Reproductive biology

Loud courtship displays involve male-female chases and vigorous wing-rattling and wing-cracking. They pursue each other, often at lightning speed, weaving around foliage in parabolic arcs and circles. Another stunning component of courtship is the flank display, best developed in the pink-thighed species. For example, when the Cuban tody's display is at its height, its tiny body inflates into a green, neckless fuzzball with bright rosy flank tufts touching mid-dorsally. Simultaneously, this fluffy avian ball hops and bobs rapidly, uttering loud vocalizations to attract the perfect mate. Once paired, a mutual gift exchange of fresh insects occurs, like a bridal couple feeding each other slices of wedding cake.

The first (and rather quaint) published description of tody nesting habits comes from Moritz of Puerto Rico (1836): "In shady trees is seen once in a while the lovely green San Pedrito, rattling hoarsely...The locals believe that it nests in holes in the earth." It is true; todies are burrow-nesters, like their kingfisher cousins. They excavate cylindrical, angled tunnels in vertical soil embankments that are typically low, amphitheater-shaped slippages, roadside cuts, or natural inclines. The most successful burrows are those hewn from moderately overgrown embankments providing soil stabilization and partial concealment from predators.

Fresh tunnels are dug annually, primarily February to May. Each requires about eight weeks. Long, strong tody bills act as chisels to gouge out soil, while their tiny feet scrape away underneath. They tunnel energetically, initially visiting up to 60 times per hour.

Tody eggs are exceptional in the avian world in that they are huge compared to the bird's size. Average egg weights are 26% of the adult's body weight, comparable to the well-known case of New Zealand kiwis. For comparison, egg-to-body-weight ratios of most birds range from 1.8-11%. Normally todies lay only one clutch (average 2.4 eggs), but will re-lay if it is destroyed. Eggs are tiny, white, glossy, and ovate.

Known incubation periods are 21-22 days, while nestling periods are 19-20 days. Each parent spends only two to three daylight hours incubating, a stark contrast to the assiduous kingfishers, which incubate up to seven continuous hours daily. Hatching occurs principally in the late afternoon, with one attendant adult in the nest chamber. Nestlings are naked, bearing conspicuous cushioned heels that cover the feet and legs with thick pads of swollen skin and leathery tubercles, like a baby born with leather boots.

Tody parents may not be over-attentive incubators, but once the chicks hatch they become highly diligent, supplying enormous quantities of insects to the offspring.

Notable also is nest-helping. As of 2001, nest assistance by one or two other adults during incubation and nestling periods is only known in the Puerto Rican tody. Two independent studies concluded that at least 50% of breeding pairs were given assistance. Nests with helpers contained significantly larger clutches (2.9 eggs) than did those without (2.3); chicks also grew quicker and fledged earlier than normal. Nest-helping is especially favorable in rainforests, where torrential rain often limits tody foraging rates. Banding studies suggest that helpers are not young from the previous year, and are likely adults from nearby territories whose breeding activities were curtailed or that did not breed at all. Nest cooperation in todies is unique because there is no apparent genetic relationship between helpers and recipients.

Adult todies use many innovations in teaching independence to newly fledged chicks. Weaning is not easy. Parents sometimes force them to fly by pushing them off perches or hovering in front of them with food in the bill, then pulling away at the last moment. Females are more likely to give in to a hungry chick than males. At times males physically prevent females from feeding fledglings. For the first six weeks, young todies have short black bills and gray bibs whose feathers gradually turn crimson. The entire repertoire of adult behavior is not achieved for several months.

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