Harbingers Of Spring Return
Red-winged Blackbirds, Brown-headed Cowbirds and Common Grackles, all harbingers of spring, have started to return to Vermont over the past week or two. In southern and western United States Red-wings are thought to be nonmigratory, but individuals breeding in the Northeast on average migrate roughly 500 miles or more south in the fall. When spring comes, males migrate first and arrive back in the Northeast several weeks before females.
When they do arrive back, Red-winged Blackbirds often encounter several snow storms while on their breeding grounds. This is when life can become challenging for these voracious seed-eaters. They have a couple of months before nesting begins, during which time they are establishing territories and attracting a mate, both of which demand good nutrition. Corn and weed seeds make up a majority of their food during this time; insects are their mainstay during the breeding season.
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Common Grackles Raising Young
Although female Common Grackles do all the incubating, both males and females provide food for their nestlings. Males average almost two feedings an hour, females almost four. Judging from the size of the larvae the pictured Grackle has in its beak, its nestlings are midway to fledging, perhaps a week old. The older/larger the nestlings, the greater the size of the food they receive. Male and female nestlings received items of equal quality and quantity.
During the breeding season, both nestlings and adults feed primarily on insects in addition to a small amount of grain (and an occasional fish, small rodent or leech). During the winter, their diet consists mostly of agricultural grains and tree seeds such as acorns.
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Newly-emerged Dragonflies Vulnerable
When a dragonfly larva crawls up out of the water onto emergent vegetation or a rock to split its skin and emerge as a winged adult, it is in its most vulnerable state, for until its wings are pumped up and dry, it is incapable of flying.
Often for two or three hours a newly-emerged dragonfly will cling to the substrate, pumping hemolymph into its wings until they are fully expanded and then hang there defenseless while its exoskeleton and wings begin to harden. Only then does pigment in the dragonfly’s body become apparent, and its formerly pale, colorless head, thorax, abdomen and wings (see inset) assume their true colors.
The pictured Common Grackle has taken advantage of this precarious stage in a dragonfly’s life cycle and collected several dragonflies to feed to its offspring. The dragonflies’ lack of color indicates that this predation took place while the dragonflies were still flightless and before pigmentation was present.
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Common Grackles Nest-building
Common Grackles are hard to miss and hard to mistake for any other bird, with their yellow eyes, iridescent bronze or purple plumage and long, keel-shaped tails. Most of the spring migrants have reached their breeding grounds, and courtship, mating and nest-building are underway.
Because grackles begin reproduction so early in the season, conifers are the nesting site of choice due to the cover they provide. Females tend to choose the actual site for a nest, and in so doing can be quite fickle, often abandoning partially constructed nests and selecting alternative sites. They earn this right, as they’re usually doing all the construction work, although males have been observed with nesting materials, helping to build and repair nests.
Look for their 6-8”-diameter, large bulky nests near water, agricultural fields or near human habitation. They are usually built four to twenty feet above the ground. If you find a bird on the nest, it will most likely be an incubating female (slightly less glossy than male) – males not only do not have a brood patch and do not participate in incubating the eggs or brooding the young, but roughly half of the males desert their mates during this time. Those that do remain participate in the feeding of their young nestlings.
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Mystery Photo I.D. – Leeches feeding on the blood of a Snapping Turtle
Leeches are segmented worms (annnelids) which feed predominantly on blood, although some species do eat insects. Of the 700 species of leeches, 500 inhabit fresh water, as opposed to salt water or land. Blood-sucking leeches are common parasites of many freshwater vertebrates including turtles, amphibians and fish.
Generally speaking, leeches of the genus Placobdella are commonly found on turtles. Bottom-dwelling species such as the Common Snapping Turtle, Mud Turtle and Musk Turtle usually have more leeches than other turtles, and they are often attached to the skin at the limb sockets. Aerially-basking species such as Painted Turtles often have fewer of these parasites, possibly because basking forces leeches to detach in order to avoid desiccation.
A leech can ingest several times its weight in blood from one host before dropping off and not feeding again for weeks, or even months. Leeches inject hirudin, an anesthetic, to keep the hosts from feeling them break the skin. They also inject an anticoagulant to keep the blood from clotting so that they can feed. Although leeches (especially large ones) can be a significant health detriment to smaller animals, they are not harmful to most large animals, such as Snapping Turtles.
Some of the most common predators of leeches include turtles, fish, ducks, and other birds. Map Turtles allow Common Grackles to land in basking areas and peck at leeches clinging to their skin, and minnows have been seen cleaning leeches from Wood Turtles in the water. At times turtles bury themselves in ant mounds to rid themselves of these pesky parasites.
For those readers who may hesitate before going into a leech-laden pond, it may be comforting to know that leeches are mainly nocturnal. (Photo by Jeannie Killam)
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Nestling or Fledgling?
We are at the time of year where finding a young bird on the ground is not unusual, and many well-meaning people assume that if a bird can’t fly, it has been abandoned by its parents. While some of these birds may be young that have fallen out of their nest, the fledglings of many species spend as many as two to five days on the ground before they can fly any distance. While they are on the ground, the birds are cared for and protected by their parents and are taught vital life skills (finding food, identifying predators, flying). To deprive such a fledgling of this developmental stage by removing it from its parents is to lessen its chances of survival, so it’s behooves us to be able to tell whether or not a young bird belongs out of the nest or not.
If the young bird is nearly naked or covered with down, not quill feathers, or its eyes haven’t opened, it is obviously a nestling. If you can’t find its nest, a berry basket in the vicinity of where you found it, suspended from a branch, is a good facsimile. Birds have a poor sense of smell and very strong parental instincts and more often than not continue to care for their young after a disturbance, although it may be a few hours before they do so. If, after several hours, there is no sign of a parent, a local museum or nature center should be able to direct you to a nearby wildlife rehabilitator.
Fledgling birds, birds that have voluntarily left their nest, are usually fully feathered and have a very short (one inch or so) tail. They are able to walk, hop and flap, and they may attempt short flights. You may not see them, but a parent or two is nearby, keeping an eye on them, feeding them and teaching them how to survive on their own (see insert). These are the birds that humans often mistakenly “rescue.” If you find a fledgling, it should be left alone or, at the most, placed in a nearby shrub. If possible, keep people and pets away so the parents will continue to care for it until it can fly. (Photos: fledgling and attending adult Common Grackle)
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Common Grackles Returning
Male Common Grackles have started to arrive on their northeastern breeding grounds (females will arrive in another week or so), having migrated from southern U.S. Common Grackles typically migrate in large flocks containing hundreds of birds, not all grackles. Red-winged Blackbirds, Brown-headed Cowbirds, European Starlings and occasionally American Robins can be found alongside Common Grackles in these migrating flocks. In the early 1990’s, magnetic material was found in the heads and necks of Common Grackles, indicating that the geomagnetic field may play a role in their migratory navigation.
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Common Grackle Threat Display
Although the common grackle, a member of the blackbird family, is the bane of many corn growers as well as a threat to songbirds trying to raise young (grackles eat other birds’ eggs and nestlings), it is quite a colorful bird, with its pale yellow eyes and iridescent purple plumage. Grackles have already begun nesting and defending their territory, as can be seen from the stance of the bird in this image. This “bill-up display” is a position assumed when a male is being approached on its territory by another male. It moves its head upwards so that its bill is almost vertical, signaling to the approaching grackle that it would be in its best interest to depart.
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