Nest Defence Behaviour Research Articles

Field study of the relationship between personality and reproductive strategy in the White‐collared Blackbird Turdus albocinctus

The discovery of personality traits in animal populations may help to explain individual variation in breeding strategies. In the White‐collared Blackbird Turdus albocinctus, females, but not males, exhibited different nest defence behaviours that can be used to classify them into bold and shy personalities. Bold females had higher nest success, lower fecundity and higher parental investment than shy females, and the social mates of bold females had lower parental investment than that of shy females. Our findings suggest that the reproductive strategy of birds may be closely related to their personality traits.

Similarity in nest defense intensity in Canada goose pairs

Individuals consistently differ in their behavior, and such personality differences are often linked to fitness. For biparental care species, the behavior of both parents can impact reproductive success. Behavioral similarity within pairs has been shown to provide selective advantages for many species. In this study, we tested for behavioral similarity in 129 pairs of nesting Canada geese (Branta canadensis) with respect to nest defense behavior, an individually consistent trait. We used a bivariate mixed model to provide unbiased estimates of correlations between partners’ traits. We also tested for the effect of behavioral similarity between mates on reproductive success and predicted greater success for positively assorted pairs. We found that over four consecutive years, pairs of Canada geese were formed of individuals showing similar nest defense intensities. Assortment between mates may result both from personality-dependent non-random mate choice and from behavioral adjustments after pairing that are maintained in the long term. However, behavioral adjustment to a shared environment, among and within breeding seasons, had negligible effects on the covariation between partners’ traits. We also found that similarity in nest defense intensity did not result in higher reproductive success. The factors at the origin of the evolution of long-term behavioral similarity based on nest defense in Canada geese pairs remain to be identified. Individual consistency in behavioral traits has been demonstrated for many animal species, and its importance in ecology and evolution is now accepted. The maintenance of personality traits in a population may in fact be explained by non-random mate choice like assortative mating, where paired individuals show similar phenotypes. We studied the nest defense behavior, a highly repeatable trait, of 129 Canada goose pairs during four consecutive years and found that paired individuals had similar personalities, suggesting personality-dependent mate choice or post-pairing adjustments maintained in the long term. Our findings also show that the phenotypic similarity between mated individuals is not always related to reproductive success and can possibly result from non-adaptive mechanisms.

Nest-defense Behavior of Mississippi Kites in Urban and Exurban Areas

Nest-defense Behavior of Mississippi Kites in Urban and Exurban Areas

Plasticity, state-dependency, and individual consistency in Canada goose nest defense behavior

Animals are thought to adjust the intensity of their parental defense to fitness benefits associated with their current reproduction. They should be more defensive when they breed early in the season, when they produce more young, or as their young get older. Beyond these plastic changes, associations among traits could be explained by consistent among-individual differences. Separating the mechanisms at the origin of behavioral phenotypic variation is essential to understand the determinants and evolution of parental care. During four breeding seasons, we investigated whether variation in Canada goose (Branta canadensis) nest defense resulted from individual short-term plastic adjustments to reproductive stage within breeding seasons, plastic adjustments to brood value across breeding seasons, or from long-term among-individual differences. We thus estimated the among- and within-individual relationships between nest defense, clutch size, and laying date. Female and male nest defense behaviors were highly repeatable in time (R = 0.72 and 0.67 on the short term). At the among-individual level, we found no significant association between female nest defense and life history traits, but the more defensive males were mated with the more fecund females. Female and male nest defense was not adjusted to annual variation in laying date nor in clutch size. However, females adjusted their nest defense within each breeding season and became more defensive when approaching egg hatching. Thus, Canada goose nest defense behavior is partly explained by plastic adjustments, but also by consistent among-individual differences which indicate the evolutionary potential of nest defense behavior. An association between traits at the phenotypic level can be partitioned into association at the among- and within-individual levels. This allows to better understand covariation of traits resulting from both among-individual differences and phenotypic plasticity. We observed 141 Canada goose pairs to identify what affected the intensity of their nest defense behavior. We found that geese were very consistent in their nest defense behavior and that female fecundity was related to male personality. Females also became more defensive as their young got older. Analyzing different sources of variation in parental behaviors enables a better understanding of their evolution. Our study also demonstrates the importance of studying nest defense in both sexes even in species where only females incubate eggs, as both sexes can invest in nest defense.

