A classic question revisited in red-winged blackbirds: disentangling confounding hypotheses surrounding parental investment theory and nest defense intensity

Shew, Justin J.; Merwe, Jorista van der; Schauber, Eric M.; Tallitsch, Briana K.; Nielsen, Clayton K.

doi:10.1007/s00265-016-2190-3

Cited by 13 publications

(16 citation statements)

References 57 publications

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“…Female barnacle geese plastically increased their nest defence over the season, as reflected by a decrease in their FID. Parental investment theory and the renesting potential hypothesis are two non‐exclusive explanations for this pattern (see Introduction; Shew et al., 2016). Arctic‐breeding birds such as barnacle geese experience a very short breeding season, as the snow‐free season is limited (mean snow‐free season length in Kongsfjorden is 81 days ± 12: Lameris et al., 2019) which seems to prohibit renesting (from laying till fledge takes approx.…”

Section: Discussionmentioning

confidence: 99%

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State dependence explains individual variation in nest defence behaviour in a long‐lived bird

Jong

Nicolaus

Fokkema

et al. 2021

Journal of Animal Ecology

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Parental care, such as nest or offspring defence, is crucial for offspring survival in many species. Yet, despite its obvious fitness benefits, the level of defence can consistently vary between individuals of the same species. One prominent adaptive explanation for consistent individual differences in behaviours involves state dependency: relatively stable differences in individual state should lead to the emergence of repeatable behavioural variation whereas changes in state should lead to a readjustment of behaviour. Therefore, empirical testing of adaptive state dependence requires longitudinal data where behaviour and state of individuals of the same population are repeatedly measured. Here, we test if variation in states predicts nest defence behaviour (a ‘risky’ behaviour) in a long‐lived species, the barnacle goose Branta leucopsis. Adaptive models have predicted that an individual's residual reproductive value or ‘asset’ is an important state variable underlying variation in risk‐taking behaviour. Hence, we investigate how nest defence varies as a function of time of the season and individual age, two state variables that can vary between and within individuals and determine asset. Repeated measures of nest defence towards a human intruder (flight initiation distance or FID) of females of known age were collected during 15 breeding seasons. Increasing values of FID represent increasing shyness. We found that females strongly and consistently differed in FID within‐ and between‐years. As predicted by theory, females adjusted their behaviour to state by decreasing their FID with season and age. Decomposing these population patterns into within‐ and between‐individual effects showed that the state‐dependent change in FID was driven by individual plasticity in FID and that bolder females were more plastic than shyer females. This study shows that nest defence behaviour differs consistently among individuals and is adjusted to individual state in a direction predicted by adaptive personality theory.

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Section: Discussionmentioning

confidence: 99%

Section: Plastic Adjustment Of Nest Defence Behaviour To Changes In Assetmentioning

confidence: 99%

State dependence explains individual variation in nest defence behaviour in a long‐lived bird

Jong

Nicolaus

Fokkema

et al. 2021

Journal of Animal Ecology

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“…Most studies conclude that males defend nests more aggressively than females (Redmond et al 2009;Klvanova et al 2011;Svagelj et al 2012;Shew et al 2016) and this difference is attributed to the larger size of males compared with females in many species. Larger individuals should be able to defend nests either more efficiently or aggressively with less risk than their smaller counterparts (Wallin 1987).…”

Section: Differences In Nest Defense Between the Sexesmentioning

confidence: 99%

The effect of offspring value on variation of nest defense intensity in gray catbirds (Dumetella carolinensis)

