4.4 Competition for resources in Huevos de Caballo
In Table 4 I have noted the number of antagonistic observations that were made, the aggressor and the target, and again noted the length of each bird in brackets. As previously noted, in Huevos de Caballothe number of seed husks that contained edible (and accessible fruit) was limited at any time. Thus, it could be expected that antagonisms and competition would be more
frequent. There were indeed more frequent instances of antagonism, and in most instances the aggressor was the larger bird. However, there were four instances where the aggressor was smaller — both antagonisms by the Lesson’s Motmot, the antagonism of Great Kiskadee toward White-winged Dove, and the antagonism by Red-legged Honeycreeper toward Yellow-green Vireo. There was also one instance in which the aggressor and recipient were the same length.
While there were more antagonisms in the Huevos de Caballos I studied, nevertheless given that out of 299 feeding observations I observed only 11 instances of antagonism and displacement, they were still comparatively rare. In this respect my observations are consistent with those made by McDiarmid et al. (1977) that interspecific displacements are rare.
While one might impute these antagonisms to the relative belligerence of each species (some flycatchers are known to be especially pugnacious), there might be an alternative explanation. Looking at Table 4 and back to my notes, I find that after the Yellow-green Vireo had fed it was chased by a pair of Red-legged Honeycreepers, which subsequently fed themselves (presumably on the same fruits). Thus, it took two birds to dislodge one. In the two cases of Lesson’s Motmot aggressive behavior, which occurred on the same day, the motmot chased away the Hoffmann’s Woodpecker, after the woodpecker had fed; later, while it was itself feeding, the motmot chased away a Baltimore Oriole which flew in attempting to feed. The first situation of the Great Kiskadee is even more complicated. According to my notes, both the White-winged Dove and the Great Kiskadee had been feeding (presumably on different fruits) prior to the altercation. With regard to the antagonistic behavior toward the Clay-colored Thrush, the Great Kiskadee had been feeding before it chased the Clay-colored Thrush away. Thus, excepting the situation where a pair of birds dislodged a larger bird, there does not seem to be enough evidence to support an alternative explanation, other than that of an innate belligerence of a species, although further study is clearly needed.
[ On March 3, 2022 I observed intraspecific antagonism. A female Red-legged Honeycreeper was perched on a hanging (vertical) branch, which enabled it to reach sideways and feed on an openedHuevos de Caballo fruit. When a second female Red-legged Honeycreeper came down the branch to also feed from that fruit, the first female aggressively chased it away. This is the only intraspecific antagonism I ever noted in either tree].