. Animal Ecology. Animal ecology. FIG. 13-1 Adaptations in the bills of birds, (a) (b) an insect-eating warbler; (c) a plant-eating duck; (e) a predaceous hawk; (f) an aerial (d) a fish-eating heron insect-eating whippoorwi Many species eat both plant and animal matter, on occasion, or at particular seasons, but animals are considered to be truly omnivorous only if they feed on plants and animals in nearly equal amounts or in- discriminately. Omnivores occasionally also consume dead organic matter. Some aquatic organisms are filter-feeders and may consume everything within a particular size ra
. Animal Ecology. Animal ecology. FIG. 13-1 Adaptations in the bills of birds, (a) (b) an insect-eating warbler; (c) a plant-eating duck; (e) a predaceous hawk; (f) an aerial (d) a fish-eating heron insect-eating whippoorwi Many species eat both plant and animal matter, on occasion, or at particular seasons, but animals are considered to be truly omnivorous only if they feed on plants and animals in nearly equal amounts or in- discriminately. Omnivores occasionally also consume dead organic matter. Some aquatic organisms are filter-feeders and may consume everything within a particular size range that passes through their feeding apparatus (Jorgensen 1955). However, filter-feeders may demonstrate selectivity by feeding in neighbor- hoods where certain species predominate. Some copepods select particles of a particular size, reject- ing larger ones, by regulating the distance between the maxillae in the filter mechanism (Hutchinson 1951). Probably most, if not all, animals have chemore- ceptors of some sort, either to discriminate chemical substances dissolved in drinking water or food (taste), or chemical substances that are water- or air-borne (smell). Essential oils and alkaloids in plants are important as conditions of acceptability to insects. Hairiness, other surface features, or the visual stimuli that plants present are also conditions of attractiveness or acceptability of a food item. The food preference of any species depends on chromosomal inheritance, parental training, and per- sonal experience of that species, but the relative sig- nificance of each of these factors has not been evalu- ated for most animals. Young birds and mammals, in their first experiences at independent feeding, may pick up a variety of material but reject those items that are distasteful or indigestible; they soon learn to distinguish acceptable substances. This process is established as the parents feed offspring only those things traditional to the species, or so direct the feed-
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Keywords: ., bookcentury1900, bookcollectionbiodive, booksubjectanimalecology
