Impact of predation on early stages of the armoured catfish Hoplosternum thoracatum (Siluriformes-Callichthyidae) and implications for the syntopic occurrence with other related catfishes in a neotropical multi-predator swamp

This study investigated the role of predators in preventing competitive exclusion among three closely related armoured catfishes (Callichthys callichthys, Hoplosternum littorale and H. thoracatum) that occur synthopically in multi-predator freshwater swamps of Suriname, South America. The potential impact of predation on armoured catfish was determined by combining laboratory measurements of predation rates on five early developmental stages of the armoured catfish H. thoracatum for 24 aquatic predators with field studies of the density of the predators in the swamps. The contribution of a particular predator to the total predation pressure on its prey was determined to a large extent by the density of the predator in the swamp. Seemingly innocuous predators with low or moderate predation rates in the laboratory may be extremely important in the swamps due to their high abundance. Small-sized omnivorous fishes and aquatic invertebrates were major predators of early developmental stages of armoured catfish. Both qualitative and quantitative ontogenetic changes in the predation pressure on armoured catfish were observed. Major predation on eggs, larvae and juveniles of H. thoracatum resulted from a different set of predators in each developmental stage of the prey. In all developmental stages of H. thoracatum the predation pressure involved several predator species and not a single, dominant predator. The potential predation pressure of the 24 predators taken together and the number of predators that were able to prey on H. thoracatum decreased sharply with increasing age (size) of the prey. Even if egg (nest) predation is prevented by the guarding male, the potential impact of the 24 predators on the populations of armoured catfish is large. Predation may account for the high mortality of H. thoracatum observed in the swamps. The high predation pressure on callichthyid catfishes may help to explain the coexistence of three closely related and morphologically quite similar armoured catfishes in Surinamese swamps.     

Testing hypotheses about the function of repeated nest abandonment as a life history strategy in a passerine bird

Nest structures are essential for successful reproduction in most bird species. Nest construction costs time and energy, and most bird species typically build one nest per breeding attempt. Some species, however, build more than one nest, and the reason for this behaviour is often unclear. In the Grey Fantail Rhipidura albiscapa, nest abandonment before egg‐laying is very common. Fantails will build up to seven nests within a breeding season, and pairs abandon up to 71% of their nests before egg‐laying. We describe multiple nest‐building behaviour in the Grey Fantail and test four hypotheses explaining nest abandonment in this species: cryptic depredation, destruction of nests during storm events, and two anti‐predatory responses (construction of decoy nests to confuse predators, and increasing concealment to ‘hide’ nests more effectively). We found support for only one hypothesis – that abandonment is related to nest concealment. Abandoned nests were significantly less concealed than nests that received eggs. Most abandoned nests were not completely built and none received eggs, thus ruling out cryptic predation. Nests were not more likely to be abandoned following storm events. The decoy nest hypothesis was refuted as abandoned nests were constructed at any point during the breeding season and some nests were dismantled and the material used to build the subsequent nest. Thus, Grey Fantails are flexible about nest‐site locations during the nest‐building phase and readily abandon nest locations if they are found to have deficient security.     

Trade-off between digestion and respiration in two airbreathing callichthyid catfishes Holposternum littorale (Hancock) and Corydoras aeneus (Gill)

In callichthyid catfishes, the posterior intestine is modified to function as an air breathing organ by being air-filled, thin-walled and highly vascularized. These modifications make it unsuitable for digestive functions and digesta has to be transported quickly through this region to minimize disruption of vital respiratory functions. However, the weak muscles of the wall of the respiratory intestine make this problematic. It is hypothesized that the unidirectional ventilatory air current within the respiratory intestine is responsible for the quick transport of digesta through the respiratory intestine. To verify this, movement of digesta through the alimentary tract was examined in Hoplosternum littorale and Corydoras aeneus that were either allowed to breathe air or prevented from air breathing. When air breathing was prevented, digesta was not transported to the rectum in H. littorale and there was a 94% reduction in the amount of digesta in the rectum of C. aeneus. This study suggests that the anterior digestive intestine facilitates the passage of air although it is filled with digesta. The anterior digestive intestine packages digesta into a string of slightly compressed boluses, creating an air channel in the digestive intestine thus allowing air to pass unimpeded.     

