Moles are digging, Woolly Bears are emerging and preparing to pupate and develop into Isabella Tiger Moths, and Painted Turtles are emerging and warming their cool bodies by basking in the sun. Red-winged Blackbirds, Killdeer and Wood Ducks are back. Silver Maple buds are beginning to swell. Ticks are out and about. New signs of spring are appearing on a daily basis, and those of us who keep nature journals are busy recording our discoveries. These events may happen every year, but they never get old.
Studies based on the records that Henry David Thoreau and other naturalists kept for Concord, MA in the middle of the 19th century have found that the flowering of plants, leaf-out, butterfly emergence and the arrivals of some migratory birds are occurring earlier now than they did 165 years ago — anywhere from a day to three weeks earlier depending on the species — driven mostly by warmer spring temperatures. Since the mid-1800’s Concord has lost roughly a quarter of its wildflowers while an additional third have become rare.
Whether it be through a written journal, sketches, photographs, videos or taped voice recordings, the observations we make today are a valuable resource for phenology (the timing of biological events) and climate change studies and for our own personal histories of natural places we visit year after year. We are so fortunate that the current state of the world doesn’t prevent our appreciation of and participation in this annual spring ritual.
Except for the coast, most of northern New England doesn’t see many Red-winged Blackbirds during the winter months. Numbers usually start increasing the last week of February with males arriving before females. In the fall it’s the reverse, with males departing after females.
Practically as soon as male Red-winged Blackbirds return, you can hear them singing and see them displaying as they claim their territories. If you could tell the females apart, you might well recognize some of them, as research shows that nearly half of the females return to the previous year’s territory.
While Red-winged Blackbirds are present year-round in southern New England, their return is one of the key indicators that spring has sprung further north. Males have just started appearing in northern New England, and females will follow shortly. Hearing these harbingers of spring is as delightful as seeing them.
Both males and females have a repertoire of songs and calls. The male redwing has nine distinct song types, the most familiar of which is its “konk-la-ree” song. Females have three main categories of much shorter songs.
The male sings throughout the year, but most frequently during the breeding season when territories are being established. In addition, he uses this song to initiate female courtship behavior once she is settled on his territory. Initially the female redwing does not answer the male’s song, but she does so frequently once she becomes a regular resident of his territory.
Singing is obviously a successful procreation strategy for male Red-winged Blackbirds, for up to 15 females have been observed nesting on the territory of a single male (although he does not necessarily sire all of the offspring).
To hear Red-winged Blackbird songs and calls, go to https://www.allaboutbirds.org/guide/Red-winged_Blackbird/sounds. (Photo: singing male Red-winged Blackbird)
As yesterday’s post indicated, the progression in which signs of spring appear remains much the same, but the timing of this progression is changing. Ornithologists have determined that modern climate change has resulted in an advancement of spring phenology throughout the Northern Hemisphere.
Many birds are arriving on their breeding grounds earlier in response to these changing conditions. Past research has focused on correlating climatic changes on breeding grounds with early arrival. However, it appears that climate variability on the wintering grounds of temperate species also plays a part in these short-distance migrants’ arrival on their breeding grounds.
Many climatic factors are involved in this phenomenon. The annual variation in temperature on the wintering grounds of American robins was found to be strongly related to their first-arrival date. Red-winged blackbirds’ first arrival dates were most influenced by precipitation during winter and spring months.
These and other changes in migratory patterns can have life or death consequences — birds arriving early on their breeding grounds face the possibility of adverse conditions and limited resources.
Regardless of the deep snow that remains on the ground and the frigid temperatures we’ve had recently, spring has announced itself with the arrival of red-winged blackbirds this week. Most redwings that breed in New England migrate approximately 500 miles further south to spend the winter. In the spring, males begin migrating first, flying north in flocks during the day to their breeding grounds. (In the fall, females depart first.) While they eat primarily insects during the breeding season, redwings subsist mainly on seeds and grain this early in the season. Before you know it, females will return, and up to fifteen of them will be nesting on the territory of each male (though he doesn’t sire all of the nestlings).
During the breeding season, insects make up the bulk of a Red-winged Blackbird’s diet, but during the rest of the year, plant seeds are preferred. While the seeds of ragweed, corn, oats and smartweed are more staple food sources, cattail seeds are not overlooked. At maturity, and under dry conditions, the cattail spike bursts, releasing the seeds (some estimates are as high as 228,000 seeds/spike). When this happens, blackbirds take advantage of the easily accessible source of food, but the minute size of each seed (.0079 inches long) means obtaining a meal is a labor-intensive endeavor.
Male red-winged blackbirds have returned to Vermont, and their most notable features are the brightly-colored reddish-orange feathers on their “shoulders”, referred to as epaulettes. In the military, an epaulette is a shoulder ornament that indicates, through its position, color, length and diameter, the bearer’s rank. Some birds, including male redwings, also possess this badge, or visual cue, which indicates the social status of the bird to other birds of the same species. Studies of male red-winged blackbirds and their epaulettes indicate (through dyeing their bright orange/red shoulder patches black) that epaulettes play a significant role in the male’s defense of his territory. Over 60% of the redwings that had their epaulettes dyed black lost their territories to other males. Further research revealed that aggression by a territorial male redwing is proportional to the epaulette size of the encroaching male redwing. It also indicated that male redwings intruding into redwing-occupied territories greatly limit the exposure of their epaulettes by covering them with black feathers. (Female red-winged blackbird plumage is brown and lacks epaulettes.)