Hummingbirds and ornithophilous flowers

Hummingbirds belong to the avian family Trochilidae. They are the most specialized avian nectarivores (Stiles, 1981). The most specialized hummingbirds are very closely tied to the flowers they feed upon in almost every aspect of their biology, and are often very coevolved with a small number of flower species (Stiles, 1981). Coadaptation refers to the degree of ecological interdependence of bird and flower, as well as the degree of morphological correspondence (Stiles, 1981). The most highly coevolved system is one where the flower completely depends on the bird for pollination, and the bird requires the energy provided by the flower for survival (Stiles, 1981). This extreme coadaptation makes the involved species vulnerable (Stiles, 1981).

Flowers

Flowers have converged to take advantage of similar birds (Brown et.al, 1979). Flowers compete for pollinators and adaptations reduce deleterious effects of this competition (Brown et al 1979). Bird-pollinated flowers usually show higher nectar volumes and sugar production (Stiles 1981). This reflects high energy requirements of the birds (Stiles 1981). Energetic criteria are the most important determinants of flower choice by birds (Stiles 1981). Following their respective breeding seasons, several species of hummingbirds co occur in North America, and several hummingbird flowers bloom simultaneously in these habitats. These flowers have seemed to have converged to a common morphology and color (Stiles 1981). Different lengths and curvatures if the corolla tubes can affect the efficiency of extraction in hummingbird species in relation to differences in bill morphology (Stiles 1981). Tubular flowers force the birds to orient its bill in a particular way when probing the flower, especially when the bill and corolla are both curved; this also allows the plant to place pollen on a certain part of the bird’s body(Stiles 1981). This opens the door for a variety of morphological coadaptations.

Birds
An important requisite for attraction is conspicuousness to birds, which reflects the properties of avian vision and habitat features (Stiles 1981). Birds have their greatest spectral sensitivity and finest hue discrimination at the long wavelength end of the visual spectrum (Stiles 1981). This is why red is so conspicuous to birds. Hummingbirds may also be able to see ultraviolet “colors” (Stiles 1981). The prevalence of ultraviolet patterns and nectar guides in nectar poor entomophilous flowers allows the bird to avoid these flowers on sight (Stiles 1981). Two subfamilies in the family Trochilidae are Phaethorninae and Trochlinae. Each of these groups has evolved in conjunction with a particular set of flowers. Most Phaethorninae species are associated with large monocotyledonous herbs and members of the subfamily Trochilinae are associated with dicotyledonous plant species (Stiles 1981).

Conclusion

Hummingbirds and ornithophilous flowers have evolved to form a mutualistic relationship. It is prevalent in the bird’s biology as well as in the flower’s. Hummingbird flowers have nectar chemistry associated with the bird’s diet. Their color and morphology also coincide with the bird’s vision and morphology. The blooming times of these ornithophilous flowers have also been found to coincide with hummingbird’s breeding seasons. When species are closely tied together things that affect one species will affect the other.

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