Foraged Research Articles

Some factors influencing colony spacing and survival in the grass-cutting ant Acromyrmex landolti fracticornis (Forel) (Formicidae: Attini) in Paraguay

Various aspects of the ecology of the Paraguayan grass-cutting ant, Acromyrmex Iandolti fracticornis (Forel), were studied in the field. Colonies were found lo linearly orient their foraging territories, partitioning the habitat in a mosaic pattern. The distance foraged by workers were found to be a function of colony size: (Log 10 maximum distance foraged) = -0,5156 + 0.4121 (Log 10 area of nest). Colony .pacing, however, was found to be not immediate y dependent on colony size. Colony spacing patterns are influenced by intra-specific aggression, and perhaps by the predation or execution of founding queens. Both the mound and superficial detritus heap of nests were found to favor the survivorship of forbs. Colony numbers were found to decrease significantly as grass coverage decreased and forb species became dominant.

THE SPECTER OF PREDATION: THE EFFECTS OF VIPERS ON THE FORAGING BEHAVIOR OF TWO GERBILLINE RODENTS

ABSTRACT Predation may have profound effects on individual growth rates, population dynamics, and species interactions via its influence on prey foraging behavior. Here, we examine the response of two gerbil species (Gerbillus alletibyi and G. pyramidum) to greater sand vipers (Cerastes cerastes) and to added illumination (a factor associated with increased risk of predation from owls). We measured gerbil foraging behavior using the number of seed trays (resource patches) foraged and amount of seed resources left in each tray (giving-up densities; GUDs). Fewer seed trays foraged and higher GUDs indicate a higher perceived risk of predation. Accordingly, G. allenbyi foraged fewer seed trays in response to illumination and in the open microhabitat. In addition, vipers may have affected foraging activity in both gerbil species and caused G. pyramidum to forage in fewer trays in the bush microhabitat. Viper activity also caused both species to abandon seed trays at higher GUDs. Overall, gerbils altered their ...

MOVEMENTS OF A RADIO-COLLARED WOLF (CANISLUPUS PALLIPES) IN THE NEGEV HIGHLANDS, ISRAEL

ABSTRACT An adult female wolf, live-captured and equipped with a collar transmitter in February 1982, was radio-tracked and observed visually for 7 months in the Sede Boqer region of the Negev highlands. She was accompanied by an adult male throughout the study. Based on 36 relocations, the minimum home range of the pair was estimated as 60.3 km2 but may have been much smaller in summer. A maximum daily movement of 10.5 km (straight line) was observed. The animals rested during the day, and were active at night when they foraged at refuse dumps. They did not breed successfully nor use permanent dens. Other wolves were absent from their range during most of the study, but one den of a female and litter was found about 3 km from home range boundary, and a pack of nine wolves appeared in the area in August 1982.

Observations on Microhabitat Use and Activity Patterns in Sitana ponticeriana (Sauria: Agamidae)

Microhabitat use and activity patterns of Sitana ponticeriana were observed in their natural habitat over two consecutive years at Balukhand-Konark Wildlife Sanctuary, Orissa, India. Lizards perched above the ground, mainly on herbaceous vegetation, sandy areas, cracks and crevices and small shrubs/bushes of the canopy. During the morning and late afternoon, the lizards favored herbaceous vegetation, and during early afternoon used a variety of microhabitats including shrubs/bushes, cracks and crevices, and root of the trees. Lizards were sighted in large numbers during morning and late afternoon. Sightings declined in the early afternoon with rise in ambient temperature. Daily activity patterns of all lizard size classes typically involved basking in the morning hours followed by foraging, moving and other activities. S. ponticeriana was found to be active foragers with frequent wandering movement. Foraging behavior did not vary significantly between males and females, whereas juveniles foraged near their retreats.

Honey bee (<i>Apis mellifera</i>) distribution and behaviour on hybrid radish (<i>Raphanus sativus</i> L) crops

Commercial hybrid vegetable seed production involves movement of pollen between two distinct groups of plants (parent lines) a pollen donor and seed production lines The aim of this study was to observe the distribution and behaviour of honey bees (Apis mellifera) on hybrid radish (Raphanus sativus L) crops in New Zealand Honey bees were observed to have an even distribution across the parent lines although individual bees largely maintained fidelity to the particular line on which they foraged Of the bees observed on malefertile flowers 72 did not switch to the other line When plants from the different lines were manipulated so that they appeared to be a single plant 695 of honey bees remained constant to the line visited To maximise the effectiveness of honey bees as pollinators of hybrid radish techniques should focus on better matching of lines or breeding of lines to reduce pollinator differentiation

Individual Variation of Foraging Behavior and Food Provisioning in Adélie Penguins (Pygoscelis adeliae) in a Fast-Sea-Ice Area

