Soil softness, nest initiation and nest sharing in the wasp, Cerceris antipodes (Hymenoptera: Sphecidae)

Abstract. 1. The relationship between soil softness and nest initiation was studied at two aggregations of a ground nesting sphecid wasp, Cerceris antipodes Smith, in New South Wales, Australia.
2. Nests of C.antipodes were initiated throughout the active season. Nests were started more frequently during moist conditions and when more wasps were active.
3. Nest initiation was clumped on days after periods of rain. Nest initiation was only observed when the soil was soft.
4. Two experimental plots that were watered had significantly softer soil and more nests initiated on them than two control plots. Searching female wasps spent considerably more time on the watered plots than the controls.
5. Nest initiation through hard surface soils presents a problem to C.antipodes. Soil softness must be considered in any analysis of nest sharing in this species.     

Incidental nest predation in freshwater turtles: inter- and intraspecific differences in vulnerability are explained by relative crypsis

There has long been interest in the influence of predators on prey populations, although most predator–prey studies have focused on prey species that are targets of directed predator searching. Conversely, few have addressed depredation that occurs after incidental encounters with predators. We tested two predictions stemming from the hypothesis that nest predation on two sympatric freshwater turtle species whose nests are differentially prone to opportunistic detection—painted turtles (Chrysemys picta) and snapping turtles (Chelydra serpentina)—is incidental: (1) predation rates should be density independent, and (2) individual predators should not alter their foraging behavior after encountering nests. After monitoring nest survival and predator behavior following nest depredation over 2 years, we confirmed that predation by raccoons (Procyon lotor), the primary nest predators in our study area, matched both predictions. Furthermore, cryptic C. picta nests were victimized with lower frequency than more detectable C. serpentina nests, and nests of both species were more vulnerable in human-modified areas where opportunistic nest discovery is facilitated. Despite apparently being incidental, predation on nests of both species was intensive (57% for painted turtles, 84% for snapping turtles), and most depredations occurred within 1 day of nest establishment. By implication, predation need not be directed to affect prey demography, and factors influencing prey crypsis are drivers of the impact of incidental predation on prey. Our results also imply that efforts to conserve imperiled turtle populations in human-modified landscapes should include restoration of undisturbed conditions that are less likely to expose nests to incidental predators.     

DIET OF SOUTH AMERICAN FUR SEALS (ARCTOCEPHALUS AUSTRALIS) IN ISLA DE LOBOS, URUGUAY

The diet of Arctocephalus australis was studied through fecal analysis, from September of 1995 to May of 1998, in Isla de Lobos (35°01'50"S-54°53'00"W), Uruguay. A total of 539 scats analyzed indicated that the weakfish ( Cynoscion guatucupa ), the cutlasfish ( Trichiurus lepturus ), the anchoveta ( Engraulis anchoita ), the anchovy ( Anchoa marinii ), and cephalopods were the main prey consumed by these fur seals. Prey richness was higher during January. The diet of A. australis varied between years, apparently related to changes in prey availability. C. guatucupa and E. anchoita decreased while T. lepturus and cephalopods increased from 1996 to 1998. South American fur seals fed on fish ranging in length from 5.4 to 104.8 cm and from 0.7 to 629.9 g in wet mass. However, the mean mass of the main items was never more than 200 g. Observations suggests that A. australis is a trophic generalist with the potential to prey on a wide range of species, although most of the diet is comprised of relatively few species. Fur seals and artisan fisheries both took C. guatucupa , with fur seals taking younger individuals (1–2 yr) than artisan fisheries (> 3 yr).     

Cooperative prey-retrieving in the ant Cataglyphis floricola: an unusual short-distance recruitment

Cataglyphis ants are mostly scavengers adapted to forage individually in arid environments. Although they are widely thought to have lost the capacity of recruitment, we provide evidence that C. floricola foragers that find a large prey near their nest are able to solicit the help of nestmates to carry it cooperatively. After discovering a non-transportable prey, these ants readily return to their nest and stimulate the exit of several recruits. This rudimentary form of recruitment, which is absent in the sympatric species C. rosenhaueri, is only employed when the prey is sufficiently close to the nest entrance (<1 m) and does not allow the food location to be communicated. Instead, C. floricola recruits search for the prey in all directions until they discover it and transport it cooperatively to their nest.     

