scholarly journals Calling at a cost: elevated nestling calling attracts predators to active nests

2011 ◽  
Vol 7 (4) ◽  
pp. 493-495 ◽  
Author(s):  
Tonya M. Haff ◽  
Robert D. Magrath
Keyword(s):  
Experimental Evidence ◽  
Predation Risk ◽  
Background Noise ◽  
Alarm Calls ◽  
Evolutionary Models ◽  
Antipredator Strategies ◽  
Artificial Nests ◽  
Signal Honesty ◽  
Nestling Begging

Begging by nestling birds has been used to test evolutionary models of signalling but theory has outstripped evidence. Eavesdropping predators potentially impose a cost on begging that ensures signal honesty, yet little experimental evidence exists for such a cost at active nests because the use of artificial nests, long playback bouts and absence of parents may have exaggerated costs. We broadcast short periods (1 h) of either nestling vocalizations or background noise at active white-browed scrubwren, Sericornis frontalis , nests. Nestlings called naturally during both treatments, allowing us to test whether elevated calling increases risk, a key but rarely tested assumption of evolutionary models. Predators visited nests exclusively during periods of elevated calling. Furthermore, playbacks affected neither adult visits nor nestling activity, suggesting that calling alone attracted predators. Adults gave alarm calls and nestlings usually called less when predators approached nests. Predation risk to broods is, therefore, likely to fluctuate substantially over short periods of time, depending on nestling hunger and whether adults or young have detected predators. This study confirms a present-day cost of nestling begging, demonstrates that this cost can be incurred over short periods and supports the importance of parent–offspring antipredator strategies in reducing predation risk.

scholarly journals Experimental evidence that sentinel behaviour is affected by risk

2010 ◽  
Vol 6 (4) ◽  
pp. 445-448 ◽  
Author(s):  
A. R. Ridley ◽  
N. J. Raihani ◽  
M. B. V. Bell
Keyword(s):  
Experimental Evidence ◽  
Predation Risk ◽  
Alarm Calls ◽  
Predator Detection ◽  
Conspicuous Feature ◽  
Cooperatively Breeding ◽  
The Cost ◽  
Investment Patterns ◽  
Perceived Predation Risk

Sentinels are a conspicuous feature of some cooperative societies and are often assumed to provide benefits in terms of increased predator detection. Similar to other cooperative behaviours, variation in investment in sentinel behaviour should reflect variation in the benefits of such behaviour. However, evidence for this is inconclusive: to date experiments have manipulated the cost of sentinel behaviour, and considerations of changes in the benefits of sentinel activity on investment patterns are lacking. Here, we experimentally manipulated the benefits of sentinel behaviour in the cooperatively breeding pied babbler ( Turdoides bicolor ) to assess whether this had any impact on sentinel activity. We simulated the presence of an unseen predator using playbacks of heterospecific alarm calls, and the presence of an actual predator using a model snake. In both cases, the increase in perceived predation risk caused an increase in sentinel activity, demonstrating that investment in sentinel activity increases when the benefits are greater.

Vegetation height and egg coloration differentially affect predation rate and overheating risk: an experimental test mimicking a ground-nesting bird

2012 ◽  
Vol 90 (6) ◽  
pp. 694-703 ◽  
Author(s):  
H. Gillis ◽  
B. Gauffre ◽  
R. Huot ◽  
V. Bretagnolle
Keyword(s):  
Predation Risk ◽  
Breeding Season ◽  
Nest Site Selection ◽  
Artificial Nests ◽  
Vegetation Height ◽  
Selective Pressures ◽  
Wide Range ◽  
Nest Microclimate ◽  
Egg Coloration ◽  
Ground Nesting

