In the literal sense, symbiosis means living together. Biologically, symbiotic interactions have been cultivated through evolutionary time and can be beneficial to both symbionts (mutualistic), to one of the partners (parasitic), or neutral to one, yet beneficial to the other (commensal). In life, symbiosis is more of the rule than the exception. For example, root systems are symbiotic with a near neural network of fungi and bacteria, corals and lichen rely on their algal symbionts for energy, and most animals would be nutritionally deficient were it not for the army of symbiotic bacteria and protozoa in their gut. While symbiosis is critical to many ecological systems, few symbiotic relationships are more captivating than those between hummingbirds and flowers.
With 34-36 million individual birds documented throughout North America in 2021, the ruby-throated hummingbird can be easily observed hovering over flowers and snatching airborne mosquitos. Identifying this species is not very difficult. Weighing in at about 3.5 g and 7 to 11 cm (2.8 to 4.3 in) ruby-throats are aggressive mighty-mights that dart about in a competitive rampage to keep members of their type and larger birds away from nectar-rich flowers. Distinguishing males from females is easy because the species is sexually dimorphic. Mature males have a forked tail and an iridescent ruby red patch, known as the gorget, while the larger females have a white throat with streaks of black and a notched iridescent green tail. Despite their diminutive size, this smallest of North American hummingbirds are migratory wonders as they traverse thousands of miles between a breeding range that extends into Canada and the wintering territories throughout Central America.
To cross the continental U.S., ruby-throats need to fuel up before their migration. With a heart rate of up to 1260 beats per minute, a respiratory rate of 250 breaths per minute, and 53 wingbeats per second (3180/minute), these hummers have one of the highest metabolic rates of any animal species. To meet this need, the typical hummingbird must consume 1.5 to 3 times their body mass in nectar and insects every day. So, if you want to see a ruby-throat, you need to find their food.
I’ve been a ruby-throat watcher ever since I discovered their attraction to Impatience capensis. Also known as jewelweed or touch-me-not, the species is a relatively common plant with bright yellow or orange flowers that can be found in ditches and along creeks that feed lakes or rivers. Jewelweed’s nectar-rich trumpet-shaped flowers are a perfect fit for a hummingbird’s long and narrow bill.
Jewelweed and hummingbirds have a coevolved mutualistic relationship in which both species benefit from the interaction. When birds dip their bills to extract some nectar, a bit of plant pollen will attach to the beak. When these ever-hungry birds hover over and visit another flower, they become “flying penises,” as they inadvertently transfer the pollen to a new individual thus facilitating sexual reproduction by the plants. Food for sex,… not a bad deal.
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