Predation as a landscape effect: the trading off by prey species between predation risks and protection benefits

1. Predators impose costs on their prey but may also provide benefits such as protection against other (e.g. nest) predators. The optimal breeding location in relation to the distance from a nesting raptor varies so as to minimize the sum of costs of adult and nest predation. We provide a conceptual model to account for variation in the relative predation risks and derive qualitative predictions for how different prey species should respond to the distance from goshawk Accipiter gentilis nests. 2. We test the model predictions using a comprehensive collection of data from northern Finland and central Norway. First, we carried out a series of experiments with artificial bird nests to test if goshawks may provide protection against nest predation. Second, we conducted standard bird censuses and nest-box experiments to detect how the density or territory occupancy of several prey species varies with distance from the nearest goshawk nest. 3. Nest predation rate increased with distance from goshawk nest indicating that goshawks may provide protection for birds' nests against nest predation. Abundance (or probability of presence) of the main prey species of goshawks peaked at intermediate distances from goshawk nests, reflecting the trade-off. The abundance of small songbird species decreased with distance from goshawk nests. The goshawk poses little risk to small songbirds and they may benefit from goshawk proximity in protection against nest predation. Finally, no pattern with distance in pied flycatcher territory (nest box) occupation rate or the onset of egg-laying was detected. This is expected, as flycatchers neither suffer from marked nest predation risk nor are favoured goshawk prey. 4. Our results suggest that territory location in relation to the nest of a predator is a trade-off situation where adult birds weigh the risk of themselves being predated against the benefits accrued from increased nest survival. Prey species appear able to detect and measure alternative predation risks, and respond adaptively. From the prey perspective, the landscape is a mosaic of habitat patches the quality of which varies according to structural and floristic features, but also to the spatial distribution of predators.     

Comparative study of the nesting behaviour of Tachysphex inconspicuus (Kirby) (Hymenoptera: Crabronidae) in two locations in southeast Brazil

The nesting behaviour of the solitary wasp Tachysphex inconspicuus (Kirby) was comparatively studied based on observations made in two environmentally distinct locations in southeast Brazil: upper portions of two sandy beaches and a dirt road in a forested area. Motor patterns related to nest construction were similar in all observed wasps, but some behavioural features, which were different among the observed wasps in the two environments, seem to be constrained by ecological factors. T. inconspicuus can be behaviourally differentiated from several other species of the genus by the following combination of features: they close the nest temporarily during its provision, do not let the excavated sand to form into a mound in front of the nest entrance, construct unicellular nests, and provision the nest with cockroaches. Moreover, females T. inscospicuus use their hind legs in a peculiar way to manipulate the prey, which allows them to associate the use of the mandibles in prey transport with the possibility of excavating the temporary plug and entering the nest without releasing the prey. Chorisoneura lopesi Albuquerque, C. excelsa Albuquerque & Silva, and unidentified species of Riatia (Blattodea: Blatellidae) were found as prey and Amobia floridensis (Towsend) (Diptera: Sarcophagidae) as parasitoid of T. insconspicuus.     

Of mice and mallards: positive indirect effects of coexisting prey on waterfowl nest success

Coexisting prey species interact indirectly via their shared predators when one prey type influences predation rates of the second prey type. In a temperate system where the predominant shared predator is a generalist, I studied the indirect effects of rodent populations on waterfowl nest success, both within the nesting season among sites and among years. Among six to ten upland fields (14 to 27 ha), mallard ( Anas platyrhynchos ) nest success was positively correlated with rodent abundance in all three years of the study. After removing year effects, mallard nest success remained positively correlated with the relative abundance of rodents. Of the rodent species present, California voles ( Microtus californicus ) were the most important coexisting prey type influencing nest success. Among years, mallard nest success was positively correlated with vole abundance; the asymptotic relationship suggests a threshold response to vole abundance, beyond which predators become satiated and additional voles do little to affect nest success. I tested and rejected three alternative explanations for the observed positive correlation between mallard nest success and rodent abundance that do not involve an indirect effect of coexisting prey populations. The influences of dense nesting cover, nesting density, and predator activity did not explain the observed patterns of nest success. These results suggest that rodent populations buffer predation on waterfowl nests, both within and among years, via the behavioral responses of shared predators to coexisting prey.     

