Do Contrastingly Colored Unripe Fruits of the Neotropical Tree Ardisia nigropunctata Attract Avian Seed Dispersers?

Abstract

Visual cues in fruit displays from foliage, accessory structures, and ripe fruit color are known to be important in attracting bird seed dispersers to ripe fruit, but the role of color in unripe fruit has not been thoroughly studied. Here, we tested the effects of unripe fruit presence and fruit abundance by offering fruit of a Neotropical tree, Ardisia nigropunctata (Myrsinaceae), in bunches of mixed unripe and ripe fruit and bunches of all‐ripe fruit. Additionally, foraging bird species identification and behavior information was collected. Contrary to expectation, birds removed more fruit from all‐ripe bunches with the most fruit than from contrastingly colored fruit bunches. We therefore discuss alternate explanations for unripe fruit colors in mixed bunches.

Bicolored display ofMiconia albicansfruits: Evaluating visual and physiological functions of fruit colors

“…In contrast, fruit removal was higher in infructescences with only green, ripe fruits of Pistacia terebinthus compared with treatments that offered red, unripe and green, ripe fruits together in the same infructescence (Fuentes, 1995). Amsberry and Steffen (2008) found higher fruit removal by birds in infructescences with only red, ripe fruits than when combined with white and pink, unripe fruits of Ardisia nigropunctata . Finally, Burns, (2005) also found no preference for experimental bicolored display in Rubus spectabilis .…”

“…Since unripe, reddish fruits did not influence the probability that infructescences were detected by birds, the higher fruit removal in infructescences with only ripe fruits is probably related to the higher number of ripe fruits available in this treatment. Instead of serving as a communicative function, the bicolored display of M. albicans could be related to limited resources for synchronous fruit maturation or to a sequential anthesis strategy in the inflorescence, conferring asynchronous fruit ripening in the infructescence (see also Amsberry and Steffen, 2008).…”

“…Second, only the number of fruits removed was compared between treatments, without considering the detection of infructescences. Third, the experimental design used by these studies differs among them, with infructescences being paired or randomly distributed, and with variations in the number of fruits of different colors offered in each experimental infructescence (e.g., Willson and Melampy, 1983; Amsberry and Steffen, 2008). Finally, in most studies fruits that drop beneath the infructescences are often not differentiated from those actually removed by birds.…”

Hiding in plain sight: experimental evidence for birds as selective agents for host mimicry in mistletoes

“…While seven different species of non-specialist birds were observed visiting the mistletoes, they favoured intact mistletoes, unlike the specialist Mistletoebird, which demonstrated no visitation preference. For non-specialists, potentially in search of foods other than fruits, this visitation pattern suggests that they rely primarily on canopy density or other holistic visual cues when seeking mistletoe, with a defoliated or unhealthy looking plant signalling poor quality fruits and poor forage available to the birds (Amsberry and Steffen 2008).…”

“…Here we used defoliation to increase mistletoe crypsis within host canopies and evaluate the effect on seed dispersal, estimated by comparing bird visitation (after Watson 2012). Few studies have used artificial manipulation of plants to test visual search image hypotheses (but see Amsberry and Steffen 2008). This study uses a novel technique to test the effects of visual disturbance (mistletoe with or without foliage) on foraging bird search patterns and the potential use of a mistletoe-based search image.…”