Bobolink...What's that?

Male Bobolink. Photo by Bill Hubick.

Well, it’s a bird and a fascinating one at that. The Bobolink, Dolichonyx oryzivorus, is a songbird in the blackbird family (Icteridae).  As you can see from the pictures to the right and below, males and female are sexually dimorphic in the spring and summer months when the male has unmistakable black and white plumage with a straw colored nape. The female retains cryptic coloration year-round which is made up of straw colored body plumage with black streaking on the flanks.  Bobolinks are long distant migrants traveling thousands of miles annually from their breeding grounds in North America to their wintering grounds in South America, roughly 6000 miles one way!!! Males not only have unique plumage, but have a very unique song, follow this link to hear what they sound like, http://www.xeno-canto.org/sounds/uploaded/CDTGHVBGZP/BOBO2007-6-3-2.mp3, recorded by Andrew Spencer.  Some people think they sound like R2-D2 from Star Wars.

Female Bobolink. Photo by Bill Hubick.

Bobolinks require grasslands or something very similar, like alfalfa or hay fields, in which to nest. They can be found in Maryland during migration in both spring and fall and they breed in western and northern counties in the state. Maryland is at the very southern end of the breeding range for Bobolinks. They don’t breed on the eastern shore, but some attempt to nest in the northern reaches of Cecil County in hay fields.

Bobolinks have experienced range-wide population declines due to a variety of reasons, with habitat loss considered the single biggest factor. Most native grasslands and wet meadows have disappeared and they have been forced to nest in crop and hay fields as a result.  In terms of habitat quality, hay fields are not bad, but the problem is harvesting the hay while birds are still nesting. Farmers need to cut the hay at its nutritional peak which is often prior to young birds fledging or when they are still too young to fly. Biologists, especially in Vermont, are working with farmers to delay the cutting to allow nests to fledge.

Adult male Bobolink in breeding plumage.

Many Bobolinks use the CRFRS restored grassland on Chino Farm as stopover and refueling site during spring migration. But, the best time to see them in the grasslands is July through September. Adult males arrive first, still in their distinctive breeding plumage, followed by adult females and then in August and September by the young of the year. The restored grasslands provide critical habitat for the Bobolinks that stop here in the fall. Not only do the grasslands provide a bounty of food, in the form of insects and unlimited grass seed, but the tall thick fields act as a refuge. Bobolinks are somewhat unique among east coast birds in that they do not molt on their breeding grounds or the wintering grounds, but rather somewhere in between. This is where the restored grasslands are important.  

Adult male Bobolink undergoing flight feather molt.

 

 

Molt is the process of feather replacement that all birds under take annually. Soon after the adult Bobolinks arrive in the grasslands they begin the pre-basic molt which is complete, meaning they will molt, or replace, all their feathers. Only after this molt is complete in about 3-4 weeks will these birds continue their south-bound migration. All Bobolinks will again undergo a complete molt prior to leaving their wintering grounds for their spring migration back north. Flocks of over 300 individuals have been seen in the fields. What we don’t know yet is whether the same individuals use the grasslands as a molting ground every year or whether we always see different individuals. There are only two bird species in North America that go through two complete molts each year, Bobolinks are one of them, do you know what the other species is?

Sweeping views of the CRFRS restored grasslands on Chino Farm.

The CRFRS restored grasslands are not only providing critical breeding habitat for declining species such as Grasshopper Sparrow, Field Sparrow, Dickcissel and Northern Bobwhite and are a great winter habitat for a diversity of grassland dependent species but are also playing a fundamental role in the life cycle of Bobolinks.

Thanks to Bill Hubick for the use of his photographs. More of his photos can be seen at www.billhubick.com

Dan Small is a field ecologist at the Chester River Field Research Station and spends just about everyday in the summer months in the restored grasslands. For more information go to www.facebook.com/crfrc or www.washcoll.edu/ces/chesterriverfieldresearchcenter