Egg concealment is an antipredatory strategy in a cavity‐nesting bird

Saavedra, Irene; Amo, Luisa

doi:10.1111/eth.12932

Cited by 8 publications

(9 citation statements)

References 43 publications

(63 reference statements)

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“…Therefore, the positive correlation between use of egg covering in great tits and rate of nest predation across Europe (Loukola et al 2020 ) may be partly explained by the mechanism of nest illumination as proposed here by the usurpation hypothesis. Blue tits exposed to predator chemical cues in the nest more frequently covered their eggs than birds exposed to an odorous control (Saavedra and Amo 2019 ). However, more broadly, the nest predation hypothesis proposes that egg covering reduces the likelihood that a nest predator will enter the cavity because of costs of entering without certainty of a reward (Haftorn and Slagsvold 1995 ; Loukola et al 2020 ).…”

Section: Discussionmentioning

confidence: 99%

Egg covering in cavity nesting birds may prevent nest usurpation by other species

Slagsvold

Wiebe

2021

Behav Ecol Sociobiol

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Some birds cover their eggs with nest material when they leave to forage. It has been suggested that such egg-covering aids thermoregulation or prevents predation but here we present a new hypothesis, that secondary cavity-nesting species cover their eggs to prevent nest usurpation by other birds. When the bottom of the cavity is dark, as when eggs are covered by nest material, it may be difficult for a prospecting competitor to see whether a defending nest owner or a predator is hiding inside the cavity. Competitors may therefore hesitate to enter dark cavities. We filmed 21 great tit (Parus major) nests during the egg-laying period and found that the female spent bouts of highly variable length outside the nest box (range 0.3–250 min, n = 51), so prospecting small passerines would have difficulty predicting whether an aggressive tit owner was in the box or would soon return. We presented prospecting male pied flycatchers (Ficedula hypoleuca) with a dyad of boxes (n = 93), each containing a great tit nest but only one with visible eggs. Flycatchers hesitated more to enter a nest box with no visible tit eggs than a box with exposed eggs. This was most evident for nest boxes with dark versus light interior paint, supporting the idea that better interior illumination makes prospecting birds more confident about entering an unfamiliar cavity. The usurpation and predation hypotheses are not mutually exclusive because both competitors and small predators may hesitate to enter dark, enclosed spaces if visibility is low. Significance statement Some birds deposit a layer of material on top of the eggs when they leave the nest. Several hypotheses have been proposed for such egg covering, for example that it may insulate the eggs and reduce the risk of nest predation. We propose a new hypothesis, namely that secondary hole-nesting birds cover their eggs when they leave the nest to prevent usurpation of the cavity by other birds. Great tits that we filmed at the nest during the egg-laying period could be absent for long periods. To test the hypothesis, we presented male pied flycatchers, potential nest competitors, with a dyad of nest boxes, each containing a great tit nest but only one with visible tit eggs. In support of the prediction, prospecting flycatchers hesitated to enter dark cavities with dark floors relative to boxes with exposed, reflective eggs.

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Section: Discussionmentioning

confidence: 99%

Egg covering in cavity nesting birds may prevent nest usurpation by other species

Slagsvold

Wiebe

2021

Behav Ecol Sociobiol

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“…This method of odor collection has been used in previous studies (Amo et al , , b, ). Ferret scent is recognized by blue tits as a predatory threat (Amo et al , , Saavedra and Amo ) and rabbit scent has been used as an odorous control in other studies (Amo et al , , ). The odorless control treatment was prepared by adding several drops of water to clean pieces of absorbent paper.…”

Section: Methodsmentioning

confidence: 99%

The importance of chemical, visual and behavioral cues of predators on the antipredatory behavior of birds

Saavedra

Amo

2020

Journal of Avian Biology

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Nesting mortality in birds is caused primarily by predation. The ability to use different predator cues to assess the level of predation risk could be essential to minimize the predation risk during the breeding period. Previous studies show that birds modified their parental behavior when they detected chemical or visual cues of predators in the surrounding of the nest. However, according to the threat sensitivity hypothesis, birds may use more than one predator cue in order to accurately assess the level of predation risk. In this assessment, the behavior of predators can provide important information to evaluate the motivation of the predator to launch an attack. However, there are no studies that examined the importance of chemical, visual and behavioral cues of predators on the antipredatory behavior of birds. We examined the antipredatory behavior of blue tit Cyanistes caeruleus parents when they were exposed to live predators or stuffed models of predators that also had predator chemical cues. Blue tits were able to detect the behavioral cues of predators and exhibited greater antipredatory behaviors when exposed to a live predator than to a stuffed model with chemical cues. The results suggest that birds use the chemical, visual and behavioral cues of the predators to assess the level of predation risk and adjust their antipredatory behavior accordingly.

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“…This method of odor collection has been used in previous studies [11,14,[48][49][50][51]. Ferret scent is recognized by blue tits and great tits (Parus major) as a predatory threat [11,14,48,49] and rabbit scent has been used as an odorous control in other studies [14,50,52]. The two male scents within each treatment were alternately assigned to blue tit nests.…”

Section: Experimental Design and Proceduresmentioning

confidence: 99%

“…Papers soiled with feces were discarded. This method of odor collection has been used in previous studies [11,14,[48][49][50][51]. Ferret scent is recognized by blue tits and great tits (Parus major) as a predatory threat [11,14,48,49] and rabbit scent has been used as an odorous control in other studies [14,50,52].…”

Section: Experimental Design and Proceduresmentioning

confidence: 99%

Assessing behavioral sex differences to chemical cues of predation risk while provisioning nestlings in a hole-nesting bird

Saavedra

Tomás

Amo

2022

Preprint

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Birds can assess nest predation risk and adjust their parental activity accordingly. Risk taking behavior should be related to investment in reproduction as well as to confidence in parenthood that often differ between sexes. In those cases, sexual differences in risk taking behavior may be expected. For example, in blue tits, females invest more time and energy than males in nest-building, egg laying and incubation. Furthermore, confidence in parenthood is supposed to be higher for females, as extrapair paternity is common in this species. Therefore, the reproductive value of nestlings may be higher for females than for males and the former may assume greater risks to ensure nestling growth and maximize their reproductive success. We examined potential sexual differences in the risk assumed by parents in relation to perceived risk of predation inside the nest cavity, where predation risk perception may be higher. We increased perceived predation risk by adding predator chemical cues inside blue tit (Cyanistes caeruleus) nest-boxes, and we tested whether female and male parents differed in the risk assumed when taking care of nestlings. Females and males did not differ in the risk assumed in response to perceived predation risk. However, females reduced time devoted to nest sanitation activities when predator chemical cues were detected inside the nest-box, likely as an anti-predatory strategy to minimize their own risk of predation. Therefore, these results add to the evidence that birds can detect chemical cues of predators inside the nest cavity and suggest that the behavioral response to an increase in risk of predation perceived through olfactory cues is not sex-dependent in blue tit.

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Egg concealment is an antipredatory strategy in a cavity‐nesting bird

Cited by 8 publications

References 43 publications

Egg covering in cavity nesting birds may prevent nest usurpation by other species

Egg covering in cavity nesting birds may prevent nest usurpation by other species

The importance of chemical, visual and behavioral cues of predators on the antipredatory behavior of birds

Assessing behavioral sex differences to chemical cues of predation risk while provisioning nestlings in a hole-nesting bird

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