Ontogenetic diet shifts and diet overlap among three closely related neotropical armoured catfishes

Analysis of stomach contents of larvae, juveniles and adults of three closely related armoured catfishes in coastal plain swamps of Suriname, South America, revealed major ontogenetic diet shifts. Larvae of Hoplosternum littorale, H. thoracatum and Callichthys callichthys showed a restricted diet of rotifers and microcrustacea. Diets of juveniles and adults were more diverse, but large volumes of microcrustacea, aquatic insect larvae and detritus were always present. In all three species diet overlap was especially low between larvae and adults. The proportion of detritus in the stomach was positively related to fish size, which probably reflected the inability of larger size classes to separate effectively benthic invertebrate prey from bottom substrata, and not a specialization towards detritivory. Adults showed only minor seasonality in diet composition, and no effect of season on diet breadth. Interspecific diet overlap among larvae, juveniles and adults did not differ significantly from 1 (complete overlap). Lack of food partitioning was probably related to a similar morphology of the three catfishes. Intraspecific between-size class diet overlap was considerably lower than interspecific within-size class overlap. It is suggested that large interspecific diet overlap occurred because food was not limiting the populations of these catfish. However, the nest habitats of the three species differed.     

Nest defence in the meadow pipit <Emphasis Type="Italic">Anthus pratensis</Emphasis>: the influence of renesting potential

The reproductive value hypothesis predicts that the level of nest defence is determined by the expected chance of offspring to survive until reproduction, and by the reproductive potential of the parents. Rates of survival from one breeding season to the next are low in small passerines, and their residual reproductive potential strongly declines as the current breeding season terminates. Therefore, we can expect that parents which have only one breeding attempt per season should defend their nests more intensively than parents with a possibility to renest. We studied nest defence in populations of meadow pipit (Anthus pratensis) breeding in Norway and the Czech Republic, differing in renesting potential. To simulate the threat from a predator, we placed a stuffed stoat (Mustela erminea) first 5 m and then 1 m away from a nest with nestlings. Parents increased or kept nest defence constant when the stoat approached their nests in Norway and, during a breeding season shortened by severe weather, in the Czech Republic (when renesting potential was limited). Parents decreased nest defence when the stoat approached the nest during “normal” breeding seasons in the Czech Republic (when renesting was common). These findings give support to the reproductive value hypothesis.     

Interspecific interference for nest sites betweenLeptothorax congruus andMonomorium intrudens

Summary Interference competition for nest sites was studied in ant communities dominated byLeptothorax congruus in the suburbs of Tokyo, central Japan. At the two study plots located in a deciduous wood and in grassland,L. congruus constructed nests in dead branches or stems of dead grasses. Approximately 50% of the nests were physically broken within a year, suggesting that they were very fragile. Of totals of 67 and 91 nests ofL. congruus marked at the two sites, 12 (17.5%) and 53 (58.2%) nests, respectively, were replaced by other ant species (Monomorium intrudens,Crematogaster brunnea teranishii,Camponotus itoi andLasius sp.) which were common in both habitats. Field observation suggested that, among these ants,M. intrudens was a major competitor usurping the nests ofL. congruus by aggressive invasion.     

Nesting biology and nest re-use ofEulaema nigrita (Hymenoptera: Apidae,Euglossini)

Summary The nesting behavior of the euglossine beeEulaema nigrita was observed in the laboratory after being transferred from three nests to observation boxes. Nests were re-used by successive generations with more than one female working in each re-use process. Associated females were always of the same generation. All females that shared a nest foraged for construction materials (mud, excrement and resin) and each constructed, provisioned and oviposited in her own cells. The number of cells constructed by each female ranged from one to 23. Females stayed in the nests for periods ranging from 15 to 59 days during the hot and wet season and from five to 78 days during the cool and dry season. The egg-to-adult period was related to climatic conditions, and in all re-use processes it was longer than the time of residence of the females in the nests. The meloid beetleMeloetyphlus attacephalus was the only nest parasite. Due to the attack method employed by this parasite, the presence of more than one female in the nest did not result in improved nest defense.     

