Laying sequence,diploid males,and nest usurpation in the leafcutter bee,Megachile rotundata (Hymenoptera: Megachilidae)

Variations from the normal female-male sequence of eggs in nests of the leafcutter bee,Megachile rotundata, were examined. Three alternatives were considered: Out-of-sequence males (i) were diploids, (ii) were the result of supersedure of nests or intraspecific brood parasitism, or (iii) were the result of females occasionally laying a male-female sequence. Electrophoretic data provided definitive evidence of diploid males and of multiple females laying in 7 of 18 nests. In the others, the remaining explanation is that females occasionally lay male eggs before female eggs in a nest.     

Factors associated with nest survival of Black‐throated Sparrows,desert‐breeding nest‐site generalists

Black‐throated Sparrows (Amphispiza bilineata) are common breeding birds throughout the desert regions of North America and can be considered nest‐site generalists. Information about how spatial (e.g., vegetation) and temporal factors influence nest survival of these sparrows is lacking throughout their range. Our objective was to examine the spatial and temporal factors associated with nest survival of Black‐throated Sparrows at the nest and nest‐patch scales in the predator‐rich environment of the northern Chihuahuan Desert of New Mexico. We used a logistic‐exposure model fit within a Bayesian framework to model the daily survival probability of Black‐throated Sparrow nests. Predation was the leading cause of nest failure, accounting for 86% of failed nests. We found evidence of negative associations between nest survival and both vegetative cover above nests and shrub density within 5 m of nests. We found no support for other habitat covariates, but did find strong evidence that daily survival rate was higher earlier in the breeding season and during the egg‐laying stage. A decline in nest survival later in the breeding period may be due to increased predator activity due to warmer ambient temperatures, whereas lower survival during the incubation and nestling stages could be a result of increased activity at nests. A generalist approach to nest‐site selection may be an adaptive response to the presence of a diverse assemblage of nest predators that results in the reduced influence of spatial factors on nest survival for Black‐throated Sparrows.     

Contrasting effects of high‐intensity photosynthetically active radiation on two bloom‐forming dinoflagellates

While light limitation can inhibit bloom formation in dinoflagellates, the potential for high‐intensity photosynthetically active radiation (PAR) to inhibit blooms by causing stress or damage has not been well‐studied. We measured the effects of high‐intensity PAR on the bloom‐forming dinoflagellates Alexandrium fundyense and Heterocapsa rotundata. Various physiological parameters (photosynthetic efficiency F_v/F_m, cell permeability, dimethylsulfoniopropionate [DMSP], cell volume, and chlorophyll‐a content) were measured before and after exposure to high‐intensity natural sunlight in short‐term light stress experiments. In addition, photosynthesis‐irradiance (P‐E) responses were compared for cells grown at different light levels to assess the capacity for photophysiological acclimation in each species. Experiments revealed distinct species‐specific responses to high PAR. While high light decreased F_v/F_m in both species, A. fundyense showed little additional evidence of light stress in short‐term experiments, although increased membrane permeability and intracellular DMSP indicated a response to handling. P‐E responses further indicated a high light‐adapted species with Chl‐a inversely proportional to growth irradiance and no evidence of photoinhibition; reduced maximum per‐cell photosynthesis rates suggest a trade‐off between photoprotection and C fixation in high light‐acclimated cells. Heterocapsa rotundata cells, in contrast, swelled in response to high light and sometimes lysed in short‐term experiments, releasing DMSP. P‐E responses confirmed a low light‐adapted species with high photosynthetic efficiencies associated with trade‐offs in the form of substantial photoinhibition and a lack of plasticity in Chl‐a content. These contrasting responses illustrate that high light constrains dinoflagellate community composition through species‐specific stress effects, with consequences for bloom formation and ecological interactions within the plankton.     

