly mean sea-level values. The word "apparent" is used since it is often not possible to know whether a trend is truly nonperiodic or merely a segment of a very long (relative to the length of the series) oscillation.
Time based upon the true position of the Sun as distinguished from mean time, which is measured by a fictitious Sun moving at a uniform rate. Apparent time is that shown by the sundial, and its noon is the time when the Sun crosses the meridian. The difference between apparent time and mean time is known as the equation of time. Although quite common many years ago, apparent time is seldom used now.
The points in the orbit of a planet or moon which are the nearest and farthest from the center of attraction. In the Earth's orbit these are called perihelion and aphelion, and in the Moon's orbit, perigee and apogee. The line passing through the apsides of an orbit is called the line of apsides.
A body of rock that is saturated with water or transmits water. When people drill wells, they tap water contained within an aquifer.
A geologic formation that is water-bearing, and which transmits water from one point to another.
an expanse of water with many scattered islands; a group of islands
See equilibrium argument.
A submarine ridge with which no earthquakes are associated.
The direction a slope faces. A hillside facing east has an eastern aspect.
ASQ (allowable sale quantity)
The amount of timber that may be sold within a certain time period from an area of suitable land. The suitability of the land and the time period are specified in the Forest Plan.
Fictitious celestial bodies which are assumed to move in the celestial equator at uniform rates corresponding to the speeds of the several harmonic constituents of the tide producing force. Each astre fictif crosses the meridian at a time corresponding to the maximum of the constituent that it represents.
See astronomical time.
The tidal levels and character which would result from gravitational effects, e.g. of the Earth, Sun and Moon, without any atmospheric influences.
Time formerly used in astronomical calculations in which the day began at noon rather than midnight. The astronomical day commenced at noon of the civil day of the same date. The hours of the day were numbered consecutively from zero (noon) to 23 (11 a.m. of the following morning). Up to the close of the year 1924, astronomical time was in general use in nautical almanacs. Beginning with the year 1925, the American Ephemeris and Nautical Almanac and similar publications of other countries abandoned the old astronomical time and adopted Greenwich civil (mean) time for the data given in their tables.
The loss or dissipation of wave energy, resulting in a reduction of wave height (amplitude).
A fly pattern that isn't tied to imitate any one particular food form; typically brightly colored.
A factor used in connection with the harmonic analysis of tides or tidal currents to allow for the fact that the tabulated hourly heights or speeds used in the summation for any constituent, other than S, do not in general occur on the exact constituent hours to which they are assigned, but may differ from the same by as much as a half hour.
AUM (animal unit month)
The quantity of forage required by one mature cow and her calf (or the equivalent, in sheep or horses, for instance) for one month.
Area around ear opening. Synonym(s): ear patch.
A term applied to shelves on which older shelf sediments are primarily being reworked by modern shelf processes.
A spiral pickup arm that engages the line automatically.
automatic tide gauge
An instrument that automatically registers the rise and fall of the tide. In some instruments, the registration is accomplished by recording the heights at regular time intervals in digital format; in others, by a continuous graph of height against time. The automatic gauges used by the National Ocean Service are of both types.
(1) Rapid EROSION of the shoreland by waves during a storm. (2) A sudden cutting off of land by flood, currents or change in course of a body of water.
Ventral area between the body and the wing. Synonym(s): wingpit.
Azimuth of a body is the arc of the horizon intercepted between the north or south point and the foot of the vertical circle passing through the body. It is reckoned in degrees from either the north or south point clockwise entirely around the horizon. Azimuth of a current is the direction toward which it is flowing, and is usually reckoned from the north point.