Does nest predation pressure influence the energetic cost of nest guarding in a teleost fish?

The energetic costs of providing parental care are widely documented, but rarely do studies consider the role of environmental variation (e.g., predation pressure) in this context. Here, we tested if variation in nest predation pressure influenced the energetic costs of parental care in smallmouth bass (Micropterus dolomieu), a teleost fish species that provides lengthy paternal care. First, we documented that nest predation pressure varied among the six lakes studied and the relative predation pressure ranking was consistent across a three year period. We used a combination of traditional proximate body composition (PBC) analyses and electromyogram (EMG) telemetry to quantify activity costs of nesting fish across these populations. The traditional approach revealed declines in energy stores across the parental care period but showed no evidence of an increased energetic cost to parents from populations with higher nest predation pressure. Comparing the distribution of EMG data from the two extremes of predation pressure revealed that males from the site of highest predation spent more time at higher EMG levels relative to the parents from the lake of lowest predation pressure. Although not statistically significant, males from the site of highest predation pressure also spent 21?C24?% of their time burst swimming when guarding young offspring compared to 10?C11?% for males at the site of lowest predation pressure. These differences in overall activity, a large contributor to the energy use of fish, may translate into longer recovery times and decreased future reproductive opportunities.     

Seasonal habitat-dependent change in nest box occupation by Tengmalm’s owl associated with a corresponding change in nest predation

We investigated the nest-site settlement of the forest-dwelling Tengmalm’s owl (Aegolius funereus) in the temperate zone of Central Europe (Czech Republic) over a 14-year period. We analysed the effect of changes in nest-site suitability (expressed as the proportion of deciduous forest) within the immediate surroundings of the nest boxes (a buffer radius of 25 m) in relation to nest box occupancy, the mean standardized laying date (further the laying date), occurrence of nest predation, and breeding density. In line with the predictions of the site dependence model, we found a positive relationship between the laying date and the proportion of deciduous trees in the nest box surrounding. Further, we found the interactive effect of the laying date and the proportion of deciduous forest surrounding a nest box on the occurrence of breeding attempts predated by pine martens. A higher proportion of deciduous forest was found in the surroundings of predated than non-predated breeding attempts, and a steeper positive relationship between the laying date and the proportion of deciduous forest was found in the surroundings of non-predated than predated breeding attempts. The change in the owls’ habitat utilization can be explained by the process of tree leafing which makes the deciduous forest a less suitable habitat with high risk of nest predation before tree foliage and a more suitable habitat with low risk of nest predation after tree foliage. We conclude that our results are in agreement with the site dependence model, and that the degree of foliage of deciduous forest in the nest surrounding of Tengmalm’s owl is a key factor determining site suitability due to predation risk from pine martens in Central Europe.     

Can variation in risk of nest predation explain altitudinal migration in tropical birds?

Migration is among the best studied of animal behaviors, yet few empirical studies have tested hypotheses explaining the ultimate causes of these cyclical annual movements. Fretwell’s (1980) hypothesis predicts that if nest predation explains why many tropical birds migrate uphill to breed, then predation risk must be negatively associated with elevation. Data from 385 artificial nests spanning 2,740 m of elevation on the Atlantic slope of Costa Rica show an overall decline in predation with increasing elevation. However, nest predation risk was highest at intermediate elevations (500–650 m), not at lowest elevations. The proportion of nests depredated by different types of predators differed among elevations. These results imply that over half of the altitudinal migrant bird species in this region migrate to safer breeding areas than their non-breeding areas, suggesting that variation in nest predation risk could be an important benefit of uphill migrations of many species. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Prolactin and parental behavior in Adélie penguins: effects of absence from nest, incubation length, and nest failure