PVC nest boxes are less at risk of occupancy by feral honey bees than timber nest boxes and natural hollows

Feral European Honey Bee (Apis mellifera) has been identified as a potential nest competitor for Australian hollow nesting species, but few studies have investigated the impact of feral honey bee competition on Threatened species. Our study used data from Glossy Black‐cockatoo (Calyptorhynchus lathami halmaturinus) nests on Kangaroo Island, monitored and managed over an 11‐year period, and found 12% of nests became occupied by feral honey bees during that period. Our results indicate that feral honey bees were less likely to occupy nest boxes made of PVC (5%) compared with wooden nest boxes (24%) or natural hollows in Eucalyptus trees (14%). The removal of feral honey bee hives from nests is a priority for long‐term conservation of glossy black‐cockatoos on Kangaroo Island. We recommend that PVC nest boxes are chosen for future nesting habitat restoration, due to the more frequent use of wooden nest boxes by feral honey bees.     

Boldness and Stress Responsiveness as Drivers of Nest‐Site Selection in a Ground‐Nesting Bird

Nest‐site selection involves trade‐offs between the probability of nest discovery by egg predators, danger to the incubating parent from predators and provision of an appropriate microclimate for incubation, and all three components are potentially influenced by nest concealment and distance to habitat edge. Personality traits also affect habitat choice, and the trade‐off hypothesis suggests that variable stress‐coping strategies may evolve because individuals prioritize either productivity (proactive coping) or survival (reactive coping), both of which cannot be simultaneously maximized. Applying this hypothesis to understand nest‐site selection by female eider ducks (Somateria mollissima), we predicted that bold individuals with attenuated stress responsiveness should select concealed nests further away from the shore, thereby promoting clutch survival at the potential expense of reduced escape opportunities for themselves. In testing this prediction, we controlled for individual quality (female body condition and breeding experience) and verified that individual stress responses and nest‐site preferences were consistent by analysing their repeatability. Finally, we analysed how the viable proportion of the clutch was related to nest‐site and female characteristics. Our prediction was supported: bold females [short flight initiation distance (FID)] and those with lower handling‐induced body temperature were found in concealed nests, and bold females and those with lower handling‐induced corticosterone concentrations occupied nests farther from the shore. The viable proportion of the clutch peaked at intermediate proportional nest‐cover and increased linearly with increasing nest distance from the shore. Stress coping styles may thus be related to nest‐site selection, but their fitness consequences may be manifested indirectly through the nest‐site characteristics.     

Group nesting and individual variation in behavior and physiology in the orchid bee <Emphasis Type="Italic">Euglossa nigropilosa</Emphasis> Moure (Hymenoptera,Apidae)

The Euglossini are a key group for studying the traits that promote or hinder highly social behavior in bees because it is the only tribe in the Apine clade without large colonies or females with distinct life histories, e.g. queens and workers. There have been few studies on behavior of orchid bee females in nests because these nests are not found easily. Taking advantage of the relatively high abundance of Eg. nigropilosa nests at Reserva Natural La Planada, Colombia, we examined social behavior of Eg. nigropilosa individuals in five nests (3 original and 2 reused) for nine months. We report this species to have the largest colonies known for Euglossa, with nests reaching up to 22 individuals, and all nests containing more than one female bee from the same generation. These nests presented many traits that correspond to communal insect colonies. No generational overlap and no cooperative brood care were detected. We examined natural enemies and resource limitation as important factors for group nesting. We examined parasitoid attacks to cells in a nest with females and one without females. We also searched for nesting locations and examined nest re-use as indicators of nest site limitation. Lastly, we examined behavioral and physiological differences among females in the same nest. Such differences could be the bases for evolution of alternative life histories among group living females. We examined extent of ovary development and oviposition rates in similarly aged females in the same nest. We found large variation in reproductive effort of young females. We also examined differences in resin foraging and cell usurpation behaviors. Behavioral specialization was observed, with some individuals bringing only resin to the nest. Inside the nests, bees had territories in which they constructed and defended cells. This territoriality may be a defense against usurpation of provisioned cells by nest mates. Received 10 December 2007; revised 2 May 2008; accepted 7 May 2008.     