Nesting behavior of the semi-aquatic spider wasp,Anoplius eous,which transports its prey on the surface film of water (Hymenoptera,Pompilidae)

Anoplius eous Yasumatsu (Hymenoptera, Pompilidae) exhibits some outstanding nesting behavior. Females excavate a unicellular or multicellular nest in wet ground, or dig a single-celled nest in rotten wood, or build clustered mud cells in narrow spaces between walls of such substances as wood or vinyl sheets. The latter nest-type has been unknown within the subfamily Pompilinae. Females prepare a nest-cell before hunting, and construct it further after hunting, leaving the prey near the nest (behavior-formula: IVPTIOC). They transport their prey backward on the ground, grasping it in their mandibles by any part of the legs, and forward on the surface film of water or on the ground, grasping it by the middle part of the 1st or 2nd legs. Their only prey is the adult female semi-aquatic spider,Pardosa pseudoannulata (Lycosidae). These nesting and provisioning behavior patterns are compared with those of other pompilids. The position of the present species in the behavioral evolution of the Pompilidae is suggested.     

Colony productivity and foundress behaviour of a native wasp versus an invasive social wasp

Abstract.  1. Colony productivity, prey utilisation, and foundress behaviour of a North American native wasp ( Polistes fuscatus ) versus an European invasive wasp ( Polistes dominulus ) were investigated in a controlled field experiment with optimal versus natural foraging conditions. Colonies with the optimal prey foraging conditions were provided with prey ad libitum within an enclosed area. The other colonies foraged in the adjacent field–woodland but had the same nest conditions as the other treatment.
2. When given prey ad libitum , both wasp species captured similar amounts of prey and the conversion to total offspring biomass was similar. But P. dominulus colonies produced 2.5 times the number of workers as P. fuscatus colonies, reflecting the smaller size of P. dominulus wasps.
3. Foundresses of P. dominulus were observed more often building or repairing the nest, thereby contributing to the production of colonies with twice as many cells as colonies of P. fuscatus . Foundresses of P. dominulus showed more acts of aggression toward workers than did P. fuscatus foundresses, which was not a function of adult density on the nest.
4. At the end of the experiment, P. dominulus colonies with optimal prey foraging conditions still had a high level of egg-laying and peaked in the number of pupae then, whereas egg-laying and the number of pupae per colony of the other treatments began to decline 2–3 weeks earlier. These results indicate that P. dominulus is more opportunistic than P. fuscatus , which may account in part for P. dominulus 's success as an introduced species in North America.     

Nesting biology of four species of Trypoxylon (Trypargilum) (Hymenoptera: Crabronidae) in Chaco Serrano woodland, Central Argentina