Adélie penguin (Pygoscelis adeliae) males and females, nesting in Antarctica, alternate attendance at the nest with absences of many days to forage at sea. We investigated the importance of tactile input from egg and chicks on prolactin levels by observing nest attendance patterns and obtaining blood samples (1) during the first nest exchange of the incubation stage, (2) from birds whose incubation period was artificially increased or decreased by about 10 days, and (3) from birds whose nests had failed. Prolactin levels in females after 8 to 11 days of absence from the breeding colony did not differ from those in incubating males and did not change after females resumed incubation. Moving eggs between nests resulted in nests in which chicks hatched after about 26, 36 (normal), or 46 days. Duration of incubation did not affect prolactin levels in the parents measured during incubation, at the pip stage, hatch stage, or early brood stage. Adults first left their chicks unguarded on about the same calendar date, regardless of chick age. However, chicks from long incubation nests averaged 8 days younger when they were left unguarded than chicks from control or short-incubation nests. In females, there was no effect of nest failure on prolactin levels. In males, prolactin levels were slightly lower after nest failure than in males tending nests. Testosterone was significantly higher in males after nest failure than in males still tending nests. Prolactin is elevated in Adélie penguins as part of the program of cyclical hormonal changes that accompany the lengthy reproductive season and is relatively independent of tactile input. Sustained prolactin secretion is probably required for the maintenance of parental behavior in offshore feeding species that must be absent from the nest for many days at a time.     

Sex‐specific differences in Sand Martin Riparia riparia nest attentiveness

Capsule Nest attentiveness during the night is significantly lower in males but varies with the activities of the breeding cycle. Male nest attentiveness shows minima during the burrowing and egg‐laying phases, and also during the brooding of chicks in second or re‐nest broods.     

Are olfactory cues involved in nest recognition in two social species of estrildid finches?

Reliably recognizing their own nest provides parents with a necessary skill to invest time and resources efficiently in raising their offspring and thereby maximising their own reproductive success. Studies investigating nest recognition in adult birds have focused mainly on visual cues of the nest or the nest site and acoustic cues of the nestlings. To determine whether adult songbirds also use olfaction for nest recognition, we investigated the use of olfactory nest cues for two estrildid finch species, zebra finches (Taeniopygia guttata) and Bengalese finches (Lonchura striata var. domestica) during the nestling and fledgling phase of their offspring. We found similar behavioural responses to nest odours in both songbird species. Females preferred the odour of their own nest over a control and avoided the foreign conspecific nest scent over a control during the nestling phase of their offspring, but when given the own odour and the foreign conspecific odour simultaneously we did not find a preference for the own nest odour. Males of both species did not show any preferences at all. The behavioural reaction to any nest odour decreased after fledging of the offspring. Our results show that only females show a behavioural response to olfactory nest cues, indicating that the use of olfactory cues for nest recognition seems to be sex-specific and dependent on the developmental stage of the offspring. Although estrildid finches are known to use visual and acoustic cues for nest recognition, the similar behavioural pattern of both species indicates that at least females gain additional information by olfactory nest cues during the nestling phase of their offspring. Thus olfactory cues might be important in general, even in situations in which visual and acoustic cues are known to be sufficient.     

“Wall-papering” and elaborate nest architecture in the ponerine antHarpegnathos saltator

Summary Excavation of 18 nests ofHarpegnathos saltator from southern India revealed an unusually complex architecture for a ponerine ant. The inhabited chambers are not deep in the ground. The uppermost chamber is protected by a thick vaulted roof, on the outside of which is an intervening space serving as isolation from the surrounding soil. In large colonies, the vaulted roof is extended into a shell which encloses several superimposed chambers. Little openings, which may be encircled by moulded flanges, occur in the upper region of the shell. The inside of the chambers is partly or completely lined with strips of empty cocoons. A refuse chamber is always found deeper than the inhabited chambers; live dipteran larvae (family Milichiidae) are typically present. These elaborate nests represent a large energetic investment, and we speculate therefore that nest emigration is unlikely in this species. Consequently, colony fission may never occur, unlike other ants where gamergates reproduce.     