Females compensate for moult‐associated male nest desertion in Hooded Warblers

Uniparental offspring desertion occurs in a wide variety of avian taxa and usually reflects sexual conflict over parental care. In many species, desertion yields immediate reproductive benefits for deserters if they can re‐mate and breed again during the same nesting season; in such cases desertion may be selectively advantageous even if it significantly reduces the fitness of the current brood. However, in many other species, parents desert late‐season offspring when opportunities to re‐nest are absent. In these cases, any reproductive benefits of desertion are delayed, and desertion is unlikely to be advantageous unless the deserted parent can compensate for the loss of its partner and minimize costs to the current brood. We tested this parental compensation hypothesis in Hooded Warblers Setophaga citrina, a species in which males regularly desert late‐season nestlings and fledglings during moult. Females from deserted nests effectively doubled their provisioning efforts, and nestlings from deserted nests received just as much food, gained mass at the same rate, and were no more likely to die from either complete nest predation or brood reduction as young from biparental nests. The female provisioning response, however, was significantly related to nestling age; females undercompensated for male desertion when the nestlings were young, but overcompensated as nestlings approached fledging age, probably because of time constraints that brooding imposed on females with young nestlings. Overall, our results indicate that female Hooded Warblers completely compensate for male moult‐associated nest desertion, and that deserting males pay no reproductive cost for desertion, at least up to the point of fledging. Along with other studies, our findings support the general conclusion that late‐season offspring desertion is likely to evolve only when parental compensation by the deserted partner can minimize costs to the current brood.     

Provisioning behaviour at the nest in single-parent versus biparental nests and male versus female parents in the common redstart (<Emphasis Type="Italic">Phoenicurus phoenicurus</Emphasis>)

We analysed video-sequences of undisturbed parental provisioning behaviour on 12 nests of common redstart (Phoenicurus phoenicurus). In 4 of the 12 nests, chicks were fed by a single parent only. We compared provisioning rate of chicks, time spent on the nest and food allocation rules between nests with uniparental and biparental care and between male and female parents in biparental nests. In nests with a single parent, the frequency of feeding visits per parent was higher than in biparental nests. As a result, the rate of food provisioning of chicks was similar in uniparental and biparental nests. The food allocation rules did not differ between uniparental and biparental nests. In biparental nests, male and female provisioning behaviour was similar though with two exceptions: males had a strong preference for feeding chicks in front positions in the nest and females spent a longer time on the nest after feeding. We conclude that single common redstart parents are able to compensate fully for the absence of the other parent through increased provisioning efforts, and that in biparental nests, males and females contribute equally to the provisioning of the young.     

Aggressiveness,Boldness and Parental Food Provisioning in Male House Wrens (Troglodytes aedon)

Behavioural syndromes have been identified in a large number of species, yet our understanding of them in an ecological context remains poor. Specifically, there are few data that relate behavioural syndromes to other biologically important behaviours and, ultimately, to reproductive success. In this field study, we examined the aggressiveness and boldness of free‐living male house wrens (Troglodytes aedon) and found a statistically significant positive relationship between these two behaviours (i.e. a behavioural syndrome). When we examined the two axes of this behavioural syndrome in relation to the male's share of provisioning, we found a negative relation between a male's aggressiveness and his provisioning rate, but no relationship between male boldness and provisioning behaviour. These differences in provisioning behaviour among males with different levels of aggression may reflect differences in reproductive strategies or different life‐history trade‐offs among males. Moreover, these results indicate that while some behavioural traits may be correlated, this does not mean that traits that compose the behavioural syndrome cannot evolve independently of one another.     

Honey‐Making Bee Colony Abundance and Predation by Apes and Humans in a Uganda Forest Reserve1

Honey‐making bee colonies in Bwindi Impenetrable National Park were investigated with Batwa Pygmies locating 228 nests of Apis and five stingless bees (Meliponini). The relative importance of predation, food supply, nesting site, and elevation affecting abundance were studied for meliponines in particular. Nest predation and overall nest abundance had no correlation with elevation along a 1400 m gradient, nor did flowering phenology or pollen collection. Many suitable, large trees were unoccupied by bee nests. In 174 ha of forest plots, 2 Meliponula lendliana, 13 M. nebulata, 16 M. ferruginea, 16 M. bocandei, and 20 Apis mellifera adansonii nests occurred, suggesting a habitat‐wide density of 39 nests/km². Compared to other studies, Ugandan Meliponini were uncommon (0.27 colonies/ha, tropical mean = 1.9/ha), while Apis mellifera was numerous (0.12 nests/ha, tropical mean = 0.06/ha), despite park policy allowing humans to exploit Apis. Meliponine colony mortality from predators averaged 12 percent/yr and those near ground were most affected. Tool‐using humans and chimpanzees caused 82 percent of stingless bee nest predation. Selective factors affecting nest heights and habit may include auditory hunting by predators for buzzing bees, and indirect mutualists such as termites that leave potential nesting cavities. Mobility and free‐nesting by honey bee colonies should enable rapid community recovery after mortality, especially in parks where human honey hunting is frequent, compared to sedentary and nest‐site‐bound Meliponini.     