Redmond

Eroh

Haq

et al. 2020

Behav Ecol Sociobiol

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Nest defense is an adaptive strategy used by adults to increase survival of independent young. However, the risk adults face by defending young from predators represents an important trade-off and parental investment theory predicts adults will modulate nest defense based on the value of offspring. We used a model of a black rat snake, a potential nest predator on our study site, to quantify nest defense in a population of gray catbirds in eastern Pennsylvania during the breeding seasons of 2017 and 2018. Specifically, we evaluated (1) the difference in nest defense between male and female parents, (2) the relationship between nest defense and nest success, and (3) how variation in nest defense was related to factors associated with offspring value. Although male catbirds tend to be larger than females, they did not defend their nests more aggressively than female catbirds. Response to the model predator we used was also not different between individuals whose nests were successful compared with individuals that failed. Although nests that contained more and older young were not defended more aggressively, our analyses did show that adult catbirds defended young that were laid earlier in the season more intensely than those laid later in the breeding season. In birds, earlier clutch initiation is associated with an increased chance of recruitment into the breeding population. Catbirds, therefore, follow predictions of parental investment theory because they defended offspring of higher value more aggressively. Significance statement Defense of young from predators is an important component of parental care. Nest defense represents a trade-off because although it should increase reproductive success by increasing offspring survival, it presents a risk to adults, thus lowering their survival. We studied variation in nest defense of gray catbirds in relation to offspring value. Although nest defense was not related to nest success, we did find that adult catbirds defended nests that were produced earlier in the year more aggressively than later nests. In birds, the timing of reproduction is linked to prospects of juvenile survival in such a way that offspring produced early in the breeding season are more likely to survive and recruit into the breeding population. As predicted by parental investment theory, catbirds defended young that represented a higher increase in fitness more aggressively.

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“…Second, if the focal gulls became habituated to simulated predation events, then we would expect to see a directional change in the aggressive responses over time. For instance, previous research with songbirds (Knight & Temple 1986;Shew et al 2016) and research in our study system (Burger & Gochfeld 1983) showed that birds repeatedly exposed to a human intrusion responded with increasingly bold behavior over time. Alternatively, if birds became accustomed to the intrusion and realized that no real danger existed, then we might expect a decrease in aggressive responses over time.…”

Section: Figmentioning

confidence: 64%

Defending the Weak: Parental Defense Peaks When Chick Vulnerability is Greatest in the Herring Gull (Larus argentatus)

Crisologo

Bonter

2016

Ethology

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Successful reproduction often depends upon parents providing offspring with resources and protection. In birds, reproductive success can often be enhanced by parents engaging in antipredator behaviors, but these behaviors can be costly. Theoretically, individuals should temporally modify the intensity of nest defense behavior to balance the costs and benefits of current and future reproductive success. More specifically, nest defense should vary throughout a nesting attempt to maximize fitness of the adults. Here, we consider the relationship between nest defense behavior and chick vulnerability in the herring gull (Larus argentatus), where chicks are under high predation risk. We estimated chick vulnerability by quantifying survival probabilities at different periods of the nestling stage. Simultaneously, we quantified changes in parental aggression throughout the nesting cycle by simulating predation attempts using a human predator model. We found that chick survival probabilities were lowest (i.e., vulnerability was highest) and parental aggression in nest defense was greatest during the first 10 days after hatching. Thus, we show that parents are most defensive when chicks are most vulnerable and that adults optimize nest defense behaviors in a way that maximizes their fitness.

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A classic question revisited in red-winged blackbirds: disentangling confounding hypotheses surrounding parental investment theory and nest defense intensity

Abstract: ) who 34 made our research possible. We also thank data proofers/entry (J. Whitaker, A. Blackert, S. 35Ramakrishnan). We are grateful to anonymous reviewers and to D. Westneat and P. Porneluzi for their 36 reviews that greatly improved our manuscript. 37 AbstractThe

Cited by 13 publications

References 57 publications

State dependence explains individual variation in nest defence behaviour in a long‐lived bird

State dependence explains individual variation in nest defence behaviour in a long‐lived bird

The effect of offspring value on variation of nest defense intensity in gray catbirds (Dumetella carolinensis)

Defending the Weak: Parental Defense Peaks When Chick Vulnerability is Greatest in the Herring Gull (Larus argentatus)

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