Conspicuousness, not colour as foraging cue in plant–animal signalling

@article{Schmidt2004ConspicuousnessNC,
  title={Conspicuousness, not colour as foraging cue in plant–animal signalling},
  author={Veronika M. Schmidt and Hinrich Martin Schaefer and Hans Winkler},
  journal={Oikos},
  year={2004},
  volume={106},
  pages={551-557}
}
The global prevalence of red and black fruits has still not been explained. Hypotheses based on innate consumer preferences have been tested and rejected. Though colour itself plays an important role in animal foraging, it is only one component of signals. Another major component are colour contrasts against background achieving the conspicuousness of signals. In order to evaluate which signal component determines consumers behaviour, we measured fruit colour and colour contrasts of 43 species… 

Figures from this paper

Signals of profitability? Food colour preferences in migrating juvenile blackcaps differ for fruits and insects
TLDR
The results provide evidence that wild, frugivorous birds are able to differentiate between prey types, and show different colour preferences depending on whether food is insect or fruit, and that blackcaps show an attack bias against red insects.
Bird fruit preferences match the frequency of fruit colours in tropical Asia
TLDR
It is demonstrated that all birds favored red artificial fruits more than yellow, blue, black and green, although the artificial black colour was found subsequently to be similar to the artificial blue colour in its spectral reflectance.
Detectability and content as opposing signal characteristics in fruits
TLDR
Plants may employ differential signalling strategies matching conspicuous signals in red and black fruits while other colours signal fruit quality, which implies that nutrient quality and fruit defence are communicated visually.
Red flowers differ in shades between pollination systems and across continents
TLDR
Shades of red flowers differ between pollination systems and red bird flowers are more specialized in the New World than in the Old World, suggesting the evolution towards colour specialization is more likely to result in higher efficiency of bee avoidance than bird attraction.
Unlearned preference for red may facilitate recognition of palatable food in young omnivorous birds
TLDR
Unlearned colour choices by consumers should be interpreted in a broader context of foraging and not only to explain warning coloration, as red colour is a contextdependent stimulus and might facilitate food recognition in inexperienced fruit-eating birds.
Fruit colour and edge effects poorly explains frugivorous bird-plant interactions in disturbed semideciduous forests
TLDR
The findings indicate that colour and edge effects, as well as the interaction between them, may not be strong predictors of fruit choice by birds in disturbed environments, especially because generalist species, which are less sensitive to the physical alterations in forests, are favoured in these areas.
Are Fruit Colors Adapted to Consumer Vision and Birds Equally Efficient in Detecting Colorful Signals?
TLDR
It is suggested that passerines with ultraviolet cones might primarily use epigamic signals that are less conspicuous to their avian predators (presumably with violet vision) and possible examples for such signals are carotenoid‐based signals.
Geographic patterns in fruit colour diversity: do leaves constrain the colour of fleshy fruits?
TLDR
The results suggest that fruit colours in the tropics are neither more diverse nor more conspicuous than temperate fruits, and that Fruit colours may be influenced by correlated selection on leaf reflectance properties.
Adaptation of flower and fruit colours to multiple, distinct mutualists.
TLDR
The colour conspicuousness of flowers and fruits originating from one European and two South American plant communities is quantified, providing the first quantitative demonstration that flower and fruit colours are adaptations allowing plants to communicate simultaneously with distinct groups of mutualists.
Signal convergence in fruits: a result of selection by frugivores?
TLDR
Fruit colour convergence in unrelated plants is independent of phylogeny and can be better explained by disperser type, which supports the hypothesis that frugivores are important in fruit evolution.
...
...

References

SHOWING 1-10 OF 41 REFERENCES
The role of fruit colour in avian fruit selection: an objective approach
TLDR
Black and red fruits are the most conspicuous fruits, and Birds choose more contrasting displays, and conspicuousness influences fruit choice, and fruit colours seem to be an advertisement for ripe fruits.
The Evolution of Fruit Color in Fleshy-Fruited Plants
TLDR
13 nonexclusive hypotheses that may contribute to the observed frequency distribution of fruit colors are presented and a preliminary assessment of these hypotheses is made, in a preliminary way, using existing information.
Foliage color contrasts and adaptive fruit color variation in a bird-dispersed plant community
TLDR
Testing the hypothesis that fruit color varies temporally, to maximize conspicuousness against seasonal changes in foliage coloration, in a bird-dispersed plant community in western North America suggests a temporal connection between fruit color diversity, foliage color contrasts and avian color preferences.
Fruit color choices of captive silvereyes (Zosterops lateralis)
TLDR
The overall fruit color preferences of Silvereyes were based on selection of hue rather than brightness, but within the same hue, some individuals exhibited preferences for particular brightness levels.
Ecology of the fruit-colour polymorphism in Rubus spectabilis
TLDR
The need to investigate fruit and seed characteristics that correlate with fruit colour is emphasized; the colour preferences of consumers is only one of several selection pressures that determine the frequency distribution of fruit colours.
Avian selection of the color-dimorphic fruits of salmonberry, Rubus spectabilis : a field experiment
TLDR
This is the first field study demonstrating significant and consistent fruit-trait selection by birds at a scale relevant to coevolutionary processes and indicates that forces other than animal selective pressure are also shaping the occurrence of fruit color traits in bird-dispersed fruiting plants.
Colors of Fruit Displays of Bird-Dispersed Plants in Two Tropical Forests
TLDR
A model of fruit color is proposed suggesting that there is a cost of bearing conspicuous color patterns, either in attracting inappropriate consumers to the fruit or in manufacturing pigments or associated structures, which should be selected for increased conspicuousness of fruit display.
Foliar ‘flags’ for avian frugivores: signal or serendipity?
TLDR
Two hypotheses relating autumn leaf-color to fruit color (Kerner, 1895) and to potential avian consumption (Stiles, 1982) are tested and experimental data are discussed, using data from east-central Illinois.
On the measurement and classification of colour in studies of animal colour patterns
TLDR
New methods make it practical to measure the colour spectrum of pattern elements (patches) of animals and their visual backgrounds for the conditions under which patch spectra reach the conspecific's, predator's or prey's eyes.
Color Preferences of Frugivorous Birds in Relation to the Colors of Fleshy Fruits
TLDR
It is suggested hat avian color preferences may not provide strong selection favoring the evolution of the common fruit colors, and that the frequency distribution of fruit hues is best explained in other ways.
...
...