Nest defence behavioural reaction norms: testing life-history and parental investment theory predictions.

Predation is the primary source of reproductive failure in many avian taxa and nest defence behaviour against predators is hence an important aspect of parental investment. Nest defence is a complex trait that might consistently differ among individuals (personality), while simultaneously vary within individuals (plasticity) according to the reproductive value of the offspring. Both complementary aspects of individual variation can influence fitness, but the causality of links with reproductive success remains poorly understood. We repeatedly tested free-living female great tits (Parus major) for nest defence (hissing) behaviour across the nesting cycle, by presenting them with a model predator. Hissing behaviour was highly repeatable but, despite population-level plasticity, we found no support for individual differences in plasticity. Path analysis revealed that repeatable differences in hissing behaviour had no direct effect on nest success or fledgling number. However, our best supported path-model showed that more fiercely hissing females laid smaller clutches, with clutch size in turn positively influencing fledgling number, suggesting that females are most likely facing a trade-off between investment in nest defence and reproduction. Strong stabilizing selection for optimal plasticity, in combination with life-history trade-offs, might explain the high repeatability of nest defence and its link with reproductive success.

Comparison of Nest Defense Behaviors of Goshawks (Accipiter gentilis) from Finland and Montana.

Simple SummaryUnderstanding the degree to which human interaction may alter natural animal behavior has become increasingly important in developing effective conservation strategies. We examined two populations of northern goshawks (Accipiter gentilis) in Montana and Finland. Goshawks in Finland were not protected until the late 1980s, and prior to this protection were routinely shot, as it was believed that shooting goshawks would keep grouse populations high. In the United States, Goshawk were not shot as a management strategy. Though aggressive nest defense has been characterized throughout North America, goshawks in Finland do not show this same behavior. To quantify aggression, we presented nesting goshawks with an owl decoy, a human mannequin, and a live human and recorded their responses to each of the trial conditions. We used statistics to compare the two populations. Our results suggested that goshawks in Montana exhibit more aggressive nest defense behaviors than those in Finland. While this could be due to some biotic or abiotic factor that we were not able to control for in a study on such a small scale, it is also possible that the results from this study suggest another underlying cause, such as an artificial selection pressure created by shooting goshawks.As human impacts on wildlife have become a topic of increasing interest, studies have focused on issues such as overexploitation and habitat loss. However, little research has examined potential anthropogenic impacts on animal behavior. Understanding the degree to which human interaction may alter natural animal behavior has become increasingly important in developing effective conservation strategies. We examined two populations of northern goshawks (Accipiter gentilis) in Montana and Finland. Goshawks in Finland were not protected until the late 1980s, and prior to this protection were routinely shot, as it was believed that shooting goshawks would keep grouse populations high. In the United States, Goshawk were not managed as predator control. Though aggressive nest defense has been characterized throughout North America, goshawks in Finland do not show this same behavior. To quantify aggression, we presented nesting goshawks with an owl decoy, a human mannequin, and a live human and recorded their responses to each of the trial conditions. We evaluated the recordings for time of response, duration of response, whether or not an active stimulus was present to elicit the response (i.e., movement or sound), and the sex of the bird making the response. We used t-Test with unequal variance to compare mean number of responses and response duration. Our results suggested that goshawks in Montana exhibit more aggressive nest defense behaviors than those in Finland. While this could be due to some biotic or abiotic factor that we were not able to control for in a study on such a small scale, it is also possible that the results from this study suggest another underlying cause, such as an artificial selection pressure created by shooting goshawks.

