Nest Defense Research Articles

Risk‐Taking in Bluebirds After Exposure to a Nest Predator Relates to Parental Roles and Shows Little Cooperation Between Partners

ABSTRACTParents may experience a trade‐off between caring for offspring and protecting themselves from predators. The reproductive value hypothesis predicts that parents should take more risks for older, more valuable offspring, whereas the harm to offspring hypothesis predicts that parents should risk more for vulnerable offspring that would suffer most from a lack of parental care at the moment. After exposing parent mountain bluebirds (Sialia, currucoides) to a model predator, we recorded latency times for them to touch, to look into, and to enter their nestbox and the number of times they inspected the box across three breeding stages: nest‐building, incubation and nestling‐rearing. Females took greater risks than males during the nest‐building and incubation stages by inspecting and entering boxes sooner and more times, consistent with their role in parental care at those early breeding stages that requires them to enter the box. Risk‐taking in males was consistent with the reproductive value hypothesis, increasing across breeding stages. In contrast, females took the greatest risk during incubation, consistent with the harm to offspring hypothesis. Furthermore, the riskiest behaviours were not correlated between pair members, and both sexes assumed the risk to first inspect the nestbox approximately equally. This suggests there is not a ‘war of attrition’ between mates over risk‐taking, but neither was there cooperation by the male to facilitate the rapid resumption of parental care by his mate. The results highlight that patterns of investment in nest defense in birds may be sex‐specific.

Host nest defence does not act as selective agent against plumage polymorphism in brood parasites.

Batesian mimicry in brood parasites is often viewed as an evolutionary strategy to mitigate host aggression. Female common cuckoos (Cuculus canorus) exhibit two morphs: the hawk-like grey and the rufous one, potentially maintained by apostatic selection. It was hypothesized that the grey morph's predator-like appearance deters host defences, while the rufous morph benefits from its rarity by evading host attention. Previous research predominantly utilized static cuckoo dummies, lacking insights into real-world interactions. We investigated the effectiveness of the cuckoo morphs in accessing great reed warbler (Acrocephalus arundinaceus) nests under natural conditions. Analysing video-recorded cuckoo attempts, we found no significant difference in nest-access success between the morphs. Both experienced a similar probability of physical attacks when hosts were present, and the rufous morph did not evade host detection more often compared with the grey morph. These results fail to support the assumptions of (a) Batesian mimicry, that hawk-like mimicry enhances nest access or reduces host aggression, and (b) apostatic selection, that the rarity of the rufous morph confers an advantage in successfully accessing the host nest. Future research should aim to identify stages in the cuckoo's life cycle or host interactions where colour polymorphism provides an evolutionary benefit.

Nest raiding by bonnet macaques (Macaca radiata) and the response of nest guarding birds in a suburban habitat.

In many primate species, nest raiding is a form of opportunistic foraging behavior designed to acquire protein-rich eggs and nestlings. In urban environments, this is a significant cause of nest failure in birds. Here, we describe nest raiding and egg predation in bonnet macaques (Macaca radiata) inhabiting a suburban area of Salem, Tamil Nadu, India. During nest raiding, large-billed crows (Corvus macrorhynchos) and house crows (Corvus splendens), actively defended their nest from the macaques. When several macaque foragers jointly raided the nest, they were successful in obtaining and consuming the eggs. In contrast, when a solitary macaque attempted to raid the nest, it was unsuccessful. Bird size appeared to play an important role in nest defense. Small birds, such as the scaly breasted munia (Lonchura punctulata) and the purple sunbird (Cinnyris asiaticus) were not able to protect their nests from lone bonnet macaques. These observations indicate that in urban landscapes, bonnet macaques are egg predators of many bird species. When macaques coordinate their actions and forage in small subgroups, they were more successful in preying on the eggs of larger-bodied bird species.