Nest re-use and communal nesting inMicrothurge corumbae (Hymenoptera,Megachilidae), with special reference to nest defense

Summary Observations on the nesting activities ofMicrothurge corumbae, carried out at the University Campus of Ribeirão Preto, São Paulo, Brazil, from 1977 to 1981, indicated that 61.9 % of nests were re-used by succeeding generations. Re-use by one generation was more frequent than by two generations, and re-use by a third was observed only once. Nests were re-used by one or several females. Single females were more frequently in the first re-use. In these cases nest re-use did not differ essentially from the solitary foundation of a new nest, except for the adoption of a pre-existing nest without excavation. In multifemale nests, analysis of relative age (wing wear), ovarian and spermathecal conditions of associated females and the content of nests at excavation indicated that the social pattern in such colonies is communal. There is some evidence that the associated females are relatives. The chalcidoid waspLeucospis was the principal nest parasite, and ants of the genusCrematogaster were nest predators. In multifemale nests, the rate of parasitism was significantly lower than in solitary nests, indicating that nest-sharing resulted in improved nest defense. On the other hand, the absence of predation on immatures of the first generation of M.commbae in multifemale nests suggests that such nests are also more resistant to attack by predators.     

The effect of climate on nest orientation in the Rufous Hornero Furnarius rufus

ABSTRACT

Capsule: Within breeding season changes in nest orientation of the Rufous Hornero Furnarius rufus may reflect responses to the local climate.

Aims: To explore the effect of climate on the orientation of closed-cup nests of the Rufous Hornero at a subtropical urban site throughout its breeding period.

Methods: The breeding season was divided into two periods: a cold period with low rainfall and a warm, humid period. For each period, the mean nest entrance orientation and distribution were estimated and compared against a random orientation model.

Results: A total of 42 nests were found during the first period of reproduction and 32 during the second period. In both cases, the mean orientation was non-random and significantly different between the two periods: nests were more likely to be orientated towards the northwest in the first period and to the east in the second period.

Conclusions: Climate variation throughout the breeding season was reflected in differences in nest entrance orientation. This could be because this species takes advantage of solar radiation to increase the temperature within the nest during the first cold months of the breeding season and reduces the humidity of the nest, generated by intense rain, as the season progresses.     

Rediscovery of the workerless inquiline antPogonomyrmex colei and additional notes on natural history (Hymenoptera: Formicidae)

Summary Pogonomyrmex colei is a workerless inquiline ant known only from nests ofP. rugosus, its closest relative. Ten of 776 (1.3%) host nests were parasitized at a site in central Arizona, while none of 1499 potential host colonies were parasitized at two other locales. Colonies ofP. colei are perennial, and host alate females in 9 of 10 colonies demonstrates that host queens survive parasitism. Three of 10 colonies died over 19 colony years of observation, while only 1 of 601 colonies became newly parasitized. Mating occurs in morning for up to 2–3 days following summer and fall rains and in afternoon during cool fall days. Mating is intranidal just outside the nest entrance, with males returning to the natal nest. MaleP. colei may be flightless because their wing area is reduced compared to host males. Females fly from the nest and locate potential host colonies by following trunk trails. Workers are the largest barrier to nest establishment, as they removed over 90% ofP. colei females placed in trunk trails or that entered host nests. Males and females ofP. colei andP. anergismus, the only other congeneric inquiline species, are diminutive compared to their hosts, with females 30% lighter than host workers. Fat content is lower and water content is higher inP. colei andP. anergismus females than in their hosts.     

The population biology ofTapinoma minutum (Hymenoptera: Formicidae) in Australia

Summary Nests ofTapinoma minutum were collected and mapped from a wet sclerophyll forest in New South Wales during the spring, summer, and fall seasons. Queen number was variable, indicating the population is both facultatively polygynous and polydomous. Electrophoretic data from three polymorphic enzymes revealed that relatedness among workers conformed to the Hamiltonian expectation of 0.75. Colony boundaries were inferred from electrophoretic data synthesized with nest spatial locations. For this species colonies were composed of at most three nests; this simple pattern of polydomy suggests it has a recent origin in this population. The pattern of facultative polygyny may be linked to an apparent high rate of colony orphaning.     

Interaction between ants and fruits of<Emphasis Type="Italic"> Guapira opposita</Emphasis> (Nyctaginaceae) in a Brazilian sandy plain rainforest: ant effects on seeds and seedlings

