Tactile Means Research Articles

THE OCCURRENCE AND ADAPTIVE SIGNIFICANCE OF NOCTURNAL HABITS IN WATERFOWL

SummaryThis paper reviews the occurrence of nocturnal activity, particularly foraging, in wildfowl (Anseriformes) and shorebirds (Charadrii), and discusses its significance. Many duck species are mainly active at night while others regularly feed during both the day and night. Some ducks and geese are normally day feeders and occasionally forage during darkness. In a few duck species, courtship also has been observed at night. Most shorebirds forage both by day and night, in temperate and in tropical latitudes. Some are mainly crepuscular and nocturnal feeders and also display at dusk and at night. Some species may use their daytime territory at night.A few shorebird species, including some visual peckers and long‐billed tactile probers, use the same foraging method to detect and capture food by night as by day. However, some long‐billed species that forage visually during daytime modify their feeding techniques and rely completely or partly on tactile means for detecting prey at night. Large eyes seem an advantage to plovers and other sight feeders for night feeding. Numerous touch‐sensitive corpuscles in the bill of ducks and many scolopacid species favour tactile feeding. Some ducks, geese and shorebirds may especially use moonlit nights for feeding though, in a few species, moonlight seems to have no effect. The possible role of bioluminescence is also discussed.Nocturnal activity may occur for two reasons. The night may be preferred because foraging is more profitable or safest from predators. Alternatively, birds may be forced to forage at night because they fail to collect all their food requirements during the day. The evidence for both hypotheses is reviewed. Nocturnal activity does appear to allow wildfowl, and perhaps shorebirds, to avoid diurnal predators (including man). Shorebirds, and some ducks also seem to take advantage of prey that are more abundant and/or accessible at night. The main evidence for the supplementary feeding hypothesis comes from studies of seasonal variations in the occurrence of nocturnal feeding, about which rather little is known at present. The increasing availability of modern night‐viewing equipment may help to fill this gap.There are two important implications arising from the widespread occurrence of nocturnal activity in wildfowl. Most knowledge on time and energy budgets is based on daytime studies, and so may need to be revised. Wintering dabbling ducks and shorebirds, at least in some regions, may use different habitats by day and by night. If confirmed, there would be a need to preserve some wintering habitats which, although little used by ducks and shorebirds during the day, may be intensively used at night.

Effect of Group Size and Location within the Group on the Foraging Behavior of White Ibises

We studied adult White Ibises (Eudocimus albus) on a South Carolina salt marsh to determine the effects of social grouping on the birds' foraging behavior. White Ibises on our study site fed almost exclusively on fiddler crabs (Uca spp.). Four social categories were recognized: (1) central adults in flocks of ≥ 15 birds, (2) peripheral adults in flocks of ≥ 15 birds, (3) adults in small flocks of five or fewer birds, and (4) solitary adults (singletons). We used a paired sampling scheme to compare the behavior of central birds with the behavior of birds in the other three social groupings. Although peripheral adults did not differ significantly from central adults in number of steps, number of crabs captured, or number of capture attempts, they looked up more often and for longer periods of time than did central adults. Behavior of solitary ibises was similar to that of ibises in small flocks, but both foraged differently than central adults in large flocks. Birds in the center of large flocks took fewer steps, probed more frequently, and scanned the surroundings less often than birds in the other two social groupings; there were no differences in capture rates. Thus, White Ibises used two distinct types of foraging strategies depending on flock size and their position within the flock. Ibises in small flocks, singletons, and, to some extent, ibises on the edges of large flocks, stepped quickly to capture fiddler crabs before the crabs could retreat into burrows. Centrally-located ibises in large flocks were unable to use this foraging technique because the surrounding members of the flock created a disturbance that caused the fiddler crabs to remain in their burrows. These birds, therefore, probed into crab burrows and found their prey by tactile means. Our results support the predator-protection advantage of feeding within a flock independent of the feeding-efficiency hypotheses.

Making Microcomputers Accessible to Blind Persons

Without specialized “access technology,” blind students are precluded from full access to microcomputers. Research on multimedia access to microcomputers has explored tactile, auditory, and visual means of access. This article considers the advantages and limitations of these means and related equipment, and concludes with a look into the future of computer access technology.

Approche sémiologique des jeux précoces dans l'interaction mère-enfant.

Between the ages of 4 to 6 months, a baby seems to be able to ' interpret ' .many and varied maternal behaviors in an emotionally primitive way. The observation of a baby's behaviors shows that he acceeds to an ' active form ' of response which is, in turn, perceived by his mother and can lead the two partners to interactive playing, especially using tactile means. The playing patterns of these interactions which allow for and serve to contain ambivalance and aggressiveness cause the scope of the mother-child relationship to be renewed. In the first weeks the tactile and motor contacts coming from the mother are rarely truly playful. And yet there are elements present in varying contexts of what will become ritualized as game sequences which are shared with the child. Among these are rhythmic finger tip contacts, pressure differences, variations in distance and hyperstimulation to obtain a better quality of alertness from the baby. From the point of view of the mother's vocal production, there are repeated syncopated syllables and onomatopoeias accompanying a quick tap followed by a small laugh. As of the third week, the baby most frequently shows nociceptive type avoidance reactions while responding to steady pressure. He also shows facial orientation and smiles as well as body arching and tonic positions which sometimes accompany an arm outstretched to his mother. She may identify this reaching out as a call. Thus, very early on, self-protective reactions coexist with others which are more ambiguous and whose meaning the mother catches better and better as the baby develops and she uses them to renew, enrich and prolong his calls to her. The descriptive picture of their interrelations differs according to the context as well as to the synchronie and asynchronic aspects of the mother-child interaction. To understand this differentiation, it is necessary to give particular importance to the maturing of motor competency of the baby, to his capacity for anticipation, ajustment, acceptance and refusal.

Making Microcomputers Accessible to Blind Persons

Without specialized “access technology,” blind students are precluded from full access to microcomputers. Research on multimedia access to microcomputers has explored tactile, auditory, and visual means of access. This article considers the advantages and limitations of these means and related equipment, and concludes with a look into the future of computer access technology.