Nest Defense Behavior of Suburban and Rural Red-shouldered Hawks†

ABSTRACT Urban and suburban raptors live in close proximity to humans, and some species defend their nests and young vigorously, even diving at or striking humans walking on the ground. Such raptors may be more defensive of their nests than rural birds. We investigated (1) whether Red-shouldered Hawk (Buteo lineatus) nest defense behavior differs between suburban and rural birds, (2) whether any environmental conditions are associated with aggressive nest defense, and (3) whether nest defense behavior is associated with reproductive rate. First, we used an experimental walk-up protocol to approach nests with incubating or brooding Red-shouldered Hawks at suburban and rural sites, and we scored the hawk’s response to our approach. We measured environmental variables (nest height, distance to the nearest road and nearest house, and habitat proportions within 500 m of the nest) and determined reproductive rate. Second, we used our historical database to retrospectively classify hawks as most aggressive, moderately aggressive, or not aggressive, and we measured the same environmental variables at their nest sites. We found that most birds at both suburban and rural study areas responded to our experimental approach with minimal nest defense, though suburban birds responded with higher levels of nest defense. Environmental variables were unrelated to nest defense intensity in the experimental study. For the retrospective study in the suburban area, nest height was the only environmental factor distinguishing aggressive hawks from non-aggressive ones; aggressive nest defensive behavior was associated with lower nests. Reproductive rate was unrelated to nest defense behavior in both studies. Knowing which environmental factors may contribute to more aggressive behavior may help researchers, managers, and residents better understand bird behavior and predict the circumstances under which problems might develop, particularly in urban/suburban environments.

Plunge-diving into dynamic body acceleration and energy expenditure in the Peruvian booby.

Daily energy expenditure (DEE) is the result of decisions on how to allocate time among activities (resting, commuting, and foraging) and the energy costs of those activities. Dynamic body acceleration (DBA), which measures acceleration associated with movement, can be used to estimate DEE. Previous studies of DBA-DEE correlations in birds occurred on species foraging below their thermoneutral zone, potentially decoupling the DBA-DEE relationship. We used doubly-labelled water (DLW) to validate the use of DBA on plunge-diving seabirds, Peruvian boobies (Sula variegata), foraging in waters above their thermoneutral zone (>19 °C). Mass-specific DEEDLW in boobies was 1.12 kJ/d/g, and higher in males than in females. DBA alone provided the best fitting model to estimate mass-specific DEEDLW compared to models partitioned per activity and time-budget models. Nonetheless, the model parametrizing activity at and away of their onshore breeding colony was the most parsimonious model (r=0.6). This r value, although high, is lower than all other avian studies, implying that temperature is not the main cause of DBA-DEE decoupling in birds. Time at the colony (∼80% of the day) was the largest contributor to DEE as it was the most time-consuming activity and involved nest defense. However, foraging was the most power-consuming activity (4.6 times higher activity-specific metabolic rate than resting at the colony), and commuting-flight was higher than in other gliding seabirds. In short, DBA alone can act as a proxy for DEE, opening avenues to measure the conservation energetics of this seabird in the rapidly-changing Peruvian Humboldt Current System.

Invasive Cichlids Display Higher Aggression During Nest Defence Compared to the Native Mexican Mojarra

Invasive Cichlids Display Higher Aggression During Nest Defence Compared to the Native Mexican Mojarra

Effect of melatonin supplementation upon parental care and nestling growth in arctic-breeding songbirds.

Arctic-breeding birds exhibit around-the-clock activity, and these activity cycles are postulated to maximize reproductive success during the short breeding season characteristic of high-latitude regions. Two closely related species of arctic-breeding songbirds, Lapland longspurs (Calcarius lapponicus; ground-nesting) and snow buntings (Plectrophenax nivalis; cavity-nesting) exhibit extended activity cycles throughout the polar day (71° N) except for 4-5 h of daily quiescence. Ground-nesting Lapland longspurs experience higher levels of nest predation than cavity-nesting snow buntings, and this difference is reflected in elevated nest vigilance in male longspurs compared with snow buntings. In this study, we examined the effect of melatonin supplementation upon male parental care, corresponding measures of nestling growth, and ability to reduce activity (and increase sleep). A pharmacological dose of melatonin in captive snow buntings dampened the amplitude of activity rhythms over the polar day with no detectable phase-shifting compared with control-implanted birds. Melatonin treatment reduced nest visits and overall time spent on the nest by male snow buntings compared with controls. There was no significant increase in time spent by female snow buntings on the nest to compensate for this, and there was no significant effect on offspring growth rates. There were no effects of melatonin supplementation on longspur adults or offspring, suggesting behavioral insensitivity to exogenous melatonin treatment. These differences in sensitivity underscore the importance of nest defense in ground-nesting longspurs compared with cavity-nesting snow buntings, which participate minimally in nest defense.