Nest height, nest concealment, and predator type predict nest predation in superb fairy-wrens (Malurus?cyaneus)

Three factors and their interaction effects are increasingly recognized as important determinants of nest predation: nest concealment, nest height, and predator type. The risk of nest predation is predicted to vary across these variables because of nest detectability and accessibility. In general, however, few studies examine how these three variables interact in relation to nest predation, focusing instead on either nest concealment or nest height (whereby predator identity is usually not known). In this study, we examine the role of nest concealment and nest height for nest survival using both artificial and natural nests in the superb fairy-wren (Malurus cyaneus). We indirectly identified potential predators through marks left on artificial eggs and footprints left on tracking tunnels. Predation level at artificial nests was lower than at natural nests, and this could be due to a failure of some nest predators to locate cryptic nests in the absence of cues provided by parental activity. Our results supported the prediction that exposed and concealed nests have different levels of nest predation, which can be explained by variation in predator type. Visual predators were only detected at exposed nests, and survival from visual predators was lower for high nests that were also exposed. However, olfactory predators were detected irrespective of nest height or nest concealment. Because rodents use olfaction to locate nests, this could explain the lack of association between nest concealment and predation outcome at low nests. In addition, rodent footmarks near nests were significantly associated with rodent tooth marks on eggs.     

Can individual heterogeneity influence self-organised patterns in the termite nest construction model?

We present investigations on the influence of individual heterogeneity on self-organised patterns in the termite nest construction model. The presented results extend the original model (Bruinsma 1979; Deneubourg 1977) from theoretical biology which has served as foundation and inspiration for computational optimisation approaches. Our findings have implications for the handling of heterogeneities inherent to physical sensing devices as well as indicate the potential of intentionally endowing software agents or their hardware embodiments (robots, sensor nodes, etc.) with a degree of individuality. We show that increasing heterogeneity is equivalent to changing the values of certain global parameters.     

Higher nest predation risk in association with a top predator: mesopredator attraction?

Breeding close to top predators is a widespread reproductive strategy. Breeding animals may gain indirect benefits if proximity to top predators results in a reduction of predation due to suppression of mesopredators. We tested if passerine birds gain protection from mesopredators by nesting within territories of a top predator, the Ural owl (Strix uralensis). We placed nest boxes for pied flycatchers (Ficedula hypoleuca) in Ural owl nest sites and in control sites (currently unoccupied by owls). The nest boxes were designed so that nest predation risk could be altered (experimentally increased) after flycatcher settlement; we considered predation rate as a proxy of mesopredator abundance. Overall, we found higher nest predation rates in treatment than in control sites. Flycatcher laying date did not differ between sites, but smaller clutches were laid in treatment sites compared to controls, suggesting a response to perceived predation risk. Relative nest predation rate varied between years, being higher in owl nest sites in 2 years but similar in another; this variation might be indirectly influenced by vole abundance. Proximity to Ural owl nests might represent a risky habitat for passerines. High predation rates within owl territories could be because small mesopredators that do not directly threaten owl nests are attracted to owl nest sites. This could be explained if some mesopredators use owl territories to gain protection from their own predators, or if top predators and mesopredators independently seek similar habitats.     

Male nest‐building activity influences clutch mass in Pied Flycatchers Ficedula hypoleuca

Capsule Some males brought building materials to nests and females who were paired with such males laid heavier clutches.     

Do field margin characteristics influence songbird nest‐site selection in adjacent hedgerows?

Capsule Dunnocks Prunella modularis showed a preference for nesting in hedgerows adjacent to sown rather than grass margins on four farms in southwest England.     

How many eggs should be laid in one's own nest and others’ in intra-specific brood parasitism?

