Photo: © Shutterstock.com/Jonathan Chancasana. Giant hummingbird: on a quick view, this bird can be mistaken for a swallow!
Here is a bird that has to be seen to be believed, says BILL NAYLOR, so why have zoos stopped keeping the sword-billed hummingbird and other notable members of its family? In this article he describes the species’ remarkable adaptation to a remarkable lifestyle.
THE 320 or so species of hummingbirds range in size from the 5cm (2in) long bee hummingbird (Mellisuga helenae) from Cuba – the smallest warm-blooded animal – to the giant hummingbird (Patagona gigas) of the Andes, which is the size of a starling. Hummingbirds also feature a variety of beak shapes, as revealed by the names fiery-tailed awlbill (Avocettula recurvirostris), white-tipped sicklebill (Eutoxeres aquila) and mountain avocetbill (Opisthoprora euryptera), which, as you would guess, possesses a beak that curves upwards.
Hummingbird’s beaks often vary in length, too. The medium sized starthroats have some of the longest beaks among hummingbirds but none are as aberrant as the sword-billed hummingbird (Ensifera ensifera), which is found extensively in the Andean chain from Venezuela to Bolivia.
This bird’s bill isn’t only extraordinary among hummers, it’s the most extreme of any bird. The little hummingbird is joined to a 10cm (4in) long rapier-type beak that is longer than its body and tail put together. Youngsters start off with a normal small beak, then, like Pinocchio, it grows faster than they do. Both sexes are equipped with the oversized bill, along with an elongated tongue to match.
The female is distinguished by her white-spotted throat but both sexes are an impressive iridescent green – and almost the same in body size as the giant. However, neither are as fast as the smaller hummingbirds, which can accelerate so swiftly that you momentarily lose sight of them.
Hummingbirds have the highest metabolism of any animal, other than insects, which is seven times that of a similar sized bird. Their heartbeat has been measured at 1,260 beats per minute. To fuel their metabolism they have become sugar junkies, feeding on plant nectar composed of glucose, fructose and sucrose. Plants are rewarded for feeding these hyperactive birds, because they inadvertently gather pollen on their beaks and facial feathers, and unwittingly pollinate their flowers.
The sword-bill’s beak is designed to reach inside the long trumpet-shaped blooms of species such as the passion flower (Passiflora mixta). Insects found in the flower’s deep, dark funnel are also eaten. The hummer usually approaches the drooping flowers from below and probes its beak upwards into the funnel of the flower, rather like a plane refuelling in mid-flight. A hummingbird’s tongue was always thought to obtain nectar by capillary action, but it’s now known to act more like a pump.
Like other hummingbirds and their food plants, the sword-billed and its flowering vine have evolved together. Hummingbirds feed mainly on the red and pink flowers, selecting those that provide nectar with a high sugar content.
When hummingbirds were first kept in captivity, it was believed that all they required was diluted sugar. Consequently, captive hummingbirds were not long-lived. In fact, hummingbirds and all nectarivores acquire most of their protein and vitamins from a wide variety of insects. Similar to the giant hummingbird, the sword-billed’s favourite invertebrates are spiders, which they are adept at probing out of crannies and holes.
The base of the sword-billed’s beak has a type of hinge which bends, enabling the bird to catch more food when there are groups or swarms of flying insects. Although lightweight, its beak is obviously cumbersome.
No bird can preen its head and throat, but the sword-bill’s beak is too long to preen any part of its plumage. Instead it uses its very small feet. Some hummingbird species grip flower petals with their sharp toenails, but most don’t use their feet much.
Preening takes up so much of a sword-billed’s time, as anyone who has observed this bird for any length of time in the wild or captivity will know. One in my care spent so much time preening I suspected it possibly had a problem with mite or some other external parasites.
This species, therefore, has to make sure it has clearance when it perches and flies. In captivity, among other birds, it constantly looks around nervously. In these situations it often perches with its head and beak raised upwards, also roosting in this position. It will build a suspended nest and feeds its young by perching above this.
Hummingbirds are found from Alaska to southern South America, with the greatest species diversity in the tropics. Ecuador boasts the highest concentration of species. This is a successful family of the high Andean mountains, where night-time temperatures drop to freezing. Like swifts, their closest relatives, hummers are able to slow their metabolism, and become torpid when temperatures fall, as though hibernating overnight. They can also do this as a precaution when food is scarce or they are in poor condition.
The heyday of hummingbirds in captivity was in the 1950s, mainly because there was no restriction on export from their country of origin. During that period 26 species were exhibited at Bronx Zoo, New York, including the sword-billed. In the 1980s Wuppertal Zoo and Walsrode Zoo, both in Germany, kept sword-billed and bred a number of other species.
Hummingbirds, especially large ones such as the sword-billed, can be exhibited with other birds, such as tanagers, honeycreepers and cotingas. Like the giant hummingbird, the sword-billed can live in harmony with even small birds sharing its enclosure, but it won’t tolerate other hummingbirds. There has been some success mixing butterflies and hummingbirds in exhibits. Sword-billed would not be suitable, however, because they chase down butterflies and moths.
In total, 20-30 species of hummingbirds were, at one time, available here. Those of the genus Amazilia were the most commonly kept but due to the difficulties involved in pairing, males were mainly kept for the show bench.
Here, hummingbirds are often able to spend time in outside aviaries. Far from being fragile, many are robust and long-lived once established. They have lived for 10 years in captivity – and have survived just as long in the wild.
Hummingbirds regularly bathe, or fly through water spray, even water from garden hoses and sprinklers. Their plumage soon suffers if they aren’t sprayed or don’t have bathing water. Sword-billed prefer a receptacle and bathe several times a day, after which they preen extensively.
Roughly 10 species have been bred in the UK. The sword-billed has never been captive bred. Some species such as streamertails (Trochilus) have been successfully kept in groups, but most hummingbirds are kept in pairs and the sexes segregated until birds are in breeding condition and compatible.
San Diego Zoo exhibits more than 100 hummingbirds and breeds about half a dozen species annually. Many zoos that previously kept hummingbirds no longer do so. Those that do keep only one or two species. This maybe due to the care regarding compatibility between the sexes.
Hummingbirds have very large brains and accounts of intelligent behaviour are numerous. It is a pity that zoos no longer regularly exhibit hummingbird species to illustrate the variety that occurs in the largest non-passerine bird family. Unfortunately, when exhibited on its own, the sword-billed hummingbird is often viewed as a freak, an avian oddity, instead of the most brilliantly adapted of all the nectar feeders.
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