Efficacy of intervention to relieve nest box competition for Orange‐bellied Parrot Neophema chrysogaster

We use an experimental approach to evaluate the effectiveness of removing nests of a dominant competitor to create vacant nest boxes for a critically endangered parrot. We compared the number of times that Tree Martin (Petrochelidon nigricans – the dominant competitor at nest boxes) perched at or entered nest boxes intended for Orange‐bellied Parrot (Neophema chrysogaster – the subordinate nest competitor) over three time periods (before, immediately after and one week after experimental nest destruction). In the before period, rates of nest attendance by martins in treatment and control nests were not explained by treatment group. After experimental nest destruction, total attendance at boxes by martins rose to a mean of 6.1 visits over three five‐minute surveys in the treatment group, compared with 3.3 visits at control boxes. Within individual surveys, martins visited treatment boxes 4.4 times per survey one week after nest destruction, compared with only 1.6 visits in the control group. Martins in the treatment group rapidly rebuilt their nests and laid replacement clutches, and within a week, all boxes were reoccupied. Nest destruction did not increase nesting opportunities for the parrot, and increased vigilance of the dominant competitor may in fact reduce nesting opportunities in nearby boxes. Our study suggests that removing martin nests is an ineffective management action for alleviating nest competition for this parrot.     

Observation of plugging behaviour reveals entrance‐guarding schedule of morphologically specialized caste in Colobopsis nipponicus

The success of social insects is often attributed to the specialized morphologies and behaviours of workers. One of the most elaborate specializations in ant species is the workers’ plugging behaviour, in which their uniquely shaped heads are used for nest defence. These species generally nest in tree cavities. Without morphologically specialized workers (major workers) plugging the nest entrance, nests are easily attacked and replaced by conspecific and heterospecific cavity‐dwelling ants and other predators. Therefore, major workers are expected to defend the nest at all times. However, empirical evidence on the social time investment for nest defence is still lacking. Here, we investigated how major workers of Colobopsis nipponicus achieve nest defence (plugging behaviour) in terms of their work schedule. Our results showed that the nests had more major workers than entrances. The observation of artificial plastic nests over 6 days in the laboratory revealed that the nest entrance was guarded almost continuously by multiple major workers. The entrance‐guarding schedule was not equally divided among major workers, and there were no clear shift patterns in the timing of changeovers. We highlight the importance of investigating the time investment of workers to fully understand the defence strategies of this morphologically specialized caste.     

Delayed egg‐laying and shortened incubation duration of Arctic‐breeding shorebirds coincide with climate cooling

Biological impacts of climate change are exemplified by shifts in phenology. As the timing of breeding advances, the within‐season relationships between timing of breeding and reproductive traits may change and cause long‐term changes in the population mean value of reproductive traits. We investigated long‐term changes in the timing of breeding and within‐season patterns of clutch size, egg volume, incubation duration, and daily nest survival of three shorebird species between two decades. Based on previously known within‐season patterns and assuming a warming trend, we hypothesized that the timing of clutch initiation would advance between decades and would be coupled with increases in mean clutch size, egg volume, and daily nest survival rate. We monitored 1,378 nests of western sandpipers, semipalmated sandpipers, and red‐necked phalaropes at a subarctic site during 1993–1996 and 2010–2014. Sandpipers have biparental incubation, whereas phalaropes have uniparental incubation. We found an unexpected long‐term cooling trend during the early part of the breeding season. Three species delayed clutch initiation by 5 days in the 2010s relative to the 1990s. Clutch size and daily nest survival showed strong within‐season declines in sandpipers, but not in phalaropes. Egg volume showed strong within‐season declines in one species of sandpiper, but increased in phalaropes. Despite the within‐season patterns in traits and shifts in phenology, clutch size, egg volume, and daily nest survival were similar between decades. In contrast, incubation duration did not show within‐season variation, but decreased by 2 days in sandpipers and increased by 2 days in phalaropes. Shorebirds demonstrated variable breeding phenology and incubation duration in relation to climate cooling, but little change in nonphenological components of traits. Our results indicate that the breeding phenology of shorebirds is closely associated with the temperature conditions on breeding ground, the effects of which can vary among reproductive traits and among sympatric species.     