This study examines the dispersal system of Guapira opposita in a tropical sandy rainforest in southeast Brazil. Guapira trees produce small fruits with a high protein content (28.4%) and low lipid content (0.3%), and the plant is primarily dispersed by birds. Mature fruits of G. opposita can fall spontaneously with the pulp intact, or be dropped by birds with bits of pulp attached. In either case, ground-dwelling ants rapidly remove the fruits to their nest (93% after 12 h). The ponerine ants Odontomachus chelifer and Pachycondyla striata are the main seed vectors among the ants, and together account for 56% (20 of 36) of the ant-fruit interactions recorded on the forest floor. Individual workers of O. chelifer and P. striata transport single fruits to their nests. Bits of pulp are fed to larvae and worker nestmates, and intact seeds are discarded outside the nest. Germination success in Guapira is higher for cleaned seeds (pulp removed) than for seeds coated by pulp. Guapira seedlings and juveniles are more frequent close to Odontomachus nests than at sites without such nests. Soil samples from Odontomachus nests had greater penetrability, and higher concentrations of P, K, and Ca than random soil samples. Field experiments suggest that the association between G. opposita seedlings and O. chelifer nests can potentially render the plant some protection against herbivores. Results indicate that fruit displacement by ponerine ants play an important role in the biology of G. opposita seeds and seedlings in the sandy forest, and illustrate the complex nature of the dispersal ecology of tropical tree species.     

Nest groups of wild bonobos at Wamba: selection of vegetation and tree species and relationships between nest group size and party size

We examined the location of nest groups, spatial distribution of nests within a nest group, and attributes of individual nests of wild bonobos at Wamba, Democratic Republic of Congo. We also examined the seasonal factors influencing nesting behavior and compared the nest group size with the 1 hr party size during daytime. We defined a nest group to be a cluster of nests that were built in the same evening and found within 30 m from the other nearest nest. Examination of the largest gap within a nest group suggested that 30 m was an acceptable cutoff value. Monthly rainfall or fruit abundance did not significantly influence the monthly mean nest group size. Nests were built in the swamp forest for as many as 13% observation days, suggesting the need for reevaluation of the use of swamp forest by bonobos. The use of swamp forest was influenced not by seasonal rainfall or fruit abundance, but by the fruiting of specific species. Preferred tree species for building nests accounted for 19.8% of standing trees, which suggested that the selection of sleeping sites was not largely restricted by the distribution of specific species. The mean 1 hr party size was almost identical through the day and was similar to the mean nest group size. Parties of bonobos sometimes split into smaller nest groups, especially when feeding on non‐preferred fruits during fruit scarcity. By contrast, when feeding on preferred fruits while ranging in large parties, they often aggregated to form even larger nest groups. When sleeping in small‐ or middle‐sized nest groups, they tended to aggregate the next morning. These tendencies may reflect the gregarious nature of bonobos who prefer to range or sleep together as far as circumstances allow. Am. J. Primatol. 72:575–586, 2010. © 2010 Wiley‐Liss, Inc.     

Effects of a habitat-altering invader on nesting sparrows: An ecological trap?

Many invading species impact native species through predation, parasitism or competition, while others affect natives indirectly by restructuring their habitat. How invasive plants affect native animals, and to what extent native animals respond to changes in their habitat and the novel selection pressures that follow, is not well known. We investigated the impacts of a habitat-altering invader, the Atlantic cordgrass Spartina alterniflora, on the nesting success of Alameda song sparrows (Melospiza melodia pusillula), a California Species of Special Concern, in tidal marshes in three sites in San Francisco Bay. Date of laying was the most influential factor in determining daily survival rate of nests, but whether the nest was placed in exotic Spartina was the most important ecological variable. Nests placed in exotic Spartina had a success rate that was 30% lower than those placed in native vegetation. Nests in exotic Spartina were significantly more likely to fail due to tidal flooding than were nests placed in native vegetation, because the densest stands of exotic Spartina occurred at significantly lower elevations relative to the tides. Our results suggest that exotic Spartina may be an ecological trap for song sparrows in San Francisco Bay, attracting birds to nest sites that are often destroyed by tidal flooding.     

An odd activity of an ant (Cataglyphis bicolor); ≪visiting≫

Summary An unexplained form of behaviour connecting nests of an antCataglyphis bicolor F. is described. Individuals from one nest visit another wandering around the nest entrance, for periods of up to half an hour or more. Their behaviour is quite distinct from any seen in normal foraging. These individuals come from the upper end of the range of size; more frequently but not always from a larger to a smaller nest. Nests are normally antagonistic. These ants back away rapidly from an ant of the nest visited.     