Avian eggs need to be laid in protected environments to develop and survive. Nest predation is known as the main cause of breeding failure for many birds, but nest microclimate conditions are also important for embryo development. These two selective pressures are particularly marked in ground-nesting birds. Vegetation height has been shown to be a critical factor for nest-site selection in ground-nesting birds because it can counteract predation and overheating simultaneously. It is therefore difficult to disentangle the respective influences of these risks on selection of a particular nest vegetation height. To develop a conceptual framework for understanding and predicting the relative effects of vegetation on predation and nest microclimate during a breeding season, we used vegetation height to manipulate differentially these two risks. We therefore exposed artificial nests to a wide range of vegetation heights, replicated the experimental tests during spring, and manipulated egg color to estimate predation risk. We confirmed that tall vegetation is relevant to protect unattended eggs against both risks. Whereas predation risk is stable for a given vegetation height, overheating risk presents inter- and intra-seasonal variations. Therefore, over a breeding season, for a given vegetation height, the respective strengths of the two risks are unbalanced and depends on egg coloration. The breeding strategy of ground-nesting birds thus should have been shaped by both selective pressures, but the ultimate choice may depend on the species-specific laying dates and alternative behavioral strategies for protecting the clutch. This study provides new perspectives to investigate avian parental behaviour.

scholarly journals Is it safe to nest near bold neighbours? Spatial patterns in predation risk associated with the density of American Golden-Plover nest

2016 ◽  
Author(s):  
Marie-Andrée Giroux ◽  
Myriam Trottier-Paquet ◽  
Joël Bêty ◽  
Vincent Lamarre ◽  
Nicolas Lecomte
Keyword(s):  
Predation Risk ◽  
Spatial Patterns ◽  
Bird Species ◽  
Artificial Nests ◽  
Species Of Conservation Concern ◽  
Composition And Structure ◽  
Negative Effect ◽  
Conservation Concern ◽  
Golden Plover ◽  
Mobbing Behaviour

Predation is one of the main factors explaining nesting mortality in most bird species. Birds can avoid nest predation or reduce predation pressure by breeding at higher latitude, showing anti-predator behaviour, and nesting in association with protective species. Plovers actively defend their territory by displaying early warning and aggressive/mobbing behaviour, potentially benefiting the neighbouring nests by decreasing their predation risk. To test for the existence of such a protective effect, we studied the influence of proximity to plover nests on predation risk of artificial nests on Igloolik Island (Nunavut, Canada) in July 2014. We predicted that the predation risk of artificial nests increases and decreases with the distance to and the density of plover nests, respectively. We monitored 18 plover nests and set 35 artificial nests at 30, 50, 100, 200 and 500 m from seven of those plover nests. Surprisingly, we showed that predation risk of artificial nests increases with the density of active plover nests. We also found a significant negative effect of the distance to the nearest active protector nest on predation risk of artificial nests. Understanding how the composition and structure of shorebird communities generate spatial patterns in predation risks represent a key step to better understand the importance of these species of conservation concern in tundra food webs.

scholarly journals Predation selects for smaller eye size in a vertebrate: effects of environmental conditions and sex

2019 ◽  
Vol 286 (1897) ◽  
pp. 20182625 ◽  
Author(s):  
Richard Svanbäck ◽  
Frank Johansson
Keyword(s):  
Visual Acuity ◽  
Phenotypic Plasticity ◽  
Experimental Evidence ◽  
Predation Risk ◽  
Environmental Conditions ◽  
Retinal Image ◽  
The Other ◽  
Eye Size ◽  
Fish Predators ◽  
Resource Levels

Increased eye size in animals results in a larger retinal image and thus improves visual acuity. Thus, larger eyes should aid both in finding food as well as detecting predators. On the other hand, eyes are usually very conspicuous and several studies have suggested that eye size is associated with predation risk. However, experimental evidence is scant. In this study, we address how predation affects variation in eye size by performing two experiments using Eurasian perch juveniles as prey and either larger perch or pike as predators. First, we used large outdoor tanks to compare selection due to predators on relative eye size in open and artificial vegetated habitats. Second, we studied the effects of both predation risk and resource levels on phenotypic plasticity in relative eye size in indoor aquaria experiments. In the first experiment, we found that habitat altered selection due to predators, since predators selected for smaller eye size in a non-vegetated habitat, but not in a vegetated habitat. In the plasticity experiment, we found that fish predators induced smaller eye size in males, but not in females, while resource levels had no effect on eye size plasticity. Our experiments provide evidence that predation risk could be one of the driving factors behind variation in eye size within species.