A comparison of life‐history and parental care in temperate and tropical wrens

Comparing closely related species that live in different environments is a powerful way to understand selective pressures that influence life‐history evolution. We examined a suite of life‐history traits and parental care in neotropical buff‐breasted wrens Cantorchilus leucotis and north‐temperate Carolina wrens Thryothorus ludovicianus (Family Troglodytidae), to test hypotheses about life‐history evolution. As expected, buff‐breasted wrens exhibited smaller clutch sizes and higher annual adult survival than Carolina wrens. We found minimal support for the nest predation hypothesis, as nest survival and age‐corrected provisioning rates to whole broods were similar between species, and number of breeding attempts and breeding season length were greater in temperate wrens. Critical predictions of the food limitation hypothesis were not supported; in particular age‐corrected provisioning rates per nestling were higher in the tropical than temperate species. The adult survival and offspring quality hypothesis garnered the most support, as buff‐breasted wrens exhibited greater age‐corrected provisioning rates per nestling, a longer nestling period, longer re‐nesting intervals following nest success, and lower annual fecundity than Carolina wrens. Despite similarly prolonged breeding seasons, reproductive strategies differ between species with buff‐breasted wrens investing considerably in single broods to optimize first‐year survival and Carolina wrens investing in multiple small broods to optimize annual fecundity.     

When beggars are choosers—How nesting of a solitary bee is affected by temporal dynamics of pollen plants in the landscape

Wild bees are declining in intensively farmed regions worldwide, threatening pollination services to flowering crops and wild plants. To halt bee declines, it is essential that conservation actions are based on a mechanistic understanding of how bee species utilize landscapes. We aimed at teasing apart how foraging resources in the landscape through the nesting season affected nesting and reproduction of a solitary bee in a farmland region. We investigated how availability of floral resources and potentially resource‐rich habitats surrounding nests affected nest provisioning and reproduction in the solitary polylectic bee Osmia bicornis. The study was performed in 18 landscape sectors dominated by agriculture, but varying in agricultural intensity in terms of proportion of organic crop fields and seminatural permanent pastures. Pasture‐rich sectors contained more oak (Quercus robur), which pollen analysis showed to be favored forage in early season. More oaks ≤100 m from nests led to higher proportions of oak pollen in nest provisions and increased speed of nest construction in early season, but this effect tapered off as flowering decreased. Late‐season pollen foraging was dominated by buttercup (Ranunculus spp.), common in various noncrop habitats. Foraging trips were longer with more oaks and increased further through the season. The opposite was found for buttercup. Oak and buttercup interacted to explain the number of offspring; buttercup had a positive effect only when the number of oaks was above the mean for the studied sectors. The results show that quality of complex and pasture‐rich landscapes for O. bicornis depends on preserving existing and generating new oak trees. Lignose plants are key early‐season forage resources in agricultural landscapes. Increasing habitat heterogeneity with trees and shrubs and promoting suitable late‐flowering forbs can benefit O. bicornis and other wild bees active in spring and early summer, something which existing agri‐environment schemes seldom target.     