Trypoxylon (Trypargilum) (Crabronidae) wasps are solitary spider predators that can build their nests in artificial trap-nests, which enables study of their nesting architecture and biology. Twenty traps (each containing 15-30 internodes of cane) were placed in each of nine sites of Chaco Serrano Woodland in Central Argentina (Córdoba) in October 2005, and were recovered in June 2006. We obtained 91 nests of four species of Trypoxylon (Trypargilum). In the laboratory, each Trypoxylon nest was sectioned longitudinally to study its architecture. The number of brood cells was counted, and the occurrence and length of vestibular and intercalary cells and the pre-closing plug space were recorded. We measured the diameter of the cane entrance, total length of the nest, length of each brood cell, maximum thickness of mud partitions and closing plug thickness. We also recorded the cell contents: the wasps, their natural enemies and the prey spiders. Mortality was assessed and the sex ratio calculated for each species. Finally, the nests were examined to help clarify the function of the vestibular cell. The nest architecture was similar in the four species, with linear brood cells located one after the other separated by mud partitions, as in other species of the subgenus Trypargilum. Forty-eight percent of the nests had vestibular cells, but only two had intercalary cells. The thickness of the mud partitions and the length of the brood cells differed among species and were related to the size of the emerged wasp. The diameter of the nest entrance was directly related to the average length of the fore-tibia. Sex ratios of all species did not deviate from 0.5. Mortality due to parasitoids (Eulophidae; Melittobia sp.) was similar among species, while the mortality due to cuckoo wasps (Chrysididae) in T. lactitarse was higher than in the other species. The presence of vestibular cells was not related either to the mortality due to natural enemies or to the orientation of the trap in the field. Spiders in the family Araneidae were the most frequently collected prey.     

Predicting species interactions from edge responses: mongoose predation on hawksbill sea turtle nests in fragmented beach habitat

Because species respond differently to habitat boundaries and spatial overlap affects encounter rates, edge responses should be strong determinants of spatial patterns of species interactions. In the Caribbean, mongooses (Herpestes javanicus) prey on hawksbill sea turtle (Eretmochelys imbricata) eggs. Turtles nest in both open sand and vegetation patches, with a peak in nest abundance near the boundary between the two microhabitats; mongooses rarely leave vegetation. Using both artificial nests and hawksbill nesting data, we examined how the edge responses of these species predict the spatial patterns of nest mortality. Predation risk was strongly related to mongoose abundance but was not affected by nest density or habitat type. The product of predator and prey edge response functions accurately described the observed pattern of total prey mortality. Hawksbill preference for vegetation edge becomes an ecological trap in the presence of mongooses. This is the first study to predict patterns of predation directly from continuous edge response functions of interacting species, establishing a link between models of edge response and species interactions.     

Snake activity affects seasonal variation in nest predation risk for birds

Variation in predator behavior has been proposed, but not tested, as a mechanism producing seasonal declines in avian nest success. We test this hypothesis by documenting seasonal activity of Texas ratsnakes Elaphe obsoleta and nest failure of endangered black-capped vireos Vireo atricapilla and golden-cheeked warblers Dendroica chrysoparia on which the snakes prey. Nest survival analysis was based on 880 vireo and 228 warbler nests and 3,060 snake locations from 62 radio-tracked snakes. Although nest success varied with snake activity for both birds, specific patterns differed substantially. Vireo daily nest survival was negatively correlated with snake activity over the three-year study, despite substantial variation among years in weather, and the fact that these birds are almost certainly a minor prey species of the ratsnakes. Warblers exhibited less clear-cut seasonal variation in nest success, and the association between nest success and snake activity was less pronounced than for vireos. Increased activity at warmer temperatures explained some of the seasonal change in snake movements, although mating may have accounted for a mid-season peak in activity. These results indicate that variation in predator behavior can be associated with and potentially cause seasonal changes in nest success, but also that these relationships are species specific even within the same community and may depend on aspects of the nesting ecology of the prey such as nest site selection.     

Meta‐analyses of nest predation in temperate Australian forests and woodlands

Nest predation is the leading cause of nesting failure. Thus it is a crucial area of research needed to inform conservation management and to understand the life history of birds. I surveyed the literature to review the identity of nest predators and the factors affecting nest predation, in Australia using 177 studies. Overall, 94 nest predators were identified when incorporating artificial nests, 69 without. Using only natural nests, the Pied Currawong Strepera graculina was the most frequently reported nest predator. Five nest predators, including Pied Currawong, depredated 40% of the prey measured by the number of prey species taken. Yet, 60% of predation was carried out by the other 64 species, which included by the order of importance birds, mammals, reptiles, frogs and ants. Predation at cup and dome nests was more frequently reported than at burrow, ground and hollow nests. Only 28% of predators were observed at both artificial and natural nests suggesting artificial nests have limited, but not negligible, ability as tools for identifying predators. There was a highly significant and positive correlation between predator and prey masses. The predator prey mass ratio was calculated with a mean 0.25 and a median 0.22, a result closely matching with the proportional size of prey taken by raptors. The finding that predator size is proportional to prey opens a pathway for more life history and conservation research.     