Experimental evidence for predation risk sensitive oviposition by a mosquito, Culiseta longiareolata

1999 ◽  
Vol 24 (2) ◽  
pp. 202-207 ◽  
Author(s):  
Gil. Stav ◽  
Leon. Blaustein ◽  
Joel. Margalith
Keyword(s):  
Experimental Evidence ◽  
Predation Risk ◽  
Risk Sensitive ◽  
Culiseta Longiareolata

scholarly journals Sharks shape the geometry of a selfish seal herd: experimental evidence from seal decoys

2009 ◽  
Vol 6 (1) ◽  
pp. 48-50 ◽  
Author(s):  
Alta De Vos ◽  
M. Justin O'Riain
Keyword(s):  
Experimental Evidence ◽  
Predation Risk ◽  
Prey Species ◽  
Group Formation ◽  
Predator Prey ◽  
Selfish Herd ◽  
Fur Seal ◽  
Cape Fur Seal ◽  
Shark Attacks ◽  
Proportional Reduction

Many animals respond to predation risk by forming groups. Evolutionary explanations for group formation in previously ungrouped, but loosely associated prey have typically evoked the selfish herd hypothesis. However, despite over 600 studies across a diverse array of taxa, the critical assumptions of this hypothesis have remained collectively untested, owing to several confounding problems in real predator–prey systems. To solve this, we manipulated the domains of danger of Cape fur seal ( Arctocephalus pusillus pusillus ) decoys to provide evidence that a selfish reduction in a seals' domain of danger results in a proportional reduction in its predation risk from ambush shark attacks. This behaviour confers a survival advantage to individual seals within a group and explains the evolution of selfish herds in a prey species. These findings empirically elevate Hamilton's selfish herd hypothesis to more than a ‘theoretical curiosity’.

scholarly journals Testing Whether Camera Presence Influences Habitat Specific Predation Pressure on Artificial Shorebird Nests in the Arctic

ARCTIC ◽  
2021 ◽  
Vol 74 (1) ◽  
pp. 22-29
Author(s):  
Kevin G. Young ◽  
Lisa V. Kennedy ◽  
Paul A. Smith ◽  
Erica Nol
Keyword(s):  
Predation Risk ◽  
Proportional Hazards Model ◽  
Habitat Type ◽  
Cox Proportional Hazards Model ◽  
The Arctic ◽  
Arctic Fox ◽  
Artificial Nests ◽  
Predator Species ◽  
Risk Of Predation ◽  
The Impact

When monitoring the breeding ecology of birds, the causes and times of nest failure can be difficult to determine. Cameras placed near nests allow for accurate monitoring of nest fate, but their presence may increase the risk of predation by attracting predators, leading to biased results. The relative influence of cameras on nest predation risk may also depend on habitat because predator numbers or behaviour can change in response to the availability or accessibility of nests. We evaluated the impact of camera presence on the predation rate of artificial nests placed within mesic tundra habitats used by Arctic-breeding shorebirds. We deployed 94 artificial nests, half with cameras and half without, during the shorebird-nesting season of 2015 in the East Bay Migratory Bird Sanctuary, Nunavut. Artificial nests were distributed evenly across sedge meadow and supratidal habitats typically used by nesting shorebirds. We used the Cox proportional hazards model to assess differential nest survival in relation to camera presence, habitat type, placement date, and all potential interactions. Artificial nests with cameras did not experience higher predation risk than those without cameras. Predation risk of artificial nests was related to an interaction between habitat type and placement date. Nests deployed in sedge meadows and in supratidal habitats later in the season were subject to a higher risk of predation than those deployed in supratidal habitats early in the season. These differences in predation risk are likely driven by the foraging behaviour of Arctic fox (Vulpes lagopus), a species that accounted for 81% of observed predation events in this study. Arctic fox prey primarily on Arvicoline prey and goose eggs at this site and take shorebird nests opportunistically, perhaps more often later in the season when their preferred prey becomes scarcer. This study demonstrates that, at this site, cameras used for nest monitoring do not influence predation risk. Evaluating the impact of cameras on predation risk is critical prior to their use, as individual study areas may differ in terms of predator species and behaviour.

