Very few organisms consume nectar exclusively over their whole life cycle, either supplementing it with other sources, particularly insects (thus overlapping with insectivores) or only consuming it exclusively for a set period. Many species are nectar robbers or nectar thieves, performing no pollination services to a plant while still consuming nectar. Nectar-feeding is widespread among birds, but no species consumes nectar exclusively. Most combine it with insects for a mixed diet. Of particular interest are four lineages of specialized nectar consuming birds in the New World: the Hummingbirds (Trochilidae) and three members of the Tanager (Thraupidae) family; Bananaquits, Flowerpiercers and Honeycreepers. These groups have adapted to permit a nectar-central diet, showing higher activity of digestive enzymes which break down sugars, higher rates of absorption of sugars, and altered kidney function. Birds need the enzyme sucrase in their bodies, in order to digest the sucrose of nectar. And most simply don’t have enough. Scientists think birds that can readily digest sugar, like warblers, have an adaptive advantage. When they fly to the tropics for the colder months, they can tap into sources of sugar that other birds just can’t handle. That sweet tooth, it turns out, is important to their survival.
Occasional Necter Feeders
Orioles are known for raiding hummingbird feeders, but they’re not the only ones. Woodpeckers, House Finches and other species tend to invade hummingbird feeders for a chance to drink the sweet nectar. In the wild, House Finches will eat flower buds and parts but not nectar specifically mostly due to the size and shape of the bill. Orioles will eat nectar in the wild and also flowers and buds. Woodpeckers share a characteristic with hummingbirds, a long tongue that can fit into the feeder’s opening. This is used in the wild to probe for insects and sweet tree sap.
The Bananaquit inhabits a variety of habitats from scrubland to tropical lowland forest edge, from the Antilles and Mexico south to Paraguay and northern Argentina. It is the most abundant and productive bird in Trinidad at all altitudes. The bananaquit is known for its ability to adjust remarkably to human environments. It often visits gardens and may become very tame. The bananaquit has a slender, curved bill, adapted to taking nectar from flowers. It sometimes pierces flowers from the side, taking the nectar without pollinating the plant. It also feeds on sweet juices by puncturing fruit with its beak, and will eat small insects on occasion. While feeding, the bananaquit must always perch as it obviously cannot hover like a hummingbird. However, the Bananaquit is extremely good at clinging, with a strong grip and combined with its small size is able to exploit smaller flowers that hummingbirds might find uneconomical due to the energy required to hover vs clinging by the Bananaquit. The short sharp slightly curved bill is of the Bananaquit is adapted for rapid probing from a perched position into a number of flowers clustered together, a feeding method for which the longer curved beaks of Honeycreepers are not suited.
It has proved difficult to classify these nectar eating birds and particularly the Bananaquit. The Bananaquit was first described by Linnaeus in his Systema Naturae in 1758 as Certhia flaveola. It was reclassified as the only member of the genus Coereba by Louis Jean Pierre Vieillot in 1809. Prior to 2005, the Bananaquit was assigned to the monotypic family Coerebidae. The Bananaquit is part of a group that includes Darwin’s finches, Tiaris (grassquits) and Antillean Bullfinches (Loxigilla) most of which were previously placed in the Buntings (Emberizidae), but are now known to actually be part of the Tanangers (Thraupidae) and for the time being the Bananaquit is thus placed in the Tanagers. The Bananaquit has currently 41 recognized subspecies which differ in throat color (white, grey or black), white wing spot visible or not, bill length, gape flange color and extent of yellow on the underparts. Some versions have a dark morph. Bananaquits are recorded to feed from over 50 species of flowers. Of these, 32 were large trees (5 introduced), 7 were small trees or shrubs (2 introduced), 7 were vines, and 4 were herbaceous plants.
Pollination by passerine birds such as the Bananaquit in Central America may be complementary to hummingbird pollination in some habitat types, such as the dry tropical lowlands, where hummingbirds are relatively poorly represented. Stiles and Stiles (1999) found 3 bromeliads (Aechmea bromeliifolia, Aechmea distichantha and Acanthostachys strobilacea) that were effectively co-pollinated by Bananaquits. They expect that additional Aechmea species and other related bromeliads with short corollas would be co-pollinated by the Bananaquit, especially in disturbed sites and other forest localities where hummingbird diversity is low, as is the case in several areas in southeastern Brazil. Snow and Snow (1971) found that Aechmea nudicaulis was also pollinated by Bananaquits in Trinidad.
An equally important source of protein for the Bananaquit appears to be the protein corpuscles (Mullerian bodies) at the base of the petioles (stalk that attaches a leaf to the plant stem) of Cecropia peltata, a fast-growing tree of the secondary forest. Protein corpuscles are tiny white granules provided by the tree for the Azteca ants that live symbiotically within its trunk and branches, and are rapidly renewed by the tree when they have been eaten, since the Azteca ants and Cecropia tree have a symbiotic relationship. (Snow and Snow 1971) As far as I know, the Bananaquit is the only bird to utilize this source of food.