Nesting behaviour of Neotropical social wasps of the genus Clypearia de Saussure (Hymenoptera: Vespidae: Polistinae)

ABSTRACT Social insects have developed different nest defence strategies; for example, social wasps use nonaggressive mechanisms or aggressiveness, including stinging. This subject has been widely examined in the literature, and it may help improve our understanding of wasps’ ecology. The nesting behaviour of some genera is still poorly known. In this paper, we report new information on the nesting behaviour of the species Clypearia in different Brazilian biomes. We observed six nesting events in natural and anthropic environments of the Amazon rainforest, Atlantic forest, and Cerrado domains, sporadically from 2004 to 2022. From our observations, we suggest that Clypearia nest defence includes (i) preference for nest camouflage rather than aggressive behaviour; (ii) selection of nesting sites close to water sources in natural or anthropic environments, and eventually obtaining food from the substrate; (iii) nesting association with ants for mutual protection against predators; and (iv) variations in the nests’ height. Our records suggest nest camouflage and association with ants are strategies for nest defence. These may have influenced nest height in relation to the ground, which may also vary according to the environment explored by the species.

Context-dependent multimodal behaviour in a coral reef fish.

Animals are expected to respond flexibly to changing circumstances, with multimodal signalling providing potential plasticity in social interactions. While numerous studies have documented context-dependent behavioural trade-offs in terrestrial species, far less work has considered such decision-making in fish, especially in natural conditions. Coral reef ecosystems host 25% of all known marine species, making them hotbeds of competition and predation. We conducted experiments with wild Ambon damselfish (Pomacentrus amboinensis) to investigate context-dependent responses to a conspecific intruder; specifically, how nest defence is influenced by an elevated predation risk. We found that nest-defending male Ambon damselfish responded aggressively to a conspecific intruder, spending less time sheltering and more time interacting, as well as signalling both visually and acoustically. In the presence of a model predator compared to a model herbivore, males spent less time interacting with the intruder, with a tendency towards reduced investment in visual displays compensated for by an increase in acoustic signalling instead. We therefore provide ecologically valid evidence that the context experienced by an individual can affect its behavioural responses and multimodal displays towards conspecific threats.

Recognizing interspecific dominance signals? Blue tits adjust nest defence based on great tit's black bib size

AbstractAnimals use colours, morphological structures and behaviour to advertise their dominance status and ability to obtain resources (Resource Holding Potential, RHP) in agonistic contexts with conspecifics. Dominance relationships are also known between species, although the interactions and the information used to assess the other species' RHP remain obscure and empirical evidence of interspecific recognition of status is hard to obtain. Using behavioural inference is particularly important when a species needs to assess the potential loss of fitness in terms of reproduction or survival (e.g., risk of damage or predation) that could be inflicted by another species acting as a predator, parasite or competitor. Our study shows for the first time the existence of interspecific recognition of status signals: Blue tits Cyanistes caeruleus (subordinate species) perceive Great tits Parus major (dominant species) as threats as hole‐nesting competitors, and respond differently based on the size of the great tit's black tie stripe. Blue tits seemed to recognize the meaning of great tits' black ties because they were bolder when defending their nests against small‐tie (less dominant) great tits than when repelling attacks by large‐tie (more dominant) great tit males. Our results stress that behavioural inference can potentially be used to assess the meaning of status signals that presumably evolved in an intraspecific signalling context.

First confirmed reproduction by a translocated female Siamese Crocodile Crocodylus siamensis (Crocodylidae: Crocodilia) with observations of nest attendance and nest-associated fauna