Nest-Defense Behavior in Response to the Chatter Call in Tachycineta bicolor (Tree Swallow)

Birds produce a variety of vocalizations ranging in function from attracting a mate to alerting others of danger. One vocalization of Tachycineta bicolor (Tree Swallow), the chatter call, is reported to serve as both a mate-attraction call and a nest-defense call. We used playback techniques to investigate the nest-defense behavior of Tree Swallows to calls of Toxostoma rufum (Brown Thrasher; control) and Sialia sialis (Eastern Bluebird; nest competitor), and Tree Swallow shriek (alarm call) and chatter calls. We measured time spent foraging, remaining in the nest box, and on nest defense. Tree Swallows spent 80% of their time on nest defense in response to the chatter call. The chatter-call and shriek-call nest-defense responses were nearly identical. Our data show that the chatter call functions as an alarm call and elicits nest-defense behavior.

Anti-predator responses in the Chilean Swallow Tachycineta leucopyga breeding in northwest Patagonia

ABSTRACTCapsuleBreeding Chilean Swallows Tachycineta leucopyga in Argentina use visual and acoustic signals in response to potential threats from a predator, but these did not vary with brood age.AimsTo study anti-predator behavioural responses in breeding Chilean Swallows from North Patagonia, Argentina, by using a nest-box experiment.MethodsAt days eight and 14 after the first nestlings hatched, Chilean Swallow breeding adults were exposed to a stuffed decoys of either a natural local predator, the Austral Pygmy-Owl Glaucidium nana, or a neutral decoy, a stuffed Rufous-Collared Sparrow Zonotrichia capensis.ResultsAnti-predator behavioural responses consisted of displaying dives, circling flights and group mobbing around the predator decoy, together with the emission of several vocalizations, among which a mobbing alarm call was the most frequent. We did not find significant differences in the intensity of parental nest defence behaviours at different nestling ages (8 and 14 days old).ConclusionAnti-predator behaviour of breeding Chilean Swallows consists of visual and acoustic signals, involving swallows other than the nest owners, and without variation during the nestling period. Our exploratory assessment on the anti-predator behaviour of Chilean Swallows is the first description of the southernmost Neotropical swallow defence behaviour and will therefore help delineate future research.

Can parental investment reduce social altruistic behaviour in Yellow-legged Gulls Larus michahellis

This study aims to test if there are differences in nest defence behaviour in single and in groups of Yellow-legged Gulls Larus michahellis during two stages of the breeding season: incubation and early chick-rearing period. When a human intruder wearing a mask approached and stood still next to the target nest during incubation, the gulls took part in passive mobbing and helped the ‘attacked’ gull, thereby showing altruistic behaviour. In contrast, during the early chick-rearing period, decreased altruistic behaviour was observed: the individuals that took part in the passive mobbing tended to remain on their own nests, in order to look after their own chicks. In this stage, a reduction of the size of passive mobbing was also noted. Furthermore, gulls from disturbed nests increased the intensity of nest defence by increasing the number of dives directed at the heads of the human intruders. Again, those gulls whose nests were directly affected by an approaching human intruder left their nests quickly to begin an aerial defence, encouraging the chicks to leave the nest and hide among rocks and shrubs. The adult gulls came back to their nests only after the danger had ceased and the chicks had come back to their nests, in agreement with the Parental Investment Theory.

Collapse of a protector species drives secondary endangerment in waterbird communities

Interactions and dependence between species can transmit the effects of species declines within and between trophic levels, resulting in secondary endangerments and, in some cases, extinctions. Many mixed-species avian breeding aggregations commonly have a protector species whose aggressive nest defense is used by other species to defend their nests. Disappearance of the protector species may have population demographic consequences on the dependent species. Aggressive nest defense behavior of small colonial gulls, such as the black-headed gull (Chroicocephalus ridibundus), is used by many waterbird species to gain protection against predators. We used data from 15 local waterbird communities in Finland to study long-term changes and dynamics of breeding numbers of other waterbirds as a response to long-term changes and dynamics of black-headed gull colonies. We found that breeding numbers of many species tracked long-term changes in the size of black-headed gull colonies. This was true even after controlling for a common trend in the size of the black-headed gull colony and the breeding numbers of the other species. The trend-controlled positive temporal association with black-headed gull was relatively stronger in species that nest in similar habitats of a lake as the black-headed gull, and in species that have a more critical conservation status due to drastic population decline. Our results suggest that the overall decline of black-headed gull colonies has resulted in secondary endangerment of many other species in waterbird communities.

