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NPWRC - Biology Encyclopedia Category: Animals and Nature > Glossary of avian terms Date & country: 22/08/2008, USA Words: 235

Source population
a population that occupies habitat suitable for reproduction, in which the output of offspring results in a population that exceeds the carrying capacity of the local habitat, promoting dispersal (adapted from Wiens and Rotenberry 1980:531).

Specialist
a species with narrow food preferences, habitat preferences, or both (after Ricklefs 1970:871) (see Generalist).

Species
a group of actually or potentially interbreeding populations that are reproductively isolated from all other kinds of organisms (Ricklefs 1970:880).

Species diversity
see Diversity.

Species richness
the number of species in a given area (Ralph 1980:578).

Species-area relationship
a plot (often log-log) of the numbers of species of a particular taxon against area, such as islands or other biogeographic regions (Brown and Gibson 1980:570).

Spot-mapping method
a census procedure that plots on a map individuals seen or heard in a surveyed area. The survey is usually conducted over a period of days or weeks in a season, and individual territories or home ranges are then demarcated by examining the clusters of observations. Used in Breeding Bird Census (Ralph 1980:578) (syn. Territory-mapping).

Stable age distribution
the proportions of the population in different age classes when the rate of increase has converged to a constant (which depends on the fixed schedules of survival and fecundity). The ratios between the numbers in the age classes are constants (Caughley 1970:89).

Station
(1) the area within which observations made from a point are recorded by the observer (or often synonymous with 'point,' see Point count method) (Ralph 1980:578); (2) a monitoring station is an area of usually less than about 50 ha where intensive censuses, nest searching, and/or mist netting are conducted (Ralph et al. in press).

Statistical bias
a difference between the expected value of an estimator and the population parameter being estimated (Gilbert 1980:12) (cf Measurement bias).

Stenotopic
found in only one or a relatively small number of habitats (MacArthur and Wilson 1960:191).

Stochastic
implies the presence of a random variable (Marriott 1990:197).

Stressor
any chemical, physical, or biological entity that can induce adverse effects on individuals, populations, communities, or ecosystems (Risk Assessment Forum 1990:1).

Strip transect method
a procedure using a strip of land, or water, of fixed direction that is sampled visually and/or aurally by an observer. Counts may be one of the following: fixed distance (width) counts limited to a strip of set width for all or specially chosen species; variable distance (width) counts, with different, species-specific widths that are determined to reflect detection attenuation; or unlimited dist...

Subclimax
a stage of succession along a sere prevented from progressing to the climatic climax (i.e., the steady-state community characteristic of a particular climate) by fire, grazing, and similar factors (Ricklefs 1970:880).

Subspecies
subpopulations within a species that are distinguishable by morphological characteristics and, sometimes, by physiological or behavioral characteristics (Ricklefs 1970:880) (syn. race).

Succession
replacement of populations in a habitat through a regular progression to a stable state (climax) (Ricklefs 1970:880).

Survey
an enumeration or index of the number of individuals in an area from which inferences about the population can be made (Ralph 1980:578) (cf Census, Count).

Survival
the proportion of newborn individuals alive at a given age (Ricklefs 1970:880).

Sympatric
occurring in the same place, usually referring to areas of overlap in species distributions (Ricklefs 1970:880).

Syntopic
pertaining to populations or species that occupy the same macrohabitat (Lincoln et al. 1980:242).

Territory
any area defended by one or more individuals against intrusion by others of the same or different species (Ricklefs 1970:881) (cf Home range).

Territory-mapping
see Spot-mapping method.

Third-year bird
a bird in its third calendar year of life (Pyle et al. 1980:27).

Transect
a cross section of an area along which the observer moves in a given direction (Ralph 1980:578) (see Line transect, Point transect, Strip transect method).

Trophic
pertaining to food or nutrition (Ricklefs 1970:881).

Trophic level
the position in the food chain determined by the number of energy-transfer steps to that level (Ricklefs 1970:881).

Trophic structure
organization of the community based on feeding relationships of populations (Ricklefs 1970:881).

Turnover
the process of local extinction (e.g., on islands) of some species and their replacement by other species. The turnover rate is the number of species eliminated and replaced per unit time (MacArthur and Wilson 1960:191).

Ultimate factors
aspects of the environment that are directly important to the well-being of an organism (for example, food) (Ricklefs 1970:881). Ultimate factors are concerned with fitness (Lack 1950:5) (cf Proximate factors).

Variable circular plot
see Point count method.

Variable-distance method
see Strip transect method, Point count method.

Variance
a statistical measure of the dispersion of a set of values about its mean (Ricklefs 1970:881).

Winter Bird Population Study (U.S.)
a program of the National Audubon Society involving census of wintering birds by counting and mapping, but not depending on persisting occupation of territories or home ranges (Ralph 1980:578) (cf Breeding Bird Census).

Xeric
referring to habitats in which plant production is limited by lack of water (Ricklefs 1970:882).