Recent field studies have demonstrated that many bird species practice intra-specific brood parasitism. They lay eggs in the nests of other individuals of the same species, let the foster parents rear their offspring and avoid the cost of parental care. It has been shown that many birds, including starlings, swallows and geese, practice intra-specific brood parasitism in various forms. Intra-specific brood parasitism can be viewed in terms of optimal resource allocation: how many eggs should be put in the nests of other individuals under the risk of being parasitized by others. The situation here is a game, because the fitness of a parasitic individual depends on how other individuals behave (how many individuals practice parasitism and to what extent). The ecology of intra-specific brood parasitism has been investigated extensively by field ornithologists recently and it is full of material for modeling population/evolutionary biology. In this paper, I present a simple individual-based model to challenge the resource allocation problem in intra-specific brood parasitism. Previous theoretical studies of intra-specific brood parasitism have been based on ESS or quantitative genetics models, where a population is implicitly assumed to be homogeneous and the distribution form of the trait being studied (the allocation rate or the number of eggs laid parasitically) is inherently monomorphic. This paper aims to explore the evolution of intra-specific brood parasitism without these restrictions. In the model, an individual is assigned a strategy, an allocation ratio of eggs that are laid parasitically in the nests of other individuals, and the strategy is inherited by offspring either asexually or sexually. Based on the simulation analysis, the evolution of the allocation rate (the extent of intra-specific brood parasitism) is discussed. The extension of this model to a tractable analytical model is also discussed.     

The scaling of colony size with nest volume in termites: a role in population dynamics?

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Does it always pay to defend one's nest? A case study in African penguin

Throughout the animal kingdom, individual variation in reproductive success is commonly observed, even under similar environmental conditions. However, the mechanisms behind such differences remain unclear. The notion of behavioural consistency in animals has developed rapidly since the early 21st century partly as an approach to understand among‐individual differences. In this context, a number of studies have highlighted the influence of pair assortment in personality on breeding success. In this study, we related breeding success to individual behaviour, specifically a risk‐taking behaviour, and pair assortment per behaviour in African penguins (Spheniscus demersus) over two breeding seasons of contrasting food availability. On Bird Island, Algoa Bay, South Africa, we used indices of boldness and overall mobility in penguins’ nest defence behaviour as a response to a standard pedestrian approach during chick‐rearing. These behaviours were consistent over the trials and indicated these traits may be related to personality in African penguins. Individuals were categorized as risk‐prone (“bold,” “mobile”) or risk‐averse (“shy,” “non‐mobile”). We then assessed their breeding success through chick growth and survival over 4 weeks in 2015 and 2016. There was weak positive assortment of pairs in relation to nest defence behaviour. However, pair assortment did not significantly influence birds’ breeding success. Shy penguins were generally the most successful (had the highest chick growth rates), which was especially apparent during a food shortage in 2016, possibly reflecting a higher energy investment when foraging. In contrast, chicks from bold parents grew significantly slower, especially in 2016. Bold parents may defend their nest successfully against predation or intra‐specific aggression when food is abundant, but when predation risks are limited and food availability is low, this strategy may not be beneficial. In the context of climate change, where food shortage events may become more frequent, risk‐averse individuals may be favoured and genetic diversity may be reduced in African penguins.     

Dynamic risk assessment: does a nearby breeding nest predator affect nest defence of its potential victim?

There is growing evidence that birds are able to discriminate different types of nest intruders and adjust their nest defence behaviour according to intruder dangerousness and distance from the nest (the dynamic risk assessment hypothesis). Here, we tested whether birds’ decisions about nest defence may additionally be affected by an increasing familiarity with a particular nest predator. We tested nest defence responses of great reed warblers Acrocephalus arundinaceus to a nest predator, the little bittern Ixobrychus minutus. Great reed warbler nests located close (≤7 m) to synchronously breeding little bitterns were “neighbour”, other nests were “solitary”. Great reed warbler specific aggression towards a little bittern dummy was much lower (~5-times) at neighbour than solitary nests. In contrast, generalised responses to a control innocuous intruder (the turtle dove, Streptopelia turtur) were statistically identical at neighbour and solitary nests. These patterns are in line with dynamic risk assessment hypothesis. We hypothesise that decreased great reed warbler aggression at neighbour nests also represents a specific behavioural adaptation to nesting in association with the little bittern. Little bitterns breeding closer to great reed warblers showed decreased risks of failure due to predation. However, further research is needed to experimentally test the causal links behind these patterns.     