Avian conservation practices strengthen ecosystem services in California vineyards

Insectivorous Western Bluebirds (Sialia mexicana) occupy vineyard nest boxes established by California winegrape growers who want to encourage avian conservation. Experimentally, the provision of available nest sites serves as an alternative to exclosure methods for isolating the potential ecosystem services provided by foraging birds. We compared the abundance and species richness of avian foragers and removal rates of sentinel prey in treatments with songbird nest boxes and controls without nest boxes. The average species richness of avian insectivores increased by over 50 percent compared to controls. Insectivorous bird density nearly quadrupled, primarily due to a tenfold increase in Western Bluebird abundance. In contrast, there was no significant difference in the abundance of omnivorous or granivorous bird species some of which opportunistically forage on grapes. In a sentinel prey experiment, 2.4 times more live beet armyworms (Spodoptera exigua) were removed in the nest box treatment than in the control. As an estimate of the maximum foraging services provided by insectivorous birds, we found that larval removal rates measured immediately below occupied boxes averaged 3.5 times greater than in the control. Consequently the presence of Western Bluebirds in vineyard nest boxes strengthened ecosystem services to winegrape growers, illustrating a benefit of agroecological conservation practices. Predator addition and sentinel prey experiments lack some disadvantages of predator exclusion experiments and were robust methodologies for detecting ecosystem services.     

Nesting biology of the Black-necked Grebe

The fish diet of young Kingfishers Alcedo atthis on the River Roding near Abridge, Essex was assessed by analysing regurgitated bones collected from the nest tunnel. More than 3000 bones recovered from two nest sites in 1979, 1981 and 1982 revealed that nine fish species were eaten. Despite variation between samples, cyprinids consistently represented the main prey, with Minnow Phoxinus phoxinus the single most important species. Stickleback Gasterosteus aculeatus was also a prominent prey item, particularly in 1981. Ignoring Stoneloach Noemacheilusbarbatulus, the proportion of fish species found in riffles within the study area was similar to that gleaned from the nest tunnel samples. Strong correlation of live fork-length and wet weight to pharyngeal bone length enabled the size of Minnow prey to be determined accurately: analysis of 2276 pharyngeal bones produced a mean size of 54 mm fork-length and 1.5 g wet weight. The mean length was comparable to that of Bullheads Cottus gobio eaten by chicks more than 10 days old on the River Lesse in Belgium.     

Effect of prey quantity and temperature on nest demography of social wasps

Abstract. 1. To determine the effect of prey quantity and temperature on nest demography of social wasps ( Polistes fuscatus ), field experiments were conducted, in which wasps were provided with a low quantity of caterpillars (approximately nest subsistence level) or high quantity (three times as much). In addition, in the third year, the nest boxes were modified to be relatively cool (white and insulated) or warm (black).
2. In 1997 and 1998, high-food nests had a high proportion of cells containing developing offspring, produced more offspring, and had disproportionately more female offspring compared with low-food nests.
3. In 1999, the cool and warm nest boxes exhibited a daily average difference of 1.3 °C and a maximum difference of 6.9 °C. The warm high-food nests produced more offspring than any other treatment. The cool high-food nests produced similar numbers of offspring as the cool low-food and warm low-food treatments.
4. As indicated by a surplus of uncapped cells, foundresses of low-food nests, which would have had the egg-laying potential to produce many offspring, apparently sacrificed eggs to provide a food supplement for the developing offspring. This pattern plus more time observed foraging suggests considerable expenditure of energy by foundresses, in response to the low supply of food.
5. Importantly, these results indicate that an interactive effect of prey quantity and temperature on offspring production occurred, which may reflect the different effects on developmental rate and growth rate at cool versus warm nest temperatures.     