The Siamese Crocodile Crocodylus siamensis is considered one of the most imperiled and poorly-studied crocodilians in the world. Translocations (reintroductions) - often in conjunction with head-starting of juveniles - are a critical component of efforts to restore viable wild populations of C. siamensis. We here report the first confirmed nesting by a known-age, head-started, and translocated female C. siamensis together with observations of nest attendance and nest-associated fauna based on camera trap imagery. Our observations occurred in the Greater Xe Champhone Wetland Complex (GXCWC) in Savannakhet Province, Lao PDR. GXCWC encompasses 45,000 ha of seasonally inundated natural and anthropogenic wetlands, agricultural ecosystems, scrubland, and forest. While collecting eggs for incubation in May 2022, we were able to identify a unique series of notched tail scutes on a female C. siamensis as she aggressively defended a nest. From these markings we determined the female was hatched on 11 August 2012 (age = 9.75 years) and released in March 2014, approximately 3.5 km from the nest site. A game camera placed at the nest on 11 May 2022 and recovered on 5 July 2022 (34 trap nights) recorded 1724 images. These images indicated the female remained in attendance at the nest throughout the monitoring period. Camera trap imagery captured eight nest repair events and two nest defense events; during the latter the female defended the nest from village dogs. Eleven species of nest-associated fauna were recorded by the game camera, including eight and three species of birds and mammals, respectively. Our observations are the first confirmed nesting by a head-started, translocated female C. siamensis indicating these are effective conservation strategies for restoring wild populations. We also unequivocally established that head-started female C. siamensis are capable of reproducing when nine-years-old.

When passive nest defence is active: support of the leave early and avoid detection hypothesis in a plover

Leaving the nest early to avoid detection by an approaching predator is an often‐cited form of nest defence among ground‐nesting birds, yet has rarely been quantitatively demonstrated. During the breeding season, we recorded Flight‐initiation Distances (FIDs) of incubating, off‐duty and non‐breeding Hooded Plovers Thinornis cucuallatus cucuallatus in Victoria, Australia. Hooded Plovers exhibited longer FIDs when incubating compared with when off‐duty or non‐breeding birds (the latter two categories had similar FIDs). Our study supports the Leave Early to Avoid Detection (LEAD) hypothesis, and demonstrates that so‐called ‘passive’ defence is in fact an active decision by the incubator to leave nests at distances which exceed those at which birds without nests or off‐duty commence escape.

Nutrients or resin? - The relationship between resin and food foraging in stingless bees.

Stingless bees are important pollinators in tropical forests. Yet, we know little about their foraging behavior (e.g., their nutritional requirements or their floral sources visited for resource collection). Many stingless bees not only depend vitally on pollen and nectar for food but also on resin for nest building and/or defense. However, it is unclear whether the large effort devoted to collecting resin as a non-food resource by certain stingless bees affects their foraging behavior. Therefore, in this study, we analyzed differences in foraging patterns (i.e., foraging activity, proportion of collected resources, and specialization in plants visited) and resource nutritional composition (i.e., sucrose amount in nectar and amino acids in pollen) of seven different stingless bee species (eleven wild colonies) in north-western Ecuador with a particular focus on the role of resin collection. We found that species with a high resin intake tended to be more active than species with a low resin intake. The foragers per minute invested for pollen collection were similar across all species. Sucrose intake per minute differed between some species but was not affected by increased resin intake. Interestingly, high and low resin collectors partly differed in the plants visited for pollen collection. Pollen amino acid profiles largely, but not completely, overlapped between the two resin collection groups. Our findings show that the foraging patterns and plant choices of stingless bees may vary depending on their resin intake, highlighting the need for more research focusing on resin collection and use by stingless bees.

Extended parental care in the mass provisioning silk wasp, Microstigmus rosae

Abstract Insurance-based mechanisms, where surviving group-members can complete parental care after the death of a nestmate, are key to the origin of cooperative group formation in insects. Selection for group living via these models is proposed to be dependent on the life expectancy of adult carers relative to the duration of offspring dependency on parental care. Progressive provisioning, where adults feed offspring gradually as they grow, is thought to extend this period of dependency and is therefore suggested to be an important factor promoting the evolution of sociality. In contrast, mass-provisioning species provide offspring with all the food they need to reach maturity at the beginning of their development. Since offspring are then nutritionally independent, the applicability of insurance models is less clear. In this paper we experimentally demonstrate that adult presence on the nest, even after the end of provisioning, is critical for brood survival in the mass provisioning silk wasp Microstigmus rosae. After 10 days, experimentally orphaned nests contained 65% fewer healthy offspring than controls. Adult females were also recorded performing post-provisioning parental care behaviours including nest maintenance and repair, putative hygienic brood care and aggressive nest defence against both ants and parasitoid wasps. By demonstrating the potential applicability of insurance advantages our results highlight how, even in mass provisioners, insurance-based mechanisms may be part of what favours group living. Significance statement Extended parental care is an important precursor to the evolution of eusociality. In this context, group living can serve as a form of “life insurance”, ensuring that dependent offspring receive the care they need to reach maturity should the mother die. Such mechanisms are especially important to our understanding of social evolution as they are able to account for the origins of cooperative group formation, not just its maintenance. However, for mass-provisioning species, where all food items are provided upfront, the significance of insurance advantages remains unclear. In this study, we experimentally demonstrate that adult attendance is critical for brood survival in the mass provisioning wasp, Microstigmus rosae. Our results reveal the applicability of insurance advantages to M. rosae with important implications for our understanding of the potential adaptive value of group living in mass provisioning species.