ABSTRACT. To understand the effects of foraging behavior on the amount of food provided to chicks (meal mass and frequency), we monitored nest attendance and diving behavior of 20 Adelie Penguin (Pygoscelis adeliae) pairs that were rearing chicks. Because ice forms on the sea surface at night, parents foraged through cracks or within leads in the sea ice mainly during 0800–2400 hours. Birds that departed the colony in the afternoon and returned in the evening of the same day fed their chicks more frequently than those that made longer trips (i.e., those that departed in the afternoon and returned the next day or departed in the early morning and returned that evening). When the duration of the longest dive bout during each trip was longer, parents brought back heavier meals that contained larger krill. On average, birds made longer dive bouts when diving to greater depths. Thus, daily foraging pattern and foraging depth affected the provisioning rate, but the proportion of time spent foraging during the p...

The structure of western warbler assemblages: Analysis of foraging behavior and habitat selection in Oregon

-This study examines the foraging behavior and habitat selection of a MacGillivray's (Oporornis tolmiei)-Orange-crowned (Vermivora celata)-Wilson's (Wilsonia pusilla) warbler assemblage that occurred on early-growth clearcuts in western Oregon during breeding. Sites were divided into two groups based on the presence or absence of deciduous trees. Density estimates for each species were nearly identical between site classes except for Wilson's, whose density declined on nondeciduous tree sites. Analysis of vegetation parameters within the territories of the species identified deciduous tree cover as the variable of primary importance in the separation of warblers on each site, so that the assemblage could be arranged on a continuum of increasing deciduous tree cover. MacGillivray's and Wilson's extensively used shrub cover and deciduous tree cover, respectively; Orange-crowns were associated with both vegetation types. When the deciduous tree cover was reduced, Orange-crowns concentrated foraging activities in shrub cover and maintained nondisturbance densities. Indices of foraging-height diversity showed a marked decrease after the removal of deciduous trees. All species except MacGillivray's foraged lower in the vegatative substrate on the nondeciduous tree sites; MacGillivray's concentrated foraging activities in the low shrub cover on both sites. Indices of foraging overlap revealed a general pattern of decreased segregation by habitat after removal of deciduous trees. I suggest that the basic patterns of foraging behavior and habitat selection evidenced today in western North America were initially developed by ancestral warblers before their invasion of the west. Species successfully colonizing western habitats were probably preadapted to the conditions they encountered, with new habitats occupied without obvious evolutionary modifications. Received 18 August 1980, accepted 20 February 1981. STUDIES of similar coexisting species usually enumerate ecological differences that presumably reduce the demand upon common resources and allow coexistence (Williams and Batzli 1979). MacArthur's (1958) classic study of niche segregation by sympatric Dendroica, followed by a series of similar studies by Morse (1967, 1968, 1971, 1973, 1976) and Ficken et al. (1968), which dealt with several genera, led to the conclusion that competition for limited resources played the primary role in structuring warbler species assemblages in the eastern United States. The identification of ecological differences alone, however, does not demonstrate the role of competition in structuring avian communities (Schoener 1974). Experimental manipulations are useful means of examining the role of foraging plasticity in species coexistence (Williams and Batzli 1979, Landres and MacMahon 1980). This study was designed to (1) document the foraging behavior, habitat selection, and population densities of a MacGillivray's (Oporornis tolmiei)-Orange-crowned (Vermnivora celata)-Wilson's (Wilsonia pusilla) warbler assemblage that occurred on clearcuts in the Oregon Coast Range, and (2) assess the response of this assemblage to removal of the deciduous tree component on the clearcuts. Results are related to an hypothesis about the formation and structure of western warbler assemblages. The species observed in this study breed commonly in many communities in western North America. In addition, races of the Wilson's Warbler range eastward 5 78 The Auk 98: 578-588. July 1981 This content downloaded from 157.55.39.215 on Wed, 31 Aug 2016 05:01:02 UTC All use subject to http://about.jstor.org/terms July 1981] Western Warbler Assemblages 579 TABLE 1. Description of study sites. Years Site postUSFS size Elevation plantSite name number (ha) (m) Aspect inge Location Deciduous tree (DT) group Bennerb.c 3403-51 21 300-450 NE 5 Lincoln County, Oregon (T14S, R9W; sec. 14, 23) Dill Pickleb 3502-16 31 110-280 NE 7 Lane County, Oregon (T15S, R9W; sec. 17) Non-deciduous tree (ND) group Green Divideb,c 3503-38 36 150-400 N 5 Lane County, Oregon (T15S, R9W; sec. 31) Bear Creekb 3404-51 24 150-370 NE/SE 5 Lincoln County, Oregon (T15S, RlOW; sec. 4, 5) Age of conifer at beginning of study. b Studied in 1979. c Studied in 1980. across Canada and the northern United States to Newfoundland, Ontario, Vermont, and Maine (A.O.U. 1957). These warblers are usually described as common inhabitants of brushlands and second-growth forests, although the Wilson's and, to a lesser extent, the Orange-crown, are often associated with riparian vegetation (Gabrielson and Jewett 1940, Bent 1953). In western Oregon, the species are primarily summer residents, arriving in early May and departing in August or September for southern wintering grounds (Gabrielson and Jewett 1940, A.O.U. 1957). STUDY AREAS AND METHODS