Patterns of nest provisioning and parental investment in the solitary digger wasp Ammophila sabulosa

Abstract.

• 1 In nest-building wasps there is a continuum from species that provision each offspring cell with one large prey item (single provisioning) to species that provision each cell with many small items (multiple provisioning). The significance of number of prey per cell was examined during two seasons in Ammophila sabulosa (L.), a species that provisions between one and five caterpillars per cell.
• 2 There was no difference between the total weight of prey in singly-provisioned and multiply-provisioned cells: individual caterpillars placed in multiply-provisioned cells were smaller.
• 3 Small caterpillars were captured and transported to the nest faster than large ones.
• 4 If the first prey provisioned was large, the cell was usually then permanently closed. If the first prey was small, additional prey were captured, and females appeared to become more selective: additional prey were rarely large.
• 5 It is suggested that the flexible provisioning strategy used by A.sabulosa allows a wide range of prey sizes to be utilized without affecting maternal control of offspring size and sex. This could be important when available prey sizes vary temporally and spatially.
• 6 There was a male-biased first generation investment ratio. Female-producing cells were provisioned with a higher total prey weight than male-producing cells, and conversion of prey weight to adult weight was more efficient for females.
• 7 Total prey weight provisioned is probably a good indirect measure of parental time investment in A.sabulosa. Other measures, particularly number of prey provisioned, will be less accurate.

     

Foraging tempo in two woodland and species

Running speeds of Myrmica punctiventris and Aphaenogaster rudis workers were measured, and a good correspondence between laboratory and field behaviour was obtained. In the laboratory, foraging tempo and foraging efficiency were calculated for two colony sizes and five patterns of prey availability. Running speeds were strongly dependent on colony size for both species; when retrieving prey, foragers from large colonies ran significantly faster than those from small colonies. In addition, ants searching for prey ran more slowly than those returning to the nest with prey. Efficiency, measured as the propensity to return to the nest in a straight line, was most strongly a function of distance from the nest. Finally, no relationship between an ant's speed and its efficiency of return was found.     

Happy is the man that findeth wisdom

The hypothesis is suggested that resource depression is one important factor behind the observed regular nest spacing of many birds of prey. It predicts that the proportion of evasive prey in the predator's diet should be reflected in the degree of regularity in its nest spacing. The idea is tested on data from 24 raptorial bird populations of 19 species. The proportion of supposed evasive prey (birds and large mammals) in the diet was positively correlated with the degree of regularity in spacing of the nests, considering all populations or species. No such significant correlation was found for the six highly territorial species, whereas the correlation was highly significant for the other 13 species. Thus, the hypothesis seems most applicable to species with widely overlapping home ranges. However, resource depression could be one reason for territoriality.     

BIOGEOGRAPHICAL AND TOPOGRAPHICAL VARIATION IN THE PREY OF THE BLACK EAGLE IN THE CAPE PROVINCE,SOUTH AFRICA

Boshoff, A.F., Palmer, N.G., Avery, G., Davies, R.A.G. & Jarvis, M.J.F. 1991. Biogeoraphical and toporaphical variation in the prey of the Black Eagle in the Cape Province, South Africa. Ostrich 62: 58–72.

Prey remains collected at or near Black Eagle Aquilu verreauxii nest sites in the Cape Province, South Africa, were analysed according to frequency of occurrence of prey scies in the samples. A total of 5748 prey individuals, collected from 73 sites, was analysed according to tree biome groups and four nest site types. The Rock Hyrax Procuvia capensis is the dominant prey species, but the eagles' diet sctrum vanestypes. The according to its availability. Indices of species richness and diversity of the prey are inverser correlated with the proportion of the prey contributed by P. capenis, which in turn is determined by topography and vegetation. Biome has a greater influence on the indices than has nest site type. The age structure of the P. capensis prey remains closely reflects the juvenile: sub- adult: adult ratios in the biomes and at the nest site tpes. hfedium-sized (aprox. 1–4,5 kg) pre is usually taken. Juvenile domestic small-stock (lambs ani goat kids) comprised onb 3,4% of the over, total.