Hawk mimicry does not reduce attacks of cuckoos by highly aggressive hosts

BackgroundResemblance to raptors such as hawks (Accipiter spp.) is considered to be an adaptive strategy of cuckoos (Cuculus spp.), which has evolved to protect cuckoos against host attacks. However, the effectiveness of the mimicry remains controversial, and is not yet fully studied for highly aggressive hosts.MethodsWe evaluated the effectiveness of sparrowhawk (Accipiter nisus) mimicry by common cuckoos (Cuculus canorus) in oriental reed warblers (Acrocephaus orientalis), which are highly aggressive hosts. Using a both the single and the paired dummy experiment, defense behaviors and attack intensities of oriental reed warblers against common cuckoos, sparrowhawks and oriental turtle doves (Streptopelia orientalis) were assessed.ResultsOriental reed warblers exhibit strong nest defense behaviors, and such behaviors do not change with breeding stage (i.e., egg stage and nestling stage). Furthermore, assistance from conspecific helpers may increase attack intensities. However, they were deterred from mobbing overall by the presence of the hawk.ConclusionsOriental reed warblers are able to distinguish cuckoos from harmless doves. However, they may be deterred from mobbing by the presence of the predatory hawk, suggesting hawk mimicry may be ineffective and does not reduce attacks of cuckoos by highly aggressive hosts.

Nest defense behavior of Greater Roadrunners (Geococcyx californianus) in south Texas

The Greater Roadrunner (Geococcyx californianus) is a medium-sized predatory bird that occurs widely across the southwestern United States. Despite its prevalence in this region, studies examining the nesting and behavioral ecology of this species are limited. In 2015 and 2016, we examined relatively unknown aspects of roadrunner natural history by using infrared video cameras to observe antipredator behaviors associated with Greater Roadrunner nest defense. Nest predation accounted for all nesting failures in our study. The Great Plains rat snake (Pantherophis emoryi) accounted for 70.0% of nest predation. We observed rat snakes entering the nest and consuming eggs or nestlings for >6 min before roadrunners flushed from nest sites. We also observed 53.3% of roadrunners actively defending nest sites from snake predators and zero defending nests from coyotes (Canis latrans), likely because of the predator size. Active defense sessions in our study lasted 1 min 20 s (95% CI 1 min 17 s) and consisted of 12.0 (95% CI 3.4) bill strikes per min of active defense. We observed no successful nest defenses because partial nest contents were lost during each event; however, >50% of predation events with an active defense session resulted in preservation of at least one viable egg or chick, indicating nest defense was a valuable behavior. Examining nest defense behaviors in larger, predatory birds may elucidate risks and rewards associated with nest defense that may not be observed in studies focusing primarily on passerines.

Supplemental food alters nest defence and incubation behaviour of an open‐nesting wetland songbird

Climate‐driven increases in spring temperatures are expected to result in higher prey availability earlier in the breeding season for insectivorous birds breeding in wetland habitats. Predation during the incubation phase is a major cause of nesting failure in open‐nesting altricial birds such as the Eurasian reed warbler. The nest predation rate in this species has recently been shown to be substantially reduced under conditions of experimentally elevated invertebrate prey availability. Food availability near the nest may be an important determinant of adult incubation and nest defence behaviours during the incubation period. We used two experimental studies to compare incubation behaviour and nest defence in food‐supplemented and unsupplemented adult Eurasian reed warblers during the incubation phase. In the first study we measured nest defence behavioural responses to a taxidermic mount of a native predator (stoat Mustela erminea). In the second study we used temperature loggers installed in nests to measure breaks in incubation as a measure of nest vulnerability. Food‐supplemented birds responded aggressively to the presence of a predator more quickly than those in the unsupplemented group, suggesting they are closer to their nest and can more quickly detect a predator in the vicinity. Food‐supplemented birds also had shorter breaks in incubation (both in terms of maximum and mean off‐bout durations), presumably because they were foraging for shorter periods or over shorter distances from the nest. This study therefore identifies the behavioural mechanisms by which changes in food availability may lead to changes in nest survival and thus breeding productivity, in open‐nesting insectivorous birds.

