Do adult eastern bluebird, Sialia sialis, males recognize juvenile-specific traits?

Ligon, Russell A.; Hill, Geoffrey E.

doi:10.1016/j.anbehav.2009.01.031

Cited by 11 publications

(17 citation statements)

References 10 publications

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“…Following previous studies [15,16,36,37] we adopted a simultaneous presentation of dummy dyads at host nests (i.e., essentially a choice test). Great reed warblers attack almost all intruders near their nests, including the mounts of both cuckoo morphs and sparrowhawks at the highest levels of aggression [5,15,16,38-40].…”

Section: Methodsmentioning

confidence: 99%

Color plumage polymorphism and predator mimicry in brood parasites

Trnka

Grim

2013

Front Zool

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BackgroundPlumage polymorphism may evolve during coevolution between brood parasites and their hosts if rare morph(s), by contravening host search image, evade host recognition systems better than common variant(s). Females of the parasitic common cuckoo (Cuculus canorus) are a classic example of discrete color polymorphism: gray females supposedly mimic the sparrowhawk (Accipiter nisus), while rufous females are believed to mimic the kestrel (Falco tinnunculus). Despite many studies on host responses to adult cuckoos comprehensive tests of the “hawk mimicry” and “kestrel mimicry” hypotheses are lacking so far.ResultsWe tested these hypotheses by examining host responses to stuffed dummies of the sparrowhawk, kestrel, cuckoo and the innocuous turtle dove (Streptopelia turtur) as a control at the nest. Our experimental data from an aggressive cuckoo host, the great reed warbler (Acrocephalus arundinaceus), showed low effectiveness of cuckoo-predator mimicry against more aggressive hosts regardless of the type of model and the degree of perfection of the mimic. Specifically, warblers discriminated gray cuckoos from sparrowhawks but did not discriminate rufous cuckoos from kestrels. However, both gray and rufous cuckoos were attacked vigorously and much more than control doves. The ratio of aggression to gray vs. rufous cuckoo was very similar to the ratio between frequencies of gray vs. rufous cuckoo morphs in our study population.ConclusionsOverall, our data combined with previous results from other localities suggest polymorphism dynamics are not strongly affected by local predator model frequencies. Instead, hosts responses and discrimination abilities are proportional, other things being equal, to the frequency with which hosts encounter various cuckoo morphs near their nests. This suggests that female cuckoo polymorphism is a counter-adaptation to thwart a specific host adaptation, namely an ability to not be fooled by predator mimicry. We hypothesize the dangerousness of a particular model predator (sparrowhawks are more dangerous to adult birds than kestrels) may be another important factor responsible for better discrimination between the gray cuckoo and its model rather than between the rufous cuckoo and its model. We also provide a review of relevant existing literature, detailed discussion of plumage polymorphism in cuckoos, methodological recommendations and new ideas for future work.

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Section: Methodsmentioning

confidence: 99%

Color plumage polymorphism and predator mimicry in brood parasites

Trnka

Grim

2013

Front Zool

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“…Moreover, in migratory passerines, there are no juveniles in the population until the earliest broods fledge, and thus the mimetic function of dull colouration is not possible until the second breeding attempt (Schwarzová, 2010). In light of the foregoing, mimicry of juveniles is rarely invoked to explain delayed plumage maturation notwithstanding that the underlying assumption that adults display less aggression to conspecific juveniles than other conspecific adults appears to be sound (Ligon & Hill, 2009).…”

Section: (B) Assessementmentioning

confidence: 99%

Delayed plumage maturation and delayed reproductive investment in birds

Hawkins¹,

2011

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Delayed plumage maturation is the delayed acquisition of a definitive colour and pattern of plumage until after the first potential breeding period in birds. Here we provide a comprehensive overview of the numerous studies of delayed plumage maturation and a revised theoretical framework for understanding the function of delayed plumage maturation in all birds. We first distinguish between hypotheses that delayed plumage maturation is attributable to a moult constraint with no adaptive function and hypotheses that propose that delayed plumage maturation is a component of an adaptive life-history strategy associated with delayed reproductive investment. We then recognize three potential benefits of delayed plumage maturation: crypsis, mimicry and status signaling. Evidence suggests that delayed plumage maturation is not a consequence of developmental constraints and instead represents a strategy to maximize reproductive success in circumstances where young adults cannot effectively compete with older adults for limited resources, particularly breeding opportunities. A multi-factorial explanation that takes into account lifespan and the degree of competition for limited breeding resources and that combines the benefits of an inconspicuous appearance with the benefits of honest signaling of reduced competitiveness provides a general explanation for the function of delayed plumage maturation in most bird species. Delayed plumage maturation should be viewed as a component of alternative reproductive strategies that can include delay in both plumage and sexual development. Such strategies are frequently facultative, with individuals breeding prior to the acquisition of definitive plumages when conditions are favourable. Presumably, the benefits of delayed plumage maturation ultimately enhance lifetime reproductive success, and studying delayed plumage maturation within the context of lifetime reproductive success should be a goal of future studies.

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“…However, the eastern bluebird is one of the few thrush species for which we have detailed information on breeding duration and territoriality, and we know that juvenile eastern bluebirds should benefit from an honest signal of age and sexual immaturity. In fact, it has recently been shown that adult males use plumage colour and pattern as cue when attacking territorial intruders and direct significantly less aggression towards models bearing juvenal plumage (Ligon and Hill 2009).…”

Section: Discussionmentioning

confidence: 99%

Is the juvenal plumage of altricial songbirds an honest signal of age? Evidence from a comparative study of thrushes (Passeriformes: Turdidae)

Ligon

Hill

2012

J Zoolog Syst Evol Res

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The function and evolution of avian plumage colouration has been the subject of many studies over the past decade, but virtually all of this research has focused on the plumages of sexually mature individuals. The colours and patterns of juvenal plumage, which is worn by altricial songbirds only for the first few months of life, have been the focus of few studies. We develop the idea that distinctive juvenile appearance may be a signal of sexual immaturity, serving to reduce aggression from conspecific adults. We use a comparative phylogenetic approach to test this hypothesis in the thrushes (Family Turdidae). Honest signals of reproductive immaturity should be more valuable when juveniles fledge into environments with aggressive adult conspecifics. Therefore, we predicted that distinctive juvenile appearance would be more likely to evolve in species with extended breeding seasons and high levels of territoriality. Because many tropical bird species exhibit year‐round territoriality and elongated breeding seasons, we used breeding latitude as a proxy for these variables. As predicted, distinctive juvenile appearance was significantly correlated with occupancy of tropical latitudes. While alternative explanations cannot be ruled out and more tests of the hypothesis are needed, the observed associations between breeding latitude and distinctiveness of juvenal plumage are consistent with our hypothesis that distinctive juvenal plumage evolved as a signal of sexual immaturity.

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Do adult eastern bluebird, Sialia sialis, males recognize juvenile-specific traits?

Cited by 11 publications

References 10 publications

Color plumage polymorphism and predator mimicry in brood parasites

Color plumage polymorphism and predator mimicry in brood parasites

Delayed plumage maturation and delayed reproductive investment in birds

Is the juvenal plumage of altricial songbirds an honest signal of age? Evidence from a comparative study of thrushes (Passeriformes: Turdidae)

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