The Elements of Evolution (48-10) Hummingbirds

 Competition in Guadalupe Canyon

In the 1870s, “Old Man” Clanton’s cattle ranch was one of the most profitable in the area. The ranch was not much more than a day’s ride out of Guadalupe Canyon, which straddles the Animas Valley of New Mexico and San Bernardino Valley of Arizona, just north of Mexico’s border.

Clanton did not own a brand; a legal requirement for cattle operations. But law was somewhat scarce in these parts. No brand made mixing in cattle smuggled from Mexico a lot easier.

In July 1881, a band of Mexican smugglers headed for Tucson or Tombstone gave up their silver, and their lives, in an ambush in nearby Skeleton Canyon. In the wake of that massacre, the Mexicans dispatched troops.

A few weeks later, on August 13, just after sunrise, a warm wind rustled Clanton, who was asleep on the Guadalupe Canyon floor in his bedroll, along with 6 other men and a stolen herd of cattle. The Mexican troops come upon Clanton and his companions.

Only 2 of Clanton’s men made it out alive to tell the tale. “Old Man” Clanton was as old as he was going to get. He had rustled his last.

The canyon is more peaceful now, humming with life. Literally.

The arid scrub of Guadalupe Canyon is not nectar-rich, but 4 species of hummingbird live there: black-chinned, broad-billed, violet-crowned, and Costa’s hummingbirds, to be precise. The black-chinned hummingbird nests 5 meters up in Arizona sycamores that grow above bare creek bottoms. Violet-crowned hummingbirds live upstairs in the sycamores, at 7 meters. Broad-billed hummingbirds nest low, only a meter or so above ground, preferring the north slope of the canyon, near rocks. Costa’s hummingbirds prefer to nest in the dry arroyo tributaries, adjacent to the main canyon, or on the south side.

As time went by, variation went to speciation. Each found a niche to hang on to.

Only rarely does a battle break out for a choice nectar spot. When that happens, the violet-crowned hummingbird dominates, by aggression and size: 6 grams to the others’ 3 grams.

Outside of insects, hummingbirds have the highest metabolism per weight of all animals; making a fight for nectar all the more understandable.

 Hummingbirds

Everything about hummingbirds is extreme. They have this incredible hovering flight, with wing beat frequencies of 60 times per second, which is nuts. They have the highest metabolic rate for their size of any vertebrate. They are little machines that run on oxygen at a high rate. It is amazing that evolution can take an animal to such extremes. ~ American zoologist Jimmy McGuire

Hummingbirds evolved 22 MYA. There are 338 known extant species in 9 clades.

As nectarivorous pollinators hummingbirds are a classic coevolution: plants willingly feeding animals in return for distance matchmaking between male plants with sperm-bearing pollen and egg-bearing females.

Hummingbirds have flower preferences by color and size, but those preferences can change as opportunities arise.

Hummingbirds are at an extreme in adaptive radiation. As many as 25 species can coexist in the same habitat.

The Andes mountains have been an especial hotspot for hummingbird evolution: speciating with the uplift of those peaks over the past 10 million years.

The smallest bird is the 5-cm bee hummingbird, which weighs only 1.6–2 gram. This tiny hummingbird is endemic to the Cuban archipelago.