Honeycreepers used to be classified in a separate family with the Bananaquit and Flowerpiercers, but are now part of the Tanager family. Tanagers display more colors and color patterns than any other tropical American bird and Honeycreepers definitely fit this profile. All “true honeycreepers” are in the tanager family, but the several different species fall in three different genera. The green honeycreeper is of the Chlorophanes genus, while another species falls under Iridophanes and four more species fall under Cyanerpes. And finally, the Hawaiian honeycreepers fit in an altogether different family tree. One more thing to clear up about honeycreepers is a common misconception about the color of their eggs. Back in 1899, Adolph Nehrkorn published an egg catalog which claimed that honeycreepers lay black eggs. A black egg would certainly be an unusual color for any bird species. In the 1940s finally revealed that, no honeycreeper species actually lay black eggs. They’re pale and speckled like most bird eggs. In this post I will focus on the three Honeycreepers seen above in Costa Rica and Trinidad.
The Red-Legged Honeycreeper (Cyanerpes cyaneus) inhabits a variety of habitats from scrubland to tropical lowland forest edge, from southern Mexico south to Peru, Bolivia and central Brazil, Trinidad and Tobago. This is a species of forest edge, open woodland, and cocoa and citrus plantations, semi-open areas with scattered trees, open woodlands and clearings. The red-legged honeycreeper is often found in small groups. The red-legged honeycreeper is on average 12.2 cm (4.8 in) long, weighs 14 g (0.49 oz) and has a medium-long black, slightly decurved, bill. The male is violet-blue with black wings, tail and back, and bright red legs. The crown of its head is turquoise, and the underwing, visible only in flight, is lemon yellow. After the breeding season, the male molts into an eclipse plumage, mainly greenish with black wings.
The Red-Legged Honeycreeper breeds from February to June. The nest is a small, thin, hemispheric cup, composed of fine fibers, rootlets, grass and flowers, is placed 10–45 feet (3–14 m) up amid foliage of slender branches. The female builds a small cup nest in a tree, and incubates the clutch of two brown-blotched white eggs for 12–13 days, with a further 14 days to fledging. The immature male looks funny but soon transforms into a beautiful male.
Red-legged Honeycreeper seeks nectar and small insects in flowers. It feeds on ripe fruits, pulp and seeds, taken into the fruit, thanks to the long slender bill. It examines the underside of small twigs and leaves, in order to catch small invertebrates.
The interaction between the red-legged honeycreepers and the flowering trees is a mutualistic bond. The small birds gain food from the flowers whilst in return the birds play the role of pollinators. The pollen from the flowers will reside on the plumage of the birds enabling them to be transported to other plants. Apart from the plant foods, they also feed on small insects. Due to their sharp eyesight they have ability to the see the tiniest of insects on the underside and crevices of branches and twigs as well as ambush the insects when they are approaching the flowers. Red-legged Honeycreepers extract nectar from the flowers of Inga, Calliandra and other legume plants. They also eat small insects, arillate seeds and many other fruits in fairly open edgy areas. These birds tend to wander in non-breeding groups after breeding season. They are not long distance migrants.
The Purple Honeycreeper (Cyanerpes caeruleus) is a small and common bird in the tanager family. It is found in the tropical New World from Colombia and Venezuela south to Brazil, and on Trinidad. The species is a bird of northern South America, and besides the Amazon Basin and the Guianas, a coastal range occurs west of the Andes, including parts of southern Panama. In the south, its range extends to the extreme western Pantanal. Though it is most frequently seen in the lowlands up to 3,300 ft (1,000 m) ASL or so, it has been encountered as high as 7,500 ft (2,300 m). The Trinidadian subspecies C. c. longirostris has a longer bill than the mainland forms.
The female purple honeycreeper builds a small cup nest in a tree, and incubates the clutch of two brown-blotched white eggs. Juveniles are very similar to the adult female. The breast, belly, and flanks are more plain, and the blue malar (streak below the eye) may be absent. Immature males in transition to adult plumage can contain numerous variations, with green backs but black lores and throat, or also with black wings and tail, or mottled wing and body plumage as they ultimately transfer from green to bluish-purple. Breeding has been reported in April to June in Trinidad and October to December in Brazil.
Honeycreepers are nectar specialists, but the Purple Honeycreeper also uses the long curved bill to pierce fruits to suck the juice. The Purple also eats insects and small berries.
