Bobolinks are unusual among passerines in that they undergo two complete molts each year: once on their austral winter grounds south of the equator in the Pantanal region of northern Argentina, as well as portions of Brazil and Paraguay, where they are considered an agricultural pest due to their voracious appetites for rice and grain crops; and once on their breeding grounds in North America. Both molts take place prior to their lengthy northward and southward migrations, which combine for some 20,000 miles of travel round-trip. At this time of year, Bobolinks are well into their molt into basic plumage, if they have not already completed the process.
Male Bobolinks in alternate or "breeding" plumage are popular subjects for photographers. Bobolinks molting from alternate to basic plumage are not so popular. (I'd like to see photos from South America of Bobolinks molting from basic plumage into alternate plumage, but maybe that's too much to wish for . . .)
Kelly Riccetti recently posted some good photos of molting male Bobolinks at the Voice of America Park in West Chester, Butler County, Ohio on her blog. As part of a six-year-long summer bird survey I ran at the VOA, I had a lot of oppurtinities to watch Bobolinks as they molted from alternate to basic plumage. In 2004, in addition to the weekly surveys, I spent more hours than I care to admit "digiscoping" Bobolinks as their molt progressed throughout July and August, prior to the initiation of their migration to the great grasslands of southern South America.
Note how worn and bedraggled the female's tail looks; in fact, she might even be missing a feather or two. All of that effort and wear and tear are put into taking care of this:
And, in time, one hopes, the effort leads to a few of these:
During the course of my summer visits to the VOA, the first evidence of dependent young usually came in early July when young Bobolinks appear, begging for food from adults. Adult Bobolinks begin molting as soon as their nesting duties are completed, with new pin feathers appearing on adult males at the VOA as early as July 3.
Adults typically delay their molt until their young are independent, but I’ve seen adult males that are clearly in the beginning stages of molt, carrying food in a manner suggesting that they’re feeding young. Additionally, the one nest I found (photo above) was revealed by an adult carrying a large praying mantis to three nestlings. This adult male showed the beginnings of the inverted yellow “U” shape on the breast that is typical of adult males in full body molt as well as new feathers growing in on his back. Adult females at the VOA usually do not show signs of molt until at least the second week of July. In his 1968 Birds of the Toledo Area, Lou Campbell noted that July 1 marked the beginning of Bobolink molt in northwest Ohio, and based on the observations of other birders in Ohio, the first week of July certainly seems to mark the beginning of Bobolink molt season throughout the state.
Adult Bobolinks molt their tail and wing feathers in dramatic and rapid fashion. It’s common to see adults with large gaps from missing feathers in their primaries, secondaries, and tails.
Though Bobolinks are never rendered flightless during their molt, they do become flight impaired. My experience at the VOA has been that during mid-July, when many adults are in active molt, they become far less conspicuous and take extra efforts to stay in cover.
Still, a few molting adults of both sexes can often be viewed at length, particularly at first light, while they busily peck, pull, and preen their mottled mix of old alternate feathers and new basic plumage feathers. This secretiveness might be part of the reason that some reports note a lack of Bobolinks in July in fields where they had been so numerous in June. I suspect that unless the field has been mowed, June’s Bobolinks are merely staying low and keeping quiet in July.
Part III will cover "tail-less" Bobolinks as well as some hatch-year birds.
Male Bobolinks in alternate or "breeding" plumage are popular subjects for photographers. Bobolinks molting from alternate to basic plumage are not so popular. (I'd like to see photos from South America of Bobolinks molting from basic plumage into alternate plumage, but maybe that's too much to wish for . . .)
Kelly Riccetti recently posted some good photos of molting male Bobolinks at the Voice of America Park in West Chester, Butler County, Ohio on her blog. As part of a six-year-long summer bird survey I ran at the VOA, I had a lot of oppurtinities to watch Bobolinks as they molted from alternate to basic plumage. In 2004, in addition to the weekly surveys, I spent more hours than I care to admit "digiscoping" Bobolinks as their molt progressed throughout July and August, prior to the initiation of their migration to the great grasslands of southern South America.
Here are photos of a female and male Bobolink taken on 12 June 2004, during the height of the Bobolink breeding season (all the photos in this posting were taken at the Voice of America Park):
Note how worn and bedraggled the female's tail looks; in fact, she might even be missing a feather or two. All of that effort and wear and tear are put into taking care of this:
(Bobolink nest, 9 July 2005)
And, in time, one hopes, the effort leads to a few of these:
(Hatch-year Bobolink, 3 July 2004)
During the course of my summer visits to the VOA, the first evidence of dependent young usually came in early July when young Bobolinks appear, begging for food from adults. Adult Bobolinks begin molting as soon as their nesting duties are completed, with new pin feathers appearing on adult males at the VOA as early as July 3.
(Adult Male Bobolink 3 July 2004)
Adult Bobolinks molt their tail and wing feathers in dramatic and rapid fashion. It’s common to see adults with large gaps from missing feathers in their primaries, secondaries, and tails.
(Adult male Bobolink, 11 July 2004. Much of the wing is being molted and the bird is actively preening. Note also the new yellow feathers on the breast.)
Though Bobolinks are never rendered flightless during their molt, they do become flight impaired. My experience at the VOA has been that during mid-July, when many adults are in active molt, they become far less conspicuous and take extra efforts to stay in cover.
(Adult male Bobolink. 10 July 2004. The tail feathers are uneven and there are a number of wing feathers either missing or not yet grown in.)
Still, a few molting adults of both sexes can often be viewed at length, particularly at first light, while they busily peck, pull, and preen their mottled mix of old alternate feathers and new basic plumage feathers. This secretiveness might be part of the reason that some reports note a lack of Bobolinks in July in fields where they had been so numerous in June. I suspect that unless the field has been mowed, June’s Bobolinks are merely staying low and keeping quiet in July.
Part III will cover "tail-less" Bobolinks as well as some hatch-year birds.
Thanks, Mike! This is such an interesting post. I learned a lot. I think there's a chance that when Matty was a newborn I looked a bit like that "worn and bedraggled" female. :-) I can't wait to see part three!!
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