Male Louisiana Waterthrush (Parkesia motacilla) successfully defends nest from juvenile ratsnake

ABSTRACT The use of video cameras to monitor avian nests has allowed identification of key nest predator species and could potentially improve our understanding of parental nest defense. For songbirds, cameras have often shown snakes to be the most common nest predator, although video evidence of passerines successfully defending nests against snakes is lacking. We describe the first evidence of a small passerine, the Louisiana Waterthrush, successfully thwarting a possible predation attempt by a juvenile ratsnake. This recording documents rarely observed nest defense behavior and allows us to consider how this event fits within theories of optimal nest defense.

Variation in personality traits across a metal pollution gradient in a free-living songbird

Anthropogenic contaminants could alter traits central to animal behavioral types, or personalities, including aggressiveness, boldness and activity level. Lead and other toxic metals are persistent inorganic pollutants that affect organisms worldwide. Metal exposure can alter behavior by affecting neurology, endocrinology, and health. However, the direction and magnitude of the behavioral effects of metal exposure remain equivocal. Moreover, the degree to which metal exposure simultaneously affects suites of correlated behavioral traits (behavioral syndromes) that are controlled by common mechanisms remains unclear, with most studies focusing on single behaviors. Using a model species for personality variation, the great tit (Parus major), we explored differences in multiple behavioral traits across a pollution gradient where levels of metals, especially lead and cadmium, are elevated close to a smelter. We employed the novel environment exploration test, a proxy for variation in personality type, and also measured territorial aggressiveness and nest defense behavior. At polluted sites birds of both sexes displayed slower exploration behavior, which could reflect impaired neurological or physiological function. Territorial aggression and nest defense behavior were individually consistent, but did not vary with proximity to the smelter, suggesting that metal exposure does not concurrently affect exploration and aggression. Rather, exploration behavior appears more sensitive to metal pollution. Effects of metal pollution on exploration behavior, a key animal personality trait, could have critical effects on fitness.

Comparative analyses of co-evolving host-parasite associations reveal unique gene expression patterns underlying slavemaker raiding and host defensive phenotypes

The transition to parasitism is a drastic shift in lifestyle, involving rapid changes in gene structure, function, and expression. After the establishment of antagonistic relationships, parasites and hosts co-evolve through reciprocal adaptations, often resulting in evolutionary arms-races. Repeated evolution of social parasitism and slavery among Temnothorax ants allows us to examine those gene expression patterns that characterize slavemaker raiding and reciprocal host defensive phenotypes. Previous behavioural studies have established that raiding strategies between Temnothorax slavemakers diverge, while host defense portfolios shift similarly under parasite pressure. We are the first to confirm this at the molecular level, revealing that slavemaking species exhibit a wider variety of genes with species-specific patterns of expression within their raiding phenotypes, whereas expression similarity is commonly found during the non-raiding phenotype. Host species response to slavemaker aggression, however, is indicated by strong changes in the expression of a relatively few number genes. Additionally, the expression of individual genes such as Acyl-CoA-Delta(11) desaturase and Trypsin-7 is strongly associated with the raiding phenotype of all three slavemaking species. Here, we provide novel insight into the gene expression patterns associated with raiding and nest defense behavior in Temnothorax ants, suggesting lineage-specific evolutionary patterns among both slavemakers and hosts.

