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By now, most of our songbirds have completed their nesting season. There are some songbirds gathering together for their migration south. If asked what the last songbird to nest in Pennsylvania is, what would you say?
If you answered the goldfinch, you were correct. Most studies show the goldfinch does not start nesting until early July, with eggs not hatching until the end of July. Goldfinch fledglings have been reported in nests as late as September 8, which indicates that some birds will have a second brood.
Many people believe that when the male goldfinches show up at their feeders in the spring they are birds returning from the sunny south, however some goldfinches stay with us throughout the winter. During the winter months, the males will take on the drab colors of the females but retain the black and white wings. In the spring. they molt into their mating plumages.
This is not to say that the American goldfinch population does not make some kind of migration, especially the northern populations. Wintering flocks often wander about nomadically in search of food. The Cornell Laboratory of Ornithology has done research that indicates winter finches can show patterns of irruptive migration, meaning they will appear in areas where they did not exist the previous year.
This type of migration, which can expand specie's winter range, is generally caused by a lack of normally abundant food sources.
The American goldfinch genus name is carduelis tristis, which comes from the Latin word carduus meaning eats seeds of thistle. The species name tristis is also Latin and means sad, in allusion to its plaintive call. Although the goldfinch feeds on many types of seeds it depends heavily on the thistle plant to survive, and in some areas is called the thistle bird.
The bull thistle is easily recognized by its leaves, which have sharp prickles on the margins. In fact, prickles occur all over the plant, including the stout stem that can grow up to six feet tall. These sharp prickles stop most animals from feeding on the plant; however, some animals and insects do use the plant. Perhaps the most famous is our goldfinch, which feeds heavily on the thistle seeds and also uses the thistle down in its nest. The thistle down is not available until July, which is the reason that the goldfinch is the last bird to nest in our area.
Of course, the thistle flowers are visited by bees and many other insects. Bees and butterflies congregate in numbers on a single head of the fragrant bull thistle's flowers to gather nectar and inadvertently bring about cross pollination. I read in one book that the bumble bee is said to often become intoxicated on the nectar of the thistle.
There are eight species of thistles found in the United States with bull thistle and Canada thistle the most common in our area. Both species are biennial, forming a rosette of prickly leaves that over winter the first year. The thistles belong to the genus sisyrinchium, which is Greek and literally translated into pig snout, which comes from the fact that at one time wild pigs fed heavily on the roots.
The thistles belong to the large composite family. The bull thistle's scientific name is cirsium vulgare. Cirsium comes from the Latin word cardus, which was the Latin term for a thistle. In the language of flowers, the thistle is the symbol of nobility, of character as well as of birth (the wounding of a thistle yields punishment). The plant is also dedicated to Thor, the God of Thunder, which is why the thistle is often known as the lightning plant.
The thistle is the national emblem of Scotland, dating back to the time when the Danes invaded Scotland. The legend says that the Danes were trying to make a surprise night time attack on the Scots, and in trying to be quiet, they took off their boots and began creeping through the field when one of the soldiers stepped on a prickly thistle and let out a cry.
The cry warned the Scots, who were ready when the attacked occurred. This legend also produced the superstition that whoever wore the thistle was safe from harm. The thistle is the national flower of Scotland and is also the symbol of the Order of the Thistle, a high chivalric order of Scotland.
The bull thistle plant has a large showy head of purple flowers, leaves with white underneath and can grow to be six feet tall. Just as all members of the composite family, the thistle has a compact group of tiny flowers attached to the end of the stem. Each flower head produces a large number of silky- haired seeds that ripen during the summer and then dispersed by the wind.
The thistle is a plant that came from Europe and Asia. Since introduced into this country, it has extended its range to most cultivated areas of the United States and Canada. Our native species are far less common than those introduced from other countries. Some of these introduced species are noxious weeds and have been labeled noxious in 42 states.
Eliminating seed production appears to be the most effective control, however close mowing must be done twice a year to prevent this seed production. Mowing after flowering has begun can result in the spread of viable seeds with the mower.
The goldfinch and the thistle are only two examples of how nature intertwines.
Bill Bower is a retired Pennsylvania Game Commission Wildlife Officer. Read his blog and listen to his podcasts on the outdoors at www.onemaningreen.com.