Cooperation and conflict in the building and maintenance of the compound nests of monk parakeets <i>Myiopsitta monachus</i>

Colonial birds often breed at high density, generating conflict among neighbours over the use of nest-building materials. However, in a few colonial species, breeders appear to cooperate in the construction of compound nests that contain multiple breeding chambers within a single nest structure. The relative contributions of individual birds and the balance between cooperation and conflict among close neighbours in such species have rarely been examined. In this study, we investigated evidence for cooperation and conflict in the building and maintenance of the nests of monk parakeets <i>Myiopsitta monachus</i> in an invasive population in which compound nests are frequent. First, we found that males invested more in nest construction than females and when more than one male occupied the same breeding chamber multiple males contributed to the same nest. Females, by contrast, invested more in nest defence than males. Second, we found that there was conflict among pairs over nest material, with kleptoparasitism of nesting material and defence against conspecifics evident. We conclude that nest-building in monk parakeets involves both cooperation and conflict. Breeders often tolerate the budding of nests, which are often built by relatives, but that pairs are also in conflict over the use of nest material.

Profiling the neuroproteomics of honeybee brain: A clue for understanding the role of neuropeptides in the modulation of aggressivity

The aggressivity is modulated in honeybee brain through a series of actions in cascade mode, with the participation of the neuropeptides AmAST A (59–76) and AmTRP (254–262). The aggressivity of honeybees was stimulated by injecting both neuropeptides in the hemocoel of the worker honeybees, which were submitted to behavioral assays of aggression. The brain of stinger individuals were removed by dissection and submitted to proteomic analysis; shotgun proteomic approach of honeybee brain revealed that both neuropeptides activate a series of biochemical processes responsible by production of energy, neuronal plasticity and cell protection. In addition to this, AmTRP (254–262) elicited the expression of proteins related to the processing of the potential of action and lipid metabolism; meanwhile AmAST A (59–76) elicited the metabolism of steroids and Juvenile hormone-related metabolism, amongst others. Apparently, the most complex biochemical process seems to be the regulation of ATP production, which occurs at two levels: i) by a subgroup of proteins common to the three experimental groups, which are over−/under-regulated through glycolysis, pyruvate pathway, Krebbs cycle and oxidative phosphorylation; ii) by a subgroup of proteins unique to the each experimental group, which seems to be regulated through Protein-Protein Interactions, where the protein network regulated by AmTRP (254–262) seems to be more complex than the other two experimental groups. SignificanceRecently we reported the effect of the neuropeptides AmAST A (59–76) and AmTRP (254–262) in the modulation of the aggressive behavior of the worker honeybees. Up to now it is known that the simple presence of the allatostatin and tachykinin-related-peptide in bee brain, is enough for inducing the aggressive behavior. However, nothing was known about how these neuropeptides perform their action, inducing the aggressive behavior. The results of the present study elucidated some of the metabolic pathways that were activated or inhibited to support the complex defensive behavior, which includes the aggressivity. These results certainly will impact the behavioral research of honeybees, since we are paving the way for understanding the molecular base of regulation, of individual /nest defense of honeybees.

