Cardinal Flowers are to Ruby-throated Hummingbirds what Goldenrod is to Honey Bees in the fall — an important source of nutrients just when it’s needed most. Just as hummingbirds are preparing for their migration south and nearly doubling their weight (from about 3.25 grams to 6 grams) before crossing the Gulf of Mexico, Cardinal Flower blossoms. A single migration can mean a nonstop flight of up to 500 miles over a period of 18 to 22 hours and nectar such as they obtain from Cardinal Flower helps sustain them. This relationship is not one-sided however – it is mutually beneficial for both the bird and the plant. In acquiring nectar from the blossoms of Cardinal Flower, hummingbirds inadvertently perform a crucial task, that of pollinating many of the flowers they visit.
The blossoms of Cardinal Flower have two phases. In one the male reproductive part of the flower (the white “moustache” you see above the petals) matures and produces pollen. After the male structure matures and disappears, the female reproductive part develops and extends out from the same place where the male flower was. The flower parts mature at different times in different flowers on a given stalk, so both male and female flowers are present on the same plant at the same time. In order to reach the nectar from Cardinal Flower, a hummingbird must get into a position where the top of its head brushes against the flower’s reproductive parts. If the flower is in the male phase the hummingbird’s head gets dusted with pollen (see inset). If the flower it visits is in the female phase, the pollen on its head (from previous visits to male flowers) is deposited on the stigma of a female flower, pollinating the flower.
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The Morse Code tapping of Yellow-bellied Sapsuckers has just started reverberating in northern New England woodlands once again – a sure sign of spring. There is an interesting relationship between sapsuckers and hummingbirds, with hummingbirds reaping most of the benefits. It is thought that the Ruby-throated Hummingbird may time its migration north to coincide with that of the Yellow-bellied Sapsucker in some areas. In northern New England, hummingbirds arrive on their breeding grounds about a month after sapsuckers, insuring that sapsucker-drilled sap wells will be waiting for them. The reason this is important is that these wells are an important source of nutrients (both sap and insects attracted to it) for hummingbirds as well as sapsuckers. In addition, and not surprisingly, hummingbirds often place their nest near sap wells. This affinity for sap continues well past the nesting season – – hummingbirds have been observed following sapsuckers throughout summer days. (Photo: male Yellow-bellied Sapsucker & male Ruby-throated Hummingbird)
The phenomenon of North American birds being killed by becoming entangled in Common Burdock (Arctium minus) has been documented since at least 1909, when one observer (in A.C. Bent’s compilation) described finding a multitude of Golden-crowned Kinglets in Common Burdock’s grasp:
They were visible in all directions, scores of them sticking to the tops of the clumps on the most exposed clusters of heads. The struggle had ended fatally for all that I saw, and its severity was evidenced by the attitudes of their bodies and the disheveled condition of their plumage. I examined a number of the burdock heads to determine that attraction had brought the kinglets within range of the hooks, and found insect larvae of two species present in considerable abundance.
Typically this phenomenon involves birds that are seeking either insects that are inhabiting the seed heads, or burdock seeds. The birds’ feathers get caught by the hooked bracts (modified leaves) that surround both the flower heads and seed heads of burdock. Small birds such as kinglets, gnatcatchers, goldfinches, nuthatches, hummingbirds, chickadees, warblers and siskins are the usual victims, but larger birds, including a Blue-headed Vireo and a Barn Swallow, have been caught as well. Most of these birds were found with their wings and tail spread, and caught by many parts of their bodies. The more they struggled, the more their feathers became entangled. Victims are not limited to birds — in 1925, a dead bat was discovered caught in a patch of burdock. (Photo by and thanks to Holly Brough)
Anyone with a hummingbird feeder knows that finally female and juvenile Ruby-throated Hummingbirds can feed without fear of being driven off by male hummingbirds, due to the fact that the males have, for the most part, headed for warmer climes. All summer the males do their very best to have sole occupancy of feeders. When the time for hummingbirds to migrate south arrives in the Northeast, males leave first, then females, and lastly, juveniles. The fall migration of hummingbirds occurs just at the time of peak of Spotted Jewelweed (Touch-Me-Not) flowering, suggesting this flower is an important nectar source during this time and may influence the timing of migration. Many of the hummingbirds visiting feeders now are migrants.
Equality of the sexes has yet to reach some avian species. Among them is the Ruby-throated Hummingbird, the only species of hummingbird that breeds in the Northeast. After courtship and mating takes place, the male has next to no contact with his mate(s), possibly visiting them during nest construction, but he does not lift a feather to assist in raising their offspring. By herself the female selects a nest site, builds a nest (six to ten days), lays two eggs, incubates the eggs (12 – 14 days), broods them (9 days), removes their waste, or fecal sacs, for the first two days (after which the nestlings eject their droppings from the rim of the nest) and feeds them (a total of 22 – 25 days — while young are in nest, and for 4 – 7 days after they fledge). Males spend the summer feeding, preening, bathing, stretching their wings and fanning their tails, sleeping, roosting and sunbathing. Not a bad life for him; an exhausting one for her. (Thanks to Jeannie Killam and Terry Ross for photo op.)
For years scientists assumed that hummingbirds passively extracted nectar from flowers with their tongue through capillary action, but it turns out that this is not the case. A hummingbird’s forked tongue (which is twice as long as its beak) is lined with hair-like extensions or fringes called lamellae. When it is inserted into a flower and immersed in fluid, the tongue separates and the lamellae extend outwards so that open grooves (between the lamellae) lay flat. As the hummingbird pulls its tongue into its mouth, the forked tips come together and the lamellae roll inward, trapping the nectar within the tongue until it is swallowed by the hummingbird. No output of energy is necessary on the part of the bird – this process is automatic, takes all of 1/20th of a second, and occurs thousands of times a day. (Thanks to Ginny Barlow for Ruby-throated Hummingbird photo op.)
A commonly held belief is that in order to be cross-pollinated, flowers have evolved to attract certain pollinators, including wind, mammals, birds and insects. These traits, or “pollination syndromes,” include the flower shape, color, odor, amount of nectar and flowering time. Flowers attractive to hummingbirds tend to be large, tubular-shaped and colored red, orange (or sometimes yellow). These flowers usually have a large supply of dilute nectar, which they secrete during the day. Since birds do not have a strong response to scent, the flowers they visit tend to be odorless.
Canada Lilies, found throughout eastern North America, have a distinct tubular shape, which appeals to Ruby-throated Hummingbirds. Their long, thin beak allows these birds to reach nectar at the base of the flower that is inaccessible to many other creatures. In order to reach the nectar, the hummingbird must enter the flower far enough so that its neck and breast press up against the orange pollen-laden anthers of the Canada Lily. When the hummingbird moves on to the next Canada Lily flower, it is very likely that some of this pollen will end up on the flower’s female structure, or stigma, thereby pollinating the flower. (Note that the stigma, in the center of the flower, is taller than the anthers, thereby discouraging self-pollination.)