Female spawning strategy in Rhinogobius sp. OR: how do females deposit their eggs in the nest?

 We tried to elucidate how females of a paternal nest brooding goby Rhinogohius sp. OR deposit their eggs in a nest, using a marking technique for live eggs under laboratory conditions in which male somatic condition, nest space, and mating pattern (monogamous or bigamous) were controlled. Whether females rejected mating was independent of either male quality, such as body size and somatic condition, or nest space. In a situation in which two females were allowed to spawn sequentially with a male, however, females rejected mating at a higher rate when they were the first to spawn than when they were the second to spawn; this is because eggs from first females were more vulnerable to cannibalism by parental males and second females. Even when nest space was limited and thus was occupied by eggs from the first females, second females could deposit all their eggs in the nest by using the minute interspace of existing eggs. In the presence of the parental male, such a female seemed less likely to suffer a cost from increased egg mortality due to crowdedness, still holding the advantage of being the second spawner. Finally, we extrapolated the field breeding ecology of this fish from the laboratory data. It was suggested that a single monolayer brood of the same age usually consisted of eggs from multiple females and thus the mating pattern would be more polygynous than previously expected. Received: March 6, 2002 / Revised: July 11, 2002 / Accepted: August 14, 2002 RID="*" ID="*" Present address: Center for Marine Environmental Studies, Ehime University, 3 Bunkyo-cho, Matsuyama 790-8577, Japan (e-mail: nokuda@sci.ehime-u.ac.jp) Acknowledgments I am grateful to S. Sone and D. Takahashi for giving us useful information and to M. Inoue and H. Miyatake for their field assistance. This study was financially supported by Research Fellowships of the Japan Society for the Promotion of Science for Young Scientists. Correspondence to:Noboru Okuda     

Adaptive host-abandonment of ectoparasites before fledging? Within-brood distribution of nest mites in house sparrow broods

We studied the within-brood distribution of a haematophagous mite Pellonyssus reedi living on nestling house sparrows (Passer domesticus) near the time of fledging. We measured the natural level of infestation of individual nestlings, and determined the feeding efficiency of mites, by scoring their feeding status. Within-brood distribution of mite loads was unrelated to nestling body mass, tarsus length, or immunocompetence. These results did not support parasite preference for large or susceptible hosts. Mite feeding-efficiency was also unrelated to these nestling characteristics, confirming that large nestlings or nestlings with less-developed immunocompetence did not provide superior feeding conditions for mites. Therefore, our results do not support the hypothesis that within-brood distribution of avian ectoparasites is explained by the parasites' preferences for characteristics, such as large body size or low immunocompetence, that make nestlings suitable hosts. On the other hand, we found that mite loads were negatively correlated with nestling age and feather length, suggesting that nestlings closer to fledging harbored fewer mites then their less-developed nestmates. Furthermore, feather length had a stronger relationship with parasite distribution than did nestling age. We presume, therefore, that feather characteristics, i.e., length, may serve as a signal for mites to perceive the ready-to-fledge state of nestlings, inducing abandonment behavior. These results support another, largely neglected hypothesis, i.e., that the avoidance or abandonment of those nestlings that are close to fledging may also explain the parasites' distribution in a brood. This hypothesis is based on the argument that many nest-dwelling ectoparasites breed in the nest material and emerge only periodically to feed on nestlings. In such parasites, the ability to recognize and avoid mature fledglings can be adaptive because this may help the parasites to avoid their removal from the nest so they can continue to reproduce by feeding on unfledged chicks of the current or later broods. Our results suggest that adaptive host-abandonment by nest-dwelling ectoparasites can influence within-brood parasite distributions around the time of fledging.