Antipredator Nest Guarding by Female Horned Lizards (Phrynosoma): Iguanian Parental Care

Abstract This is the first report of antipredator nest defense by iguanian lizards. Female Texas Horned Lizards (Phrynosoma cornutum) and Round-tailed Horned Lizards (P. modestum) consistently exhibited vigorous nest-site defensive behaviors (butting, open-mouth attacks, and biting attacks) when experimentally approached in the field by a potential predator of reptilian eggs, Western Patch-nosed Snakes (Salvadora hexalepis). During both prenesting and postnesting snake trials, such defensive attack behaviors by the female lizards were absent. Females of a viviparous congener, Greater Short-horned Lizards (Phrynosoma hernandesi), failed to exhibit postpartum defensive behaviors to S. hexalepis, and newborns did not associate in proximity to their mothers. Nest-site defense is suggested to be the ancestral behavior in the genus Phrynosoma, and it might have been lost during the evolution of viviparity in certain species. Previous failures to detect nest defense behavior in Phrynosoma, and in related clades ...

Nest-defense behaviors in fathead minnows after lifecycle exposure to the antidepressant venlafaxine.

Venlafaxine is an antidepressant and anti-anxiety drug that has been detected in municipal wastewater at low μg/L concentrations. In this study, the nest-defense behavior of adult male fathead minnows (Pimephales promelas) was observed in fish exposed for a full lifecycle to venlafaxine nominal concentrations of 0.88, 8.8, and 88μg/L (i.e. 1, 9.3, 75μg/L mean measured concentrations). Nest-defense behaviors quantified were the time taken to contact a dummy intruder fish (on a flexible stick, held near each nest) and the number of contacts made during a 1min period. In male fathead minnows exposed to venlafaxine over a full lifecycle at environmentally relevant nominal concentrations (i.e. 0.88 and 8.8μg/L) no significant effects were observed in behavior. However, in males exposed over a full lifecycle to the highest concentration of venlafaxine (i.e. 88μg/L), nest-defense behaviors were increased in males with empty nests, as shown by the significantly elevated percentage of empty-nest males that made contact with the dummy intruder fish (89%) relative to the lower percentage of contacts (65%) among the Control males (p=0.046). Lifecycle exposure to high venlafaxine (88μg/L) caused males to over-protect their empty nests. Environmental venlafaxine concentrations are approximately 70 x lower than this, so it is unlikely that behavioral changes from venlafaxine exposure would occur in the environment. Normal nest defense behaviours in control males varied, depending on whether they were protecting empty nests or nests with eggs. Compared to Control males with empty nests, more Control males with eggs in their nests made contact with the dummy intruder fish (p=0.014), contact was faster (i.e. <10s, p=0.011), and they hit the dummy intruder fish more times in 1min (p=0.031) This study is the first to assess reproductive behaviors in fish exposed to an antidepressant over a full lifecycle.

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

AbstractThroughout 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.

Negative phenotypic and genetic correlation between natal dispersal propensity and nest-defence behaviour in a wild bird

Natural selection is expected to favour the integration of dispersal and phenotypic traits allowing individuals to reduce dispersal costs. Accordingly, associations have been found between dispersal and personality traits such as aggressiveness and exploration, which may facilitate settlement in a novel environment. However, the determinism of these associations has only rarely been explored. Here, we highlight the functional integration of individual personality in nest-defence behaviour and natal dispersal propensity in a long-lived colonial bird, the Alpine swift (Apus melba), providing insights into genetic constraints shaping the coevolution of these two traits. We report a negative association between natal dispersal and nest-defence (i.e. risk taking) behaviour at both the phenotypic and genetic level. This negative association may result from direct selection if risk-averseness benefits natal dispersers by reducing the costs of settlement in an unfamiliar environment, or from indirect selection if individuals with lower levels of nest defence also show lower levels of aggressiveness, reducing costs of settlement among unfamiliar neighbours in a colony. In both cases, these results highlight that risk taking is an important behavioural trait to consider in the study of dispersal evolution.