Effects of Fungicide and Adjuvant Sprays on Nesting Behavior in Two Managed Solitary Bees,Osmia lignaria and Megachile rotundata

There is a growing body of empirical evidence showing that wild and managed bees are negatively impacted by various pesticides that are applied in agroecosystems around the world. The lethal and sublethal effects of two widely used fungicides and one adjuvant were assessed in cage studies in California on blue orchard bees, Osmia lignaria, and in cage studies in Utah on alfalfa leafcutting bees, Megachile rotundata. The fungicides tested were Rovral 4F (iprodione) and Pristine (mixture of pyraclostrobin + boscalid), and the adjuvant tested was N-90, a non-ionic wetting agent (90% polyethoxylated nonylphenol) added to certain tank mixtures of fungicides to improve the distribution and contact of sprays to plants. In separate trials, we erected screened cages and released 20 paint-marked females plus 30–50 males per cage to document the behavior of nesting bees under treated and control conditions. For all females in each cage, we recorded pollen-collecting trip times, nest substrate-collecting trip times (i.e., mud for O. lignaria and cut leaf pieces for M. rotundata), cell production rate, and the number of attempts each female made to enter her own or to enter other nest entrances upon returning from a foraging trip. No lethal effects of treatments were observed on adults, nor were there effects on time spent foraging for pollen and nest substrates and on cell production rate. However, Rovral 4F, Pristine, and N-90 disrupted the nest recognition abilities of O. lignaria females. Pristine, N-90, and Pristine + N-90 disrupted nest recognition ability of M. rotundata females. Electroantennogram responses of antennae of O. lignaria females maintained in the laboratory did not differ significantly between the fungicide-exposed and control bees. Our results provide the first empirical evidence that two commonly used fungicides and a non-ionic adjuvant can disrupt nest recognition in two managed solitary bee species.     

Phenology largely explains taller grass at successful nests in greater sage‐grouse

Much interest lies in the identification of manageable habitat variables that affect key vital rates for species of concern. For ground‐nesting birds, vegetation surrounding the nest may play an important role in mediating nest success by providing concealment from predators. Height of grasses surrounding the nest is thought to be a driver of nest survival in greater sage‐grouse (Centrocercus urophasianus; sage‐grouse), a species that has experienced widespread population declines throughout their range. However, a growing body of the literature has found that widely used field methods can produce misleading inference on the relationship between grass height and nest success. Specifically, it has been demonstrated that measuring concealment following nest fate (failure or hatch) introduces a temporal bias whereby successful nests are measured later in the season, on average, than failed nests. This sampling bias can produce inference suggesting a positive effect of grass height on nest survival, though the relationship arises due to the confounding effect of plant phenology, not an effect on predation risk. To test the generality of this finding for sage‐grouse, we reanalyzed existing datasets comprising >800 sage‐grouse nests from three independent studies across the range where there was a positive relationship found between grass height and nest survival, including two using methods now known to be biased. Correcting for phenology produced equivocal relationships between grass height and sage‐grouse nest survival. Viewed in total, evidence for a ubiquitous biological effect of grass height on sage‐grouse nest success across time and space is lacking. In light of these findings, a reevaluation of land management guidelines emphasizing specific grass height targets to promote nest success may be merited.     

Darwin's Finch Begging Intensity Does Not Honestly Signal Need in Parasitised Nests

Parental care should be selected to respond to honest cues that increase offspring survival. When offspring are parasitised, the parental food compensation hypothesis predicts that parents can provision extra food to compensate for energy loss due to parasitism. Chick begging behaviour is a possible mechanism to solicit increased feeding from attending parents. We experimentally manipulated parasite intensity from Philornis downsi in nests of Darwin's small ground finch (Geospiza fuliginosa) to test its effects on chick begging intensity and parental food provisioning. We used in‐nest video recordings of individually marked chicks to quantify nocturnal parasite feeding on chicks, subsequent diurnal chick begging intensity and parental feeding care. Our video analysis showed that one chick per brood had the highest parasite intensity during the night (supporting the tasty chick hypothesis) and weakest begging intensity during the day, which correlated with low parental care and rapid death. We observed sequential chick death on different days rather than total brood loss on a given day. Our within‐nest video images showed that (1) high nocturnal larval feeding correlated with low diurnal begging intensity and (2) parent birds ignored weakly begging chicks and provisioned strongly begging chicks. Excluding predation, all parasite‐free chicks survived (100% survival) and all parasitised chicks died in the nest (100% mortality). Weak begging intensity in parasitised chicks, which honestly signalled recent parasite attack, was not used as a cue for parental provisioning. Parents consistently responded to the strongest chick in both parasitised and parasite‐free nests.