The Purple Honeycreeper is the smallest of the four true honeycreepers and has the longest, most slender and most curved beak. The beak is probably adapted not only to eating nectar, of which the purple honeycreeper takes more than the other three species but also to its particular method of insect hunting. The purple honeycreeper takes a smaller percentage of fruit than the other Honeycreepers, and it’s narrow bill probably prevents it from including many of the fruits the other species eat. Miconia fruits are probably near the upper size limit for purple honeycreepers which they have been recorded eating frequently. They are known to consume the fruits of Trema micrantha (Cannabaceae) in Trinidad (Snow and Snow 1971). A detailed and systematic record of the feeding behavior of tanagers in Trinidad recorded a number of species of fruits consumed by the Purple Honeycreeper, including Wulffia baccata (Asteraceae), Ficus clusiifolia (Moraceae), three species of Euphorbiaceae (Sapium aucuparium, Hieronyma caribaea, and Alchornea glandulosa), a Loranthaceae sp., Miconia sp., Myrcia sp., and Clusia sp. (Snow and Snow 1971). You can see most of these fairly small fruits above. The Purple Honeycreeper also will pierce larger fruit like oranges and tangerines with its slender bill and suck the juices out.
The Green Honeycreeper (Chlorophanes spiza) is found in the tropical New World from southern Mexico south to Brazil, and on Trinidad. It is the only member of the genus Chlorophanes. The green honeycreeper is 5–5.5 inches (13–14 cm) long and weighs 14 to 23 grams, averaging about 19 grams. It is less heavily dependent on nectar than the other honeycreepers, fruit being its main food (60%), with nectar (20%) and insects (15%) as less important components of its diet. The green honeycreeper is 5–5.5 inches (13–14 cm) long and weighs 14 to 23 grams, averaging about 19 grams. It has a long decurved bill. The male is mainly blue-tinged green with a black head and a mostly bright yellow bill. The apparent color of the male changes from blue-green to green-blue according to the lighting.
This is a forest canopy species. The female green honeycreeper builds a small cup nest in a tree, and incubates the clutch of two brown-blotched white eggs for 13 days. It is less heavily dependent on nectar than the other honeycreepers, fruit being its main food (60%), with nectar (20%) and insects (15%) as less important components of its diet. Immature are plumaged similar to females with blotches of the blue-green colors to come.
The female green honeycreeper is grass-green, paler on the throat, and lacks the male’s black head. Both male and females have a shiny iridescence. Even though there were many insects at the fruit feeders at the Asa Wright Nature Center, I only saw the Green Honeycreepers eating the insects.
Fruit forms a major part of the Green Honeycreepers diet. All of the Trinidad Miconia species are of suitable size for it to take whole. It takes nearly all fruit from a perched position and eats it whole, but it also pulls off pieces from fruits of Protium Heptaphyllum which are almost certainly too big for it to swallow. It was also seen to chew and drop Ficus tobagensis/Ficus yoponensis taht are about 3/4” in diameter. The Green Honeycreeper has a specialized technique of insect-catching not seen in the other Honeycreeper species. More than half of the insect-searching records were at flowers, mainly tree flowers with long stamens that attract insects. Green Honeycreepers perch among such flowers and dart about catching small insects that come to them, usually snapping them up in flight. For this their beaks are well adapted, being wide at the gape. Green Honeycreepers occasionally take nectar from the same kinds of flowering trees, e.g. Eugenia jambos, Calliandra guildingii, Inga species and Zanthoxylum species. (Snow and Snow 1971)
Seasonality of Nectar and Flowers in Trinidad
“The proportion of nectar taken varies most during the year, owing to the fact that 80 per cent of the nectar (according to our records) is taken from only three species, the introduced but now widespread tree Erythrina micropteryx, the native tree Symphonia globulifera and the vine Norantea guianensis. These all flower mainly in the last 3 and first 3 months of the year, the latter being the main dry season. Fewest fruits ripen during the dry season, and the honeycreepers take the lowest proportion of fruits then. For the rest of the year, from April to December, fruit-eating remains at a high level, accounting for at least half the feeding record.” Snow and Snow 1971
The seasonal variation in nectar-feeding by the honeycreepers is in contrast to the stable seasonal pattern for the Bananaquit, for which nectar-feeding provided about 75 per cent of the records throughout the year. The Bananaquit exploits far more different kinds of flowers than the Honeycreepers, including many small ones, and many of them are in flower at all seasons. In general the trees with large flowers bloom during the dry season and those with small flowers during the wet season (Snow and Snow, 1964).
The Evolution of Flowers and Co-Evolution
It is thought that flowering plants first appeared sometime between 250 and 140 million years ago. The origin of flowering plants and their rapid conquest of the world’s habitats has been a puzzle for nearly a century and a half. In 1879, Charles Darwin described it as an “abominable mystery” that flowers had evolved so late in the history of life yet were still able to take over from the more ancient seed-bearing pines and cycads. While hummingbirds and insects are well known pollinators of flowers, Bananaquits and Honeycreepers can accomplish the same functions for the plants and possibly extend the growing range of some plants like bromeliads. The co-evolution of Bananaquits and Honeycreepers puts the amazing resiliency of nature’s ecosystems on display in beautiful form.
As always, I hope you enjoyed the post. I am indebted to the hard work of Barbara and DW Snow for their groundbreaking study of feeding patterns of Tanagers and Honeycreepers in Trinidad in 1971.