Parental Roles of Nesting Prairie Falcons in Relation to Reversed Sexual Dimorphism

Abstract In Prairie Falcons (Falco mexicanus), females are considerably larger than males, as in most diurnal birds of prey. This phenomenon, known as reversed sexual dimorphism (RSD), is usually associated with asymmetry in parental care: the smaller male provides most of the food during the nesting season, whereas the larger female incubates the eggs, and broods and protects the young. To evaluate this relationship in Prairie Falcons, we quantitatively assessed parental roles of 52 pairs of Prairie Falcons nesting in southwestern Idaho, over a 4-yr period (1984–1987). We collected behavioral observations for each pair, from the establishment of a nesting territory until young were 30–35 d old (fledging age), for a total of 613 observation days (9089 hr). We found that male and female falcons shared some tasks, although not necessarily equally, including incubation, provisioning prey and nest defense. Females accounted for two-thirds of the diurnal incubation responsibility and males for one-third. Males and females made comparable efforts in food provisioning; similarly, nest defense, here defined as aggressive interactions with (potential) nest predators, did not differ between the sexes. Other behaviors, such as brooding, hunting, and nest attendance were performed more by one sex than the other. Brooding was carried out primarily by females, and they showed consistently higher nest attendance compared to males. Males hunted significantly more than females and delivered most prey items to the nest site. Overall, sex roles exhibited by nesting Prairie Falcons in our study largely agreed with predictions based on RSD.

Nest defence of urban and rural Common Kestrels Falco tinnunculus against different predators

ABSTRACT Common Kestrels Falco tinnunculus breeding in a rural environment reacted more aggressively to dummies of potential predators than did those breeding in an urban environment. During the nestling phase, the Kestrels reacted more frequently than during the incubation phase and males reacted more often than females. The reactions to dummies partially reflected the distribution of predators in the urban and rural areas.

Blacklegged ticks, Ixodes scapularis, reduce predation risk by eavesdropping on communication signals of Formica oreas thatching ants.

Ticks spend most of their life inhabiting leaf litter and detritus where they are protected from sun but preyed upon by ants. Ants secrete chemical communication signals to coordinate group tasks such as nest defence. Ticks that avoid ant semiochemicals-as indicators of ant presence-would reduce predation risk by ants. We tested the hypotheses that: (i) chemical deposits from the thatching ant Formica oreas deter blacklegged ticks, Ixodes scapularis, (ii) deterrent semiochemicals originate from the ants' poison and/or Dufour's gland(s), and (iii) tick-deterrent semiochemicals serve as alarm-recruitment pheromone components in F. oreas. In two-choice olfactometer bioassays, filter paper soiled with ant chemical deposits significantly deterred female and male ticks. Poison and Dufour's gland extracts deterred ticks in combination but not alone. Gas chromatographic-mass spectrometric analyses of gland extracts revealed formic acid as the major constituent in the poison gland and eight hydrocarbons as constituents in the Dufour's gland. Synthetic formic acid and hydrocarbons deterred ticks only when combined. F. oreas workers sprayed both formic acid and hydrocarbons when distressed. A synthetic blend of these compounds elicited alarm-recruitment responses by F. oreas in behavioural bioassays. All results combined indicate that ticks eavesdrop on the ants' communication system.

Seasonal increase in nest defense, but not egg rejection, in a cuckoo host

The interactions between avian brood parasites and their hosts provide an informative and easy-to-handle system for studying coevolution. Avian brood parasitism reduces the reproductive success of hosts, and thus, hosts have evolved anti-parasitic strategies, such as rejecting parasitic eggs and adopting aggressive nest defense strategies, to avoid the cost brought on by brood parasitism. To test whether host anti-parasitic strategies are adjusted with the risk of being parasitized when the breeding seasons of brood parasites and hosts are not synchronous, we conducted a field experiment assessing nest defense and egg recognition behaviors of the Isabelline Shrike (Lanius isabellinus), a host of the Common Cuckoo (Cuculus canorus). In the local area, the host Isabelline Shrike begins to breed in April, whereas the summer migratory Common Cuckoo migrates to the local area in May and begins to lay parasitic eggs. Results showed that nest defense behaviors of the Isabelline Shrike increases significantly after cuckoo arrival, showing higher aggressiveness to cuckoo dummies, with no significant difference in attack rates among cuckoo, sparrowhawk and dove dummies, but their egg rejection did not change significantly. These results imply that Isabelline Shrikes may adjust their nest defense behavior, but not egg rejection behavior, with seasonality.