Need for Stimulation Crosses Species

Researchers have observed brain plasticity across species — e.g., in rodents and primates. These investigators have extended the parallel to honey bees by focusing on a brain region called the mushroom body, which consists of interneurons and neuropil (a complex network of nerve fibers). The bees foraged for 1 week; afterwards, some bees continued foraging for …

Vertical stratification and use of vegetation and light habitats by Neotropical forest birds

The vertical stratification of bird species has been intensively studied in both temperate and tropical bird communities. I investigated the vertical stratification of bird species and their use of vegetation structures and light habitats using observation data from 92 rainforest species. Most observations were made from a 40 m high canopy crane situated close to the Surumoni river (65°40′W, 3°10′N) near Esmeralda, Estado Amazonas, southern Venezuela. Further observations were made at several forest sites nearby. Previous analyses had shown that bird species foraged in stratified vertical niches, with wider niches for midstorey birds than for either canopy or understorey birds. In this study, I used across-species as well as phylogenetically-controlled analyses to correlate the vertical position of bird species with variables relating to vegetation structures and the amount of illumination. I found that species which foraged low in the forest were mostly found in small gap and forest shade light habitats, while species that foraged high were mostly found in large gap and woodland shade light habitats. Furthermore it was the lower-foraging species that were more often found in dimmer light conditions inside denser cover. In correspondence with their wider vertical niches, midstorey birds foraged in a wider range of light habitats and illumination than either canopy or understorey birds. While preserving their overall stratification, species actively moved within their preferred stratum, e. g. downwards and into denser vegetation during hours of strong sunlight and around midday when temperatures are highest. Bird activity appeared to be lowest shortly after midday, as I discovered when controlling for the effects of chance encounters with multi-species flocks. These observations are important not only for the determination of foraging niches, but also for the study of crypsis and the conspicuousness of a bird species in relation to its foraging stratum.

Diet selection in Amazonian antwrens: consequences of substrate specialization

I used an observational and experimental approach to investigate the dietary consequences of substrate specialization in six species of Amazonian antwrens (Myrmotherula). Three species (leucophthalma, haematonota, and ornata) foraged exclusively at curled dead leaves suspended above ground, axillaris and longipennis foraged on live foliage, and hauxwelli was a substrate generalist, feeding at both live and dead foliage. Diet composition of all species was qualitatively similar, with soft-bodied orthopterans consistently the most important prey type. Dead-leaf specialists took other prey roughly in proportion to their availability in dead leaves, whereas diets of live-leaf foragers differed greatly from prey available on live foliage. Dead-leaf specialists also ate larger prey and especially larger orthopterans than did other antwrens. Substrate generalization in hauxwelli was associated with higher diet breadth and greater heterogeneity among individuals, compared with substrate-restricted foragers. Diet breadth was negatively correlated with prey size across all six species. When tested in outdoor cages, live-leaf foraging and generalist species showed little interest in dead- or live-leaf substrates, whereas all dead-leafers repeatedly inspected and manipulated dead and curled leaves in the absence of food. All foraging groups showed a similar degree of selectivity of prey types in feeding trials. Dead-leaf specialists did not differ from other species in their preference for orthopterans of different colors, although specialists were better able to catch and handle the largest katydids (>30 mm). Individual hauxwelli (the generalist) showed elevated levels of exploration at dead leaves with food reinforcement, suggesting short-term plasticity in search behavior. I conclude that substrate specialization in these birds involves fundamental differences in search behavior, but is not accompanied by equivalent changes in prey selectivity or preference. Dead-leaf specialists search for suitable substrates and then inspect them for hidden prey, taking prey roughly in proportion to their availability. In contrast live-leaf foragers search directly for prey and select suitable items from the wider array of arthropods available on live foliage. Substrate-restricted foraging may reduce diet breadth and promote diet stereotypy in both groups, whereas the single most important factor promoting specialization on dead leaves may be the predictable abundance of relatively large orthopterans. Received 25 November 1991, accepted 27 May 1992.

The pollination of hybrid kale (Brassica oleraceae L.)

SUMMARYHoneybees were able to distinguish between the flowers of two different oultivars of kale grown to produce hybrid seed and most foraged only on one or other of them.