Nesting Biology of Microstigmus thripoctenus Richards, with a Study on Nest Recognition (Hymenoptera: Crabronidae)

In a study carried out on Microstigmus thripoctenus on Barro Colorado Island (Republic of Panama) between March and May 1998, 29 active nests were located. The nests contained between one and seven cells, with one (female) to six (three females and three males) adults. Using simple manipulations in which wasps were offered a choice between experimentally emptied foreign nests and their own nest when the adults were away, it was observed that returning adults were able to recognize their own nest. Foreign nests were always rejected by females coming from nests with a single adult, whereas individuals from nests with several adults in five of seven cases did accept the foreign nests, continuing their normal activities in them, without destroying their contents. Adopted foreign nests were inspected at a higher rate following adoption. Nests containing several adults tended to remain longer on leaves supporting them, and their external surfaces were inspected more frequently and longer than those of nests containing only one occupant. Nests are not associated with any particular plant and were found attached to leaves of 19 species of understory plants.     

5. FIELD OBSERVATIONS,NORTHERN PROVINCE,NORTHERN RHODESIA

Cooper, J. 1986. Biology of the Bank Cormorant, Part 4: Nest construction and characteristics. Ostrich 57: 170–179.

Bank Cormorants Phalacrocorax neglectus construct their nests of material gathered by diving. Males undertake diving bouts of approximately 3–5 min, made up of several dives lasting on average 28 s. Nest material is gathered throughout the breeding cycle: number of diving bouts per day varies from a mean of 7,6 during pre-egg laying to 1,5 bouts per day when rearing young in the nest. Nest building recommences within 24 h of loss of nest due to storms. Both sexes occasionally steal nest material from the nests of neighbours. Bank Cormorants sometimes defecate onto their nests. This is assumed to make the nests better able to withstand rough seas. Nest construction takes approximately 34 d, a period similar to that of other ground-nesting species of cormorants. Construction of a nest in 34 d represents 238 diving bouts of a total duration of 18 h. Nests are heavy (up to 6 kg) and are made up primarily of seaweed. Feathers, sticks and artificial material are also incorporated into the nest. Bank Cormorant nests are large (up to 54 litres in total volume). Nests do not change significantly in size between egg laying and hatching. Nests in which at least one egg hatches are larger in all dimensions measured than those in which no eggs hatch. Nests are larger at the time of laying of repeat clutches than at the time of laying the first clutch. The Bank Cormorant's seaweed nest has enabled it to breed on bare offshore rocks where no nest material exists. The species' large nest is a necessary prerequisite for successful breeding close to the sea.     

Effects of climate variation on timing of nesting,reproductive success,and offspring sex ratios of red-winged blackbirds

Predicting ecological consequences of climate change will be improved by understanding how species are affected by contemporary climate variation, particularly if analyses involve more than single ecological variables and focus on large-scale climate phenomena. I used 18 years of data from red-winged blackbirds (Agelaius phoeniceus) studied over a 25-year period in eastern Ontario to explore chronological and climate-related patterns of reproduction. Although blackbirds started nesting earlier in years with warmer springs, associated with low winter values of the North Atlantic Oscillation Index (NAOI), there was no advance in laying dates over the study. Nesting ended progressively later and the breeding season lasted longer over the study, however, associated with higher spring values of NAOI. As the length of the nesting season increased, offspring sex ratios became more female biased, apparently as a result of females adjusting the sex of the eggs they laid, rather than from sex-biased nestling mortality. Clutch size did not vary systematically over the study or with climate. Opposing trends of declining nest success and increasing productivity of successful nests over the study resulted in no chronological change in productivity per female. Higher productivity of successful nests was associated with higher winter NAOI values, possibly because synchrony between nesting and food availability was higher in years with high NAOI values. Other than the association between the start of nesting and spring temperatures, local weather (e.g., temperature, rainfall) patterns that linked NAOI with reproduction were not identified, suggesting that weather patterns may be complex. Because climate affected most aspects of red-winged blackbird reproduction examined, focusing on associations between climate and single variables (e.g., first-egg dates) will have limited value in predicting how future climates will affect populations.     

Parasite presence acts as a proximate cue in the nest-site selection process of the solitary digger wasp,Ammophila dysmica (Hymenoptera: Sphecidae)

Nest-site selection by the solitary ground-nesting wasp Ammophila dysmicaMenke was studied during 1982–1986 in California's Sierra Nevada Mountains. Digging females detected and discriminated among members of a complex of insect intruders, including a number of predators and parasites. In response to some natural enemies, wasps sometimes permanently abandoned nests under construction. These selective nest abandonments reduced the mean number of cleptoparasitic chrysidid wasps, Argochrysis armillaBohart, attending the excavation of completed nests. The number of A. armillaattending a nest excavation correlated positively with the probability of nest parasitism by this species. Selective nest abandonment may reduce parasitism rates.