scholarly journals Nestling begging calls increase predation risk by corvids

2019 ◽  
Vol 69 (2) ◽  
pp. 137-155
Author(s):  
Magne Husby
Keyword(s):  
Nest Predation ◽  
Predation Rate ◽  
Artificial Nest ◽  
Auditory Cues ◽  
Artificial Nests ◽  
Breeding Failure ◽  
Nestling Begging ◽  
Real Costs ◽  
Insight Into ◽  
Nest Predators

Abstract Despite nest predation being the most common cause of breeding failure in open-nesting birds, we have little insight into the cues used by nest predators when they search for nests. So far we have assumed that nest-predating birds are visually oriented while mammal predators to a large extent use scent and auditory cues like nestling begging calls. To evaluate how important nestling begging calls are for corvid nest predators searching for nests, I used artificial nests, which made it possible to find the real costs of the begging without mitigation by parental and nestling behavior. I used paired artificial nests, one with and one without nestling begging call playback. Within 10 days, 62.9% of the nests were predated. The analyses showed that nests with begging calls suffered a significantly higher predation rate than nests without begging calls, especially when the nests were placed close to corvid nests. Moreover, nests with begging calls were predated significantly earlier than nests without begging calls. In artificial nest pairs with both nests predated but on different days, nests with begging calls were predated first. In nest pairs with only one predated nest, nests with begging calls were predated most often. This experiment shows that nestling begging calls imply a cost in terms of increased and earlier nest predation, and that corvids use nestling begging calls as a cue to find and depredate bird nests, challenging earlier expectations.

scholarly journals Is it safe to nest near conspicuous neighbours? Spatial patterns in predation risk associated with the density of American Golden-Plover nests

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e2193 ◽  
Author(s):  
Marie-Andrée Giroux ◽  
Myriam Trottier-Paquet ◽  
Joël Bêty ◽  
Vincent Lamarre ◽  
Nicolas Lecomte
Keyword(s):  
Predation Risk ◽  
Spatial Patterns ◽  
Bird Species ◽  
Antipredator Behaviour ◽  
Artificial Nests ◽  
Nest Sites ◽  
Species Of Conservation Concern ◽  
Composition And Structure ◽  
Negative Effect ◽  
Conservation Concern

Predation is one of the main factors explaining nesting mortality in most bird species. Birds can avoid nest predation or reduce predation pressure by breeding at higher latitude, showing anti-predator behaviour, selecting nest sites protected from predators, and nesting in association with protective species. American Golden-Plovers (Pluvialis dominica) defend their territory by using various warning and distraction behaviours displayed at varying levels of intensity (hereafter “conspicuous behaviour”), as well as more aggressive behaviours such as aerial attacks, but only in some populations. Such antipredator behaviour has the potential to repel predators and thus benefit the neighbouring nests by decreasing their predation risk. Yet, conspicuous behaviour could also attract predators by signalling the presence of a nest. To test for the existence of a protective effect associated with the conspicuous antipredator behaviour of American Golden-Plovers, we studied the influence of proximity to plover nests on predation risk of artificial nests on Igloolik Island (Nunavut, Canada) in July 2014. We predicted that the predation risk of artificial nests would decrease with proximity to and density of plover nests. We monitored 18 plover nests and set 35 artificial nests at 30, 50, 100, 200, and 500 m from seven of those plover nests. We found that the predation risk of artificial nests increases with the density of active plover nests. We also found a significant negative effect of the distance to the nearest active protector nest on predation risk of artificial nests. Understanding how the composition and structure of shorebird communities generate spatial patterns in predation risks represents a key step to better understand the importance of these species of conservation concern in tundra food webs.

scholarly journals Signal honesty and predation risk among a closely related group of aposematic species

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Lina María Arenas ◽  
Dominic Walter ◽  
Martin Stevens
Keyword(s):  
Predation Risk ◽  
Related Group ◽  
Signal Honesty
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